MDL-41197 normalize ascii text conversion

[moodle.git] / lib / moodlelib.php

<?php
// This file is part of Moodle - http://moodle.org/
//
// Moodle is free software: you can redistribute it and/or modify
// it under the terms of the GNU General Public License as published by
// the Free Software Foundation, either version 3 of the License, or
// (at your option) any later version.
//
// Moodle is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
// GNU General Public License for more details.
//
// You should have received a copy of the GNU General Public License
// along with Moodle.  If not, see <http://www.gnu.org/licenses/>.

/**
 * moodlelib.php - Moodle main library
 *
 * Main library file of miscellaneous general-purpose Moodle functions.
 * Other main libraries:
 *  - weblib.php      - functions that produce web output
 *  - datalib.php     - functions that access the database
 *
 * @package    core
 * @subpackage lib
 * @copyright  1999 onwards Martin Dougiamas  http://dougiamas.com
 * @license    http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later
 */

defined('MOODLE_INTERNAL') || die();

// CONSTANTS (Encased in phpdoc proper comments).

// Date and time constants.
/**
 * Time constant - the number of seconds in a year
 */
define('YEARSECS', 31536000);

/**
 * Time constant - the number of seconds in a week
 */
define('WEEKSECS', 604800);

/**
 * Time constant - the number of seconds in a day
 */
define('DAYSECS', 86400);

/**
 * Time constant - the number of seconds in an hour
 */
define('HOURSECS', 3600);

/**
 * Time constant - the number of seconds in a minute
 */
define('MINSECS', 60);

/**
 * Time constant - the number of minutes in a day
 */
define('DAYMINS', 1440);

/**
 * Time constant - the number of minutes in an hour
 */
define('HOURMINS', 60);

// Parameter constants - every call to optional_param(), required_param()
// or clean_param() should have a specified type of parameter.

/**
 * PARAM_ALPHA - contains only english ascii letters a-zA-Z.
 */
define('PARAM_ALPHA',    'alpha');

/**
 * PARAM_ALPHAEXT the same contents as PARAM_ALPHA plus the chars in quotes: "_-" allowed
 * NOTE: originally this allowed "/" too, please use PARAM_SAFEPATH if "/" needed
 */
define('PARAM_ALPHAEXT', 'alphaext');

/**
 * PARAM_ALPHANUM - expected numbers and letters only.
 */
define('PARAM_ALPHANUM', 'alphanum');

/**
 * PARAM_ALPHANUMEXT - expected numbers, letters only and _-.
 */
define('PARAM_ALPHANUMEXT', 'alphanumext');

/**
 * PARAM_AUTH - actually checks to make sure the string is a valid auth plugin
 */
define('PARAM_AUTH',  'auth');

/**
 * PARAM_BASE64 - Base 64 encoded format
 */
define('PARAM_BASE64',   'base64');

/**
 * PARAM_BOOL - converts input into 0 or 1, use for switches in forms and urls.
 */
define('PARAM_BOOL',     'bool');

/**
 * PARAM_CAPABILITY - A capability name, like 'moodle/role:manage'. Actually
 * checked against the list of capabilities in the database.
 */
define('PARAM_CAPABILITY',   'capability');

/**
 * PARAM_CLEANHTML - cleans submitted HTML code. Note that you almost never want
 * to use this. The normal mode of operation is to use PARAM_RAW when recieving
 * the input (required/optional_param or formslib) and then sanitse the HTML
 * using format_text on output. This is for the rare cases when you want to
 * sanitise the HTML on input. This cleaning may also fix xhtml strictness.
 */
define('PARAM_CLEANHTML', 'cleanhtml');

/**
 * PARAM_EMAIL - an email address following the RFC
 */
define('PARAM_EMAIL',   'email');

/**
 * PARAM_FILE - safe file name, all dangerous chars are stripped, protects against XSS, SQL injections and directory traversals
 */
define('PARAM_FILE',   'file');

/**
 * PARAM_FLOAT - a real/floating point number.
 *
 * Note that you should not use PARAM_FLOAT for numbers typed in by the user.
 * It does not work for languages that use , as a decimal separator.
 * Instead, do something like
 *     $rawvalue = required_param('name', PARAM_RAW);
 *     // ... other code including require_login, which sets current lang ...
 *     $realvalue = unformat_float($rawvalue);
 *     // ... then use $realvalue
 */
define('PARAM_FLOAT',  'float');

/**
 * PARAM_HOST - expected fully qualified domain name (FQDN) or an IPv4 dotted quad (IP address)
 */
define('PARAM_HOST',     'host');

/**
 * PARAM_INT - integers only, use when expecting only numbers.
 */
define('PARAM_INT',      'int');

/**
 * PARAM_LANG - checks to see if the string is a valid installed language in the current site.
 */
define('PARAM_LANG',  'lang');

/**
 * PARAM_LOCALURL - expected properly formatted URL as well as one that refers to the local server itself. (NOT orthogonal to the
 * others! Implies PARAM_URL!)
 */
define('PARAM_LOCALURL', 'localurl');

/**
 * PARAM_NOTAGS - all html tags are stripped from the text. Do not abuse this type.
 */
define('PARAM_NOTAGS',   'notags');

/**
 * PARAM_PATH - safe relative path name, all dangerous chars are stripped, protects against XSS, SQL injections and directory
 * traversals note: the leading slash is not removed, window drive letter is not allowed
 */
define('PARAM_PATH',     'path');

/**
 * PARAM_PEM - Privacy Enhanced Mail format
 */
define('PARAM_PEM',      'pem');

/**
 * PARAM_PERMISSION - A permission, one of CAP_INHERIT, CAP_ALLOW, CAP_PREVENT or CAP_PROHIBIT.
 */
define('PARAM_PERMISSION',   'permission');

/**
 * PARAM_RAW specifies a parameter that is not cleaned/processed in any way except the discarding of the invalid utf-8 characters
 */
define('PARAM_RAW', 'raw');

/**
 * PARAM_RAW_TRIMMED like PARAM_RAW but leading and trailing whitespace is stripped.
 */
define('PARAM_RAW_TRIMMED', 'raw_trimmed');

/**
 * PARAM_SAFEDIR - safe directory name, suitable for include() and require()
 */
define('PARAM_SAFEDIR',  'safedir');

/**
 * PARAM_SAFEPATH - several PARAM_SAFEDIR joined by "/", suitable for include() and require(), plugin paths, etc.
 */
define('PARAM_SAFEPATH',  'safepath');

/**
 * PARAM_SEQUENCE - expects a sequence of numbers like 8 to 1,5,6,4,6,8,9.  Numbers and comma only.
 */
define('PARAM_SEQUENCE',  'sequence');

/**
 * PARAM_TAG - one tag (interests, blogs, etc.) - mostly international characters and space, <> not supported
 */
define('PARAM_TAG',   'tag');

/**
 * PARAM_TAGLIST - list of tags separated by commas (interests, blogs, etc.)
 */
define('PARAM_TAGLIST',   'taglist');

/**
 * PARAM_TEXT - general plain text compatible with multilang filter, no other html tags. Please note '<', or '>' are allowed here.
 */
define('PARAM_TEXT',  'text');

/**
 * PARAM_THEME - Checks to see if the string is a valid theme name in the current site
 */
define('PARAM_THEME',  'theme');

/**
 * PARAM_URL - expected properly formatted URL. Please note that domain part is required, http://localhost/ is not accepted but
 * http://localhost.localdomain/ is ok.
 */
define('PARAM_URL',      'url');

/**
 * PARAM_USERNAME - Clean username to only contains allowed characters. This is to be used ONLY when manually creating user
 * accounts, do NOT use when syncing with external systems!!
 */
define('PARAM_USERNAME',    'username');

/**
 * PARAM_STRINGID - used to check if the given string is valid string identifier for get_string()
 */
define('PARAM_STRINGID',    'stringid');

// DEPRECATED PARAM TYPES OR ALIASES - DO NOT USE FOR NEW CODE.
/**
 * PARAM_CLEAN - obsoleted, please use a more specific type of parameter.
 * It was one of the first types, that is why it is abused so much ;-)
 * @deprecated since 2.0
 */
define('PARAM_CLEAN',    'clean');

/**
 * PARAM_INTEGER - deprecated alias for PARAM_INT
 * @deprecated since 2.0
 */
define('PARAM_INTEGER',  'int');

/**
 * PARAM_NUMBER - deprecated alias of PARAM_FLOAT
 * @deprecated since 2.0
 */
define('PARAM_NUMBER',  'float');

/**
 * PARAM_ACTION - deprecated alias for PARAM_ALPHANUMEXT, use for various actions in forms and urls
 * NOTE: originally alias for PARAM_APLHA
 * @deprecated since 2.0
 */
define('PARAM_ACTION',   'alphanumext');

/**
 * PARAM_FORMAT - deprecated alias for PARAM_ALPHANUMEXT, use for names of plugins, formats, etc.
 * NOTE: originally alias for PARAM_APLHA
 * @deprecated since 2.0
 */
define('PARAM_FORMAT',   'alphanumext');

/**
 * PARAM_MULTILANG - deprecated alias of PARAM_TEXT.
 * @deprecated since 2.0
 */
define('PARAM_MULTILANG',  'text');

/**
 * PARAM_TIMEZONE - expected timezone. Timezone can be int +-(0-13) or float +-(0.5-12.5) or
 * string separated by '/' and can have '-' &/ '_' (eg. America/North_Dakota/New_Salem
 * America/Port-au-Prince)
 */
define('PARAM_TIMEZONE', 'timezone');

/**
 * PARAM_CLEANFILE - deprecated alias of PARAM_FILE; originally was removing regional chars too
 */
define('PARAM_CLEANFILE', 'file');

/**
 * PARAM_COMPONENT is used for full component names (aka frankenstyle) such as 'mod_forum', 'core_rating', 'auth_ldap'.
 * Short legacy subsystem names and module names are accepted too ex: 'forum', 'rating', 'user'.
 * Only lowercase ascii letters, numbers and underscores are allowed, it has to start with a letter.
 * NOTE: numbers and underscores are strongly discouraged in plugin names!
 */
define('PARAM_COMPONENT', 'component');

/**
 * PARAM_AREA is a name of area used when addressing files, comments, ratings, etc.
 * It is usually used together with context id and component.
 * Only lowercase ascii letters, numbers and underscores are allowed, it has to start with a letter.
 */
define('PARAM_AREA', 'area');

/**
 * PARAM_PLUGIN is used for plugin names such as 'forum', 'glossary', 'ldap', 'radius', 'paypal', 'completionstatus'.
 * Only lowercase ascii letters, numbers and underscores are allowed, it has to start with a letter.
 * NOTE: numbers and underscores are strongly discouraged in plugin names! Underscores are forbidden in module names.
 */
define('PARAM_PLUGIN', 'plugin');


// Web Services.

/**
 * VALUE_REQUIRED - if the parameter is not supplied, there is an error
 */
define('VALUE_REQUIRED', 1);

/**
 * VALUE_OPTIONAL - if the parameter is not supplied, then the param has no value
 */
define('VALUE_OPTIONAL', 2);

/**
 * VALUE_DEFAULT - if the parameter is not supplied, then the default value is used
 */
define('VALUE_DEFAULT', 0);

/**
 * NULL_NOT_ALLOWED - the parameter can not be set to null in the database
 */
define('NULL_NOT_ALLOWED', false);

/**
 * NULL_ALLOWED - the parameter can be set to null in the database
 */
define('NULL_ALLOWED', true);

// Page types.

/**
 * PAGE_COURSE_VIEW is a definition of a page type. For more information on the page class see moodle/lib/pagelib.php.
 */
define('PAGE_COURSE_VIEW', 'course-view');

/** Get remote addr constant */
define('GETREMOTEADDR_SKIP_HTTP_CLIENT_IP', '1');
/** Get remote addr constant */
define('GETREMOTEADDR_SKIP_HTTP_X_FORWARDED_FOR', '2');

// Blog access level constant declaration.
define ('BLOG_USER_LEVEL', 1);
define ('BLOG_GROUP_LEVEL', 2);
define ('BLOG_COURSE_LEVEL', 3);
define ('BLOG_SITE_LEVEL', 4);
define ('BLOG_GLOBAL_LEVEL', 5);


// Tag constants.
/**
 * To prevent problems with multibytes strings,Flag updating in nav not working on the review page. this should not exceed the
 * length of "varchar(255) / 3 (bytes / utf-8 character) = 85".
 * TODO: this is not correct, varchar(255) are 255 unicode chars ;-)
 *
 * @todo define(TAG_MAX_LENGTH) this is not correct, varchar(255) are 255 unicode chars ;-)
 */
define('TAG_MAX_LENGTH', 50);

// Password policy constants.
define ('PASSWORD_LOWER', 'abcdefghijklmnopqrstuvwxyz');
define ('PASSWORD_UPPER', 'ABCDEFGHIJKLMNOPQRSTUVWXYZ');
define ('PASSWORD_DIGITS', '0123456789');
define ('PASSWORD_NONALPHANUM', '.,;:!?_-+/*@#&$');

// Feature constants.
// Used for plugin_supports() to report features that are, or are not, supported by a module.

/** True if module can provide a grade */
define('FEATURE_GRADE_HAS_GRADE', 'grade_has_grade');
/** True if module supports outcomes */
define('FEATURE_GRADE_OUTCOMES', 'outcomes');
/** True if module supports advanced grading methods */
define('FEATURE_ADVANCED_GRADING', 'grade_advanced_grading');
/** True if module controls the grade visibility over the gradebook */
define('FEATURE_CONTROLS_GRADE_VISIBILITY', 'controlsgradevisbility');
/** True if module supports plagiarism plugins */
define('FEATURE_PLAGIARISM', 'plagiarism');

/** True if module has code to track whether somebody viewed it */
define('FEATURE_COMPLETION_TRACKS_VIEWS', 'completion_tracks_views');
/** True if module has custom completion rules */
define('FEATURE_COMPLETION_HAS_RULES', 'completion_has_rules');

/** True if module has no 'view' page (like label) */
define('FEATURE_NO_VIEW_LINK', 'viewlink');
/** True if module supports outcomes */
define('FEATURE_IDNUMBER', 'idnumber');
/** True if module supports groups */
define('FEATURE_GROUPS', 'groups');
/** True if module supports groupings */
define('FEATURE_GROUPINGS', 'groupings');
/** True if module supports groupmembersonly */
define('FEATURE_GROUPMEMBERSONLY', 'groupmembersonly');

/** Type of module */
define('FEATURE_MOD_ARCHETYPE', 'mod_archetype');
/** True if module supports intro editor */
define('FEATURE_MOD_INTRO', 'mod_intro');
/** True if module has default completion */
define('FEATURE_MODEDIT_DEFAULT_COMPLETION', 'modedit_default_completion');

define('FEATURE_COMMENT', 'comment');

define('FEATURE_RATE', 'rate');
/** True if module supports backup/restore of moodle2 format */
define('FEATURE_BACKUP_MOODLE2', 'backup_moodle2');

/** True if module can show description on course main page */
define('FEATURE_SHOW_DESCRIPTION', 'showdescription');

/** True if module uses the question bank */
define('FEATURE_USES_QUESTIONS', 'usesquestions');

/** Unspecified module archetype */
define('MOD_ARCHETYPE_OTHER', 0);
/** Resource-like type module */
define('MOD_ARCHETYPE_RESOURCE', 1);
/** Assignment module archetype */
define('MOD_ARCHETYPE_ASSIGNMENT', 2);
/** System (not user-addable) module archetype */
define('MOD_ARCHETYPE_SYSTEM', 3);

/** Return this from modname_get_types callback to use default display in activity chooser */
define('MOD_SUBTYPE_NO_CHILDREN', 'modsubtypenochildren');

/**
 * Security token used for allowing access
 * from external application such as web services.
 * Scripts do not use any session, performance is relatively
 * low because we need to load access info in each request.
 * Scripts are executed in parallel.
 */
define('EXTERNAL_TOKEN_PERMANENT', 0);

/**
 * Security token used for allowing access
 * of embedded applications, the code is executed in the
 * active user session. Token is invalidated after user logs out.
 * Scripts are executed serially - normal session locking is used.
 */
define('EXTERNAL_TOKEN_EMBEDDED', 1);

/**
 * The home page should be the site home
 */
define('HOMEPAGE_SITE', 0);
/**
 * The home page should be the users my page
 */
define('HOMEPAGE_MY', 1);
/**
 * The home page can be chosen by the user
 */
define('HOMEPAGE_USER', 2);

/**
 * Hub directory url (should be moodle.org)
 */
define('HUB_HUBDIRECTORYURL', "http://hubdirectory.moodle.org");


/**
 * Moodle.org url (should be moodle.org)
 */
define('HUB_MOODLEORGHUBURL', "http://hub.moodle.org");

/**
 * Moodle mobile app service name
 */
define('MOODLE_OFFICIAL_MOBILE_SERVICE', 'moodle_mobile_app');

/**
 * Indicates the user has the capabilities required to ignore activity and course file size restrictions
 */
define('USER_CAN_IGNORE_FILE_SIZE_LIMITS', -1);

/**
 * Course display settings: display all sections on one page.
 */
define('COURSE_DISPLAY_SINGLEPAGE', 0);
/**
 * Course display settings: split pages into a page per section.
 */
define('COURSE_DISPLAY_MULTIPAGE', 1);

/**
 * Authentication constant: String used in password field when password is not stored.
 */
define('AUTH_PASSWORD_NOT_CACHED', 'not cached');

// PARAMETER HANDLING.

/**
 * Returns a particular value for the named variable, taken from
 * POST or GET.  If the parameter doesn't exist then an error is
 * thrown because we require this variable.
 *
 * This function should be used to initialise all required values
 * in a script that are based on parameters.  Usually it will be
 * used like this:
 *    $id = required_param('id', PARAM_INT);
 *
 * Please note the $type parameter is now required and the value can not be array.
 *
 * @param string $parname the name of the page parameter we want
 * @param string $type expected type of parameter
 * @return mixed
 * @throws coding_exception
 */
function required_param($parname, $type) {
    if (func_num_args() != 2 or empty($parname) or empty($type)) {
        throw new coding_exception('required_param() requires $parname and $type to be specified (parameter: '.$parname.')');
    }
    // POST has precedence.
    if (isset($_POST[$parname])) {
        $param = $_POST[$parname];
    } else if (isset($_GET[$parname])) {
        $param = $_GET[$parname];
    } else {
        print_error('missingparam', '', '', $parname);
    }

    if (is_array($param)) {
        debugging('Invalid array parameter detected in required_param(): '.$parname);
        // TODO: switch to fatal error in Moodle 2.3.
        return required_param_array($parname, $type);
    }

    return clean_param($param, $type);
}

/**
 * Returns a particular array value for the named variable, taken from
 * POST or GET.  If the parameter doesn't exist then an error is
 * thrown because we require this variable.
 *
 * This function should be used to initialise all required values
 * in a script that are based on parameters.  Usually it will be
 * used like this:
 *    $ids = required_param_array('ids', PARAM_INT);
 *
 *  Note: arrays of arrays are not supported, only alphanumeric keys with _ and - are supported
 *
 * @param string $parname the name of the page parameter we want
 * @param string $type expected type of parameter
 * @return array
 * @throws coding_exception
 */
function required_param_array($parname, $type) {
    if (func_num_args() != 2 or empty($parname) or empty($type)) {
        throw new coding_exception('required_param_array() requires $parname and $type to be specified (parameter: '.$parname.')');
    }
    // POST has precedence.
    if (isset($_POST[$parname])) {
        $param = $_POST[$parname];
    } else if (isset($_GET[$parname])) {
        $param = $_GET[$parname];
    } else {
        print_error('missingparam', '', '', $parname);
    }
    if (!is_array($param)) {
        print_error('missingparam', '', '', $parname);
    }

    $result = array();
    foreach ($param as $key => $value) {
        if (!preg_match('/^[a-z0-9_-]+$/i', $key)) {
            debugging('Invalid key name in required_param_array() detected: '.$key.', parameter: '.$parname);
            continue;
        }
        $result[$key] = clean_param($value, $type);
    }

    return $result;
}

/**
 * Returns a particular value for the named variable, taken from
 * POST or GET, otherwise returning a given default.
 *
 * This function should be used to initialise all optional values
 * in a script that are based on parameters.  Usually it will be
 * used like this:
 *    $name = optional_param('name', 'Fred', PARAM_TEXT);
 *
 * Please note the $type parameter is now required and the value can not be array.
 *
 * @param string $parname the name of the page parameter we want
 * @param mixed  $default the default value to return if nothing is found
 * @param string $type expected type of parameter
 * @return mixed
 * @throws coding_exception
 */
function optional_param($parname, $default, $type) {
    if (func_num_args() != 3 or empty($parname) or empty($type)) {
        throw new coding_exception('optional_param requires $parname, $default + $type to be specified (parameter: '.$parname.')');
    }
    if (!isset($default)) {
        $default = null;
    }

    // POST has precedence.
    if (isset($_POST[$parname])) {
        $param = $_POST[$parname];
    } else if (isset($_GET[$parname])) {
        $param = $_GET[$parname];
    } else {
        return $default;
    }

    if (is_array($param)) {
        debugging('Invalid array parameter detected in required_param(): '.$parname);
        // TODO: switch to $default in Moodle 2.3.
        return optional_param_array($parname, $default, $type);
    }

    return clean_param($param, $type);
}

/**
 * Returns a particular array value for the named variable, taken from
 * POST or GET, otherwise returning a given default.
 *
 * This function should be used to initialise all optional values
 * in a script that are based on parameters.  Usually it will be
 * used like this:
 *    $ids = optional_param('id', array(), PARAM_INT);
 *
 * Note: arrays of arrays are not supported, only alphanumeric keys with _ and - are supported
 *
 * @param string $parname the name of the page parameter we want
 * @param mixed $default the default value to return if nothing is found
 * @param string $type expected type of parameter
 * @return array
 * @throws coding_exception
 */
function optional_param_array($parname, $default, $type) {
    if (func_num_args() != 3 or empty($parname) or empty($type)) {
        throw new coding_exception('optional_param_array requires $parname, $default + $type to be specified (parameter: '.$parname.')');
    }

    // POST has precedence.
    if (isset($_POST[$parname])) {
        $param = $_POST[$parname];
    } else if (isset($_GET[$parname])) {
        $param = $_GET[$parname];
    } else {
        return $default;
    }
    if (!is_array($param)) {
        debugging('optional_param_array() expects array parameters only: '.$parname);
        return $default;
    }

    $result = array();
    foreach ($param as $key => $value) {
        if (!preg_match('/^[a-z0-9_-]+$/i', $key)) {
            debugging('Invalid key name in optional_param_array() detected: '.$key.', parameter: '.$parname);
            continue;
        }
        $result[$key] = clean_param($value, $type);
    }

    return $result;
}

/**
 * Strict validation of parameter values, the values are only converted
 * to requested PHP type. Internally it is using clean_param, the values
 * before and after cleaning must be equal - otherwise
 * an invalid_parameter_exception is thrown.
 * Objects and classes are not accepted.
 *
 * @param mixed $param
 * @param string $type PARAM_ constant
 * @param bool $allownull are nulls valid value?
 * @param string $debuginfo optional debug information
 * @return mixed the $param value converted to PHP type
 * @throws invalid_parameter_exception if $param is not of given type
 */
function validate_param($param, $type, $allownull=NULL_NOT_ALLOWED, $debuginfo='') {
    if (is_null($param)) {
        if ($allownull == NULL_ALLOWED) {
            return null;
        } else {
            throw new invalid_parameter_exception($debuginfo);
        }
    }
    if (is_array($param) or is_object($param)) {
        throw new invalid_parameter_exception($debuginfo);
    }

    $cleaned = clean_param($param, $type);

    if ($type == PARAM_FLOAT) {
        // Do not detect precision loss here.
        if (is_float($param) or is_int($param)) {
            // These always fit.
        } else if (!is_numeric($param) or !preg_match('/^[\+-]?[0-9]*\.?[0-9]*(e[-+]?[0-9]+)?$/i', (string)$param)) {
            throw new invalid_parameter_exception($debuginfo);
        }
    } else if ((string)$param !== (string)$cleaned) {
        // Conversion to string is usually lossless.
        throw new invalid_parameter_exception($debuginfo);
    }

    return $cleaned;
}

/**
 * Makes sure array contains only the allowed types, this function does not validate array key names!
 *
 * <code>
 * $options = clean_param($options, PARAM_INT);
 * </code>
 *
 * @param array $param the variable array we are cleaning
 * @param string $type expected format of param after cleaning.
 * @param bool $recursive clean recursive arrays
 * @return array
 * @throws coding_exception
 */
function clean_param_array(array $param = null, $type, $recursive = false) {
    // Convert null to empty array.
    $param = (array)$param;
    foreach ($param as $key => $value) {
        if (is_array($value)) {
            if ($recursive) {
                $param[$key] = clean_param_array($value, $type, true);
            } else {
                throw new coding_exception('clean_param_array can not process multidimensional arrays when $recursive is false.');
            }
        } else {
            $param[$key] = clean_param($value, $type);
        }
    }
    return $param;
}

/**
 * Used by {@link optional_param()} and {@link required_param()} to
 * clean the variables and/or cast to specific types, based on
 * an options field.
 * <code>
 * $course->format = clean_param($course->format, PARAM_ALPHA);
 * $selectedgradeitem = clean_param($selectedgradeitem, PARAM_INT);
 * </code>
 *
 * @param mixed $param the variable we are cleaning
 * @param string $type expected format of param after cleaning.
 * @return mixed
 * @throws coding_exception
 */
function clean_param($param, $type) {
    global $CFG;

    if (is_array($param)) {
        throw new coding_exception('clean_param() can not process arrays, please use clean_param_array() instead.');
    } else if (is_object($param)) {
        if (method_exists($param, '__toString')) {
            $param = $param->__toString();
        } else {
            throw new coding_exception('clean_param() can not process objects, please use clean_param_array() instead.');
        }
    }

    switch ($type) {
        case PARAM_RAW:
            // No cleaning at all.
            $param = fix_utf8($param);
            return $param;

        case PARAM_RAW_TRIMMED:
            // No cleaning, but strip leading and trailing whitespace.
            $param = fix_utf8($param);
            return trim($param);

        case PARAM_CLEAN:
            // General HTML cleaning, try to use more specific type if possible this is deprecated!
            // Please use more specific type instead.
            if (is_numeric($param)) {
                return $param;
            }
            $param = fix_utf8($param);
            // Sweep for scripts, etc.
            return clean_text($param);

        case PARAM_CLEANHTML:
            // Clean html fragment.
            $param = fix_utf8($param);
            // Sweep for scripts, etc.
            $param = clean_text($param, FORMAT_HTML);
            return trim($param);

        case PARAM_INT:
            // Convert to integer.
            return (int)$param;

        case PARAM_FLOAT:
            // Convert to float.
            return (float)$param;

        case PARAM_ALPHA:
            // Remove everything not `a-z`.
            return preg_replace('/[^a-zA-Z]/i', '', $param);

        case PARAM_ALPHAEXT:
            // Remove everything not `a-zA-Z_-` (originally allowed "/" too).
            return preg_replace('/[^a-zA-Z_-]/i', '', $param);

        case PARAM_ALPHANUM:
            // Remove everything not `a-zA-Z0-9`.
            return preg_replace('/[^A-Za-z0-9]/i', '', $param);

        case PARAM_ALPHANUMEXT:
            // Remove everything not `a-zA-Z0-9_-`.
            return preg_replace('/[^A-Za-z0-9_-]/i', '', $param);

        case PARAM_SEQUENCE:
            // Remove everything not `0-9,`.
            return preg_replace('/[^0-9,]/i', '', $param);

        case PARAM_BOOL:
            // Convert to 1 or 0.
            $tempstr = strtolower($param);
            if ($tempstr === 'on' or $tempstr === 'yes' or $tempstr === 'true') {
                $param = 1;
            } else if ($tempstr === 'off' or $tempstr === 'no'  or $tempstr === 'false') {
                $param = 0;
            } else {
                $param = empty($param) ? 0 : 1;
            }
            return $param;

        case PARAM_NOTAGS:
            // Strip all tags.
            $param = fix_utf8($param);
            return strip_tags($param);

        case PARAM_TEXT:
            // Leave only tags needed for multilang.
            $param = fix_utf8($param);
            // If the multilang syntax is not correct we strip all tags because it would break xhtml strict which is required
            // for accessibility standards please note this cleaning does not strip unbalanced '>' for BC compatibility reasons.
            do {
                if (strpos($param, '</lang>') !== false) {
                    // Old and future mutilang syntax.
                    $param = strip_tags($param, '<lang>');
                    if (!preg_match_all('/<.*>/suU', $param, $matches)) {
                        break;
                    }
                    $open = false;
                    foreach ($matches[0] as $match) {
                        if ($match === '</lang>') {
                            if ($open) {
                                $open = false;
                                continue;
                            } else {
                                break 2;
                            }
                        }
                        if (!preg_match('/^<lang lang="[a-zA-Z0-9_-]+"\s*>$/u', $match)) {
                            break 2;
                        } else {
                            $open = true;
                        }
                    }
                    if ($open) {
                        break;
                    }
                    return $param;

                } else if (strpos($param, '</span>') !== false) {
                    // Current problematic multilang syntax.
                    $param = strip_tags($param, '<span>');
                    if (!preg_match_all('/<.*>/suU', $param, $matches)) {
                        break;
                    }
                    $open = false;
                    foreach ($matches[0] as $match) {
                        if ($match === '</span>') {
                            if ($open) {
                                $open = false;
                                continue;
                            } else {
                                break 2;
                            }
                        }
                        if (!preg_match('/^<span(\s+lang="[a-zA-Z0-9_-]+"|\s+class="multilang"){2}\s*>$/u', $match)) {
                            break 2;
                        } else {
                            $open = true;
                        }
                    }
                    if ($open) {
                        break;
                    }
                    return $param;
                }
            } while (false);
            // Easy, just strip all tags, if we ever want to fix orphaned '&' we have to do that in format_string().
            return strip_tags($param);

        case PARAM_COMPONENT:
            // We do not want any guessing here, either the name is correct or not
            // please note only normalised component names are accepted.
            if (!preg_match('/^[a-z]+(_[a-z][a-z0-9_]*)?[a-z0-9]$/', $param)) {
                return '';
            }
            if (strpos($param, '__') !== false) {
                return '';
            }
            if (strpos($param, 'mod_') === 0) {
                // Module names must not contain underscores because we need to differentiate them from invalid plugin types.
                if (substr_count($param, '_') != 1) {
                    return '';
                }
            }
            return $param;

        case PARAM_PLUGIN:
        case PARAM_AREA:
            // We do not want any guessing here, either the name is correct or not.
            if (!is_valid_plugin_name($param)) {
                return '';
            }
            return $param;

        case PARAM_SAFEDIR:
            // Remove everything not a-zA-Z0-9_- .
            return preg_replace('/[^a-zA-Z0-9_-]/i', '', $param);

        case PARAM_SAFEPATH:
            // Remove everything not a-zA-Z0-9/_- .
            return preg_replace('/[^a-zA-Z0-9\/_-]/i', '', $param);

        case PARAM_FILE:
            // Strip all suspicious characters from filename.
            $param = fix_utf8($param);
            $param = preg_replace('~[[:cntrl:]]|[&<>"`\|\':\\\\/]~u', '', $param);
            if ($param === '.' || $param === '..') {
                $param = '';
            }
            return $param;

        case PARAM_PATH:
            // Strip all suspicious characters from file path.
            $param = fix_utf8($param);
            $param = str_replace('\\', '/', $param);

            // Explode the path and clean each element using the PARAM_FILE rules.
            $breadcrumb = explode('/', $param);
            foreach ($breadcrumb as $key => $crumb) {
                if ($crumb === '.' && $key === 0) {
                    // Special condition to allow for relative current path such as ./currentdirfile.txt.
                } else {
                    $crumb = clean_param($crumb, PARAM_FILE);
                }
                $breadcrumb[$key] = $crumb;
            }
            $param = implode('/', $breadcrumb);

            // Remove multiple current path (./././) and multiple slashes (///).
            $param = preg_replace('~//+~', '/', $param);
            $param = preg_replace('~/(\./)+~', '/', $param);
            return $param;

        case PARAM_HOST:
            // Allow FQDN or IPv4 dotted quad.
            $param = preg_replace('/[^\.\d\w-]/', '', $param );
            // Match ipv4 dotted quad.
            if (preg_match('/(\d{1,3})\.(\d{1,3})\.(\d{1,3})\.(\d{1,3})/', $param, $match)) {
                // Confirm values are ok.
                if ( $match[0] > 255
                     || $match[1] > 255
                     || $match[3] > 255
                     || $match[4] > 255 ) {
                    // Hmmm, what kind of dotted quad is this?
                    $param = '';
                }
            } else if ( preg_match('/^[\w\d\.-]+$/', $param) // Dots, hyphens, numbers.
                       && !preg_match('/^[\.-]/',  $param) // No leading dots/hyphens.
                       && !preg_match('/[\.-]$/',  $param) // No trailing dots/hyphens.
                       ) {
                // All is ok - $param is respected.
            } else {
                // All is not ok...
                $param='';
            }
            return $param;

        case PARAM_URL:          // Allow safe ftp, http, mailto urls.
            $param = fix_utf8($param);
            include_once($CFG->dirroot . '/lib/validateurlsyntax.php');
            if (!empty($param) && validateUrlSyntax($param, 's?H?S?F?E?u-P-a?I?p?f?q?r?')) {
                // All is ok, param is respected.
            } else {
                // Not really ok.
                $param ='';
            }
            return $param;

        case PARAM_LOCALURL:
            // Allow http absolute, root relative and relative URLs within wwwroot.
            $param = clean_param($param, PARAM_URL);
            if (!empty($param)) {
                if (preg_match(':^/:', $param)) {
                    // Root-relative, ok!
                } else if (preg_match('/^'.preg_quote($CFG->wwwroot, '/').'/i', $param)) {
                    // Absolute, and matches our wwwroot.
                } else {
                    // Relative - let's make sure there are no tricks.
                    if (validateUrlSyntax('/' . $param, 's-u-P-a-p-f+q?r?')) {
                        // Looks ok.
                    } else {
                        $param = '';
                    }
                }
            }
            return $param;

        case PARAM_PEM:
            $param = trim($param);
            // PEM formatted strings may contain letters/numbers and the symbols:
            //   forward slash: /
            //   plus sign:     +
            //   equal sign:    =
            //   , surrounded by BEGIN and END CERTIFICATE prefix and suffixes.
            if (preg_match('/^-----BEGIN CERTIFICATE-----([\s\w\/\+=]+)-----END CERTIFICATE-----$/', trim($param), $matches)) {
                list($wholething, $body) = $matches;
                unset($wholething, $matches);
                $b64 = clean_param($body, PARAM_BASE64);
                if (!empty($b64)) {
                    return "-----BEGIN CERTIFICATE-----\n$b64\n-----END CERTIFICATE-----\n";
                } else {
                    return '';
                }
            }
            return '';

        case PARAM_BASE64:
            if (!empty($param)) {
                // PEM formatted strings may contain letters/numbers and the symbols
                //   forward slash: /
                //   plus sign:     +
                //   equal sign:    =.
                if (0 >= preg_match('/^([\s\w\/\+=]+)$/', trim($param))) {
                    return '';
                }
                $lines = preg_split('/[\s]+/', $param, -1, PREG_SPLIT_NO_EMPTY);
                // Each line of base64 encoded data must be 64 characters in length, except for the last line which may be less
                // than (or equal to) 64 characters long.
                for ($i=0, $j=count($lines); $i < $j; $i++) {
                    if ($i + 1 == $j) {
                        if (64 < strlen($lines[$i])) {
                            return '';
                        }
                        continue;
                    }

                    if (64 != strlen($lines[$i])) {
                        return '';
                    }
                }
                return implode("\n", $lines);
            } else {
                return '';
            }

        case PARAM_TAG:
            $param = fix_utf8($param);
            // Please note it is not safe to use the tag name directly anywhere,
            // it must be processed with s(), urlencode() before embedding anywhere.
            // Remove some nasties.
            $param = preg_replace('~[[:cntrl:]]|[<>`]~u', '', $param);
            // Convert many whitespace chars into one.
            $param = preg_replace('/\s+/', ' ', $param);
            $param = core_text::substr(trim($param), 0, TAG_MAX_LENGTH);
            return $param;

        case PARAM_TAGLIST:
            $param = fix_utf8($param);
            $tags = explode(',', $param);
            $result = array();
            foreach ($tags as $tag) {
                $res = clean_param($tag, PARAM_TAG);
                if ($res !== '') {
                    $result[] = $res;
                }
            }
            if ($result) {
                return implode(',', $result);
            } else {
                return '';
            }

        case PARAM_CAPABILITY:
            if (get_capability_info($param)) {
                return $param;
            } else {
                return '';
            }

        case PARAM_PERMISSION:
            $param = (int)$param;
            if (in_array($param, array(CAP_INHERIT, CAP_ALLOW, CAP_PREVENT, CAP_PROHIBIT))) {
                return $param;
            } else {
                return CAP_INHERIT;
            }

        case PARAM_AUTH:
            $param = clean_param($param, PARAM_PLUGIN);
            if (empty($param)) {
                return '';
            } else if (exists_auth_plugin($param)) {
                return $param;
            } else {
                return '';
            }

        case PARAM_LANG:
            $param = clean_param($param, PARAM_SAFEDIR);
            if (get_string_manager()->translation_exists($param)) {
                return $param;
            } else {
                // Specified language is not installed or param malformed.
                return '';
            }

        case PARAM_THEME:
            $param = clean_param($param, PARAM_PLUGIN);
            if (empty($param)) {
                return '';
            } else if (file_exists("$CFG->dirroot/theme/$param/config.php")) {
                return $param;
            } else if (!empty($CFG->themedir) and file_exists("$CFG->themedir/$param/config.php")) {
                return $param;
            } else {
                // Specified theme is not installed.
                return '';
            }

        case PARAM_USERNAME:
            $param = fix_utf8($param);
            $param = str_replace(" " , "", $param);
            // Convert uppercase to lowercase MDL-16919.
            $param = core_text::strtolower($param);
            if (empty($CFG->extendedusernamechars)) {
                // Regular expression, eliminate all chars EXCEPT:
                // alphanum, dash (-), underscore (_), at sign (@) and period (.) characters.
                $param = preg_replace('/[^-\.@_a-z0-9]/', '', $param);
            }
            return $param;

        case PARAM_EMAIL:
            $param = fix_utf8($param);
            if (validate_email($param)) {
                return $param;
            } else {
                return '';
            }

        case PARAM_STRINGID:
            if (preg_match('|^[a-zA-Z][a-zA-Z0-9\.:/_-]*$|', $param)) {
                return $param;
            } else {
                return '';
            }

        case PARAM_TIMEZONE:
            // Can be int, float(with .5 or .0) or string seperated by '/' and can have '-_'.
            $param = fix_utf8($param);
            $timezonepattern = '/^(([+-]?(0?[0-9](\.[5|0])?|1[0-3](\.0)?|1[0-2]\.5))|(99)|[[:alnum:]]+(\/?[[:alpha:]_-])+)$/';
            if (preg_match($timezonepattern, $param)) {
                return $param;
            } else {
                return '';
            }

        default:
            // Doh! throw error, switched parameters in optional_param or another serious problem.
            print_error("unknownparamtype", '', '', $type);
    }
}

/**
 * Makes sure the data is using valid utf8, invalid characters are discarded.
 *
 * Note: this function is not intended for full objects with methods and private properties.
 *
 * @param mixed $value
 * @return mixed with proper utf-8 encoding
 */
function fix_utf8($value) {
    if (is_null($value) or $value === '') {
        return $value;

    } else if (is_string($value)) {
        if ((string)(int)$value === $value) {
            // Shortcut.
            return $value;
        }
        // No null bytes expected in our data, so let's remove it.
        $value = str_replace("\0", '', $value);

        // Lower error reporting because glibc throws bogus notices.
        $olderror = error_reporting();
        if ($olderror & E_NOTICE) {
            error_reporting($olderror ^ E_NOTICE);
        }

        // Note: this duplicates min_fix_utf8() intentionally.
        static $buggyiconv = null;
        if ($buggyiconv === null) {
            $buggyiconv = (!function_exists('iconv') or iconv('UTF-8', 'UTF-8//IGNORE', '100'.chr(130).'€') !== '100€');
        }

        if ($buggyiconv) {
            if (function_exists('mb_convert_encoding')) {
                $subst = mb_substitute_character();
                mb_substitute_character('');
                $result = mb_convert_encoding($value, 'utf-8', 'utf-8');
                mb_substitute_character($subst);

            } else {
                // Warn admins on admin/index.php page.
                $result = $value;
            }

        } else {
            $result = iconv('UTF-8', 'UTF-8//IGNORE', $value);
        }

        if ($olderror & E_NOTICE) {
            error_reporting($olderror);
        }

        return $result;

    } else if (is_array($value)) {
        foreach ($value as $k => $v) {
            $value[$k] = fix_utf8($v);
        }
        return $value;

    } else if (is_object($value)) {
        // Do not modify original.
        $value = clone($value);
        foreach ($value as $k => $v) {
            $value->$k = fix_utf8($v);
        }
        return $value;

    } else {
        // This is some other type, no utf-8 here.
        return $value;
    }
}

/**
 * Return true if given value is integer or string with integer value
 *
 * @param mixed $value String or Int
 * @return bool true if number, false if not
 */
function is_number($value) {
    if (is_int($value)) {
        return true;
    } else if (is_string($value)) {
        return ((string)(int)$value) === $value;
    } else {
        return false;
    }
}

/**
 * Returns host part from url.
 *
 * @param string $url full url
 * @return string host, null if not found
 */
function get_host_from_url($url) {
    preg_match('|^[a-z]+://([a-zA-Z0-9-.]+)|i', $url, $matches);
    if ($matches) {
        return $matches[1];
    }
    return null;
}

/**
 * Tests whether anything was returned by text editor
 *
 * This function is useful for testing whether something you got back from
 * the HTML editor actually contains anything. Sometimes the HTML editor
 * appear to be empty, but actually you get back a <br> tag or something.
 *
 * @param string $string a string containing HTML.
 * @return boolean does the string contain any actual content - that is text,
 * images, objects, etc.
 */
function html_is_blank($string) {
    return trim(strip_tags($string, '<img><object><applet><input><select><textarea><hr>')) == '';
}

/**
 * Set a key in global configuration
 *
 * Set a key/value pair in both this session's {@link $CFG} global variable
 * and in the 'config' database table for future sessions.
 *
 * Can also be used to update keys for plugin-scoped configs in config_plugin table.
 * In that case it doesn't affect $CFG.
 *
 * A NULL value will delete the entry.
 *
 * @param string $name the key to set
 * @param string $value the value to set (without magic quotes)
 * @param string $plugin (optional) the plugin scope, default null
 * @return bool true or exception
 */
function set_config($name, $value, $plugin=null) {
    global $CFG, $DB;

    if (empty($plugin)) {
        if (!array_key_exists($name, $CFG->config_php_settings)) {
            // So it's defined for this invocation at least.
            if (is_null($value)) {
                unset($CFG->$name);
            } else {
                // Settings from db are always strings.
                $CFG->$name = (string)$value;
            }
        }

        if ($DB->get_field('config', 'name', array('name' => $name))) {
            if ($value === null) {
                $DB->delete_records('config', array('name' => $name));
            } else {
                $DB->set_field('config', 'value', $value, array('name' => $name));
            }
        } else {
            if ($value !== null) {
                $config = new stdClass();
                $config->name  = $name;
                $config->value = $value;
                $DB->insert_record('config', $config, false);
            }
        }
        if ($name === 'siteidentifier') {
            cache_helper::update_site_identifier($value);
        }
        cache_helper::invalidate_by_definition('core', 'config', array(), 'core');
    } else {
        // Plugin scope.
        if ($id = $DB->get_field('config_plugins', 'id', array('name' => $name, 'plugin' => $plugin))) {
            if ($value===null) {
                $DB->delete_records('config_plugins', array('name' => $name, 'plugin' => $plugin));
            } else {
                $DB->set_field('config_plugins', 'value', $value, array('id' => $id));
            }
        } else {
            if ($value !== null) {
                $config = new stdClass();
                $config->plugin = $plugin;
                $config->name   = $name;
                $config->value  = $value;
                $DB->insert_record('config_plugins', $config, false);
            }
        }
        cache_helper::invalidate_by_definition('core', 'config', array(), $plugin);
    }

    return true;
}

/**
 * Get configuration values from the global config table
 * or the config_plugins table.
 *
 * If called with one parameter, it will load all the config
 * variables for one plugin, and return them as an object.
 *
 * If called with 2 parameters it will return a string single
 * value or false if the value is not found.
 *
 * @static string|false $siteidentifier The site identifier is not cached. We use this static cache so
 *     that we need only fetch it once per request.
 * @param string $plugin full component name
 * @param string $name default null
 * @return mixed hash-like object or single value, return false no config found
 * @throws dml_exception
 */
function get_config($plugin, $name = null) {
    global $CFG, $DB;

    static $siteidentifier = null;

    if ($plugin === 'moodle' || $plugin === 'core' || empty($plugin)) {
        $forced =& $CFG->config_php_settings;
        $iscore = true;
        $plugin = 'core';
    } else {
        if (array_key_exists($plugin, $CFG->forced_plugin_settings)) {
            $forced =& $CFG->forced_plugin_settings[$plugin];
        } else {
            $forced = array();
        }
        $iscore = false;
    }

    if ($siteidentifier === null) {
        try {
            // This may fail during installation.
            // If you have a look at {@link initialise_cfg()} you will see that this is how we detect the need to
            // install the database.
            $siteidentifier = $DB->get_field('config', 'value', array('name' => 'siteidentifier'));
        } catch (dml_exception $ex) {
            // Set siteidentifier to false. We don't want to trip this continually.
            $siteidentifier = false;
            throw $ex;
        }
    }

    if (!empty($name)) {
        if (array_key_exists($name, $forced)) {
            return (string)$forced[$name];
        } else if ($name === 'siteidentifier' && $plugin == 'core') {
            return $siteidentifier;
        }
    }

    $cache = cache::make('core', 'config');
    $result = $cache->get($plugin);
    if ($result === false) {
        // The user is after a recordset.
        if (!$iscore) {
            $result = $DB->get_records_menu('config_plugins', array('plugin' => $plugin), '', 'name,value');
        } else {
            // This part is not really used any more, but anyway...
            $result = $DB->get_records_menu('config', array(), '', 'name,value');;
        }
        $cache->set($plugin, $result);
    }

    if (!empty($name)) {
        if (array_key_exists($name, $result)) {
            return $result[$name];
        }
        return false;
    }

    if ($plugin === 'core') {
        $result['siteidentifier'] = $siteidentifier;
    }

    foreach ($forced as $key => $value) {
        if (is_null($value) or is_array($value) or is_object($value)) {
            // We do not want any extra mess here, just real settings that could be saved in db.
            unset($result[$key]);
        } else {
            // Convert to string as if it went through the DB.
            $result[$key] = (string)$value;
        }
    }

    return (object)$result;
}

/**
 * Removes a key from global configuration.
 *
 * @param string $name the key to set
 * @param string $plugin (optional) the plugin scope
 * @return boolean whether the operation succeeded.
 */
function unset_config($name, $plugin=null) {
    global $CFG, $DB;

    if (empty($plugin)) {
        unset($CFG->$name);
        $DB->delete_records('config', array('name' => $name));
        cache_helper::invalidate_by_definition('core', 'config', array(), 'core');
    } else {
        $DB->delete_records('config_plugins', array('name' => $name, 'plugin' => $plugin));
        cache_helper::invalidate_by_definition('core', 'config', array(), $plugin);
    }

    return true;
}

/**
 * Remove all the config variables for a given plugin.
 *
 * NOTE: this function is called from lib/db/upgrade.php
 *
 * @param string $plugin a plugin, for example 'quiz' or 'qtype_multichoice';
 * @return boolean whether the operation succeeded.
 */
function unset_all_config_for_plugin($plugin) {
    global $DB;
    // Delete from the obvious config_plugins first.
    $DB->delete_records('config_plugins', array('plugin' => $plugin));
    // Next delete any suspect settings from config.
    $like = $DB->sql_like('name', '?', true, true, false, '|');
    $params = array($DB->sql_like_escape($plugin.'_', '|') . '%');
    $DB->delete_records_select('config', $like, $params);
    // Finally clear both the plugin cache and the core cache (suspect settings now removed from core).
    cache_helper::invalidate_by_definition('core', 'config', array(), array('core', $plugin));

    return true;
}

/**
 * Use this function to get a list of users from a config setting of type admin_setting_users_with_capability.
 *
 * All users are verified if they still have the necessary capability.
 *
 * @param string $value the value of the config setting.
 * @param string $capability the capability - must match the one passed to the admin_setting_users_with_capability constructor.
 * @param bool $includeadmins include administrators.
 * @return array of user objects.
 */
function get_users_from_config($value, $capability, $includeadmins = true) {
    if (empty($value) or $value === '$@NONE@$') {
        return array();
    }

    // We have to make sure that users still have the necessary capability,
    // it should be faster to fetch them all first and then test if they are present
    // instead of validating them one-by-one.
    $users = get_users_by_capability(context_system::instance(), $capability);
    if ($includeadmins) {
        $admins = get_admins();
        foreach ($admins as $admin) {
            $users[$admin->id] = $admin;
        }
    }

    if ($value === '$@ALL@$') {
        return $users;
    }

    $result = array(); // Result in correct order.
    $allowed = explode(',', $value);
    foreach ($allowed as $uid) {
        if (isset($users[$uid])) {
            $user = $users[$uid];
            $result[$user->id] = $user;
        }
    }

    return $result;
}


/**
 * Invalidates browser caches and cached data in temp.
 *
 * IMPORTANT - If you are adding anything here to do with the cache directory you should also have a look at
 * {@link phpunit_util::reset_dataroot()}
 *
 * @return void
 */
function purge_all_caches() {
    global $CFG, $DB;

    reset_text_filters_cache();
    js_reset_all_caches();
    theme_reset_all_caches();
    get_string_manager()->reset_caches();
    core_text::reset_caches();
    if (class_exists('plugin_manager')) {
        plugin_manager::reset_caches();
    }

    // Bump up cacherev field for all courses.
    try {
        increment_revision_number('course', 'cacherev', '');
    } catch (moodle_exception $e) {
        // Ignore exception since this function is also called before upgrade script when field course.cacherev does not exist yet.
    }

    $DB->reset_caches();
    cache_helper::purge_all();

    // Purge all other caches: rss, simplepie, etc.
    remove_dir($CFG->cachedir.'', true);

    // Make sure cache dir is writable, throws exception if not.
    make_cache_directory('');

    // This is the only place where we purge local caches, we are only adding files there.
    // The $CFG->localcachedirpurged flag forces local directories to be purged on cluster nodes.
    remove_dir($CFG->localcachedir, true);
    set_config('localcachedirpurged', time());
    make_localcache_directory('', true);
}

/**
 * Get volatile flags
 *
 * @param string $type
 * @param int $changedsince default null
 * @return array records array
 */
function get_cache_flags($type, $changedsince = null) {
    global $DB;

    $params = array('type' => $type, 'expiry' => time());
    $sqlwhere = "flagtype = :type AND expiry >= :expiry";
    if ($changedsince !== null) {
        $params['changedsince'] = $changedsince;
        $sqlwhere .= " AND timemodified > :changedsince";
    }
    $cf = array();
    if ($flags = $DB->get_records_select('cache_flags', $sqlwhere, $params, '', 'name,value')) {
        foreach ($flags as $flag) {
            $cf[$flag->name] = $flag->value;
        }
    }
    return $cf;
}

/**
 * Get volatile flags
 *
 * @param string $type
 * @param string $name
 * @param int $changedsince default null
 * @return string|false The cache flag value or false
 */
function get_cache_flag($type, $name, $changedsince=null) {
    global $DB;

    $params = array('type' => $type, 'name' => $name, 'expiry' => time());

    $sqlwhere = "flagtype = :type AND name = :name AND expiry >= :expiry";
    if ($changedsince !== null) {
        $params['changedsince'] = $changedsince;
        $sqlwhere .= " AND timemodified > :changedsince";
    }

    return $DB->get_field_select('cache_flags', 'value', $sqlwhere, $params);
}

/**
 * Set a volatile flag
 *
 * @param string $type the "type" namespace for the key
 * @param string $name the key to set
 * @param string $value the value to set (without magic quotes) - null will remove the flag
 * @param int $expiry (optional) epoch indicating expiry - defaults to now()+ 24hs
 * @return bool Always returns true
 */
function set_cache_flag($type, $name, $value, $expiry = null) {
    global $DB;

    $timemodified = time();
    if ($expiry === null || $expiry < $timemodified) {
        $expiry = $timemodified + 24 * 60 * 60;
    } else {
        $expiry = (int)$expiry;
    }

    if ($value === null) {
        unset_cache_flag($type, $name);
        return true;
    }

    if ($f = $DB->get_record('cache_flags', array('name' => $name, 'flagtype' => $type), '*', IGNORE_MULTIPLE)) {
        // This is a potential problem in DEBUG_DEVELOPER.
        if ($f->value == $value and $f->expiry == $expiry and $f->timemodified == $timemodified) {
            return true; // No need to update.
        }
        $f->value        = $value;
        $f->expiry       = $expiry;
        $f->timemodified = $timemodified;
        $DB->update_record('cache_flags', $f);
    } else {
        $f = new stdClass();
        $f->flagtype     = $type;
        $f->name         = $name;
        $f->value        = $value;
        $f->expiry       = $expiry;
        $f->timemodified = $timemodified;
        $DB->insert_record('cache_flags', $f);
    }
    return true;
}

/**
 * Removes a single volatile flag
 *
 * @param string $type the "type" namespace for the key
 * @param string $name the key to set
 * @return bool
 */
function unset_cache_flag($type, $name) {
    global $DB;
    $DB->delete_records('cache_flags', array('name' => $name, 'flagtype' => $type));
    return true;
}

/**
 * Garbage-collect volatile flags
 *
 * @return bool Always returns true
 */
function gc_cache_flags() {
    global $DB;
    $DB->delete_records_select('cache_flags', 'expiry < ?', array(time()));
    return true;
}

// USER PREFERENCE API.

/**
 * Refresh user preference cache. This is used most often for $USER
 * object that is stored in session, but it also helps with performance in cron script.
 *
 * Preferences for each user are loaded on first use on every page, then again after the timeout expires.
 *
 * @package  core
 * @category preference
 * @access   public
 * @param    stdClass         $user          User object. Preferences are preloaded into 'preference' property
 * @param    int              $cachelifetime Cache life time on the current page (in seconds)
 * @throws   coding_exception
 * @return   null
 */
function check_user_preferences_loaded(stdClass $user, $cachelifetime = 120) {
    global $DB;
    // Static cache, we need to check on each page load, not only every 2 minutes.
    static $loadedusers = array();

    if (!isset($user->id)) {
        throw new coding_exception('Invalid $user parameter in check_user_preferences_loaded() call, missing id field');
    }

    if (empty($user->id) or isguestuser($user->id)) {
        // No permanent storage for not-logged-in users and guest.
        if (!isset($user->preference)) {
            $user->preference = array();
        }
        return;
    }

    $timenow = time();

    if (isset($loadedusers[$user->id]) and isset($user->preference) and isset($user->preference['_lastloaded'])) {
        // Already loaded at least once on this page. Are we up to date?
        if ($user->preference['_lastloaded'] + $cachelifetime > $timenow) {
            // No need to reload - we are on the same page and we loaded prefs just a moment ago.
            return;

        } else if (!get_cache_flag('userpreferenceschanged', $user->id, $user->preference['_lastloaded'])) {
            // No change since the lastcheck on this page.
            $user->preference['_lastloaded'] = $timenow;
            return;
        }
    }

    // OK, so we have to reload all preferences.
    $loadedusers[$user->id] = true;
    $user->preference = $DB->get_records_menu('user_preferences', array('userid' => $user->id), '', 'name,value'); // All values.
    $user->preference['_lastloaded'] = $timenow;
}

/**
 * Called from set/unset_user_preferences, so that the prefs can be correctly reloaded in different sessions.
 *
 * NOTE: internal function, do not call from other code.
 *
 * @package core
 * @access private
 * @param integer $userid the user whose prefs were changed.
 */
function mark_user_preferences_changed($userid) {
    global $CFG;

    if (empty($userid) or isguestuser($userid)) {
        // No cache flags for guest and not-logged-in users.
        return;
    }

    set_cache_flag('userpreferenceschanged', $userid, 1, time() + $CFG->sessiontimeout);
}

/**
 * Sets a preference for the specified user.
 *
 * If a $user object is submitted it's 'preference' property is used for the preferences cache.
 *
 * @package  core
 * @category preference
 * @access   public
 * @param    string            $name  The key to set as preference for the specified user
 * @param    string            $value The value to set for the $name key in the specified user's
 *                                    record, null means delete current value.
 * @param    stdClass|int|null $user  A moodle user object or id, null means current user
 * @throws   coding_exception
 * @return   bool                     Always true or exception
 */
function set_user_preference($name, $value, $user = null) {
    global $USER, $DB;

    if (empty($name) or is_numeric($name) or $name === '_lastloaded') {
        throw new coding_exception('Invalid preference name in set_user_preference() call');
    }

    if (is_null($value)) {
        // Null means delete current.
        return unset_user_preference($name, $user);
    } else if (is_object($value)) {
        throw new coding_exception('Invalid value in set_user_preference() call, objects are not allowed');
    } else if (is_array($value)) {
        throw new coding_exception('Invalid value in set_user_preference() call, arrays are not allowed');
    }
    // Value column maximum length is 1333 characters.
    $value = (string)$value;
    if (core_text::strlen($value) > 1333) {
        throw new coding_exception('Invalid value in set_user_preference() call, value is is too long for the value column');
    }

    if (is_null($user)) {
        $user = $USER;
    } else if (isset($user->id)) {
        // It is a valid object.
    } else if (is_numeric($user)) {
        $user = (object)array('id' => (int)$user);
    } else {
        throw new coding_exception('Invalid $user parameter in set_user_preference() call');
    }

    check_user_preferences_loaded($user);

    if (empty($user->id) or isguestuser($user->id)) {
        // No permanent storage for not-logged-in users and guest.
        $user->preference[$name] = $value;
        return true;
    }

    if ($preference = $DB->get_record('user_preferences', array('userid' => $user->id, 'name' => $name))) {
        if ($preference->value === $value and isset($user->preference[$name]) and $user->preference[$name] === $value) {
            // Preference already set to this value.
            return true;
        }
        $DB->set_field('user_preferences', 'value', $value, array('id' => $preference->id));

    } else {
        $preference = new stdClass();
        $preference->userid = $user->id;
        $preference->name   = $name;
        $preference->value  = $value;
        $DB->insert_record('user_preferences', $preference);
    }

    // Update value in cache.
    $user->preference[$name] = $value;

    // Set reload flag for other sessions.
    mark_user_preferences_changed($user->id);

    return true;
}

/**
 * Sets a whole array of preferences for the current user
 *
 * If a $user object is submitted it's 'preference' property is used for the preferences cache.
 *
 * @package  core
 * @category preference
 * @access   public
 * @param    array             $prefarray An array of key/value pairs to be set
 * @param    stdClass|int|null $user      A moodle user object or id, null means current user
 * @return   bool                         Always true or exception
 */
function set_user_preferences(array $prefarray, $user = null) {
    foreach ($prefarray as $name => $value) {
        set_user_preference($name, $value, $user);
    }
    return true;
}

/**
 * Unsets a preference completely by deleting it from the database
 *
 * If a $user object is submitted it's 'preference' property is used for the preferences cache.
 *
 * @package  core
 * @category preference
 * @access   public
 * @param    string            $name The key to unset as preference for the specified user
 * @param    stdClass|int|null $user A moodle user object or id, null means current user
 * @throws   coding_exception
 * @return   bool                    Always true or exception
 */
function unset_user_preference($name, $user = null) {
    global $USER, $DB;

    if (empty($name) or is_numeric($name) or $name === '_lastloaded') {
        throw new coding_exception('Invalid preference name in unset_user_preference() call');
    }

    if (is_null($user)) {
        $user = $USER;
    } else if (isset($user->id)) {
        // It is a valid object.
    } else if (is_numeric($user)) {
        $user = (object)array('id' => (int)$user);
    } else {
        throw new coding_exception('Invalid $user parameter in unset_user_preference() call');
    }

    check_user_preferences_loaded($user);

    if (empty($user->id) or isguestuser($user->id)) {
        // No permanent storage for not-logged-in user and guest.
        unset($user->preference[$name]);
        return true;
    }

    // Delete from DB.
    $DB->delete_records('user_preferences', array('userid' => $user->id, 'name' => $name));

    // Delete the preference from cache.
    unset($user->preference[$name]);

    // Set reload flag for other sessions.
    mark_user_preferences_changed($user->id);

    return true;
}

/**
 * Used to fetch user preference(s)
 *
 * If no arguments are supplied this function will return
 * all of the current user preferences as an array.
 *
 * If a name is specified then this function
 * attempts to return that particular preference value.  If
 * none is found, then the optional value $default is returned,
 * otherwise null.
 *
 * If a $user object is submitted it's 'preference' property is used for the preferences cache.
 *
 * @package  core
 * @category preference
 * @access   public
 * @param    string            $name    Name of the key to use in finding a preference value
 * @param    mixed|null        $default Value to be returned if the $name key is not set in the user preferences
 * @param    stdClass|int|null $user    A moodle user object or id, null means current user
 * @throws   coding_exception
 * @return   string|mixed|null          A string containing the value of a single preference. An
 *                                      array with all of the preferences or null
 */
function get_user_preferences($name = null, $default = null, $user = null) {
    global $USER;

    if (is_null($name)) {
        // All prefs.
    } else if (is_numeric($name) or $name === '_lastloaded') {
        throw new coding_exception('Invalid preference name in get_user_preferences() call');
    }

    if (is_null($user)) {
        $user = $USER;
    } else if (isset($user->id)) {
        // Is a valid object.
    } else if (is_numeric($user)) {
        $user = (object)array('id' => (int)$user);
    } else {
        throw new coding_exception('Invalid $user parameter in get_user_preferences() call');
    }

    check_user_preferences_loaded($user);

    if (empty($name)) {
        // All values.
        return $user->preference;
    } else if (isset($user->preference[$name])) {
        // The single string value.
        return $user->preference[$name];
    } else {
        // Default value (null if not specified).
        return $default;
    }
}

// FUNCTIONS FOR HANDLING TIME.

/**
 * Given date parts in user time produce a GMT timestamp.
 *
 * @package core
 * @category time
 * @param int $year The year part to create timestamp of
 * @param int $month The month part to create timestamp of
 * @param int $day The day part to create timestamp of
 * @param int $hour The hour part to create timestamp of
 * @param int $minute The minute part to create timestamp of
 * @param int $second The second part to create timestamp of
 * @param int|float|string $timezone Timezone modifier, used to calculate GMT time offset.
 *             if 99 then default user's timezone is used {@link http://docs.moodle.org/dev/Time_API#Timezone}
 * @param bool $applydst Toggle Daylight Saving Time, default true, will be
 *             applied only if timezone is 99 or string.
 * @return int GMT timestamp
 */
function make_timestamp($year, $month=1, $day=1, $hour=0, $minute=0, $second=0, $timezone=99, $applydst=true) {

    // Save input timezone, required for dst offset check.
    $passedtimezone = $timezone;

    $timezone = get_user_timezone_offset($timezone);

    if (abs($timezone) > 13) {
        // Server time.
        $time = mktime((int)$hour, (int)$minute, (int)$second, (int)$month, (int)$day, (int)$year);
    } else {
        $time = gmmktime((int)$hour, (int)$minute, (int)$second, (int)$month, (int)$day, (int)$year);
        $time = usertime($time, $timezone);

        // Apply dst for string timezones or if 99 then try dst offset with user's default timezone.
        if ($applydst && ((99 == $passedtimezone) || !is_numeric($passedtimezone))) {
            $time -= dst_offset_on($time, $passedtimezone);
        }
    }

    return $time;

}

/**
 * Format a date/time (seconds) as weeks, days, hours etc as needed
 *
 * Given an amount of time in seconds, returns string
 * formatted nicely as weeks, days, hours etc as needed
 *
 * @package core
 * @category time
 * @uses MINSECS
 * @uses HOURSECS
 * @uses DAYSECS
 * @uses YEARSECS
 * @param int $totalsecs Time in seconds
 * @param stdClass $str Should be a time object
 * @return string A nicely formatted date/time string
 */
function format_time($totalsecs, $str = null) {

    $totalsecs = abs($totalsecs);

    if (!$str) {
        // Create the str structure the slow way.
        $str = new stdClass();
        $str->day   = get_string('day');
        $str->days  = get_string('days');
        $str->hour  = get_string('hour');
        $str->hours = get_string('hours');
        $str->min   = get_string('min');
        $str->mins  = get_string('mins');
        $str->sec   = get_string('sec');
        $str->secs  = get_string('secs');
        $str->year  = get_string('year');
        $str->years = get_string('years');
    }

    $years     = floor($totalsecs/YEARSECS);
    $remainder = $totalsecs - ($years*YEARSECS);
    $days      = floor($remainder/DAYSECS);
    $remainder = $totalsecs - ($days*DAYSECS);
    $hours     = floor($remainder/HOURSECS);
    $remainder = $remainder - ($hours*HOURSECS);
    $mins      = floor($remainder/MINSECS);
    $secs      = $remainder - ($mins*MINSECS);

    $ss = ($secs == 1)  ? $str->sec  : $str->secs;
    $sm = ($mins == 1)  ? $str->min  : $str->mins;
    $sh = ($hours == 1) ? $str->hour : $str->hours;
    $sd = ($days == 1)  ? $str->day  : $str->days;
    $sy = ($years == 1)  ? $str->year  : $str->years;

    $oyears = '';
    $odays = '';
    $ohours = '';
    $omins = '';
    $osecs = '';

    if ($years) {
        $oyears  = $years .' '. $sy;
    }
    if ($days) {
        $odays  = $days .' '. $sd;
    }
    if ($hours) {
        $ohours = $hours .' '. $sh;
    }
    if ($mins) {
        $omins  = $mins .' '. $sm;
    }
    if ($secs) {
        $osecs  = $secs .' '. $ss;
    }

    if ($years) {
        return trim($oyears .' '. $odays);
    }
    if ($days) {
        return trim($odays .' '. $ohours);
    }
    if ($hours) {
        return trim($ohours .' '. $omins);
    }
    if ($mins) {
        return trim($omins .' '. $osecs);
    }
    if ($secs) {
        return $osecs;
    }
    return get_string('now');
}

/**
 * Returns a formatted string that represents a date in user time.
 *
 * @package core
 * @category time
 * @param int $date the timestamp in UTC, as obtained from the database.
 * @param string $format strftime format. You should probably get this using
 *        get_string('strftime...', 'langconfig');
 * @param int|float|string $timezone by default, uses the user's time zone. if numeric and
 *        not 99 then daylight saving will not be added.
 *        {@link http://docs.moodle.org/dev/Time_API#Timezone}
 * @param bool $fixday If true (default) then the leading zero from %d is removed.
 *        If false then the leading zero is maintained.
 * @param bool $fixhour If true (default) then the leading zero from %I is removed.
 * @return string the formatted date/time.
 */
function userdate($date, $format = '', $timezone = 99, $fixday = true, $fixhour = true) {
    $calendartype = \core_calendar\type_factory::get_calendar_instance();
    return $calendartype->timestamp_to_date_string($date, $format, $timezone, $fixday, $fixhour);
}

/**
 * Returns a formatted date ensuring it is UTF-8.
 *
 * If we are running under Windows convert to Windows encoding and then back to UTF-8
 * (because it's impossible to specify UTF-8 to fetch locale info in Win32).
 *
 * This function does not do any calculation regarding the user preferences and should
 * therefore receive the final date timestamp, format and timezone. Timezone being only used
 * to differentiate the use of server time or not (strftime() against gmstrftime()).
 *
 * @param int $date the timestamp.
 * @param string $format strftime format.
 * @param int|float $tz the numerical timezone, typically returned by {@link get_user_timezone_offset()}.
 * @return string the formatted date/time.
 * @since 2.3.3
 */
function date_format_string($date, $format, $tz = 99) {
    global $CFG;
    if (abs($tz) > 13) {
        if ($CFG->ostype == 'WINDOWS' and $localewincharset = get_string('localewincharset', 'langconfig')) {
            $format = core_text::convert($format, 'utf-8', $localewincharset);
            $datestring = strftime($format, $date);
            $datestring = core_text::convert($datestring, $localewincharset, 'utf-8');
        } else {
            $datestring = strftime($format, $date);
        }
    } else {
        if ($CFG->ostype == 'WINDOWS' and $localewincharset = get_string('localewincharset', 'langconfig')) {
            $format = core_text::convert($format, 'utf-8', $localewincharset);
            $datestring = gmstrftime($format, $date);
            $datestring = core_text::convert($datestring, $localewincharset, 'utf-8');
        } else {
            $datestring = gmstrftime($format, $date);
        }
    }
    return $datestring;
}

/**
 * Given a $time timestamp in GMT (seconds since epoch),
 * returns an array that represents the date in user time
 *
 * @package core
 * @category time
 * @uses HOURSECS
 * @param int $time Timestamp in GMT
 * @param float|int|string $timezone offset's time with timezone, if float and not 99, then no
 *        dst offset is applied {@link http://docs.moodle.org/dev/Time_API#Timezone}
 * @return array An array that represents the date in user time
 */
function usergetdate($time, $timezone=99) {

    // Save input timezone, required for dst offset check.
    $passedtimezone = $timezone;

    $timezone = get_user_timezone_offset($timezone);

    if (abs($timezone) > 13) {
        // Server time.
        return getdate($time);
    }

    // Add daylight saving offset for string timezones only, as we can't get dst for
    // float values. if timezone is 99 (user default timezone), then try update dst.
    if ($passedtimezone == 99 || !is_numeric($passedtimezone)) {
        $time += dst_offset_on($time, $passedtimezone);
    }

    $time += intval((float)$timezone * HOURSECS);

    $datestring = gmstrftime('%B_%A_%j_%Y_%m_%w_%d_%H_%M_%S', $time);

    // Be careful to ensure the returned array matches that produced by getdate() above.
    list(
        $getdate['month'],
        $getdate['weekday'],
        $getdate['yday'],
        $getdate['year'],
        $getdate['mon'],
        $getdate['wday'],
        $getdate['mday'],
        $getdate['hours'],
        $getdate['minutes'],
        $getdate['seconds']
    ) = explode('_', $datestring);

    // Set correct datatype to match with getdate().
    $getdate['seconds'] = (int)$getdate['seconds'];
    $getdate['yday'] = (int)$getdate['yday'] - 1; // The function gmstrftime returns 0 through 365.
    $getdate['year'] = (int)$getdate['year'];
    $getdate['mon'] = (int)$getdate['mon'];
    $getdate['wday'] = (int)$getdate['wday'];
    $getdate['mday'] = (int)$getdate['mday'];
    $getdate['hours'] = (int)$getdate['hours'];
    $getdate['minutes'] = (int)$getdate['minutes'];
    return $getdate;
}

/**
 * Given a GMT timestamp (seconds since epoch), offsets it by
 * the timezone.  eg 3pm in India is 3pm GMT - 7 * 3600 seconds
 *
 * @package core
 * @category time
 * @uses HOURSECS
 * @param int $date Timestamp in GMT
 * @param float|int|string $timezone timezone to calculate GMT time offset before
 *        calculating user time, 99 is default user timezone
 *        {@link http://docs.moodle.org/dev/Time_API#Timezone}
 * @return int
 */
function usertime($date, $timezone=99) {

    $timezone = get_user_timezone_offset($timezone);

    if (abs($timezone) > 13) {
        return $date;
    }
    return $date - (int)($timezone * HOURSECS);
}

/**
 * Given a time, return the GMT timestamp of the most recent midnight
 * for the current user.
 *
 * @package core
 * @category time
 * @param int $date Timestamp in GMT
 * @param float|int|string $timezone timezone to calculate GMT time offset before
 *        calculating user midnight time, 99 is default user timezone
 *        {@link http://docs.moodle.org/dev/Time_API#Timezone}
 * @return int Returns a GMT timestamp
 */
function usergetmidnight($date, $timezone=99) {

    $userdate = usergetdate($date, $timezone);

    // Time of midnight of this user's day, in GMT.
    return make_timestamp($userdate['year'], $userdate['mon'], $userdate['mday'], 0, 0, 0, $timezone);

}

/**
 * Returns a string that prints the user's timezone
 *
 * @package core
 * @category time
 * @param float|int|string $timezone timezone to calculate GMT time offset before
 *        calculating user timezone, 99 is default user timezone
 *        {@link http://docs.moodle.org/dev/Time_API#Timezone}
 * @return string
 */
function usertimezone($timezone=99) {

    $tz = get_user_timezone($timezone);

    if (!is_float($tz)) {
        return $tz;
    }

    if (abs($tz) > 13) {
        // Server time.
        return get_string('serverlocaltime');
    }

    if ($tz == intval($tz)) {
        // Don't show .0 for whole hours.
        $tz = intval($tz);
    }

    if ($tz == 0) {
        return 'UTC';
    } else if ($tz > 0) {
        return 'UTC+'.$tz;
    } else {
        return 'UTC'.$tz;
    }

}

/**
 * Returns a float which represents the user's timezone difference from GMT in hours
 * Checks various settings and picks the most dominant of those which have a value
 *
 * @package core
 * @category time
 * @param float|int|string $tz timezone to calculate GMT time offset for user,
 *        99 is default user timezone
 *        {@link http://docs.moodle.org/dev/Time_API#Timezone}
 * @return float
 */
function get_user_timezone_offset($tz = 99) {
    $tz = get_user_timezone($tz);

    if (is_float($tz)) {
        return $tz;
    } else {
        $tzrecord = get_timezone_record($tz);
        if (empty($tzrecord)) {
            return 99.0;
        }
        return (float)$tzrecord->gmtoff / HOURMINS;
    }
}

/**
 * Returns an int which represents the systems's timezone difference from GMT in seconds
 *
 * @package core
 * @category time
 * @param float|int|string $tz timezone for which offset is required.
 *        {@link http://docs.moodle.org/dev/Time_API#Timezone}
 * @return int|bool if found, false is timezone 99 or error
 */
function get_timezone_offset($tz) {
    if ($tz == 99) {
        return false;
    }

    if (is_numeric($tz)) {
        return intval($tz * 60*60);
    }

    if (!$tzrecord = get_timezone_record($tz)) {
        return false;
    }
    return intval($tzrecord->gmtoff * 60);
}

/**
 * Returns a float or a string which denotes the user's timezone
 * A float value means that a simple offset from GMT is used, while a string (it will be the name of a timezone in the database)
 * means that for this timezone there are also DST rules to be taken into account
 * Checks various settings and picks the most dominant of those which have a value
 *
 * @package core
 * @category time
 * @param float|int|string $tz timezone to calculate GMT time offset before
 *        calculating user timezone, 99 is default user timezone
 *        {@link http://docs.moodle.org/dev/Time_API#Timezone}
 * @return float|string
 */
function get_user_timezone($tz = 99) {
    global $USER, $CFG;

    $timezones = array(
        $tz,
        isset($CFG->forcetimezone) ? $CFG->forcetimezone : 99,
        isset($USER->timezone) ? $USER->timezone : 99,
        isset($CFG->timezone) ? $CFG->timezone : 99,
        );

    $tz = 99;

    // Loop while $tz is, empty but not zero, or 99, and there is another timezone is the array.
    while (((empty($tz) && !is_numeric($tz)) || $tz == 99) && $next = each($timezones)) {
        $tz = $next['value'];
    }
    return is_numeric($tz) ? (float) $tz : $tz;
}

/**
 * Returns cached timezone record for given $timezonename
 *
 * @package core
 * @param string $timezonename name of the timezone
 * @return stdClass|bool timezonerecord or false
 */
function get_timezone_record($timezonename) {
    global $DB;
    static $cache = null;

    if ($cache === null) {
        $cache = array();
    }

    if (isset($cache[$timezonename])) {
        return $cache[$timezonename];
    }

    return $cache[$timezonename] = $DB->get_record_sql('SELECT * FROM {timezone}
                                                        WHERE name = ? ORDER BY year DESC', array($timezonename), IGNORE_MULTIPLE);
}

/**
 * Build and store the users Daylight Saving Time (DST) table
 *
 * @package core
 * @param int $fromyear Start year for the table, defaults to 1971
 * @param int $toyear End year for the table, defaults to 2035
 * @param int|float|string $strtimezone timezone to check if dst should be applied.
 * @return bool
 */
function calculate_user_dst_table($fromyear = null, $toyear = null, $strtimezone = null) {
    global $SESSION, $DB;

    $usertz = get_user_timezone($strtimezone);

    if (is_float($usertz)) {
        // Trivial timezone, no DST.
        return false;
    }

    if (!empty($SESSION->dst_offsettz) && $SESSION->dst_offsettz != $usertz) {
        // We have pre-calculated values, but the user's effective TZ has changed in the meantime, so reset.
        unset($SESSION->dst_offsets);
        unset($SESSION->dst_range);
    }

    if (!empty($SESSION->dst_offsets) && empty($fromyear) && empty($toyear)) {
        // Repeat calls which do not request specific year ranges stop here, we have already calculated the table.
        // This will be the return path most of the time, pretty light computationally.
        return true;
    }

    // Reaching here means we either need to extend our table or create it from scratch.

    // Remember which TZ we calculated these changes for.
    $SESSION->dst_offsettz = $usertz;

    if (empty($SESSION->dst_offsets)) {
        // If we 're creating from scratch, put the two guard elements in there.
        $SESSION->dst_offsets = array(1 => null, 0 => null);
    }
    if (empty($SESSION->dst_range)) {
        // If creating from scratch.
        $from = max((empty($fromyear) ? intval(date('Y')) - 3 : $fromyear), 1971);
        $to   = min((empty($toyear)   ? intval(date('Y')) + 3 : $toyear),   2035);

        // Fill in the array with the extra years we need to process.
        $yearstoprocess = array();
        for ($i = $from; $i <= $to; ++$i) {
            $yearstoprocess[] = $i;
        }

        // Take note of which years we have processed for future calls.
        $SESSION->dst_range = array($from, $to);
    } else {
        // If needing to extend the table, do the same.
        $yearstoprocess = array();

        $from = max((empty($fromyear) ? $SESSION->dst_range[0] : $fromyear), 1971);
        $to   = min((empty($toyear)   ? $SESSION->dst_range[1] : $toyear),   2035);

        if ($from < $SESSION->dst_range[0]) {
            // Take note of which years we need to process and then note that we have processed them for future calls.
            for ($i = $from; $i < $SESSION->dst_range[0]; ++$i) {
                $yearstoprocess[] = $i;
            }
            $SESSION->dst_range[0] = $from;
        }
        if ($to > $SESSION->dst_range[1]) {
            // Take note of which years we need to process and then note that we have processed them for future calls.
            for ($i = $SESSION->dst_range[1] + 1; $i <= $to; ++$i) {
                $yearstoprocess[] = $i;
            }
            $SESSION->dst_range[1] = $to;
        }
    }

    if (empty($yearstoprocess)) {
        // This means that there was a call requesting a SMALLER range than we have already calculated.
        return true;
    }

    // From now on, we know that the array has at least the two guard elements, and $yearstoprocess has the years we need
    // Also, the array is sorted in descending timestamp order!

    // Get DB data.

    static $presetscache = array();
    if (!isset($presetscache[$usertz])) {
        $presetscache[$usertz] = $DB->get_records('timezone', array('name' => $usertz),
            'year DESC', 'year, gmtoff, dstoff, dst_month, dst_startday, dst_weekday, dst_skipweeks, dst_time, std_month, '.
            'std_startday, std_weekday, std_skipweeks, std_time');
    }
    if (empty($presetscache[$usertz])) {
        return false;
    }

    // Remove ending guard (first element of the array).
    reset($SESSION->dst_offsets);
    unset($SESSION->dst_offsets[key($SESSION->dst_offsets)]);

    // Add all required change timestamps.
    foreach ($yearstoprocess as $y) {
        // Find the record which is in effect for the year $y.
        foreach ($presetscache[$usertz] as $year => $preset) {
            if ($year <= $y) {
                break;
            }
        }

        $changes = dst_changes_for_year($y, $preset);

        if ($changes === null) {
            continue;
        }
        if ($changes['dst'] != 0) {
            $SESSION->dst_offsets[$changes['dst']] = $preset->dstoff * MINSECS;
        }
        if ($changes['std'] != 0) {
            $SESSION->dst_offsets[$changes['std']] = 0;
        }
    }

    // Put in a guard element at the top.
    $maxtimestamp = max(array_keys($SESSION->dst_offsets));
    $SESSION->dst_offsets[($maxtimestamp + DAYSECS)] = null; // DAYSECS is arbitrary, any "small" number will do.

    // Sort again.
    krsort($SESSION->dst_offsets);

    return true;
}

/**
 * Calculates the required DST change and returns a Timestamp Array
 *
 * @package core
 * @category time
 * @uses HOURSECS
 * @uses MINSECS
 * @param int|string $year Int or String Year to focus on
 * @param object $timezone Instatiated Timezone object
 * @return array|null Array dst => xx, 0 => xx, std => yy, 1 => yy or null
 */
function dst_changes_for_year($year, $timezone) {

    if ($timezone->dst_startday == 0 && $timezone->dst_weekday == 0 &&
        $timezone->std_startday == 0 && $timezone->std_weekday == 0) {
        return null;
    }

    $monthdaydst = find_day_in_month($timezone->dst_startday, $timezone->dst_weekday, $timezone->dst_month, $year);
    $monthdaystd = find_day_in_month($timezone->std_startday, $timezone->std_weekday, $timezone->std_month, $year);

    list($dsthour, $dstmin) = explode(':', $timezone->dst_time);
    list($stdhour, $stdmin) = explode(':', $timezone->std_time);

    $timedst = make_timestamp($year, $timezone->dst_month, $monthdaydst, 0, 0, 0, 99, false);
    $timestd = make_timestamp($year, $timezone->std_month, $monthdaystd, 0, 0, 0, 99, false);

    // Instead of putting hour and minute in make_timestamp(), we add them afterwards.
    // This has the advantage of being able to have negative values for hour, i.e. for timezones
    // where GMT time would be in the PREVIOUS day than the local one on which DST changes.

    $timedst += $dsthour * HOURSECS + $dstmin * MINSECS;
    $timestd += $stdhour * HOURSECS + $stdmin * MINSECS;

    return array('dst' => $timedst, 0 => $timedst, 'std' => $timestd, 1 => $timestd);
}

/**
 * Calculates the Daylight Saving Offset for a given date/time (timestamp)
 * - Note: Daylight saving only works for string timezones and not for float.
 *
 * @package core
 * @category time
 * @param int $time must NOT be compensated at all, it has to be a pure timestamp
 * @param int|float|string $strtimezone timezone for which offset is expected, if 99 or null
 *        then user's default timezone is used. {@link http://docs.moodle.org/dev/Time_API#Timezone}
 * @return int
 */
function dst_offset_on($time, $strtimezone = null) {
    global $SESSION;

    if (!calculate_user_dst_table(null, null, $strtimezone) || empty($SESSION->dst_offsets)) {
        return 0;
    }

    reset($SESSION->dst_offsets);
    while (list($from, $offset) = each($SESSION->dst_offsets)) {
        if ($from <= $time) {
            break;
        }
    }

    // This is the normal return path.
    if ($offset !== null) {
        return $offset;
    }

    // Reaching this point means we haven't calculated far enough, do it now:
    // Calculate extra DST changes if needed and recurse. The recursion always
    // moves toward the stopping condition, so will always end.

    if ($from == 0) {
        // We need a year smaller than $SESSION->dst_range[0].
        if ($SESSION->dst_range[0] == 1971) {
            return 0;
        }
        calculate_user_dst_table($SESSION->dst_range[0] - 5, null, $strtimezone);
        return dst_offset_on($time, $strtimezone);
    } else {
        // We need a year larger than $SESSION->dst_range[1].
        if ($SESSION->dst_range[1] == 2035) {
            return 0;
        }
        calculate_user_dst_table(null, $SESSION->dst_range[1] + 5, $strtimezone);
        return dst_offset_on($time, $strtimezone);
    }
}

/**
 * Calculates when the day appears in specific month
 *
 * @package core
 * @category time
 * @param int $startday starting day of the month
 * @param int $weekday The day when week starts (normally taken from user preferences)
 * @param int $month The month whose day is sought
 * @param int $year The year of the month whose day is sought
 * @return int
 */
function find_day_in_month($startday, $weekday, $month, $year) {

    $daysinmonth = days_in_month($month, $year);

    if ($weekday == -1) {
        // Don't care about weekday, so return:
        //    abs($startday) if $startday != -1
        //    $daysinmonth otherwise.
        return ($startday == -1) ? $daysinmonth : abs($startday);
    }

    // From now on we 're looking for a specific weekday.

    // Give "end of month" its actual value, since we know it.
    if ($startday == -1) {
        $startday = -1 * $daysinmonth;
    }

    // Starting from day $startday, the sign is the direction.

    if ($startday < 1) {

        $startday = abs($startday);
        $lastmonthweekday  = strftime('%w', mktime(12, 0, 0, $month, $daysinmonth, $year));

        // This is the last such weekday of the month.
        $lastinmonth = $daysinmonth + $weekday - $lastmonthweekday;
        if ($lastinmonth > $daysinmonth) {
            $lastinmonth -= 7;
        }

        // Find the first such weekday <= $startday.
        while ($lastinmonth > $startday) {
            $lastinmonth -= 7;
        }

        return $lastinmonth;

    } else {

        $indexweekday = strftime('%w', mktime(12, 0, 0, $month, $startday, $year));

        $diff = $weekday - $indexweekday;
        if ($diff < 0) {
            $diff += 7;
        }

        // This is the first such weekday of the month equal to or after $startday.
        $firstfromindex = $startday + $diff;

        return $firstfromindex;

    }
}

/**
 * Calculate the number of days in a given month
 *
 * @package core
 * @category time
 * @param int $month The month whose day count is sought
 * @param int $year The year of the month whose day count is sought
 * @return int
 */
function days_in_month($month, $year) {
    return intval(date('t', mktime(12, 0, 0, $month, 1, $year)));
}

/**
 * Calculate the position in the week of a specific calendar day
 *
 * @package core
 * @category time
 * @param int $day The day of the date whose position in the week is sought
 * @param int $month The month of the date whose position in the week is sought
 * @param int $year The year of the date whose position in the week is sought
 * @return int
 */
function dayofweek($day, $month, $year) {
    // I wonder if this is any different from strftime('%w', mktime(12, 0, 0, $month, $daysinmonth, $year, 0));.
    return intval(date('w', mktime(12, 0, 0, $month, $day, $year)));
}

// USER AUTHENTICATION AND LOGIN.

/**
 * Returns full login url.
 *
 * @return string login url
 */
function get_login_url() {
    global $CFG;

    $url = "$CFG->wwwroot/login/index.php";

    if (!empty($CFG->loginhttps)) {
        $url = str_replace('http:', 'https:', $url);
    }

    return $url;
}

/**
 * This function checks that the current user is logged in and has the
 * required privileges
 *
 * This function checks that the current user is logged in, and optionally
 * whether they are allowed to be in a particular course and view a particular
 * course module.
 * If they are not logged in, then it redirects them to the site login unless
 * $autologinguest is set and {@link $CFG}->autologinguests is set to 1 in which
 * case they are automatically logged in as guests.
 * If $courseid is given and the user is not enrolled in that course then the
 * user is redirected to the course enrolment page.
 * If $cm is given and the course module is hidden and the user is not a teacher
 * in the course then the user is redirected to the course home page.
 *
 * When $cm parameter specified, this function sets page layout to 'module'.
 * You need to change it manually later if some other layout needed.
 *
 * @package    core_access
 * @category   access
 *
 * @param mixed $courseorid id of the course or course object
 * @param bool $autologinguest default true
 * @param object $cm course module object
 * @param bool $setwantsurltome Define if we want to set $SESSION->wantsurl, defaults to
 *             true. Used to avoid (=false) some scripts (file.php...) to set that variable,
 *             in order to keep redirects working properly. MDL-14495
 * @param bool $preventredirect set to true in scripts that can not redirect (CLI, rss feeds, etc.), throws exceptions
 * @return mixed Void, exit, and die depending on path
 * @throws coding_exception
 * @throws require_login_exception
 */
function require_login($courseorid = null, $autologinguest = true, $cm = null, $setwantsurltome = true, $preventredirect = false) {
    global $CFG, $SESSION, $USER, $PAGE, $SITE, $DB, $OUTPUT;

    // Must not redirect when byteserving already started.
    if (!empty($_SERVER['HTTP_RANGE'])) {
        $preventredirect = true;
    }

    // Setup global $COURSE, themes, language and locale.
    if (!empty($courseorid)) {
        if (is_object($courseorid)) {
            $course = $courseorid;
        } else if ($courseorid == SITEID) {
            $course = clone($SITE);
        } else {
            $course = $DB->get_record('course', array('id' => $courseorid), '*', MUST_EXIST);
        }
        if ($cm) {
            if ($cm->course != $course->id) {
                throw new coding_exception('course and cm parameters in require_login() call do not match!!');
            }
            // Make sure we have a $cm from get_fast_modinfo as this contains activity access details.
            if (!($cm instanceof cm_info)) {
                // Note: nearly all pages call get_fast_modinfo anyway and it does not make any
                // db queries so this is not really a performance concern, however it is obviously
                // better if you use get_fast_modinfo to get the cm before calling this.
                $modinfo = get_fast_modinfo($course);
                $cm = $modinfo->get_cm($cm->id);
            }
            $PAGE->set_cm($cm, $course); // Set's up global $COURSE.
            $PAGE->set_pagelayout('incourse');
        } else {
            $PAGE->set_course($course); // Set's up global $COURSE.
        }
    } else {
        // Do not touch global $COURSE via $PAGE->set_course(),
        // the reasons is we need to be able to call require_login() at any time!!
        $course = $SITE;
        if ($cm) {
            throw new coding_exception('cm parameter in require_login() requires valid course parameter!');
        }
    }

    // If this is an AJAX request and $setwantsurltome is true then we need to override it and set it to false.
    // Otherwise the AJAX request URL will be set to $SESSION->wantsurl and events such as self enrolment in the future
    // risk leading the user back to the AJAX request URL.
    if ($setwantsurltome && defined('AJAX_SCRIPT') && AJAX_SCRIPT) {
        $setwantsurltome = false;
    }

    // Redirect to the login page if session has expired, only with dbsessions enabled (MDL-35029) to maintain current behaviour.
    if ((!isloggedin() or isguestuser()) && !empty($SESSION->has_timed_out) && !$preventredirect && !empty($CFG->dbsessions)) {
        if ($setwantsurltome) {
            $SESSION->wantsurl = qualified_me();
        }
        redirect(get_login_url());
    }

    // If the user is not even logged in yet then make sure they are.
    if (!isloggedin()) {
        if ($autologinguest and !empty($CFG->guestloginbutton) and !empty($CFG->autologinguests)) {
            if (!$guest = get_complete_user_data('id', $CFG->siteguest)) {
                // Misconfigured site guest, just redirect to login page.
                redirect(get_login_url());
                exit; // Never reached.
            }
            $lang = isset($SESSION->lang) ? $SESSION->lang : $CFG->lang;
            complete_user_login($guest);
            $USER->autologinguest = true;
            $SESSION->lang = $lang;
        } else {
            // NOTE: $USER->site check was obsoleted by session test cookie, $USER->confirmed test is in login/index.php.
            if ($preventredirect) {
                throw new require_login_exception('You are not logged in');
            }

            if ($setwantsurltome) {
                $SESSION->wantsurl = qualified_me();
            }
            if (!empty($_SERVER['HTTP_REFERER'])) {
                $SESSION->fromurl  = $_SERVER['HTTP_REFERER'];
            }
            redirect(get_login_url());
            exit; // Never reached.
        }
    }

    // Loginas as redirection if needed.
    if ($course->id != SITEID and \core\session\manager::is_loggedinas()) {
        if ($USER->loginascontext->contextlevel == CONTEXT_COURSE) {
            if ($USER->loginascontext->instanceid != $course->id) {
                print_error('loginasonecourse', '', $CFG->wwwroot.'/course/view.php?id='.$USER->loginascontext->instanceid);
            }
        }
    }

    // Check whether the user should be changing password (but only if it is REALLY them).
    if (get_user_preferences('auth_forcepasswordchange') && !\core\session\manager::is_loggedinas()) {
        $userauth = get_auth_plugin($USER->auth);
        if ($userauth->can_change_password() and !$preventredirect) {
            if ($setwantsurltome) {
                $SESSION->wantsurl = qualified_me();
            }
            if ($changeurl = $userauth->change_password_url()) {
                // Use plugin custom url.
                redirect($changeurl);
            } else {
                // Use moodle internal method.
                if (empty($CFG->loginhttps)) {
                    redirect($CFG->wwwroot .'/login/change_password.php');
                } else {
                    $wwwroot = str_replace('http:', 'https:', $CFG->wwwroot);
                    redirect($wwwroot .'/login/change_password.php');
                }
            }
        } else {
            print_error('nopasswordchangeforced', 'auth');
        }
    }

    // Check that the user account is properly set up.
    if (user_not_fully_set_up($USER)) {
        if ($preventredirect) {
            throw new require_login_exception('User not fully set-up');
        }
        if ($setwantsurltome) {
            $SESSION->wantsurl = qualified_me();
        }
        redirect($CFG->wwwroot .'/user/edit.php?id='. $USER->id .'&amp;course='. SITEID);
    }

    // Make sure the USER has a sesskey set up. Used for CSRF protection.
    sesskey();

    // Do not bother admins with any formalities.
    if (is_siteadmin()) {
        // Set accesstime or the user will appear offline which messes up messaging.
        user_accesstime_log($course->id);
        return;
    }

    // Check that the user has agreed to a site policy if there is one - do not test in case of admins.
    if (!$USER->policyagreed and !is_siteadmin()) {
        if (!empty($CFG->sitepolicy) and !isguestuser()) {
            if ($preventredirect) {
                throw new require_login_exception('Policy not agreed');
            }
            if ($setwantsurltome) {
                $SESSION->wantsurl = qualified_me();
            }
            redirect($CFG->wwwroot .'/user/policy.php');
        } else if (!empty($CFG->sitepolicyguest) and isguestuser()) {
            if ($preventredirect) {
                throw new require_login_exception('Policy not agreed');
            }
            if ($setwantsurltome) {
                $SESSION->wantsurl = qualified_me();
            }
            redirect($CFG->wwwroot .'/user/policy.php');
        }
    }

    // Fetch the system context, the course context, and prefetch its child contexts.
    $sysctx = context_system::instance();
    $coursecontext = context_course::instance($course->id, MUST_EXIST);
    if ($cm) {
        $cmcontext = context_module::instance($cm->id, MUST_EXIST);
    } else {
        $cmcontext = null;
    }

    // If the site is currently under maintenance, then print a message.
    if (!empty($CFG->maintenance_enabled) and !has_capability('moodle/site:config', $sysctx)) {
        if ($preventredirect) {
            throw new require_login_exception('Maintenance in progress');
        }

        print_maintenance_message();
    }

    // Make sure the course itself is not hidden.
    if ($course->id == SITEID) {
        // Frontpage can not be hidden.
    } else {
        if (is_role_switched($course->id)) {
            // When switching roles ignore the hidden flag - user had to be in course to do the switch.
        } else {
            if (!$course->visible and !has_capability('moodle/course:viewhiddencourses', $coursecontext)) {
                // Originally there was also test of parent category visibility, BUT is was very slow in complex queries
                // involving "my courses" now it is also possible to simply hide all courses user is not enrolled in :-).
                if ($preventredirect) {
                    throw new require_login_exception('Course is hidden');
                }
                // We need to override the navigation URL as the course won't have been added to the navigation and thus
                // the navigation will mess up when trying to find it.
                navigation_node::override_active_url(new moodle_url('/'));
                notice(get_string('coursehidden'), $CFG->wwwroot .'/');
            }
        }
    }

    // Is the user enrolled?
    if ($course->id == SITEID) {
        // Everybody is enrolled on the frontpage.
    } else {
        if (\core\session\manager::is_loggedinas()) {
            // Make sure the REAL person can access this course first.
            $realuser = \core\session\manager::get_realuser();
            if (!is_enrolled($coursecontext, $realuser->id, '', true) and
                !is_viewing($coursecontext, $realuser->id) and !is_siteadmin($realuser->id)) {
                if ($preventredirect) {
                    throw new require_login_exception('Invalid course login-as access');
                }
                echo $OUTPUT->header();
                notice(get_string('studentnotallowed', '', fullname($USER, true)), $CFG->wwwroot .'/');
            }
        }

        $access = false;

        if (is_role_switched($course->id)) {
            // Ok, user had to be inside this course before the switch.
            $access = true;

        } else if (is_viewing($coursecontext, $USER)) {
            // Ok, no need to mess with enrol.
            $access = true;

        } else {
            if (isset($USER->enrol['enrolled'][$course->id])) {
                if ($USER->enrol['enrolled'][$course->id] > time()) {
                    $access = true;
                    if (isset($USER->enrol['tempguest'][$course->id])) {
                        unset($USER->enrol['tempguest'][$course->id]);
                        remove_temp_course_roles($coursecontext);
                    }
                } else {
                    // Expired.
                    unset($USER->enrol['enrolled'][$course->id]);
                }
            }
            if (isset($USER->enrol['tempguest'][$course->id])) {
                if ($USER->enrol['tempguest'][$course->id] == 0) {
                    $access = true;
                } else if ($USER->enrol['tempguest'][$course->id] > time()) {
                    $access = true;
                } else {
                    // Expired.
                    unset($USER->enrol['tempguest'][$course->id]);
                    remove_temp_course_roles($coursecontext);
                }
            }

            if (!$access) {
                // Cache not ok.
                $until = enrol_get_enrolment_end($coursecontext->instanceid, $USER->id);
                if ($until !== false) {
                    // Active participants may always access, a timestamp in the future, 0 (always) or false.
                    if ($until == 0) {
                        $until = ENROL_MAX_TIMESTAMP;
                    }
                    $USER->enrol['enrolled'][$course->id] = $until;
                    $access = true;

                } else {
                    $params = array('courseid' => $course->id, 'status' => ENROL_INSTANCE_ENABLED);
                    $instances = $DB->get_records('enrol', $params, 'sortorder, id ASC');
                    $enrols = enrol_get_plugins(true);
                    // First ask all enabled enrol instances in course if they want to auto enrol user.
                    foreach ($instances as $instance) {
                        if (!isset($enrols[$instance->enrol])) {
                            continue;
                        }
                        // Get a duration for the enrolment, a timestamp in the future, 0 (always) or false.
                        $until = $enrols[$instance->enrol]->try_autoenrol($instance);
                        if ($until !== false) {
                            if ($until == 0) {
                                $until = ENROL_MAX_TIMESTAMP;
                            }
                            $USER->enrol['enrolled'][$course->id] = $until;
                            $access = true;
                            break;
                        }
                    }
                    // If not enrolled yet try to gain temporary guest access.
                    if (!$access) {
                        foreach ($instances as $instance) {
                            if (!isset($enrols[$instance->enrol])) {
                                continue;
                            }
                            // Get a duration for the guest access, a timestamp in the future or false.
                            $until = $enrols[$instance->enrol]->try_guestaccess($instance);
                            if ($until !== false and $until > time()) {
                                $USER->enrol['tempguest'][$course->id] = $until;
                                $access = true;
                                break;
                            }
                        }
                    }
                }
            }
        }

        if (!$access) {
            if ($preventredirect) {
                throw new require_login_exception('Not enrolled');
            }
            if ($setwantsurltome) {
                $SESSION->wantsurl = qualified_me();
            }
            redirect($CFG->wwwroot .'/enrol/index.php?id='. $course->id);
        }
    }

    // Check visibility of activity to current user; includes visible flag, groupmembersonly, conditional availability, etc.
    if ($cm && !$cm->uservisible) {
        if ($preventredirect) {
            throw new require_login_exception('Activity is hidden');
        }
        if ($course->id != SITEID) {
            $url = new moodle_url('/course/view.php', array('id' => $course->id));
        } else {
            $url = new moodle_url('/');
        }
        redirect($url, get_string('activityiscurrentlyhidden'));
    }

    // Finally access granted, update lastaccess times.
    user_accesstime_log($course->id);
}


/**
 * This function just makes sure a user is logged out.
 *
 * @package    core_access
 * @category   access
 */
function require_logout() {
    global $USER, $DB;

    if (!isloggedin()) {
        // This should not happen often, no need for hooks or events here.
        \core\session\manager::terminate_current();
        return;
    }

    // Execute hooks before action.
    $authsequence = get_enabled_auth_plugins();
    foreach ($authsequence as $authname) {
        $authplugin = get_auth_plugin($authname);
        $authplugin->prelogout_hook();
    }

    // Store info that gets removed during logout.
    $sid = session_id();
    $event = \core\event\user_loggedout::create(
        array(
            'userid' => $USER->id,
            'objectid' => $USER->id,
            'other' => array('sessionid' => $sid),
        )
    );
    if ($session = $DB->get_record('sessions', array('sid'=>$sid))) {
        $event->add_record_snapshot('sessions', $session);
    }

    // Delete session record and drop $_SESSION content.
    \core\session\manager::terminate_current();

    // Trigger event AFTER action.
    $event->trigger();
}

/**
 * Weaker version of require_login()
 *
 * This is a weaker version of {@link require_login()} which only requires login
 * when called from within a course rather than the site page, unless
 * the forcelogin option is turned on.
 * @see require_login()
 *
 * @package    core_access
 * @category   access
 *
 * @param mixed $courseorid The course object or id in question
 * @param bool $autologinguest Allow autologin guests if that is wanted
 * @param object $cm Course activity module if known
 * @param bool $setwantsurltome Define if we want to set $SESSION->wantsurl, defaults to
 *             true. Used to avoid (=false) some scripts (file.php...) to set that variable,
 *             in order to keep redirects working properly. MDL-14495
 * @param bool $preventredirect set to true in scripts that can not redirect (CLI, rss feeds, etc.), throws exceptions
 * @return void
 * @throws coding_exception
 */
function require_course_login($courseorid, $autologinguest = true, $cm = null, $setwantsurltome = true, $preventredirect = false) {
    global $CFG, $PAGE, $SITE;
    $issite = (is_object($courseorid) and $courseorid->id == SITEID)
          or (!is_object($courseorid) and $courseorid == SITEID);
    if ($issite && !empty($cm) && !($cm instanceof cm_info)) {
        // Note: nearly all pages call get_fast_modinfo anyway and it does not make any
        // db queries so this is not really a performance concern, however it is obviously
        // better if you use get_fast_modinfo to get the cm before calling this.
        if (is_object($courseorid)) {
            $course = $courseorid;
        } else {
            $course = clone($SITE);
        }
        $modinfo = get_fast_modinfo($course);
        $cm = $modinfo->get_cm($cm->id);
    }
    if (!empty($CFG->forcelogin)) {
        // Login required for both SITE and courses.
        require_login($courseorid, $autologinguest, $cm, $setwantsurltome, $preventredirect);

    } else if ($issite && !empty($cm) and !$cm->uservisible) {
        // Always login for hidden activities.
        require_login($courseorid, $autologinguest, $cm, $setwantsurltome, $preventredirect);

    } else if ($issite) {
        // Login for SITE not required.
        if ($cm and empty($cm->visible)) {
            // Hidden activities are not accessible without login.
            require_login($courseorid, $autologinguest, $cm, $setwantsurltome, $preventredirect);
        } else if ($cm and !empty($CFG->enablegroupmembersonly) and $cm->groupmembersonly) {
            // Not-logged-in users do not have any group membership.
            require_login($courseorid, $autologinguest, $cm, $setwantsurltome, $preventredirect);
        } else {
            // We still need to instatiate PAGE vars properly so that things that rely on it like navigation function correctly.
            if (!empty($courseorid)) {
                if (is_object($courseorid)) {
                    $course = $courseorid;
                } else {
                    $course = clone($SITE);
                }
                if ($cm) {
                    if ($cm->course != $course->id) {
                        throw new coding_exception('course and cm parameters in require_course_login() call do not match!!');
                    }
                    $PAGE->set_cm($cm, $course);
                    $PAGE->set_pagelayout('incourse');
                } else {
                    $PAGE->set_course($course);
                }
            } else {
                // If $PAGE->course, and hence $PAGE->context, have not already been set up properly, set them up now.
                $PAGE->set_course($PAGE->course);
            }
            // TODO: verify conditional activities here.
            user_accesstime_log(SITEID);
            return;
        }

    } else {
        // Course login always required.
        require_login($courseorid, $autologinguest, $cm, $setwantsurltome, $preventredirect);
    }
}

/**
 * Require key login. Function terminates with error if key not found or incorrect.
 *
 * @uses NO_MOODLE_COOKIES
 * @uses PARAM_ALPHANUM
 * @param string $script unique script identifier
 * @param int $instance optional instance id
 * @return int Instance ID
 */
function require_user_key_login($script, $instance=null) {
    global $DB;

    if (!NO_MOODLE_COOKIES) {
        print_error('sessioncookiesdisable');
    }

    // Extra safety.
    \core\session\manager::write_close();

    $keyvalue = required_param('key', PARAM_ALPHANUM);

    if (!$key = $DB->get_record('user_private_key', array('script' => $script, 'value' => $keyvalue, 'instance' => $instance))) {
        print_error('invalidkey');
    }

    if (!empty($key->validuntil) and $key->validuntil < time()) {
        print_error('expiredkey');
    }

    if ($key->iprestriction) {
        $remoteaddr = getremoteaddr(null);
        if (empty($remoteaddr) or !address_in_subnet($remoteaddr, $key->iprestriction)) {
            print_error('ipmismatch');
        }
    }

    if (!$user = $DB->get_record('user', array('id' => $key->userid))) {
        print_error('invaliduserid');
    }

    // Emulate normal session.
    enrol_check_plugins($user);
    \core\session\manager::set_user($user);

    // Note we are not using normal login.
    if (!defined('USER_KEY_LOGIN')) {
        define('USER_KEY_LOGIN', true);
    }

    // Return instance id - it might be empty.
    return $key->instance;
}

/**
 * Creates a new private user access key.
 *
 * @param string $script unique target identifier
 * @param int $userid
 * @param int $instance optional instance id
 * @param string $iprestriction optional ip restricted access
 * @param timestamp $validuntil key valid only until given data
 * @return string access key value
 */
function create_user_key($script, $userid, $instance=null, $iprestriction=null, $validuntil=null) {
    global $DB;

    $key = new stdClass();
    $key->script        = $script;
    $key->userid        = $userid;
    $key->instance      = $instance;
    $key->iprestriction = $iprestriction;
    $key->validuntil    = $validuntil;
    $key->timecreated   = time();

    // Something long and unique.
    $key->value         = md5($userid.'_'.time().random_string(40));
    while ($DB->record_exists('user_private_key', array('value' => $key->value))) {
        // Must be unique.
        $key->value     = md5($userid.'_'.time().random_string(40));
    }
    $DB->insert_record('user_private_key', $key);
    return $key->value;
}

/**
 * Delete the user's new private user access keys for a particular script.
 *
 * @param string $script unique target identifier
 * @param int $userid
 * @return void
 */
function delete_user_key($script, $userid) {
    global $DB;
    $DB->delete_records('user_private_key', array('script' => $script, 'userid' => $userid));
}

/**
 * Gets a private user access key (and creates one if one doesn't exist).
 *
 * @param string $script unique target identifier
 * @param int $userid
 * @param int $instance optional instance id
 * @param string $iprestriction optional ip restricted access
 * @param timestamp $validuntil key valid only until given data
 * @return string access key value
 */
function get_user_key($script, $userid, $instance=null, $iprestriction=null, $validuntil=null) {
    global $DB;

    if ($key = $DB->get_record('user_private_key', array('script' => $script, 'userid' => $userid,
                                                         'instance' => $instance, 'iprestriction' => $iprestriction,
                                                         'validuntil' => $validuntil))) {
        return $key->value;
    } else {
        return create_user_key($script, $userid, $instance, $iprestriction, $validuntil);
    }
}


/**
 * Modify the user table by setting the currently logged in user's last login to now.
 *
 * @return bool Always returns true
 */
function update_user_login_times() {
    global $USER, $DB, $CFG;

    require_once($CFG->dirroot.'/user/lib.php');

    if (isguestuser()) {
        // Do not update guest access times/ips for performance.
        return true;
    }

    $now = time();

    $user = new stdClass();
    $user->id = $USER->id;

    // Make sure all users that logged in have some firstaccess.
    if ($USER->firstaccess == 0) {
        $USER->firstaccess = $user->firstaccess = $now;
    }

    // Store the previous current as lastlogin.
    $USER->lastlogin = $user->lastlogin = $USER->currentlogin;

    $USER->currentlogin = $user->currentlogin = $now;

    // Function user_accesstime_log() may not update immediately, better do it here.
    $USER->lastaccess = $user->lastaccess = $now;
    $USER->lastip = $user->lastip = getremoteaddr();

    user_update_user($user, false);
    return true;
}

/**
 * Determines if a user has completed setting up their account.
 *
 * @param stdClass $user A {@link $USER} object to test for the existence of a valid name and email
 * @return bool
 */
function user_not_fully_set_up($user) {
    if (isguestuser($user)) {
        return false;
    }
    return (empty($user->firstname) or empty($user->lastname) or empty($user->email) or over_bounce_threshold($user));
}

/**
 * Check whether the user has exceeded the bounce threshold
 *
 * @param stdClass $user A {@link $USER} object
 * @return bool true => User has exceeded bounce threshold
 */
function over_bounce_threshold($user) {
    global $CFG, $DB;

    if (empty($CFG->handlebounces)) {
        return false;
    }

    if (empty($user->id)) {
        // No real (DB) user, nothing to do here.
        return false;
    }

    // Set sensible defaults.
    if (empty($CFG->minbounces)) {
        $CFG->minbounces = 10;
    }
    if (empty($CFG->bounceratio)) {
        $CFG->bounceratio = .20;
    }
    $bouncecount = 0;
    $sendcount = 0;
    if ($bounce = $DB->get_record('user_preferences', array ('userid' => $user->id, 'name' => 'email_bounce_count'))) {
        $bouncecount = $bounce->value;
    }
    if ($send = $DB->get_record('user_preferences', array('userid' => $user->id, 'name' => 'email_send_count'))) {
        $sendcount = $send->value;
    }
    return ($bouncecount >= $CFG->minbounces && $bouncecount/$sendcount >= $CFG->bounceratio);
}

/**
 * Used to increment or reset email sent count
 *
 * @param stdClass $user object containing an id
 * @param bool $reset will reset the count to 0
 * @return void
 */
function set_send_count($user, $reset=false) {
    global $DB;

    if (empty($user->id)) {
        // No real (DB) user, nothing to do here.
        return;
    }

    if ($pref = $DB->get_record('user_preferences', array('userid' => $user->id, 'name' => 'email_send_count'))) {
        $pref->value = (!empty($reset)) ? 0 : $pref->value+1;
        $DB->update_record('user_preferences', $pref);
    } else if (!empty($reset)) {
        // If it's not there and we're resetting, don't bother. Make a new one.
        $pref = new stdClass();
        $pref->name   = 'email_send_count';
        $pref->value  = 1;
        $pref->userid = $user->id;
        $DB->insert_record('user_preferences', $pref, false);
    }
}

/**
 * Increment or reset user's email bounce count
 *
 * @param stdClass $user object containing an id
 * @param bool $reset will reset the count to 0
 */
function set_bounce_count($user, $reset=false) {
    global $DB;

    if ($pref = $DB->get_record('user_preferences', array('userid' => $user->id, 'name' => 'email_bounce_count'))) {
        $pref->value = (!empty($reset)) ? 0 : $pref->value+1;
        $DB->update_record('user_preferences', $pref);
    } else if (!empty($reset)) {
        // If it's not there and we're resetting, don't bother. Make a new one.
        $pref = new stdClass();
        $pref->name   = 'email_bounce_count';
        $pref->value  = 1;
        $pref->userid = $user->id;
        $DB->insert_record('user_preferences', $pref, false);
    }
}

/**
 * Determines if the logged in user is currently moving an activity
 *
 * @param int $courseid The id of the course being tested
 * @return bool
 */
function ismoving($courseid) {
    global $USER;

    if (!empty($USER->activitycopy)) {
        return ($USER->activitycopycourse == $courseid);
    }
    return false;
}

/**
 * Returns a persons full name
 *
 * Given an object containing all of the users name values, this function returns a string with the full name of the person.
 * The result may depend on system settings or language.  'override' will force both names to be used even if system settings
 * specify one.
 *
 * @param stdClass $user A {@link $USER} object to get full name of.
 * @param bool $override If true then the name will be firstname followed by lastname rather than adhering to fullnamedisplay.
 * @return string
 */
function fullname($user, $override=false) {
    global $CFG, $SESSION;

    if (!isset($user->firstname) and !isset($user->lastname)) {
        return '';
    }

    if (!$override) {
        if (!empty($CFG->forcefirstname)) {
            $user->firstname = $CFG->forcefirstname;
        }
        if (!empty($CFG->forcelastname)) {
            $user->lastname = $CFG->forcelastname;
        }
    }

    if (!empty($SESSION->fullnamedisplay)) {
        $CFG->fullnamedisplay = $SESSION->fullnamedisplay;
    }

    $template = null;
    // If the fullnamedisplay setting is available, set the template to that.
    if (isset($CFG->fullnamedisplay)) {
        $template = $CFG->fullnamedisplay;
    }
    // If the template is empty, or set to language, or $override is set, return the language string.
    if (empty($template) || $template == 'language' || $override) {
        return get_string('fullnamedisplay', null, $user);
    }

    // Get all of the name fields.
    $allnames = get_all_user_name_fields();
    $requirednames = array();
    // With each name, see if it is in the display name template, and add it to the required names array if it is.
    foreach ($allnames as $allname) {
        if (strpos($template, $allname) !== false) {
            $requirednames[] = $allname;
            // If the field is in the template but not set in the user object then notify the programmer that it needs to be fixed.
            if (!array_key_exists($allname, $user)) {
                debugging('You need to update your sql to include additional name fields in the user object.', DEBUG_DEVELOPER);
            }
        }
    }

    $displayname = $template;
    // Switch in the actual data into the template.
    foreach ($requirednames as $altname) {
        if (isset($user->$altname)) {
            // Using empty() on the below if statement causes breakages.
            if ((string)$user->$altname == '') {
                $displayname = str_replace($altname, 'EMPTY', $displayname);
            } else {
                $displayname = str_replace($altname, $user->$altname, $displayname);
            }
        } else {
            $displayname = str_replace($altname, 'EMPTY', $displayname);
        }
    }
    // Tidy up any misc. characters (Not perfect, but gets most characters).
    // Don't remove the "u" at the end of the first expression unless you want garbled characters when combining hiragana or
    // katakana and parenthesis.
    $patterns = array();
    // This regular expression replacement is to fix problems such as 'James () Kirk' Where 'Tiberius' (middlename) has not been
    // filled in by a user.
    // The special characters are Japanese brackets that are common enough to make allowances for them (not covered by :punct:).
    $patterns[] = '/[[:punct:]「」]*EMPTY[[:punct:]「」]*/u';
    // This regular expression is to remove any double spaces in the display name.
    $patterns[] = '/\s{2,}/';
    foreach ($patterns as $pattern) {
        $displayname = preg_replace($pattern, ' ', $displayname);
    }

    // Trimming $displayname will help the next check to ensure that we don't have a display name with spaces.
    $displayname = trim($displayname);
    if (empty($displayname)) {
        // Going with just the first name if no alternate fields are filled out. May be changed later depending on what
        // people in general feel is a good setting to fall back on.
        $displayname = $user->firstname;
    }
    return $displayname;
}

/**
 * A centralised location for the all name fields. Returns an array / sql string snippet.
 *
 * @param bool $returnsql True for an sql select field snippet.
 * @param string $alias table alias to use in front of each field.
 * @return array|string All name fields.
 */
function get_all_user_name_fields($returnsql = false, $alias = null) {
    $alternatenames = array('firstnamephonetic',
                            'lastnamephonetic',
                            'middlename',
                            'alternatename',
                            'firstname',
                            'lastname');
    if ($returnsql) {
        if ($alias) {
            foreach ($alternatenames as $key => $altname) {
                $alternatenames[$key] = "$alias.$altname";
            }
        }
        $alternatenames = implode(',', $alternatenames);
    }
    return $alternatenames;
}

/**
 * Returns an array of values in order of occurance in a provided string.
 * The key in the result is the character postion in the string.
 *
 * @param array $values Values to be found in the string format
 * @param string $stringformat The string which may contain values being searched for.
 * @return array An array of values in order according to placement in the string format.
 */
function order_in_string($values, $stringformat) {
    $valuearray = array();
    foreach ($values as $value) {
        $pattern = "/$value\b/";
        // Using preg_match as strpos() may match values that are similar e.g. firstname and firstnamephonetic.
        if (preg_match($pattern, $stringformat)) {
            $replacement = "thing";
            // Replace the value with something more unique to ensure we get the right position when using strpos().
            $newformat = preg_replace($pattern, $replacement, $stringformat);
            $position = strpos($newformat, $replacement);
            $valuearray[$position] = $value;
        }
    }
    ksort($valuearray);
    return $valuearray;
}

/**
 * Checks if current user is shown any extra fields when listing users.
 *
 * @param object $context Context
 * @param array $already Array of fields that we're going to show anyway
 *   so don't bother listing them
 * @return array Array of field names from user table, not including anything
 *   listed in $already
 */
function get_extra_user_fields($context, $already = array()) {
    global $CFG;

    // Only users with permission get the extra fields.
    if (!has_capability('moodle/site:viewuseridentity', $context)) {
        return array();
    }

    // Split showuseridentity on comma.
    if (empty($CFG->showuseridentity)) {
        // Explode gives wrong result with empty string.
        $extra = array();
    } else {
        $extra =  explode(',', $CFG->showuseridentity);
    }
    $renumber = false;
    foreach ($extra as $key => $field) {
        if (in_array($field, $already)) {
            unset($extra[$key]);
            $renumber = true;
        }
    }
    if ($renumber) {
        // For consistency, if entries are removed from array, renumber it
        // so they are numbered as you would expect.
        $extra = array_merge($extra);
    }
    return $extra;
}

/**
 * If the current user is to be shown extra user fields when listing or
 * selecting users, returns a string suitable for including in an SQL select
 * clause to retrieve those fields.
 *
 * @param context $context Context
 * @param string $alias Alias of user table, e.g. 'u' (default none)
 * @param string $prefix Prefix for field names using AS, e.g. 'u_' (default none)
 * @param array $already Array of fields that we're going to include anyway so don't list them (default none)
 * @return string Partial SQL select clause, beginning with comma, for example ',u.idnumber,u.department' unless it is blank
 */
function get_extra_user_fields_sql($context, $alias='', $prefix='', $already = array()) {
    $fields = get_extra_user_fields($context, $already);
    $result = '';
    // Add punctuation for alias.
    if ($alias !== '') {
        $alias .= '.';
    }
    foreach ($fields as $field) {
        $result .= ', ' . $alias . $field;
        if ($prefix) {
            $result .= ' AS ' . $prefix . $field;
        }
    }
    return $result;
}

/**
 * Returns the display name of a field in the user table. Works for most fields that are commonly displayed to users.
 * @param string $field Field name, e.g. 'phone1'
 * @return string Text description taken from language file, e.g. 'Phone number'
 */
function get_user_field_name($field) {
    // Some fields have language strings which are not the same as field name.
    switch ($field) {
        case 'phone1' : {
            return get_string('phone');
        }
        case 'url' : {
            return get_string('webpage');
        }
        case 'icq' : {
            return get_string('icqnumber');
        }
        case 'skype' : {
            return get_string('skypeid');
        }
        case 'aim' : {
            return get_string('aimid');
        }
        case 'yahoo' : {
            return get_string('yahooid');
        }
        case 'msn' : {
            return get_string('msnid');
        }
    }
    // Otherwise just use the same lang string.
    return get_string($field);
}

/**
 * Returns whether a given authentication plugin exists.
 *
 * @param string $auth Form of authentication to check for. Defaults to the global setting in {@link $CFG}.
 * @return boolean Whether the plugin is available.
 */
function exists_auth_plugin($auth) {
    global $CFG;

    if (file_exists("{$CFG->dirroot}/auth/$auth/auth.php")) {
        return is_readable("{$CFG->dirroot}/auth/$auth/auth.php");
    }
    return false;
}

/**
 * Checks if a given plugin is in the list of enabled authentication plugins.
 *
 * @param string $auth Authentication plugin.
 * @return boolean Whether the plugin is enabled.
 */
function is_enabled_auth($auth) {
    if (empty($auth)) {
        return false;
    }

    $enabled = get_enabled_auth_plugins();

    return in_array($auth, $enabled);
}

/**
 * Returns an authentication plugin instance.
 *
 * @param string $auth name of authentication plugin
 * @return auth_plugin_base An instance of the required authentication plugin.
 */
function get_auth_plugin($auth) {
    global $CFG;

    // Check the plugin exists first.
    if (! exists_auth_plugin($auth)) {
        print_error('authpluginnotfound', 'debug', '', $auth);
    }

    // Return auth plugin instance.
    require_once("{$CFG->dirroot}/auth/$auth/auth.php");
    $class = "auth_plugin_$auth";
    return new $class;
}

/**
 * Returns array of active auth plugins.
 *
 * @param bool $fix fix $CFG->auth if needed
 * @return array
 */
function get_enabled_auth_plugins($fix=false) {
    global $CFG;

    $default = array('manual', 'nologin');

    if (empty($CFG->auth)) {
        $auths = array();
    } else {
        $auths = explode(',', $CFG->auth);
    }

    if ($fix) {
        $auths = array_unique($auths);
        foreach ($auths as $k => $authname) {
            if (!exists_auth_plugin($authname) or in_array($authname, $default)) {
                unset($auths[$k]);
            }
        }
        $newconfig = implode(',', $auths);
        if (!isset($CFG->auth) or $newconfig != $CFG->auth) {
            set_config('auth', $newconfig);
        }
    }

    return (array_merge($default, $auths));
}

/**
 * Returns true if an internal authentication method is being used.
 * if method not specified then, global default is assumed
 *
 * @param string $auth Form of authentication required
 * @return bool
 */
function is_internal_auth($auth) {
    // Throws error if bad $auth.
    $authplugin = get_auth_plugin($auth);
    return $authplugin->is_internal();
}

/**
 * Returns true if the user is a 'restored' one.
 *
 * Used in the login process to inform the user and allow him/her to reset the password
 *
 * @param string $username username to be checked
 * @return bool
 */
function is_restored_user($username) {
    global $CFG, $DB;

    return $DB->record_exists('user', array('username' => $username, 'mnethostid' => $CFG->mnet_localhost_id, 'password' => 'restored'));
}

/**
 * Returns an array of user fields
 *
 * @return array User field/column names
 */
function get_user_fieldnames() {
    global $DB;

    $fieldarray = $DB->get_columns('user');
    unset($fieldarray['id']);
    $fieldarray = array_keys($fieldarray);

    return $fieldarray;
}

/**
 * Creates a bare-bones user record
 *
 * @todo Outline auth types and provide code example
 *
 * @param string $username New user's username to add to record
 * @param string $password New user's password to add to record
 * @param string $auth Form of authentication required
 * @return stdClass A complete user object
 */
function create_user_record($username, $password, $auth = 'manual') {
    global $CFG, $DB;
    require_once($CFG->dirroot.'/user/profile/lib.php');
    require_once($CFG->dirroot.'/user/lib.php');

    // Just in case check text case.
    $username = trim(core_text::strtolower($username));

    $authplugin = get_auth_plugin($auth);
    $customfields = $authplugin->get_custom_user_profile_fields();
    $newuser = new stdClass();
    if ($newinfo = $authplugin->get_userinfo($username)) {
        $newinfo = truncate_userinfo($newinfo);
        foreach ($newinfo as $key => $value) {
            if (in_array($key, $authplugin->userfields) || (in_array($key, $customfields))) {
                $newuser->$key = $value;
            }
        }
    }

    if (!empty($newuser->email)) {
        if (email_is_not_allowed($newuser->email)) {
            unset($newuser->email);
        }
    }

    if (!isset($newuser->city)) {
        $newuser->city = '';
    }

    $newuser->auth = $auth;
    $newuser->username = $username;

    // Fix for MDL-8480
    // user CFG lang for user if $newuser->lang is empty
    // or $user->lang is not an installed language.
    if (empty($newuser->lang) || !get_string_manager()->translation_exists($newuser->lang)) {
        $newuser->lang = $CFG->lang;
    }
    $newuser->confirmed = 1;
    $newuser->lastip = getremoteaddr();
    $newuser->timecreated = time();
    $newuser->timemodified = $newuser->timecreated;
    $newuser->mnethostid = $CFG->mnet_localhost_id;

    $newuser->id = user_create_user($newuser, false);

    // Save user profile data.
    profile_save_data($newuser);

    $user = get_complete_user_data('id', $newuser->id);
    if (!empty($CFG->{'auth_'.$newuser->auth.'_forcechangepassword'})) {
        set_user_preference('auth_forcepasswordchange', 1, $user);
    }
    // Set the password.
    update_internal_user_password($user, $password);

    return $user;
}

/**
 * Will update a local user record from an external source (MNET users can not be updated using this method!).
 *
 * @param string $username user's username to update the record
 * @return stdClass A complete user object
 */
function update_user_record($username) {
    global $DB, $CFG;
    require_once($CFG->dirroot."/user/profile/lib.php");
    require_once($CFG->dirroot.'/user/lib.php');
    // Just in case check text case.
    $username = trim(core_text::strtolower($username));

    $oldinfo = $DB->get_record('user', array('username' => $username, 'mnethostid' => $CFG->mnet_localhost_id), '*', MUST_EXIST);
    $newuser = array();
    $userauth = get_auth_plugin($oldinfo->auth);

    if ($newinfo = $userauth->get_userinfo($username)) {
        $newinfo = truncate_userinfo($newinfo);
        $customfields = $userauth->get_custom_user_profile_fields();

        foreach ($newinfo as $key => $value) {
            $key = strtolower($key);
            $iscustom = in_array($key, $customfields);
            if ((!property_exists($oldinfo, $key) && !$iscustom) or $key === 'username' or $key === 'id'
                    or $key === 'auth' or $key === 'mnethostid' or $key === 'deleted') {
                // Unknown or must not be changed.
                continue;
            }
            $confval = $userauth->config->{'field_updatelocal_' . $key};
            $lockval = $userauth->config->{'field_lock_' . $key};
            if (empty($confval) || empty($lockval)) {
                continue;
            }
            if ($confval === 'onlogin') {
                // MDL-4207 Don't overwrite modified user profile values with
                // empty LDAP values when 'unlocked if empty' is set. The purpose
                // of the setting 'unlocked if empty' is to allow the user to fill
                // in a value for the selected field _if LDAP is giving
                // nothing_ for this field. Thus it makes sense to let this value
                // stand in until LDAP is giving a value for this field.
                if (!(empty($value) && $lockval === 'unlockedifempty')) {
                    if ($iscustom || (in_array($key, $userauth->userfields) &&
                            ((string)$oldinfo->$key !== (string)$value))) {
                        $newuser[$key] = (string)$value;
                    }
                }
            }
        }
        if ($newuser) {
            $newuser['id'] = $oldinfo->id;
            $newuser['timemodified'] = time();
            user_update_user((object) $newuser, false);

            // Save user profile data.
            profile_save_data((object) $newuser);
        }
    }

    return get_complete_user_data('id', $oldinfo->id);
}

/**
 * Will truncate userinfo as it comes from auth_get_userinfo (from external auth) which may have large fields.
 *
 * @param array $info Array of user properties to truncate if needed
 * @return array The now truncated information that was passed in
 */
function truncate_userinfo(array $info) {
    // Define the limits.
    $limit = array(
        'username'    => 100,
        'idnumber'    => 255,
        'firstname'   => 100,
        'lastname'    => 100,
        'email'       => 100,
        'icq'         =>  15,
        'phone1'      =>  20,
        'phone2'      =>  20,
        'institution' =>  40,
        'department'  =>  30,
        'address'     =>  70,
        'city'        => 120,
        'country'     =>   2,
        'url'         => 255,
    );

    // Apply where needed.
    foreach (array_keys($info) as $key) {
        if (!empty($limit[$key])) {
            $info[$key] = trim(core_text::substr($info[$key], 0, $limit[$key]));
        }
    }

    return $info;
}

/**
 * Marks user deleted in internal user database and notifies the auth plugin.
 * Also unenrols user from all roles and does other cleanup.
 *
 * Any plugin that needs to purge user data should register the 'user_deleted' event.
 *
 * @param stdClass $user full user object before delete
 * @return boolean success
 * @throws coding_exception if invalid $user parameter detected
 */
function delete_user(stdClass $user) {
    global $CFG, $DB;
    require_once($CFG->libdir.'/grouplib.php');
    require_once($CFG->libdir.'/gradelib.php');
    require_once($CFG->dirroot.'/message/lib.php');
    require_once($CFG->dirroot.'/tag/lib.php');
    require_once($CFG->dirroot.'/user/lib.php');

    // Make sure nobody sends bogus record type as parameter.
    if (!property_exists($user, 'id') or !property_exists($user, 'username')) {
        throw new coding_exception('Invalid $user parameter in delete_user() detected');
    }

    // Better not trust the parameter and fetch the latest info this will be very expensive anyway.
    if (!$user = $DB->get_record('user', array('id' => $user->id))) {
        debugging('Attempt to delete unknown user account.');
        return false;
    }

    // There must be always exactly one guest record, originally the guest account was identified by username only,
    // now we use $CFG->siteguest for performance reasons.
    if ($user->username === 'guest' or isguestuser($user)) {
        debugging('Guest user account can not be deleted.');
        return false;
    }

    // Admin can be theoretically from different auth plugin, but we want to prevent deletion of internal accoutns only,
    // if anything goes wrong ppl may force somebody to be admin via config.php setting $CFG->siteadmins.
    if ($user->auth === 'manual' and is_siteadmin($user)) {
        debugging('Local administrator accounts can not be deleted.');
        return false;
    }

    // Keep a copy of user context, we need it for event.
    $usercontext = context_user::instance($user->id);

    // Delete all grades - backup is kept in grade_grades_history table.
    grade_user_delete($user->id);

    // Move unread messages from this user to read.
    message_move_userfrom_unread2read($user->id);

    // TODO: remove from cohorts using standard API here.

    // Remove user tags.
    tag_set('user', $user->id, array());

    // Unconditionally unenrol from all courses.
    enrol_user_delete($user);

    // Unenrol from all roles in all contexts.
    // This might be slow but it is really needed - modules might do some extra cleanup!
    role_unassign_all(array('userid' => $user->id));

    // Now do a brute force cleanup.

    // Remove from all cohorts.
    $DB->delete_records('cohort_members', array('userid' => $user->id));

    // Remove from all groups.
    $DB->delete_records('groups_members', array('userid' => $user->id));

    // Brute force unenrol from all courses.
    $DB->delete_records('user_enrolments', array('userid' => $user->id));

    // Purge user preferences.
    $DB->delete_records('user_preferences', array('userid' => $user->id));

    // Purge user extra profile info.
    $DB->delete_records('user_info_data', array('userid' => $user->id));

    // Last course access not necessary either.
    $DB->delete_records('user_lastaccess', array('userid' => $user->id));
    // Remove all user tokens.
    $DB->delete_records('external_tokens', array('userid' => $user->id));

    // Unauthorise the user for all services.
    $DB->delete_records('external_services_users', array('userid' => $user->id));

    // Remove users private keys.
    $DB->delete_records('user_private_key', array('userid' => $user->id));

    // Force logout - may fail if file based sessions used, sorry.
    \core\session\manager::kill_user_sessions($user->id);

    // Workaround for bulk deletes of users with the same email address.
    $delname = "$user->email.".time();
    while ($DB->record_exists('user', array('username' => $delname))) { // No need to use mnethostid here.
        $delname++;
    }

    // Mark internal user record as "deleted".
    $updateuser = new stdClass();
    $updateuser->id           = $user->id;
    $updateuser->deleted      = 1;
    $updateuser->username     = $delname;            // Remember it just in case.
    $updateuser->email        = md5($user->username);// Store hash of username, useful importing/restoring users.
    $updateuser->idnumber     = '';                  // Clear this field to free it up.
    $updateuser->picture      = 0;
    $updateuser->timemodified = time();

    user_update_user($updateuser, false);

    // Now do a final accesslib cleanup - removes all role assignments in user context and context itself.
    context_helper::delete_instance(CONTEXT_USER, $user->id);

    // Any plugin that needs to cleanup should register this event.
    // Trigger event.
    $event = \core\event\user_deleted::create(
            array(
                'objectid' => $user->id,
                'context' => $usercontext,
                'other' => array('user' => (array)clone $user)
                )
            );
    $event->add_record_snapshot('user', $updateuser);
    $event->trigger();

    // We will update the user's timemodified, as it will be passed to the user_deleted event, which
    // should know about this updated property persisted to the user's table.
    $user->timemodified = $updateuser->timemodified;

    // Notify auth plugin - do not block the delete even when plugin fails.
    $authplugin = get_auth_plugin($user->auth);
    $authplugin->user_delete($user);

    return true;
}

/**
 * Retrieve the guest user object.
 *
 * @return stdClass A {@link $USER} object
 */
function guest_user() {
    global $CFG, $DB;

    if ($newuser = $DB->get_record('user', array('id' => $CFG->siteguest))) {
        $newuser->confirmed = 1;
        $newuser->lang = $CFG->lang;
        $newuser->lastip = getremoteaddr();
    }

    return $newuser;
}

/**
 * Authenticates a user against the chosen authentication mechanism
 *
 * Given a username and password, this function looks them
 * up using the currently selected authentication mechanism,
 * and if the authentication is successful, it returns a
 * valid $user object from the 'user' table.
 *
 * Uses auth_ functions from the currently active auth module
 *
 * After authenticate_user_login() returns success, you will need to
 * log that the user has logged in, and call complete_user_login() to set
 * the session up.
 *
 * Note: this function works only with non-mnet accounts!
 *
 * @param string $username  User's username
 * @param string $password  User's password
 * @param bool $ignorelockout useful when guessing is prevented by other mechanism such as captcha or SSO
 * @param int $failurereason login failure reason, can be used in renderers (it may disclose if account exists)
 * @return stdClass|false A {@link $USER} object or false if error
 */
function authenticate_user_login($username, $password, $ignorelockout=false, &$failurereason=null) {
    global $CFG, $DB;
    require_once("$CFG->libdir/authlib.php");

    $authsenabled = get_enabled_auth_plugins();

    if ($user = get_complete_user_data('username', $username, $CFG->mnet_localhost_id)) {
        // Use manual if auth not set.
        $auth = empty($user->auth) ? 'manual' : $user->auth;
        if (!empty($user->suspended)) {
            add_to_log(SITEID, 'login', 'error', 'index.php', $username);
            error_log('[client '.getremoteaddr()."]  $CFG->wwwroot  Suspended Login:  $username  ".$_SERVER['HTTP_USER_AGENT']);
            $failurereason = AUTH_LOGIN_SUSPENDED;
            return false;
        }
        if ($auth=='nologin' or !is_enabled_auth($auth)) {
            add_to_log(SITEID, 'login', 'error', 'index.php', $username);
            error_log('[client '.getremoteaddr()."]  $CFG->wwwroot  Disabled Login:  $username  ".$_SERVER['HTTP_USER_AGENT']);
            // Legacy way to suspend user.
            $failurereason = AUTH_LOGIN_SUSPENDED;
            return false;
        }
        $auths = array($auth);

    } else {
        // Check if there's a deleted record (cheaply), this should not happen because we mangle usernames in delete_user().
        if ($DB->get_field('user', 'id', array('username' => $username, 'mnethostid' => $CFG->mnet_localhost_id,  'deleted' => 1))) {
            error_log('[client '.getremoteaddr()."]  $CFG->wwwroot  Deleted Login:  $username  ".$_SERVER['HTTP_USER_AGENT']);
            $failurereason = AUTH_LOGIN_NOUSER;
            return false;
        }

        // Do not try to authenticate non-existent accounts when user creation is not disabled.
        if (!empty($CFG->authpreventaccountcreation)) {
            add_to_log(SITEID, 'login', 'error', 'index.php', $username);
            error_log('[client '.getremoteaddr()."]  $CFG->wwwroot  Unknown user, can not create new accounts:  $username  ".$_SERVER['HTTP_USER_AGENT']);
            $failurereason = AUTH_LOGIN_NOUSER;
            return false;
        }

        // User does not exist.
        $auths = $authsenabled;
        $user = new stdClass();
        $user->id = 0;
    }

    if ($ignorelockout) {
        // Some other mechanism protects against brute force password guessing, for example login form might include reCAPTCHA
        // or this function is called from a SSO script.
    } else if ($user->id) {
        // Verify login lockout after other ways that may prevent user login.
        if (login_is_lockedout($user)) {
            add_to_log(SITEID, 'login', 'error', 'index.php', $username);
            error_log('[client '.getremoteaddr()."]  $CFG->wwwroot  Login lockout:  $username  ".$_SERVER['HTTP_USER_AGENT']);
            $failurereason = AUTH_LOGIN_LOCKOUT;
            return false;
        }
    } else {
        // We can not lockout non-existing accounts.
    }

    foreach ($auths as $auth) {
        $authplugin = get_auth_plugin($auth);

        // On auth fail fall through to the next plugin.
        if (!$authplugin->user_login($username, $password)) {
            continue;
        }

        // Successful authentication.
        if ($user->id) {
            // User already exists in database.
            if (empty($user->auth)) {
                // For some reason auth isn't set yet.
                $DB->set_field('user', 'auth', $auth, array('username' => $username));
                $user->auth = $auth;
            }

            // If the existing hash is using an out-of-date algorithm (or the legacy md5 algorithm), then we should update to
            // the current hash algorithm while we have access to the user's password.
            update_internal_user_password($user, $password);

            if ($authplugin->is_synchronised_with_external()) {
                // Update user record from external DB.
                $user = update_user_record($username);
            }
        } else {
            // Create account, we verified above that user creation is allowed.
            $user = create_user_record($username, $password, $auth);
        }

        $authplugin->sync_roles($user);

        foreach ($authsenabled as $hau) {
            $hauth = get_auth_plugin($hau);
            $hauth->user_authenticated_hook($user, $username, $password);
        }

        if (empty($user->id)) {
            $failurereason = AUTH_LOGIN_NOUSER;
            return false;
        }

        if (!empty($user->suspended)) {
            // Just in case some auth plugin suspended account.
            add_to_log(SITEID, 'login', 'error', 'index.php', $username);
            error_log('[client '.getremoteaddr()."]  $CFG->wwwroot  Suspended Login:  $username  ".$_SERVER['HTTP_USER_AGENT']);
            $failurereason = AUTH_LOGIN_SUSPENDED;
            return false;
        }

        login_attempt_valid($user);
        $failurereason = AUTH_LOGIN_OK;
        return $user;
    }

    // Failed if all the plugins have failed.
    add_to_log(SITEID, 'login', 'error', 'index.php', $username);
    if (debugging('', DEBUG_ALL)) {
        error_log('[client '.getremoteaddr()."]  $CFG->wwwroot  Failed Login:  $username  ".$_SERVER['HTTP_USER_AGENT']);
    }

    if ($user->id) {
        login_attempt_failed($user);
        $failurereason = AUTH_LOGIN_FAILED;
    } else {
        $failurereason = AUTH_LOGIN_NOUSER;
    }

    return false;
}

/**
 * Call to complete the user login process after authenticate_user_login()
 * has succeeded. It will setup the $USER variable and other required bits
 * and pieces.
 *
 * NOTE:
 * - It will NOT log anything -- up to the caller to decide what to log.
 * - this function does not set any cookies any more!
 *
 * @param stdClass $user
 * @return stdClass A {@link $USER} object - BC only, do not use
 */
function complete_user_login($user) {
    global $CFG, $USER;

    \core\session\manager::login_user($user);

    // Reload preferences from DB.
    unset($USER->preference);
    check_user_preferences_loaded($USER);

    // Update login times.
    update_user_login_times();

    // Extra session prefs init.
    set_login_session_preferences();

    // Trigger login event.
    $event = \core\event\user_loggedin::create(
        array(
            'userid' => $USER->id,
            'objectid' => $USER->id,
            'other' => array('username' => $USER->username),
        )
    );
    $event->add_record_snapshot('user', $user);
    $event->trigger();

    if (isguestuser()) {
        // No need to continue when user is THE guest.
        return $USER;
    }

    if (CLI_SCRIPT) {
        // We can redirect to password change URL only in browser.
        return $USER;
    }

    // Select password change url.
    $userauth = get_auth_plugin($USER->auth);

    // Check whether the user should be changing password.
    if (get_user_preferences('auth_forcepasswordchange', false)) {
        if ($userauth->can_change_password()) {
            if ($changeurl = $userauth->change_password_url()) {
                redirect($changeurl);
            } else {
                redirect($CFG->httpswwwroot.'/login/change_password.php');
            }
        } else {
            print_error('nopasswordchangeforced', 'auth');
        }
    }
    return $USER;
}

/**
 * Check a password hash to see if it was hashed using the legacy hash algorithm (md5).
 *
 * @param string $password String to check.
 * @return boolean True if the $password matches the format of an md5 sum.
 */
function password_is_legacy_hash($password) {
    return (bool) preg_match('/^[0-9a-f]{32}$/', $password);
}

/**
 * Checks whether the password compatibility library will work with the current
 * version of PHP. This cannot be done using PHP version numbers since the fix
 * has been backported to earlier versions in some distributions.
 *
 * See https://github.com/ircmaxell/password_compat/issues/10 for more details.
 *
 * @return bool True if the library is NOT supported.
 */
function password_compat_not_supported() {

    $hash = '$2y$04$usesomesillystringfore7hnbRJHxXVLeakoG8K30oukPsA.ztMG';

    // Create a one off application cache to store bcrypt support status as
    // the support status doesn't change and crypt() is slow.
    $cache = cache::make_from_params(cache_store::MODE_APPLICATION, 'core', 'password_compat');

    if (!$bcryptsupport = $cache->get('bcryptsupport')) {
        $test = crypt('password', $hash);
        // Cache string instead of boolean to avoid MDL-37472.
        if ($test == $hash) {
            $bcryptsupport = 'supported';
        } else {
            $bcryptsupport = 'not supported';
        }
        $cache->set('bcryptsupport', $bcryptsupport);
    }

    // Return true if bcrypt *not* supported.
    return ($bcryptsupport !== 'supported');
}

/**
 * Compare password against hash stored in user object to determine if it is valid.
 *
 * If necessary it also updates the stored hash to the current format.
 *
 * @param stdClass $user (Password property may be updated).
 * @param string $password Plain text password.
 * @return bool True if password is valid.
 */
function validate_internal_user_password($user, $password) {
    global $CFG;
    require_once($CFG->libdir.'/password_compat/lib/password.php');

    if ($user->password === AUTH_PASSWORD_NOT_CACHED) {
        // Internal password is not used at all, it can not validate.
        return false;
    }

    // If hash isn't a legacy (md5) hash, validate using the library function.
    if (!password_is_legacy_hash($user->password)) {
        return password_verify($password, $user->password);
    }

    // Otherwise we need to check for a legacy (md5) hash instead. If the hash
    // is valid we can then update it to the new algorithm.

    $sitesalt = isset($CFG->passwordsaltmain) ? $CFG->passwordsaltmain : '';
    $validated = false;

    if ($user->password === md5($password.$sitesalt)
            or $user->password === md5($password)
            or $user->password === md5(addslashes($password).$sitesalt)
            or $user->password === md5(addslashes($password))) {
        // Note: we are intentionally using the addslashes() here because we
        //       need to accept old password hashes of passwords with magic quotes.
        $validated = true;

    } else {
        for ($i=1; $i<=20; $i++) { // 20 alternative salts should be enough, right?
            $alt = 'passwordsaltalt'.$i;
            if (!empty($CFG->$alt)) {
                if ($user->password === md5($password.$CFG->$alt) or $user->password === md5(addslashes($password).$CFG->$alt)) {
                    $validated = true;
                    break;
                }
            }
        }
    }

    if ($validated) {
        // If the password matches the existing md5 hash, update to the
        // current hash algorithm while we have access to the user's password.
        update_internal_user_password($user, $password);
    }

    return $validated;
}

/**
 * Calculate hash for a plain text password.
 *
 * @param string $password Plain text password to be hashed.
 * @param bool $fasthash If true, use a low cost factor when generating the hash
 *                       This is much faster to generate but makes the hash
 *                       less secure. It is used when lots of hashes need to
 *                       be generated quickly.
 * @return string The hashed password.
 *
 * @throws moodle_exception If a problem occurs while generating the hash.
 */
function hash_internal_user_password($password, $fasthash = false) {
    global $CFG;
    require_once($CFG->libdir.'/password_compat/lib/password.php');

    // Use the legacy hashing algorithm (md5) if PHP is not new enough to support bcrypt properly.
    if (password_compat_not_supported()) {
        if (isset($CFG->passwordsaltmain)) {
            return md5($password.$CFG->passwordsaltmain);
        } else {
            return md5($password);
        }
    }

    // Set the cost factor to 4 for fast hashing, otherwise use default cost.
    $options = ($fasthash) ? array('cost' => 4) : array();

    $generatedhash = password_hash($password, PASSWORD_DEFAULT, $options);

    if ($generatedhash === false || $generatedhash === null) {
        throw new moodle_exception('Failed to generate password hash.');
    }

    return $generatedhash;
}

/**
 * Update password hash in user object (if necessary).
 *
 * The password is updated if:
 * 1. The password has changed (the hash of $user->password is different
 *    to the hash of $password).
 * 2. The existing hash is using an out-of-date algorithm (or the legacy
 *    md5 algorithm).
 *
 * Updating the password will modify the $user object and the database
 * record to use the current hashing algorithm.
 *
 * @param stdClass $user User object (password property may be updated).
 * @param string $password Plain text password.
 * @return bool Always returns true.
 */
function update_internal_user_password($user, $password) {
    global $CFG, $DB;
    require_once($CFG->libdir.'/password_compat/lib/password.php');

    // Use the legacy hashing algorithm (md5) if PHP doesn't support bcrypt properly.
    $legacyhash = password_compat_not_supported();

    // Figure out what the hashed password should be.
    $authplugin = get_auth_plugin($user->auth);
    if ($authplugin->prevent_local_passwords()) {
        $hashedpassword = AUTH_PASSWORD_NOT_CACHED;
    } else {
        $hashedpassword = hash_internal_user_password($password);
    }

    if ($legacyhash) {
        $passwordchanged = ($user->password !== $hashedpassword);
        $algorithmchanged = false;
    } else {
        // If verification fails then it means the password has changed.
        $passwordchanged = !password_verify($password, $user->password);
        $algorithmchanged = password_needs_rehash($user->password, PASSWORD_DEFAULT);
    }

    if ($passwordchanged || $algorithmchanged) {
        $DB->set_field('user', 'password',  $hashedpassword, array('id' => $user->id));
        $user->password = $hashedpassword;
    }

    return true;
}

/**
 * Get a complete user record, which includes all the info in the user record.
 *
 * Intended for setting as $USER session variable
 *
 * @param string $field The user field to be checked for a given value.
 * @param string $value The value to match for $field.
 * @param int $mnethostid
 * @return mixed False, or A {@link $USER} object.
 */
function get_complete_user_data($field, $value, $mnethostid = null) {
    global $CFG, $DB;

    if (!$field || !$value) {
        return false;
    }

    // Build the WHERE clause for an SQL query.
    $params = array('fieldval' => $value);
    $constraints = "$field = :fieldval AND deleted <> 1";

    // If we are loading user data based on anything other than id,
    // we must also restrict our search based on mnet host.
    if ($field != 'id') {
        if (empty($mnethostid)) {
            // If empty, we restrict to local users.
            $mnethostid = $CFG->mnet_localhost_id;
        }
    }
    if (!empty($mnethostid)) {
        $params['mnethostid'] = $mnethostid;
        $constraints .= " AND mnethostid = :mnethostid";
    }

    // Get all the basic user data.
    if (! $user = $DB->get_record_select('user', $constraints, $params)) {
        return false;
    }

    // Get various settings and preferences.

    // Preload preference cache.
    check_user_preferences_loaded($user);

    // Load course enrolment related stuff.
    $user->lastcourseaccess    = array(); // During last session.
    $user->currentcourseaccess = array(); // During current session.
    if ($lastaccesses = $DB->get_records('user_lastaccess', array('userid' => $user->id))) {
        foreach ($lastaccesses as $lastaccess) {
            $user->lastcourseaccess[$lastaccess->courseid] = $lastaccess->timeaccess;
        }
    }

    $sql = "SELECT g.id, g.courseid
              FROM {groups} g, {groups_members} gm
             WHERE gm.groupid=g.id AND gm.userid=?";

    // This is a special hack to speedup calendar display.
    $user->groupmember = array();
    if (!isguestuser($user)) {
        if ($groups = $DB->get_records_sql($sql, array($user->id))) {
            foreach ($groups as $group) {
                if (!array_key_exists($group->courseid, $user->groupmember)) {
                    $user->groupmember[$group->courseid] = array();
                }
                $user->groupmember[$group->courseid][$group->id] = $group->id;
            }
        }
    }

    // Add the custom profile fields to the user record.
    $user->profile = array();
    if (!isguestuser($user)) {
        require_once($CFG->dirroot.'/user/profile/lib.php');
        profile_load_custom_fields($user);
    }

    // Rewrite some variables if necessary.
    if (!empty($user->description)) {
        // No need to cart all of it around.
        $user->description = true;
    }
    if (isguestuser($user)) {
        // Guest language always same as site.
        $user->lang = $CFG->lang;
        // Name always in current language.
        $user->firstname = get_string('guestuser');
        $user->lastname = ' ';
    }

    return $user;
}

/**
 * Validate a password against the configured password policy
 *
 * @param string $password the password to be checked against the password policy
 * @param string $errmsg the error message to display when the password doesn't comply with the policy.
 * @return bool true if the password is valid according to the policy. false otherwise.
 */
function check_password_policy($password, &$errmsg) {
    global $CFG;

    if (empty($CFG->passwordpolicy)) {
        return true;
    }

    $errmsg = '';
    if (core_text::strlen($password) < $CFG->minpasswordlength) {
        $errmsg .= '<div>'. get_string('errorminpasswordlength', 'auth', $CFG->minpasswordlength) .'</div>';

    }
    if (preg_match_all('/[[:digit:]]/u', $password, $matches) < $CFG->minpassworddigits) {
        $errmsg .= '<div>'. get_string('errorminpassworddigits', 'auth', $CFG->minpassworddigits) .'</div>';

    }
    if (preg_match_all('/[[:lower:]]/u', $password, $matches) < $CFG->minpasswordlower) {
        $errmsg .= '<div>'. get_string('errorminpasswordlower', 'auth', $CFG->minpasswordlower) .'</div>';

    }
    if (preg_match_all('/[[:upper:]]/u', $password, $matches) < $CFG->minpasswordupper) {
        $errmsg .= '<div>'. get_string('errorminpasswordupper', 'auth', $CFG->minpasswordupper) .'</div>';

    }
    if (preg_match_all('/[^[:upper:][:lower:][:digit:]]/u', $password, $matches) < $CFG->minpasswordnonalphanum) {
        $errmsg .= '<div>'. get_string('errorminpasswordnonalphanum', 'auth', $CFG->minpasswordnonalphanum) .'</div>';
    }
    if (!check_consecutive_identical_characters($password, $CFG->maxconsecutiveidentchars)) {
        $errmsg .= '<div>'. get_string('errormaxconsecutiveidentchars', 'auth', $CFG->maxconsecutiveidentchars) .'</div>';
    }

    if ($errmsg == '') {
        return true;
    } else {
        return false;
    }
}


/**
 * When logging in, this function is run to set certain preferences for the current SESSION.
 */
function set_login_session_preferences() {
    global $SESSION;

    $SESSION->justloggedin = true;

    unset($SESSION->lang);
}


/**
 * Delete a course, including all related data from the database, and any associated files.
 *
 * @param mixed $courseorid The id of the course or course object to delete.
 * @param bool $showfeedback Whether to display notifications of each action the function performs.
 * @return bool true if all the removals succeeded. false if there were any failures. If this
 *             method returns false, some of the removals will probably have succeeded, and others
 *             failed, but you have no way of knowing which.
 */
function delete_course($courseorid, $showfeedback = true) {
    global $DB;

    if (is_object($courseorid)) {
        $courseid = $courseorid->id;
        $course   = $courseorid;
    } else {
        $courseid = $courseorid;
        if (!$course = $DB->get_record('course', array('id' => $courseid))) {
            return false;
        }
    }
    $context = context_course::instance($courseid);

    // Frontpage course can not be deleted!!
    if ($courseid == SITEID) {
        return false;
    }

    // Make the course completely empty.
    remove_course_contents($courseid, $showfeedback);

    // Delete the course and related context instance.
    context_helper::delete_instance(CONTEXT_COURSE, $courseid);

    // We will update the course's timemodified, as it will be passed to the course_deleted event,
    // which should know about this updated property, as this event is meant to pass the full course record.
    $course->timemodified = time();

    $DB->delete_records("course", array("id" => $courseid));
    $DB->delete_records("course_format_options", array("courseid" => $courseid));

    // Trigger a course deleted event.
    $event = \core\event\course_deleted::create(array(
        'objectid' => $course->id,
        'context' => $context,
        'other' => array('shortname' => $course->shortname,
                         'fullname' => $course->fullname)
    ));
    $event->add_record_snapshot('course', $course);
    $event->trigger();

    return true;
}

/**
 * Clear a course out completely, deleting all content but don't delete the course itself.
 *
 * This function does not verify any permissions.
 *
 * Please note this function also deletes all user enrolments,
 * enrolment instances and role assignments by default.
 *
 * $options:
 *  - 'keep_roles_and_enrolments' - false by default
 *  - 'keep_groups_and_groupings' - false by default
 *
 * @param int $courseid The id of the course that is being deleted
 * @param bool $showfeedback Whether to display notifications of each action the function performs.
 * @param array $options extra options
 * @return bool true if all the removals succeeded. false if there were any failures. If this
 *             method returns false, some of the removals will probably have succeeded, and others
 *             failed, but you have no way of knowing which.
 */
function remove_course_contents($courseid, $showfeedback = true, array $options = null) {
    global $CFG, $DB, $OUTPUT;

    require_once($CFG->libdir.'/badgeslib.php');
    require_once($CFG->libdir.'/completionlib.php');
    require_once($CFG->libdir.'/questionlib.php');
    require_once($CFG->libdir.'/gradelib.php');
    require_once($CFG->dirroot.'/group/lib.php');
    require_once($CFG->dirroot.'/tag/coursetagslib.php');
    require_once($CFG->dirroot.'/comment/lib.php');
    require_once($CFG->dirroot.'/rating/lib.php');

    // Handle course badges.
    badges_handle_course_deletion($courseid);

    // NOTE: these concatenated strings are suboptimal, but it is just extra info...
    $strdeleted = get_string('deleted').' - ';

    // Some crazy wishlist of stuff we should skip during purging of course content.
    $options = (array)$options;

    $course = $DB->get_record('course', array('id' => $courseid), '*', MUST_EXIST);
    $coursecontext = context_course::instance($courseid);
    $fs = get_file_storage();

    // Delete course completion information, this has to be done before grades and enrols.
    $cc = new completion_info($course);
    $cc->clear_criteria();
    if ($showfeedback) {
        echo $OUTPUT->notification($strdeleted.get_string('completion', 'completion'), 'notifysuccess');
    }

    // Remove all data from gradebook - this needs to be done before course modules
    // because while deleting this information, the system may need to reference
    // the course modules that own the grades.
    remove_course_grades($courseid, $showfeedback);
    remove_grade_letters($coursecontext, $showfeedback);

    // Delete course blocks in any all child contexts,
    // they may depend on modules so delete them first.
    $childcontexts = $coursecontext->get_child_contexts(); // Returns all subcontexts since 2.2.
    foreach ($childcontexts as $childcontext) {
        blocks_delete_all_for_context($childcontext->id);
    }
    unset($childcontexts);
    blocks_delete_all_for_context($coursecontext->id);
    if ($showfeedback) {
        echo $OUTPUT->notification($strdeleted.get_string('type_block_plural', 'plugin'), 'notifysuccess');
    }

    // Delete every instance of every module,
    // this has to be done before deleting of course level stuff.
    $locations = core_component::get_plugin_list('mod');
    foreach ($locations as $modname => $moddir) {
        if ($modname === 'NEWMODULE') {
            continue;
        }
        if ($module = $DB->get_record('modules', array('name' => $modname))) {
            include_once("$moddir/lib.php");                 // Shows php warning only if plugin defective.
            $moddelete = $modname .'_delete_instance';       // Delete everything connected to an instance.
            $moddeletecourse = $modname .'_delete_course';   // Delete other stray stuff (uncommon).

            if ($instances = $DB->get_records($modname, array('course' => $course->id))) {
                foreach ($instances as $instance) {
                    if ($cm = get_coursemodule_from_instance($modname, $instance->id, $course->id)) {
                        // Delete activity context questions and question categories.
                        question_delete_activity($cm,  $showfeedback);
                    }
                    if (function_exists($moddelete)) {
                        // This purges all module data in related tables, extra user prefs, settings, etc.
                        $moddelete($instance->id);
                    } else {
                        // NOTE: we should not allow installation of modules with missing delete support!
                        debugging("Defective module '$modname' detected when deleting course contents: missing function $moddelete()!");
                        $DB->delete_records($modname, array('id' => $instance->id));
                    }

                    if ($cm) {
                        // Delete cm and its context - orphaned contexts are purged in cron in case of any race condition.
                        context_helper::delete_instance(CONTEXT_MODULE, $cm->id);
                        $DB->delete_records('course_modules', array('id' => $cm->id));
                    }
                }
            }
            if (function_exists($moddeletecourse)) {
                // Execute ptional course cleanup callback.
                $moddeletecourse($course, $showfeedback);
            }
            if ($instances and $showfeedback) {
                echo $OUTPUT->notification($strdeleted.get_string('pluginname', $modname), 'notifysuccess');
            }
        } else {
            // Ooops, this module is not properly installed, force-delete it in the next block.
        }
    }

    // We have tried to delete everything the nice way - now let's force-delete any remaining module data.

    // Remove all data from availability and completion tables that is associated
    // with course-modules belonging to this course. Note this is done even if the
    // features are not enabled now, in case they were enabled previously.
    $DB->delete_records_select('course_modules_completion',
           'coursemoduleid IN (SELECT id from {course_modules} WHERE course=?)',
           array($courseid));
    $DB->delete_records_select('course_modules_availability',
           'coursemoduleid IN (SELECT id from {course_modules} WHERE course=?)',
           array($courseid));
    $DB->delete_records_select('course_modules_avail_fields',
           'coursemoduleid IN (SELECT id from {course_modules} WHERE course=?)',
           array($courseid));

    // Remove course-module data.
    $cms = $DB->get_records('course_modules', array('course' => $course->id));
    foreach ($cms as $cm) {
        if ($module = $DB->get_record('modules', array('id' => $cm->module))) {
            try {
                $DB->delete_records($module->name, array('id' => $cm->instance));
            } catch (Exception $e) {
                // Ignore weird or missing table problems.
            }
        }
        context_helper::delete_instance(CONTEXT_MODULE, $cm->id);
        $DB->delete_records('course_modules', array('id' => $cm->id));
    }

    if ($showfeedback) {
        echo $OUTPUT->notification($strdeleted.get_string('type_mod_plural', 'plugin'), 'notifysuccess');
    }

    // Cleanup the rest of plugins.
    $cleanuplugintypes = array('report', 'coursereport', 'format');
    foreach ($cleanuplugintypes as $type) {
        $plugins = get_plugin_list_with_function($type, 'delete_course', 'lib.php');
        foreach ($plugins as $plugin => $pluginfunction) {
            $pluginfunction($course->id, $showfeedback);
        }
        if ($showfeedback) {
            echo $OUTPUT->notification($strdeleted.get_string('type_'.$type.'_plural', 'plugin'), 'notifysuccess');
        }
    }

    // Delete questions and question categories.
    question_delete_course($course, $showfeedback);
    if ($showfeedback) {
        echo $OUTPUT->notification($strdeleted.get_string('questions', 'question'), 'notifysuccess');
    }

    // Make sure there are no subcontexts left - all valid blocks and modules should be already gone.
    $childcontexts = $coursecontext->get_child_contexts(); // Returns all subcontexts since 2.2.
    foreach ($childcontexts as $childcontext) {
        $childcontext->delete();
    }
    unset($childcontexts);

    // Remove all roles and enrolments by default.
    if (empty($options['keep_roles_and_enrolments'])) {
        // This hack is used in restore when deleting contents of existing course.
        role_unassign_all(array('contextid' => $coursecontext->id, 'component' => ''), true);
        enrol_course_delete($course);
        if ($showfeedback) {
            echo $OUTPUT->notification($strdeleted.get_string('type_enrol_plural', 'plugin'), 'notifysuccess');
        }
    }

    // Delete any groups, removing members and grouping/course links first.
    if (empty($options['keep_groups_and_groupings'])) {
        groups_delete_groupings($course->id, $showfeedback);
        groups_delete_groups($course->id, $showfeedback);
    }

    // Filters be gone!
    filter_delete_all_for_context($coursecontext->id);

    // Die comments!
    comment::delete_comments($coursecontext->id);

    // Ratings are history too.
    $delopt = new stdclass();
    $delopt->contextid = $coursecontext->id;
    $rm = new rating_manager();
    $rm->delete_ratings($delopt);

    // Delete course tags.
    coursetag_delete_course_tags($course->id, $showfeedback);

    // Delete calendar events.
    $DB->delete_records('event', array('courseid' => $course->id));
    $fs->delete_area_files($coursecontext->id, 'calendar');

    // Delete all related records in other core tables that may have a courseid
    // This array stores the tables that need to be cleared, as
    // table_name => column_name that contains the course id.
    $tablestoclear = array(
        'log' => 'course',               // Course logs (NOTE: this might be changed in the future).
        'backup_courses' => 'courseid',  // Scheduled backup stuff.
        'user_lastaccess' => 'courseid', // User access info.
    );
    foreach ($tablestoclear as $table => $col) {
        $DB->delete_records($table, array($col => $course->id));
    }

    // Delete all course backup files.
    $fs->delete_area_files($coursecontext->id, 'backup');

    // Cleanup course record - remove links to deleted stuff.
    $oldcourse = new stdClass();
    $oldcourse->id               = $course->id;
    $oldcourse->summary          = '';
    $oldcourse->cacherev         = 0;
    $oldcourse->legacyfiles      = 0;
    $oldcourse->enablecompletion = 0;
    if (!empty($options['keep_groups_and_groupings'])) {
        $oldcourse->defaultgroupingid = 0;
    }
    $DB->update_record('course', $oldcourse);

    // Delete course sections and availability options.
    $DB->delete_records_select('course_sections_availability',
           'coursesectionid IN (SELECT id from {course_sections} WHERE course=?)',
           array($course->id));
    $DB->delete_records_select('course_sections_avail_fields',
           'coursesectionid IN (SELECT id from {course_sections} WHERE course=?)',
           array($course->id));
    $DB->delete_records('course_sections', array('course' => $course->id));

    // Delete legacy, section and any other course files.
    $fs->delete_area_files($coursecontext->id, 'course'); // Files from summary and section.

    // Delete all remaining stuff linked to context such as files, comments, ratings, etc.
    if (empty($options['keep_roles_and_enrolments']) and empty($options['keep_groups_and_groupings'])) {
        // Easy, do not delete the context itself...
        $coursecontext->delete_content();
    } else {
        // Hack alert!!!!
        // We can not drop all context stuff because it would bork enrolments and roles,
        // there might be also files used by enrol plugins...
    }

    // Delete legacy files - just in case some files are still left there after conversion to new file api,
    // also some non-standard unsupported plugins may try to store something there.
    fulldelete($CFG->dataroot.'/'.$course->id);

    // Delete from cache to reduce the cache size especially makes sense in case of bulk course deletion.
    $cachemodinfo = cache::make('core', 'coursemodinfo');
    $cachemodinfo->delete($courseid);

    // Trigger a course content deleted event.
    $event = \core\event\course_content_deleted::create(array(
        'objectid' => $course->id,
        'context' => $coursecontext,
        'other' => array('shortname' => $course->shortname,
                         'fullname' => $course->fullname,
                         'options' => $options) // Passing this for legacy reasons.
    ));
    $event->add_record_snapshot('course', $course);
    $event->trigger();

    return true;
}

/**
 * Change dates in module - used from course reset.
 *
 * @param string $modname forum, assignment, etc
 * @param array $fields array of date fields from mod table
 * @param int $timeshift time difference
 * @param int $courseid
 * @return bool success
 */
function shift_course_mod_dates($modname, $fields, $timeshift, $courseid) {
    global $CFG, $DB;
    include_once($CFG->dirroot.'/mod/'.$modname.'/lib.php');

    $return = true;
    foreach ($fields as $field) {
        $updatesql = "UPDATE {".$modname."}
                          SET $field = $field + ?
                        WHERE course=? AND $field<>0";
        $return = $DB->execute($updatesql, array($timeshift, $courseid)) && $return;
    }

    $refreshfunction = $modname.'_refresh_events';
    if (function_exists($refreshfunction)) {
        $refreshfunction($courseid);
    }

    return $return;
}

/**
 * This function will empty a course of user data.
 * It will retain the activities and the structure of the course.
 *
 * @param object $data an object containing all the settings including courseid (without magic quotes)
 * @return array status array of array component, item, error
 */
function reset_course_userdata($data) {
    global $CFG, $DB;
    require_once($CFG->libdir.'/gradelib.php');
    require_once($CFG->libdir.'/completionlib.php');
    require_once($CFG->dirroot.'/group/lib.php');

    $data->courseid = $data->id;
    $context = context_course::instance($data->courseid);

    $eventparams = array(
        'context' => $context,
        'courseid' => $data->id,
        'other' => array(
            'reset_options' => (array) $data
        )
    );
    $event = \core\event\course_reset_started::create($eventparams);
    $event->trigger();

    // Calculate the time shift of dates.
    if (!empty($data->reset_start_date)) {
        // Time part of course startdate should be zero.
        $data->timeshift = $data->reset_start_date - usergetmidnight($data->reset_start_date_old);
    } else {
        $data->timeshift = 0;
    }

    // Result array: component, item, error.
    $status = array();

    // Start the resetting.
    $componentstr = get_string('general');

    // Move the course start time.
    if (!empty($data->reset_start_date) and $data->timeshift) {
        // Change course start data.
        $DB->set_field('course', 'startdate', $data->reset_start_date, array('id' => $data->courseid));
        // Update all course and group events - do not move activity events.
        $updatesql = "UPDATE {event}
                         SET timestart = timestart + ?
                       WHERE courseid=? AND instance=0";
        $DB->execute($updatesql, array($data->timeshift, $data->courseid));

        $status[] = array('component' => $componentstr, 'item' => get_string('datechanged'), 'error' => false);
    }

    if (!empty($data->reset_logs)) {
        $DB->delete_records('log', array('course' => $data->courseid));
        $status[] = array('component' => $componentstr, 'item' => get_string('deletelogs'), 'error' => false);
    }

    if (!empty($data->reset_events)) {
        $DB->delete_records('event', array('courseid' => $data->courseid));
        $status[] = array('component' => $componentstr, 'item' => get_string('deleteevents', 'calendar'), 'error' => false);
    }

    if (!empty($data->reset_notes)) {
        require_once($CFG->dirroot.'/notes/lib.php');
        note_delete_all($data->courseid);
        $status[] = array('component' => $componentstr, 'item' => get_string('deletenotes', 'notes'), 'error' => false);
    }

    if (!empty($data->delete_blog_associations)) {
        require_once($CFG->dirroot.'/blog/lib.php');
        blog_remove_associations_for_course($data->courseid);
        $status[] = array('component' => $componentstr, 'item' => get_string('deleteblogassociations', 'blog'), 'error' => false);
    }

    if (!empty($data->reset_completion)) {
        // Delete course and activity completion information.
        $course = $DB->get_record('course', array('id' => $data->courseid));
        $cc = new completion_info($course);
        $cc->delete_all_completion_data();
        $status[] = array('component' => $componentstr,
                'item' => get_string('deletecompletiondata', 'completion'), 'error' => false);
    }

    $componentstr = get_string('roles');

    if (!empty($data->reset_roles_overrides)) {
        $children = $context->get_child_contexts();
        foreach ($children as $child) {
            $DB->delete_records('role_capabilities', array('contextid' => $child->id));
        }
        $DB->delete_records('role_capabilities', array('contextid' => $context->id));
        // Force refresh for logged in users.
        $context->mark_dirty();
        $status[] = array('component' => $componentstr, 'item' => get_string('deletecourseoverrides', 'role'), 'error' => false);
    }

    if (!empty($data->reset_roles_local)) {
        $children = $context->get_child_contexts();
        foreach ($children as $child) {
            role_unassign_all(array('contextid' => $child->id));
        }
        // Force refresh for logged in users.
        $context->mark_dirty();
        $status[] = array('component' => $componentstr, 'item' => get_string('deletelocalroles', 'role'), 'error' => false);
    }

    // First unenrol users - this cleans some of related user data too, such as forum subscriptions, tracking, etc.
    $data->unenrolled = array();
    if (!empty($data->unenrol_users)) {
        $plugins = enrol_get_plugins(true);
        $instances = enrol_get_instances($data->courseid, true);
        foreach ($instances as $key => $instance) {
            if (!isset($plugins[$instance->enrol])) {
                unset($instances[$key]);
                continue;
            }
        }

        foreach ($data->unenrol_users as $withroleid) {
            if ($withroleid) {
                $sql = "SELECT ue.*
                          FROM {user_enrolments} ue
                          JOIN {enrol} e ON (e.id = ue.enrolid AND e.courseid = :courseid)
                          JOIN {context} c ON (c.contextlevel = :courselevel AND c.instanceid = e.courseid)
                          JOIN {role_assignments} ra ON (ra.contextid = c.id AND ra.roleid = :roleid AND ra.userid = ue.userid)";
                $params = array('courseid' => $data->courseid, 'roleid' => $withroleid, 'courselevel' => CONTEXT_COURSE);

            } else {
                // Without any role assigned at course context.
                $sql = "SELECT ue.*
                          FROM {user_enrolments} ue
                          JOIN {enrol} e ON (e.id = ue.enrolid AND e.courseid = :courseid)
                          JOIN {context} c ON (c.contextlevel = :courselevel AND c.instanceid = e.courseid)
                     LEFT JOIN {role_assignments} ra ON (ra.contextid = c.id AND ra.userid = ue.userid)
                         WHERE ra.id IS null";
                $params = array('courseid' => $data->courseid, 'courselevel' => CONTEXT_COURSE);
            }

            $rs = $DB->get_recordset_sql($sql, $params);
            foreach ($rs as $ue) {
                if (!isset($instances[$ue->enrolid])) {
                    continue;
                }
                $instance = $instances[$ue->enrolid];
                $plugin = $plugins[$instance->enrol];
                if (!$plugin->allow_unenrol($instance) and !$plugin->allow_unenrol_user($instance, $ue)) {
                    continue;
                }

                $plugin->unenrol_user($instance, $ue->userid);
                $data->unenrolled[$ue->userid] = $ue->userid;
            }
            $rs->close();
        }
    }
    if (!empty($data->unenrolled)) {
        $status[] = array(
            'component' => $componentstr,
            'item' => get_string('unenrol', 'enrol').' ('.count($data->unenrolled).')',
            'error' => false
        );
    }

    $componentstr = get_string('groups');

    // Remove all group members.
    if (!empty($data->reset_groups_members)) {
        groups_delete_group_members($data->courseid);
        $status[] = array('component' => $componentstr, 'item' => get_string('removegroupsmembers', 'group'), 'error' => false);
    }

    // Remove all groups.
    if (!empty($data->reset_groups_remove)) {
        groups_delete_groups($data->courseid, false);
        $status[] = array('component' => $componentstr, 'item' => get_string('deleteallgroups', 'group'), 'error' => false);
    }

    // Remove all grouping members.
    if (!empty($data->reset_groupings_members)) {
        groups_delete_groupings_groups($data->courseid, false);
        $status[] = array('component' => $componentstr, 'item' => get_string('removegroupingsmembers', 'group'), 'error' => false);
    }

    // Remove all groupings.
    if (!empty($data->reset_groupings_remove)) {
        groups_delete_groupings($data->courseid, false);
        $status[] = array('component' => $componentstr, 'item' => get_string('deleteallgroupings', 'group'), 'error' => false);
    }

    // Look in every instance of every module for data to delete.
    $unsupportedmods = array();
    if ($allmods = $DB->get_records('modules') ) {
        foreach ($allmods as $mod) {
            $modname = $mod->name;
            $modfile = $CFG->dirroot.'/mod/'. $modname.'/lib.php';
            $moddeleteuserdata = $modname.'_reset_userdata';   // Function to delete user data.
            if (file_exists($modfile)) {
                if (!$DB->count_records($modname, array('course' => $data->courseid))) {
                    continue; // Skip mods with no instances.
                }
                include_once($modfile);
                if (function_exists($moddeleteuserdata)) {
                    $modstatus = $moddeleteuserdata($data);
                    if (is_array($modstatus)) {
                        $status = array_merge($status, $modstatus);
                    } else {
                        debugging('Module '.$modname.' returned incorrect staus - must be an array!');
                    }
                } else {
                    $unsupportedmods[] = $mod;
                }
            } else {
                debugging('Missing lib.php in '.$modname.' module!');
            }
        }
    }

    // Mention unsupported mods.
    if (!empty($unsupportedmods)) {
        foreach ($unsupportedmods as $mod) {
            $status[] = array(
                'component' => get_string('modulenameplural', $mod->name),
                'item' => '',
                'error' => get_string('resetnotimplemented')
            );
        }
    }

    $componentstr = get_string('gradebook', 'grades');
    // Reset gradebook,.
    if (!empty($data->reset_gradebook_items)) {
        remove_course_grades($data->courseid, false);
        grade_grab_course_grades($data->courseid);
        grade_regrade_final_grades($data->courseid);
        $status[] = array('component' => $componentstr, 'item' => get_string('removeallcourseitems', 'grades'), 'error' => false);

    } else if (!empty($data->reset_gradebook_grades)) {
        grade_course_reset($data->courseid);
        $status[] = array('component' => $componentstr, 'item' => get_string('removeallcoursegrades', 'grades'), 'error' => false);
    }
    // Reset comments.
    if (!empty($data->reset_comments)) {
        require_once($CFG->dirroot.'/comment/lib.php');
        comment::reset_course_page_comments($context);
    }

    $event = \core\event\course_reset_ended::create($eventparams);
    $event->trigger();

    return $status;
}

/**
 * Generate an email processing address.
 *
 * @param int $modid
 * @param string $modargs
 * @return string Returns email processing address
 */
function generate_email_processing_address($modid, $modargs) {
    global $CFG;

    $header = $CFG->mailprefix . substr(base64_encode(pack('C', $modid)), 0, 2).$modargs;
    return $header . substr(md5($header.get_site_identifier()), 0, 16).'@'.$CFG->maildomain;
}

/**
 * ?
 *
 * @todo Finish documenting this function
 *
 * @param string $modargs
 * @param string $body Currently unused
 */
function moodle_process_email($modargs, $body) {
    global $DB;

    // The first char should be an unencoded letter. We'll take this as an action.
    switch ($modargs{0}) {
        case 'B': { // Bounce.
            list(, $userid) = unpack('V', base64_decode(substr($modargs, 1, 8)));
            if ($user = $DB->get_record("user", array('id' => $userid), "id,email")) {
                // Check the half md5 of their email.
                $md5check = substr(md5($user->email), 0, 16);
                if ($md5check == substr($modargs, -16)) {
                    set_bounce_count($user);
                }
                // Else maybe they've already changed it?
            }
        }
        break;
        // Maybe more later?
    }
}

// CORRESPONDENCE.

/**
 * Get mailer instance, enable buffering, flush buffer or disable buffering.
 *
 * @param string $action 'get', 'buffer', 'close' or 'flush'
 * @return moodle_phpmailer|null mailer instance if 'get' used or nothing
 */
function get_mailer($action='get') {
    global $CFG;

    /** @var moodle_phpmailer $mailer */
    static $mailer  = null;
    static $counter = 0;

    if (!isset($CFG->smtpmaxbulk)) {
        $CFG->smtpmaxbulk = 1;
    }

    if ($action == 'get') {
        $prevkeepalive = false;

        if (isset($mailer) and $mailer->Mailer == 'smtp') {
            if ($counter < $CFG->smtpmaxbulk and !$mailer->isError()) {
                $counter++;
                // Reset the mailer.
                $mailer->Priority         = 3;
                $mailer->CharSet          = 'UTF-8'; // Our default.
                $mailer->ContentType      = "text/plain";
                $mailer->Encoding         = "8bit";
                $mailer->From             = "root@localhost";
                $mailer->FromName         = "Root User";
                $mailer->Sender           = "";
                $mailer->Subject          = "";
                $mailer->Body             = "";
                $mailer->AltBody          = "";
                $mailer->ConfirmReadingTo = "";

                $mailer->clearAllRecipients();
                $mailer->clearReplyTos();
                $mailer->clearAttachments();
                $mailer->clearCustomHeaders();
                return $mailer;
            }

            $prevkeepalive = $mailer->SMTPKeepAlive;
            get_mailer('flush');
        }

        require_once($CFG->libdir.'/phpmailer/moodle_phpmailer.php');
        $mailer = new moodle_phpmailer();

        $counter = 1;

        if ($CFG->smtphosts == 'qmail') {
            // Use Qmail system.
            $mailer->isQmail();

        } else if (empty($CFG->smtphosts)) {
            // Use PHP mail() = sendmail.
            $mailer->isMail();

        } else {
            // Use SMTP directly.
            $mailer->isSMTP();
            if (!empty($CFG->debugsmtp)) {
                $mailer->SMTPDebug = true;
            }
            // Specify main and backup servers.
            $mailer->Host          = $CFG->smtphosts;
            // Specify secure connection protocol.
            $mailer->SMTPSecure    = $CFG->smtpsecure;
            // Use previous keepalive.
            $mailer->SMTPKeepAlive = $prevkeepalive;

            if ($CFG->smtpuser) {
                // Use SMTP authentication.
                $mailer->SMTPAuth = true;
                $mailer->Username = $CFG->smtpuser;
                $mailer->Password = $CFG->smtppass;
            }
        }

        return $mailer;
    }

    $nothing = null;

    // Keep smtp session open after sending.
    if ($action == 'buffer') {
        if (!empty($CFG->smtpmaxbulk)) {
            get_mailer('flush');
            $m = get_mailer();
            if ($m->Mailer == 'smtp') {
                $m->SMTPKeepAlive = true;
            }
        }
        return $nothing;
    }

    // Close smtp session, but continue buffering.
    if ($action == 'flush') {
        if (isset($mailer) and $mailer->Mailer == 'smtp') {
            if (!empty($mailer->SMTPDebug)) {
                echo '<pre>'."\n";
            }
            $mailer->SmtpClose();
            if (!empty($mailer->SMTPDebug)) {
                echo '</pre>';
            }
        }
        return $nothing;
    }

    // Close smtp session, do not buffer anymore.
    if ($action == 'close') {
        if (isset($mailer) and $mailer->Mailer == 'smtp') {
            get_mailer('flush');
            $mailer->SMTPKeepAlive = false;
        }
        $mailer = null; // Better force new instance.
        return $nothing;
    }
}

/**
 * Send an email to a specified user
 *
 * @param stdClass $user  A {@link $USER} object
 * @param stdClass $from A {@link $USER} object
 * @param string $subject plain text subject line of the email
 * @param string $messagetext plain text version of the message
 * @param string $messagehtml complete html version of the message (optional)
 * @param string $attachment a file on the filesystem, relative to $CFG->dataroot
 * @param string $attachname the name of the file (extension indicates MIME)
 * @param bool $usetrueaddress determines whether $from email address should
 *          be sent out. Will be overruled by user profile setting for maildisplay
 * @param string $replyto Email address to reply to
 * @param string $replytoname Name of reply to recipient
 * @param int $wordwrapwidth custom word wrap width, default 79
 * @return bool Returns true if mail was sent OK and false if there was an error.
 */
function email_to_user($user, $from, $subject, $messagetext, $messagehtml = '', $attachment = '', $attachname = '',
                       $usetrueaddress = true, $replyto = '', $replytoname = '', $wordwrapwidth = 79) {

    global $CFG;

    if (empty($user) || empty($user->email)) {
        $nulluser = 'User is null or has no email';
        error_log($nulluser);
        if (CLI_SCRIPT) {
            mtrace('Error: lib/moodlelib.php email_to_user(): '.$nulluser);
        }
        return false;
    }

    if (!empty($user->deleted)) {
        // Do not mail deleted users.
        $userdeleted = 'User is deleted';
        error_log($userdeleted);
        if (CLI_SCRIPT) {
            mtrace('Error: lib/moodlelib.php email_to_user(): '.$userdeleted);
        }
        return false;
    }

    if (!empty($CFG->noemailever)) {
        // Hidden setting for development sites, set in config.php if needed.
        $noemail = 'Not sending email due to noemailever config setting';
        error_log($noemail);
        if (CLI_SCRIPT) {
            mtrace('Error: lib/moodlelib.php email_to_user(): '.$noemail);
        }
        return true;
    }

    if (!empty($CFG->divertallemailsto)) {
        $subject = "[DIVERTED {$user->email}] $subject";
        $user = clone($user);
        $user->email = $CFG->divertallemailsto;
    }

    // Skip mail to suspended users.
    if ((isset($user->auth) && $user->auth=='nologin') or (isset($user->suspended) && $user->suspended)) {
        return true;
    }

    if (!validate_email($user->email)) {
        // We can not send emails to invalid addresses - it might create security issue or confuse the mailer.
        $invalidemail = "User $user->id (".fullname($user).") email ($user->email) is invalid! Not sending.";
        error_log($invalidemail);
        if (CLI_SCRIPT) {
            mtrace('Error: lib/moodlelib.php email_to_user(): '.$invalidemail);
        }
        return false;
    }

    if (over_bounce_threshold($user)) {
        $bouncemsg = "User $user->id (".fullname($user).") is over bounce threshold! Not sending.";
        error_log($bouncemsg);
        if (CLI_SCRIPT) {
            mtrace('Error: lib/moodlelib.php email_to_user(): '.$bouncemsg);
        }
        return false;
    }

    // If the user is a remote mnet user, parse the email text for URL to the
    // wwwroot and modify the url to direct the user's browser to login at their
    // home site (identity provider - idp) before hitting the link itself.
    if (is_mnet_remote_user($user)) {
        require_once($CFG->dirroot.'/mnet/lib.php');

        $jumpurl = mnet_get_idp_jump_url($user);
        $callback = partial('mnet_sso_apply_indirection', $jumpurl);

        $messagetext = preg_replace_callback("%($CFG->wwwroot[^[:space:]]*)%",
                $callback,
                $messagetext);
        $messagehtml = preg_replace_callback("%href=[\"'`]($CFG->wwwroot[\w_:\?=#&@/;.~-]*)[\"'`]%",
                $callback,
                $messagehtml);
    }
    $mail = get_mailer();

    if (!empty($mail->SMTPDebug)) {
        echo '<pre>' . "\n";
    }

    $temprecipients = array();
    $tempreplyto = array();

    $supportuser = core_user::get_support_user();

    // Make up an email address for handling bounces.
    if (!empty($CFG->handlebounces)) {
        $modargs = 'B'.base64_encode(pack('V', $user->id)).substr(md5($user->email), 0, 16);
        $mail->Sender = generate_email_processing_address(0, $modargs);
    } else {
        $mail->Sender = $supportuser->email;
    }

    if (is_string($from)) { // So we can pass whatever we want if there is need.
        $mail->From     = $CFG->noreplyaddress;
        $mail->FromName = $from;
    } else if ($usetrueaddress and $from->maildisplay) {
        $mail->From     = $from->email;
        $mail->FromName = fullname($from);
    } else {
        $mail->From     = $CFG->noreplyaddress;
        $mail->FromName = fullname($from);
        if (empty($replyto)) {
            $tempreplyto[] = array($CFG->noreplyaddress, get_string('noreplyname'));
        }
    }

    if (!empty($replyto)) {
        $tempreplyto[] = array($replyto, $replytoname);
    }

    $mail->Subject = substr($subject, 0, 900);

    $temprecipients[] = array($user->email, fullname($user));

    // Set word wrap.
    $mail->WordWrap = $wordwrapwidth;

    if (!empty($from->customheaders)) {
        // Add custom headers.
        if (is_array($from->customheaders)) {
            foreach ($from->customheaders as $customheader) {
                $mail->addCustomHeader($customheader);
            }
        } else {
            $mail->addCustomHeader($from->customheaders);
        }
    }

    if (!empty($from->priority)) {
        $mail->Priority = $from->priority;
    }

    if ($messagehtml && !empty($user->mailformat) && $user->mailformat == 1) {
        // Don't ever send HTML to users who don't want it.
        $mail->isHTML(true);
        $mail->Encoding = 'quoted-printable';
        $mail->Body    =  $messagehtml;
        $mail->AltBody =  "\n$messagetext\n";
    } else {
        $mail->IsHTML(false);
        $mail->Body =  "\n$messagetext\n";
    }

    if ($attachment && $attachname) {
        if (preg_match( "~\\.\\.~" , $attachment )) {
            // Security check for ".." in dir path.
            $temprecipients[] = array($supportuser->email, fullname($supportuser, true));
            $mail->addStringAttachment('Error in attachment.  User attempted to attach a filename with a unsafe name.', 'error.txt', '8bit', 'text/plain');
        } else {
            require_once($CFG->libdir.'/filelib.php');
            $mimetype = mimeinfo('type', $attachname);
            $mail->addAttachment($CFG->dataroot .'/'. $attachment, $attachname, 'base64', $mimetype);
        }
    }

    // Check if the email should be sent in an other charset then the default UTF-8.
    if ((!empty($CFG->sitemailcharset) || !empty($CFG->allowusermailcharset))) {

        // Use the defined site mail charset or eventually the one preferred by the recipient.
        $charset = $CFG->sitemailcharset;
        if (!empty($CFG->allowusermailcharset)) {
            if ($useremailcharset = get_user_preferences('mailcharset', '0', $user->id)) {
                $charset = $useremailcharset;
            }
        }

        // Convert all the necessary strings if the charset is supported.
        $charsets = get_list_of_charsets();
        unset($charsets['UTF-8']);
        if (in_array($charset, $charsets)) {
            $mail->CharSet  = $charset;
            $mail->FromName = core_text::convert($mail->FromName, 'utf-8', strtolower($charset));
            $mail->Subject  = core_text::convert($mail->Subject, 'utf-8', strtolower($charset));
            $mail->Body     = core_text::convert($mail->Body, 'utf-8', strtolower($charset));
            $mail->AltBody  = core_text::convert($mail->AltBody, 'utf-8', strtolower($charset));

            foreach ($temprecipients as $key => $values) {
                $temprecipients[$key][1] = core_text::convert($values[1], 'utf-8', strtolower($charset));
            }
            foreach ($tempreplyto as $key => $values) {
                $tempreplyto[$key][1] = core_text::convert($values[1], 'utf-8', strtolower($charset));
            }
        }
    }

    foreach ($temprecipients as $values) {
        $mail->addAddress($values[0], $values[1]);
    }
    foreach ($tempreplyto as $values) {
        $mail->addReplyTo($values[0], $values[1]);
    }

    if ($mail->send()) {
        set_send_count($user);
        if (!empty($mail->SMTPDebug)) {
            echo '</pre>';
        }
        return true;
    } else {
        add_to_log(SITEID, 'library', 'mailer', qualified_me(), 'ERROR: '. $mail->ErrorInfo);
        if (CLI_SCRIPT) {
            mtrace('Error: lib/moodlelib.php email_to_user(): '.$mail->ErrorInfo);
        }
        if (!empty($mail->SMTPDebug)) {
            echo '</pre>';
        }
        return false;
    }
}

/**
 * Generate a signoff for emails based on support settings
 *
 * @return string
 */
function generate_email_signoff() {
    global $CFG;

    $signoff = "\n";
    if (!empty($CFG->supportname)) {
        $signoff .= $CFG->supportname."\n";
    }
    if (!empty($CFG->supportemail)) {
        $signoff .= $CFG->supportemail."\n";
    }
    if (!empty($CFG->supportpage)) {
        $signoff .= $CFG->supportpage."\n";
    }
    return $signoff;
}

/**
 * Sets specified user's password and send the new password to the user via email.
 *
 * @param stdClass $user A {@link $USER} object
 * @param bool $fasthash If true, use a low cost factor when generating the hash for speed.
 * @return bool|string Returns "true" if mail was sent OK and "false" if there was an error
 */
function setnew_password_and_mail($user, $fasthash = false) {
    global $CFG, $DB;

    // We try to send the mail in language the user understands,
    // unfortunately the filter_string() does not support alternative langs yet
    // so multilang will not work properly for site->fullname.
    $lang = empty($user->lang) ? $CFG->lang : $user->lang;

    $site  = get_site();

    $supportuser = core_user::get_support_user();

    $newpassword = generate_password();

    $hashedpassword = hash_internal_user_password($newpassword, $fasthash);
    $DB->set_field('user', 'password', $hashedpassword, array('id' => $user->id));

    $a = new stdClass();
    $a->firstname   = fullname($user, true);
    $a->sitename    = format_string($site->fullname);
    $a->username    = $user->username;
    $a->newpassword = $newpassword;
    $a->link        = $CFG->wwwroot .'/login/';
    $a->signoff     = generate_email_signoff();

    $message = (string)new lang_string('newusernewpasswordtext', '', $a, $lang);

    $subject = format_string($site->fullname) .': '. (string)new lang_string('newusernewpasswordsubj', '', $a, $lang);

    // Directly email rather than using the messaging system to ensure its not routed to a popup or jabber.
    return email_to_user($user, $supportuser, $subject, $message);

}

/**
 * Resets specified user's password and send the new password to the user via email.
 *
 * @param stdClass $user A {@link $USER} object
 * @return bool Returns true if mail was sent OK and false if there was an error.
 */
function reset_password_and_mail($user) {
    global $CFG;

    $site  = get_site();
    $supportuser = core_user::get_support_user();

    $userauth = get_auth_plugin($user->auth);
    if (!$userauth->can_reset_password() or !is_enabled_auth($user->auth)) {
        trigger_error("Attempt to reset user password for user $user->username with Auth $user->auth.");
        return false;
    }

    $newpassword = generate_password();

    if (!$userauth->user_update_password($user, $newpassword)) {
        print_error("cannotsetpassword");
    }

    $a = new stdClass();
    $a->firstname   = $user->firstname;
    $a->lastname    = $user->lastname;
    $a->sitename    = format_string($site->fullname);
    $a->username    = $user->username;
    $a->newpassword = $newpassword;
    $a->link        = $CFG->httpswwwroot .'/login/change_password.php';
    $a->signoff     = generate_email_signoff();

    $message = get_string('newpasswordtext', '', $a);

    $subject  = format_string($site->fullname) .': '. get_string('changedpassword');

    unset_user_preference('create_password', $user); // Prevent cron from generating the password.

    // Directly email rather than using the messaging system to ensure its not routed to a popup or jabber.
    return email_to_user($user, $supportuser, $subject, $message);
}

/**
 * Send email to specified user with confirmation text and activation link.
 *
 * @param stdClass $user A {@link $USER} object
 * @return bool Returns true if mail was sent OK and false if there was an error.
 */
function send_confirmation_email($user) {
    global $CFG;

    $site = get_site();
    $supportuser = core_user::get_support_user();

    $data = new stdClass();
    $data->firstname = fullname($user);
    $data->sitename  = format_string($site->fullname);
    $data->admin     = generate_email_signoff();

    $subject = get_string('emailconfirmationsubject', '', format_string($site->fullname));

    $username = urlencode($user->username);
    $username = str_replace('.', '%2E', $username); // Prevent problems with trailing dots.
    $data->link  = $CFG->wwwroot .'/login/confirm.php?data='. $user->secret .'/'. $username;
    $message     = get_string('emailconfirmation', '', $data);
    $messagehtml = text_to_html(get_string('emailconfirmation', '', $data), false, false, true);

    $user->mailformat = 1;  // Always send HTML version as well.

    // Directly email rather than using the messaging system to ensure its not routed to a popup or jabber.
    return email_to_user($user, $supportuser, $subject, $message, $messagehtml);
}

/**
 * Sends a password change confirmation email.
 *
 * @param stdClass $user A {@link $USER} object
 * @return bool Returns true if mail was sent OK and false if there was an error.
 */
function send_password_change_confirmation_email($user) {
    global $CFG;

    $site = get_site();
    $supportuser = core_user::get_support_user();

    $data = new stdClass();
    $data->firstname = $user->firstname;
    $data->lastname  = $user->lastname;
    $data->sitename  = format_string($site->fullname);
    $data->link      = $CFG->httpswwwroot .'/login/forgot_password.php?p='. $user->secret .'&s='. urlencode($user->username);
    $data->admin     = generate_email_signoff();

    $message = get_string('emailpasswordconfirmation', '', $data);
    $subject = get_string('emailpasswordconfirmationsubject', '', format_string($site->fullname));

    // Directly email rather than using the messaging system to ensure its not routed to a popup or jabber.
    return email_to_user($user, $supportuser, $subject, $message);

}

/**
 * Sends an email containinginformation on how to change your password.
 *
 * @param stdClass $user A {@link $USER} object
 * @return bool Returns true if mail was sent OK and false if there was an error.
 */
function send_password_change_info($user) {
    global $CFG;

    $site = get_site();
    $supportuser = core_user::get_support_user();
    $systemcontext = context_system::instance();

    $data = new stdClass();
    $data->firstname = $user->firstname;
    $data->lastname  = $user->lastname;
    $data->sitename  = format_string($site->fullname);
    $data->admin     = generate_email_signoff();

    $userauth = get_auth_plugin($user->auth);

    if (!is_enabled_auth($user->auth) or $user->auth == 'nologin') {
        $message = get_string('emailpasswordchangeinfodisabled', '', $data);
        $subject = get_string('emailpasswordchangeinfosubject', '', format_string($site->fullname));
        // Directly email rather than using the messaging system to ensure its not routed to a popup or jabber.
        return email_to_user($user, $supportuser, $subject, $message);
    }

    if ($userauth->can_change_password() and $userauth->change_password_url()) {
        // We have some external url for password changing.
        $data->link .= $userauth->change_password_url();

    } else {
        // No way to change password, sorry.
        $data->link = '';
    }

    if (!empty($data->link) and has_capability('moodle/user:changeownpassword', $systemcontext, $user->id)) {
        $message = get_string('emailpasswordchangeinfo', '', $data);
        $subject = get_string('emailpasswordchangeinfosubject', '', format_string($site->fullname));
    } else {
        $message = get_string('emailpasswordchangeinfofail', '', $data);
        $subject = get_string('emailpasswordchangeinfosubject', '', format_string($site->fullname));
    }

    // Directly email rather than using the messaging system to ensure its not routed to a popup or jabber.
    return email_to_user($user, $supportuser, $subject, $message);

}

/**
 * Check that an email is allowed.  It returns an error message if there was a problem.
 *
 * @param string $email Content of email
 * @return string|false
 */
function email_is_not_allowed($email) {
    global $CFG;

    if (!empty($CFG->allowemailaddresses)) {
        $allowed = explode(' ', $CFG->allowemailaddresses);
        foreach ($allowed as $allowedpattern) {
            $allowedpattern = trim($allowedpattern);
            if (!$allowedpattern) {
                continue;
            }
            if (strpos($allowedpattern, '.') === 0) {
                if (strpos(strrev($email), strrev($allowedpattern)) === 0) {
                    // Subdomains are in a form ".example.com" - matches "xxx@anything.example.com".
                    return false;
                }

            } else if (strpos(strrev($email), strrev('@'.$allowedpattern)) === 0) {
                return false;
            }
        }
        return get_string('emailonlyallowed', '', $CFG->allowemailaddresses);

    } else if (!empty($CFG->denyemailaddresses)) {
        $denied = explode(' ', $CFG->denyemailaddresses);
        foreach ($denied as $deniedpattern) {
            $deniedpattern = trim($deniedpattern);
            if (!$deniedpattern) {
                continue;
            }
            if (strpos($deniedpattern, '.') === 0) {
                if (strpos(strrev($email), strrev($deniedpattern)) === 0) {
                    // Subdomains are in a form ".example.com" - matches "xxx@anything.example.com".
                    return get_string('emailnotallowed', '', $CFG->denyemailaddresses);
                }

            } else if (strpos(strrev($email), strrev('@'.$deniedpattern)) === 0) {
                return get_string('emailnotallowed', '', $CFG->denyemailaddresses);
            }
        }
    }

    return false;
}

// FILE HANDLING.

/**
 * Returns local file storage instance
 *
 * @return file_storage
 */
function get_file_storage() {
    global $CFG;

    static $fs = null;

    if ($fs) {
        return $fs;
    }

    require_once("$CFG->libdir/filelib.php");

    if (isset($CFG->filedir)) {
        $filedir = $CFG->filedir;
    } else {
        $filedir = $CFG->dataroot.'/filedir';
    }

    if (isset($CFG->trashdir)) {
        $trashdirdir = $CFG->trashdir;
    } else {
        $trashdirdir = $CFG->dataroot.'/trashdir';
    }

    $fs = new file_storage($filedir, $trashdirdir, "$CFG->tempdir/filestorage", $CFG->directorypermissions, $CFG->filepermissions);

    return $fs;
}

/**
 * Returns local file storage instance
 *
 * @return file_browser
 */
function get_file_browser() {
    global $CFG;

    static $fb = null;

    if ($fb) {
        return $fb;
    }

    require_once("$CFG->libdir/filelib.php");

    $fb = new file_browser();

    return $fb;
}

/**
 * Returns file packer
 *
 * @param string $mimetype default application/zip
 * @return file_packer
 */
function get_file_packer($mimetype='application/zip') {
    global $CFG;

    static $fp = array();

    if (isset($fp[$mimetype])) {
        return $fp[$mimetype];
    }

    switch ($mimetype) {
        case 'application/zip':
        case 'application/vnd.moodle.backup':
        case 'application/vnd.moodle.profiling':
            $classname = 'zip_packer';
            break;
        case 'application/x-tar':
            // One day we hope to support tar - for the time being it is a pipe dream.
        default:
            return false;
    }

    require_once("$CFG->libdir/filestorage/$classname.php");
    $fp[$mimetype] = new $classname();

    return $fp[$mimetype];
}

/**
 * Returns current name of file on disk if it exists.
 *
 * @param string $newfile File to be verified
 * @return string Current name of file on disk if true
 */
function valid_uploaded_file($newfile) {
    if (empty($newfile)) {
        return '';
    }
    if (is_uploaded_file($newfile['tmp_name']) and $newfile['size'] > 0) {
        return $newfile['tmp_name'];
    } else {
        return '';
    }
}

/**
 * Returns the maximum size for uploading files.
 *
 * There are seven possible upload limits:
 * 1. in Apache using LimitRequestBody (no way of checking or changing this)
 * 2. in php.ini for 'upload_max_filesize' (can not be changed inside PHP)
 * 3. in .htaccess for 'upload_max_filesize' (can not be changed inside PHP)
 * 4. in php.ini for 'post_max_size' (can not be changed inside PHP)
 * 5. by the Moodle admin in $CFG->maxbytes
 * 6. by the teacher in the current course $course->maxbytes
 * 7. by the teacher for the current module, eg $assignment->maxbytes
 *
 * These last two are passed to this function as arguments (in bytes).
 * Anything defined as 0 is ignored.
 * The smallest of all the non-zero numbers is returned.
 *
 * @todo Finish documenting this function
 *
 * @param int $sitebytes Set maximum size
 * @param int $coursebytes Current course $course->maxbytes (in bytes)
 * @param int $modulebytes Current module ->maxbytes (in bytes)
 * @return int The maximum size for uploading files.
 */
function get_max_upload_file_size($sitebytes=0, $coursebytes=0, $modulebytes=0) {

    if (! $filesize = ini_get('upload_max_filesize')) {
        $filesize = '5M';
    }
    $minimumsize = get_real_size($filesize);

    if ($postsize = ini_get('post_max_size')) {
        $postsize = get_real_size($postsize);
        if ($postsize < $minimumsize) {
            $minimumsize = $postsize;
        }
    }

    if (($sitebytes > 0) and ($sitebytes < $minimumsize)) {
        $minimumsize = $sitebytes;
    }

    if (($coursebytes > 0) and ($coursebytes < $minimumsize)) {
        $minimumsize = $coursebytes;
    }

    if (($modulebytes > 0) and ($modulebytes < $minimumsize)) {
        $minimumsize = $modulebytes;
    }

    return $minimumsize;
}

/**
 * Returns the maximum size for uploading files for the current user
 *
 * This function takes in account {@link get_max_upload_file_size()} the user's capabilities
 *
 * @param context $context The context in which to check user capabilities
 * @param int $sitebytes Set maximum size
 * @param int $coursebytes Current course $course->maxbytes (in bytes)
 * @param int $modulebytes Current module ->maxbytes (in bytes)
 * @param stdClass $user The user
 * @return int The maximum size for uploading files.
 */
function get_user_max_upload_file_size($context, $sitebytes = 0, $coursebytes = 0, $modulebytes = 0, $user = null) {
    global $USER;

    if (empty($user)) {
        $user = $USER;
    }

    if (has_capability('moodle/course:ignorefilesizelimits', $context, $user)) {
        return USER_CAN_IGNORE_FILE_SIZE_LIMITS;
    }

    return get_max_upload_file_size($sitebytes, $coursebytes, $modulebytes);
}

/**
 * Returns an array of possible sizes in local language
 *
 * Related to {@link get_max_upload_file_size()} - this function returns an
 * array of possible sizes in an array, translated to the
 * local language.
 *
 * The list of options will go up to the minimum of $sitebytes, $coursebytes or $modulebytes.
 *
 * If $coursebytes or $sitebytes is not 0, an option will be included for "Course/Site upload limit (X)"
 * with the value set to 0. This option will be the first in the list.
 *
 * @uses SORT_NUMERIC
 * @param int $sitebytes Set maximum size
 * @param int $coursebytes Current course $course->maxbytes (in bytes)
 * @param int $modulebytes Current module ->maxbytes (in bytes)
 * @param int|array $custombytes custom upload size/s which will be added to list,
 *        Only value/s smaller then maxsize will be added to list.
 * @return array
 */
function get_max_upload_sizes($sitebytes = 0, $coursebytes = 0, $modulebytes = 0, $custombytes = null) {
    global $CFG;

    if (!$maxsize = get_max_upload_file_size($sitebytes, $coursebytes, $modulebytes)) {
        return array();
    }

    if ($sitebytes == 0) {
        // Will get the minimum of upload_max_filesize or post_max_size.
        $sitebytes = get_max_upload_file_size();
    }

    $filesize = array();
    $sizelist = array(10240, 51200, 102400, 512000, 1048576, 2097152,
                      5242880, 10485760, 20971520, 52428800, 104857600);

    // If custombytes is given and is valid then add it to the list.
    if (is_number($custombytes) and $custombytes > 0) {
        $custombytes = (int)$custombytes;
        if (!in_array($custombytes, $sizelist)) {
            $sizelist[] = $custombytes;
        }
    } else if (is_array($custombytes)) {
        $sizelist = array_unique(array_merge($sizelist, $custombytes));
    }

    // Allow maxbytes to be selected if it falls outside the above boundaries.
    if (isset($CFG->maxbytes) && !in_array(get_real_size($CFG->maxbytes), $sizelist)) {
        // Note: get_real_size() is used in order to prevent problems with invalid values.
        $sizelist[] = get_real_size($CFG->maxbytes);
    }

    foreach ($sizelist as $sizebytes) {
        if ($sizebytes < $maxsize && $sizebytes > 0) {
            $filesize[(string)intval($sizebytes)] = display_size($sizebytes);
        }
    }

    $limitlevel = '';
    $displaysize = '';
    if ($modulebytes &&
        (($modulebytes < $coursebytes || $coursebytes == 0) &&
         ($modulebytes < $sitebytes || $sitebytes == 0))) {
        $limitlevel = get_string('activity', 'core');
        $displaysize = display_size($modulebytes);
        $filesize[$modulebytes] = $displaysize; // Make sure the limit is also included in the list.

    } else if ($coursebytes && ($coursebytes < $sitebytes || $sitebytes == 0)) {
        $limitlevel = get_string('course', 'core');
        $displaysize = display_size($coursebytes);
        $filesize[$coursebytes] = $displaysize; // Make sure the limit is also included in the list.

    } else if ($sitebytes) {
        $limitlevel = get_string('site', 'core');
        $displaysize = display_size($sitebytes);
        $filesize[$sitebytes] = $displaysize; // Make sure the limit is also included in the list.
    }

    krsort($filesize, SORT_NUMERIC);
    if ($limitlevel) {
        $params = (object) array('contextname' => $limitlevel, 'displaysize' => $displaysize);
        $filesize  = array('0' => get_string('uploadlimitwithsize', 'core', $params)) + $filesize;
    }

    return $filesize;
}

/**
 * Returns an array with all the filenames in all subdirectories, relative to the given rootdir.
 *
 * If excludefiles is defined, then that file/directory is ignored
 * If getdirs is true, then (sub)directories are included in the output
 * If getfiles is true, then files are included in the output
 * (at least one of these must be true!)
 *
 * @todo Finish documenting this function. Add examples of $excludefile usage.
 *
 * @param string $rootdir A given root directory to start from
 * @param string|array $excludefiles If defined then the specified file/directory is ignored
 * @param bool $descend If true then subdirectories are recursed as well
 * @param bool $getdirs If true then (sub)directories are included in the output
 * @param bool $getfiles  If true then files are included in the output
 * @return array An array with all the filenames in all subdirectories, relative to the given rootdir
 */
function get_directory_list($rootdir, $excludefiles='', $descend=true, $getdirs=false, $getfiles=true) {

    $dirs = array();

    if (!$getdirs and !$getfiles) {   // Nothing to show.
        return $dirs;
    }

    if (!is_dir($rootdir)) {          // Must be a directory.
        return $dirs;
    }

    if (!$dir = opendir($rootdir)) {  // Can't open it for some reason.
        return $dirs;
    }

    if (!is_array($excludefiles)) {
        $excludefiles = array($excludefiles);
    }

    while (false !== ($file = readdir($dir))) {
        $firstchar = substr($file, 0, 1);
        if ($firstchar == '.' or $file == 'CVS' or in_array($file, $excludefiles)) {
            continue;
        }
        $fullfile = $rootdir .'/'. $file;
        if (filetype($fullfile) == 'dir') {
            if ($getdirs) {
                $dirs[] = $file;
            }
            if ($descend) {
                $subdirs = get_directory_list($fullfile, $excludefiles, $descend, $getdirs, $getfiles);
                foreach ($subdirs as $subdir) {
                    $dirs[] = $file .'/'. $subdir;
                }
            }
        } else if ($getfiles) {
            $dirs[] = $file;
        }
    }
    closedir($dir);

    asort($dirs);

    return $dirs;
}


/**
 * Adds up all the files in a directory and works out the size.
 *
 * @param string $rootdir  The directory to start from
 * @param string $excludefile A file to exclude when summing directory size
 * @return int The summed size of all files and subfiles within the root directory
 */
function get_directory_size($rootdir, $excludefile='') {
    global $CFG;

    // Do it this way if we can, it's much faster.
    if (!empty($CFG->pathtodu) && is_executable(trim($CFG->pathtodu))) {
        $command = trim($CFG->pathtodu).' -sk '.escapeshellarg($rootdir);
        $output = null;
        $return = null;
        exec($command, $output, $return);
        if (is_array($output)) {
            // We told it to return k.
            return get_real_size(intval($output[0]).'k');
        }
    }

    if (!is_dir($rootdir)) {
        // Must be a directory.
        return 0;
    }

    if (!$dir = @opendir($rootdir)) {
        // Can't open it for some reason.
        return 0;
    }

    $size = 0;

    while (false !== ($file = readdir($dir))) {
        $firstchar = substr($file, 0, 1);
        if ($firstchar == '.' or $file == 'CVS' or $file == $excludefile) {
            continue;
        }
        $fullfile = $rootdir .'/'. $file;
        if (filetype($fullfile) == 'dir') {
            $size += get_directory_size($fullfile, $excludefile);
        } else {
            $size += filesize($fullfile);
        }
    }
    closedir($dir);

    return $size;
}

/**
 * Converts bytes into display form
 *
 * @static string $gb Localized string for size in gigabytes
 * @static string $mb Localized string for size in megabytes
 * @static string $kb Localized string for size in kilobytes
 * @static string $b Localized string for size in bytes
 * @param int $size  The size to convert to human readable form
 * @return string
 */
function display_size($size) {

    static $gb, $mb, $kb, $b;

    if ($size === USER_CAN_IGNORE_FILE_SIZE_LIMITS) {
        return get_string('unlimited');
    }

    if (empty($gb)) {
        $gb = get_string('sizegb');
        $mb = get_string('sizemb');
        $kb = get_string('sizekb');
        $b  = get_string('sizeb');
    }

    if ($size >= 1073741824) {
        $size = round($size / 1073741824 * 10) / 10 . $gb;
    } else if ($size >= 1048576) {
        $size = round($size / 1048576 * 10) / 10 . $mb;
    } else if ($size >= 1024) {
        $size = round($size / 1024 * 10) / 10 . $kb;
    } else {
        $size = intval($size) .' '. $b; // File sizes over 2GB can not work in 32bit PHP anyway.
    }
    return $size;
}

/**
 * Cleans a given filename by removing suspicious or troublesome characters
 *
 * @see clean_param()
 * @param string $string file name
 * @return string cleaned file name
 */
function clean_filename($string) {
    return clean_param($string, PARAM_FILE);
}


// STRING TRANSLATION.

/**
 * Returns the code for the current language
 *
 * @category string
 * @return string
 */
function current_language() {
    global $CFG, $USER, $SESSION, $COURSE;

    if (!empty($COURSE->id) and $COURSE->id != SITEID and !empty($COURSE->lang)) {
        // Course language can override all other settings for this page.
        $return = $COURSE->lang;

    } else if (!empty($SESSION->lang)) {
        // Session language can override other settings.
        $return = $SESSION->lang;

    } else if (!empty($USER->lang)) {
        $return = $USER->lang;

    } else if (isset($CFG->lang)) {
        $return = $CFG->lang;

    } else {
        $return = 'en';
    }

    // Just in case this slipped in from somewhere by accident.
    $return = str_replace('_utf8', '', $return);

    return $return;
}

/**
 * Returns parent language of current active language if defined
 *
 * @category string
 * @param string $lang null means current language
 * @return string
 */
function get_parent_language($lang=null) {
    global $COURSE, $SESSION;

    // Let's hack around the current language.
    if (!empty($lang)) {
        $oldcourselang  = empty($COURSE->lang) ? '' : $COURSE->lang;
        $oldsessionlang = empty($SESSION->lang) ? '' : $SESSION->lang;
        $COURSE->lang  = '';
        $SESSION->lang = $lang;
    }

    $parentlang = get_string('parentlanguage', 'langconfig');
    if ($parentlang === 'en') {
        $parentlang = '';
    }

    // Let's hack around the current language.
    if (!empty($lang)) {
        $COURSE->lang  = $oldcourselang;
        $SESSION->lang = $oldsessionlang;
    }

    return $parentlang;
}

/**
 * Returns current string_manager instance.
 *
 * The param $forcereload is needed for CLI installer only where the string_manager instance
 * must be replaced during the install.php script life time.
 *
 * @category string
 * @param bool $forcereload shall the singleton be released and new instance created instead?
 * @return core_string_manager
 */
function get_string_manager($forcereload=false) {
    global $CFG;

    static $singleton = null;

    if ($forcereload) {
        $singleton = null;
    }
    if ($singleton === null) {
        if (empty($CFG->early_install_lang)) {

            if (empty($CFG->langlist)) {
                 $translist = array();
            } else {
                $translist = explode(',', $CFG->langlist);
            }

            $singleton = new core_string_manager_standard($CFG->langotherroot, $CFG->langlocalroot, $translist);

        } else {
            $singleton = new core_string_manager_install();
        }
    }

    return $singleton;
}

/**
 * Returns a localized string.
 *
 * Returns the translated string specified by $identifier as
 * for $module.  Uses the same format files as STphp.
 * $a is an object, string or number that can be used
 * within translation strings
 *
 * eg 'hello {$a->firstname} {$a->lastname}'
 * or 'hello {$a}'
 *
 * If you would like to directly echo the localized string use
 * the function {@link print_string()}
 *
 * Example usage of this function involves finding the string you would
 * like a local equivalent of and using its identifier and module information
 * to retrieve it.<br/>
 * If you open moodle/lang/en/moodle.php and look near line 278
 * you will find a string to prompt a user for their word for 'course'
 * <code>
 * $string['course'] = 'Course';
 * </code>
 * So if you want to display the string 'Course'
 * in any language that supports it on your site
 * you just need to use the identifier 'course'
 * <code>
 * $mystring = '<strong>'. get_string('course') .'</strong>';
 * or
 * </code>
 * If the string you want is in another file you'd take a slightly
 * different approach. Looking in moodle/lang/en/calendar.php you find
 * around line 75:
 * <code>
 * $string['typecourse'] = 'Course event';
 * </code>
 * If you want to display the string "Course event" in any language
 * supported you would use the identifier 'typecourse' and the module 'calendar'
 * (because it is in the file calendar.php):
 * <code>
 * $mystring = '<h1>'. get_string('typecourse', 'calendar') .'</h1>';
 * </code>
 *
 * As a last resort, should the identifier fail to map to a string
 * the returned string will be [[ $identifier ]]
 *
 * In Moodle 2.3 there is a new argument to this function $lazyload.
 * Setting $lazyload to true causes get_string to return a lang_string object
 * rather than the string itself. The fetching of the string is then put off until
 * the string object is first used. The object can be used by calling it's out
 * method or by casting the object to a string, either directly e.g.
 *     (string)$stringobject
 * or indirectly by using the string within another string or echoing it out e.g.
 *     echo $stringobject
 *     return "<p>{$stringobject}</p>";
 * It is worth noting that using $lazyload and attempting to use the string as an
 * array key will cause a fatal error as objects cannot be used as array keys.
 * But you should never do that anyway!
 * For more information {@link lang_string}
 *
 * @category string
 * @param string $identifier The key identifier for the localized string
 * @param string $component The module where the key identifier is stored,
 *      usually expressed as the filename in the language pack without the
 *      .php on the end but can also be written as mod/forum or grade/export/xls.
 *      If none is specified then moodle.php is used.
 * @param string|object|array $a An object, string or number that can be used
 *      within translation strings
 * @param bool $lazyload If set to true a string object is returned instead of
 *      the string itself. The string then isn't calculated until it is first used.
 * @return string The localized string.
 * @throws coding_exception
 */
function get_string($identifier, $component = '', $a = null, $lazyload = false) {
    global $CFG;

    // If the lazy load argument has been supplied return a lang_string object
    // instead.
    // We need to make sure it is true (and a bool) as you will see below there
    // used to be a forth argument at one point.
    if ($lazyload === true) {
        return new lang_string($identifier, $component, $a);
    }

    if ($CFG->debugdeveloper && clean_param($identifier, PARAM_STRINGID) === '') {
        throw new coding_exception('Invalid string identifier. The identifier cannot be empty. Please fix your get_string() call.', DEBUG_DEVELOPER);
    }

    // There is now a forth argument again, this time it is a boolean however so
    // we can still check for the old extralocations parameter.
    if (!is_bool($lazyload) && !empty($lazyload)) {
        debugging('extralocations parameter in get_string() is not supported any more, please use standard lang locations only.');
    }

    if (strpos($component, '/') !== false) {
        debugging('The module name you passed to get_string is the deprecated format ' .
                'like mod/mymod or block/myblock. The correct form looks like mymod, or block_myblock.' , DEBUG_DEVELOPER);
        $componentpath = explode('/', $component);

        switch ($componentpath[0]) {
            case 'mod':
                $component = $componentpath[1];
                break;
            case 'blocks':
            case 'block':
                $component = 'block_'.$componentpath[1];
                break;
            case 'enrol':
                $component = 'enrol_'.$componentpath[1];
                break;
            case 'format':
                $component = 'format_'.$componentpath[1];
                break;
            case 'grade':
                $component = 'grade'.$componentpath[1].'_'.$componentpath[2];
                break;
        }
    }

    $result = get_string_manager()->get_string($identifier, $component, $a);

    // Debugging feature lets you display string identifier and component.
    if (isset($CFG->debugstringids) && $CFG->debugstringids && optional_param('strings', 0, PARAM_INT)) {
        $result .= ' {' . $identifier . '/' . $component . '}';
    }
    return $result;
}

/**
 * Converts an array of strings to their localized value.
 *
 * @param array $array An array of strings
 * @param string $component The language module that these strings can be found in.
 * @return stdClass translated strings.
 */
function get_strings($array, $component = '') {
    $string = new stdClass;
    foreach ($array as $item) {
        $string->$item = get_string($item, $component);
    }
    return $string;
}

/**
 * Prints out a translated string.
 *
 * Prints out a translated string using the return value from the {@link get_string()} function.
 *
 * Example usage of this function when the string is in the moodle.php file:<br/>
 * <code>
 * echo '<strong>';
 * print_string('course');
 * echo '</strong>';
 * </code>
 *
 * Example usage of this function when the string is not in the moodle.php file:<br/>
 * <code>
 * echo '<h1>';
 * print_string('typecourse', 'calendar');
 * echo '</h1>';
 * </code>
 *
 * @category string
 * @param string $identifier The key identifier for the localized string
 * @param string $component The module where the key identifier is stored. If none is specified then moodle.php is used.
 * @param string|object|array $a An object, string or number that can be used within translation strings
 */
function print_string($identifier, $component = '', $a = null) {
    echo get_string($identifier, $component, $a);
}

/**
 * Returns a list of charset codes
 *
 * Returns a list of charset codes. It's hardcoded, so they should be added manually
 * (checking that such charset is supported by the texlib library!)
 *
 * @return array And associative array with contents in the form of charset => charset
 */
function get_list_of_charsets() {

    $charsets = array(
        'EUC-JP'     => 'EUC-JP',
        'ISO-2022-JP'=> 'ISO-2022-JP',
        'ISO-8859-1' => 'ISO-8859-1',
        'SHIFT-JIS'  => 'SHIFT-JIS',
        'GB2312'     => 'GB2312',
        'GB18030'    => 'GB18030', // GB18030 not supported by typo and mbstring.
        'UTF-8'      => 'UTF-8');

    asort($charsets);

    return $charsets;
}

/**
 * Returns a list of valid and compatible themes
 *
 * @return array
 */
function get_list_of_themes() {
    global $CFG;

    $themes = array();

    if (!empty($CFG->themelist)) {       // Use admin's list of themes.
        $themelist = explode(',', $CFG->themelist);
    } else {
        $themelist = array_keys(core_component::get_plugin_list("theme"));
    }

    foreach ($themelist as $key => $themename) {
        $theme = theme_config::load($themename);
        $themes[$themename] = $theme;
    }

    core_collator::asort_objects_by_method($themes, 'get_theme_name');

    return $themes;
}

/**
 * Returns a list of timezones in the current language
 *
 * @return array
 */
function get_list_of_timezones() {
    global $DB;

    static $timezones;

    if (!empty($timezones)) {    // This function has been called recently.
        return $timezones;
    }

    $timezones = array();

    if ($rawtimezones = $DB->get_records_sql("SELECT MAX(id), name FROM {timezone} GROUP BY name")) {
        foreach ($rawtimezones as $timezone) {
            if (!empty($timezone->name)) {
                if (get_string_manager()->string_exists(strtolower($timezone->name), 'timezones')) {
                    $timezones[$timezone->name] = get_string(strtolower($timezone->name), 'timezones');
                } else {
                    $timezones[$timezone->name] = $timezone->name;
                }
                if (substr($timezones[$timezone->name], 0, 1) == '[') {  // No translation found.
                    $timezones[$timezone->name] = $timezone->name;
                }
            }
        }
    }

    asort($timezones);

    for ($i = -13; $i <= 13; $i += .5) {
        $tzstring = 'UTC';
        if ($i < 0) {
            $timezones[sprintf("%.1f", $i)] = $tzstring . $i;
        } else if ($i > 0) {
            $timezones[sprintf("%.1f", $i)] = $tzstring . '+' . $i;
        } else {
            $timezones[sprintf("%.1f", $i)] = $tzstring;
        }
    }

    return $timezones;
}

/**
 * Factory function for emoticon_manager
 *
 * @return emoticon_manager singleton
 */
function get_emoticon_manager() {
    static $singleton = null;

    if (is_null($singleton)) {
        $singleton = new emoticon_manager();
    }

    return $singleton;
}

/**
 * Provides core support for plugins that have to deal with emoticons (like HTML editor or emoticon filter).
 *
 * Whenever this manager mentiones 'emoticon object', the following data
 * structure is expected: stdClass with properties text, imagename, imagecomponent,
 * altidentifier and altcomponent
 *
 * @see admin_setting_emoticons
 *
 * @copyright 2010 David Mudrak
 * @license   http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later
 */
class emoticon_manager {

    /**
     * Returns the currently enabled emoticons
     *
     * @return array of emoticon objects
     */
    public function get_emoticons() {
        global $CFG;

        if (empty($CFG->emoticons)) {
            return array();
        }

        $emoticons = $this->decode_stored_config($CFG->emoticons);

        if (!is_array($emoticons)) {
            // Something is wrong with the format of stored setting.
            debugging('Invalid format of emoticons setting, please resave the emoticons settings form', DEBUG_NORMAL);
            return array();
        }

        return $emoticons;
    }

    /**
     * Converts emoticon object into renderable pix_emoticon object
     *
     * @param stdClass $emoticon emoticon object
     * @param array $attributes explicit HTML attributes to set
     * @return pix_emoticon
     */
    public function prepare_renderable_emoticon(stdClass $emoticon, array $attributes = array()) {
        $stringmanager = get_string_manager();
        if ($stringmanager->string_exists($emoticon->altidentifier, $emoticon->altcomponent)) {
            $alt = get_string($emoticon->altidentifier, $emoticon->altcomponent);
        } else {
            $alt = s($emoticon->text);
        }
        return new pix_emoticon($emoticon->imagename, $alt, $emoticon->imagecomponent, $attributes);
    }

    /**
     * Encodes the array of emoticon objects into a string storable in config table
     *
     * @see self::decode_stored_config()
     * @param array $emoticons array of emtocion objects
     * @return string
     */
    public function encode_stored_config(array $emoticons) {
        return json_encode($emoticons);
    }

    /**
     * Decodes the string into an array of emoticon objects
     *
     * @see self::encode_stored_config()
     * @param string $encoded
     * @return string|null
     */
    public function decode_stored_config($encoded) {
        $decoded = json_decode($encoded);
        if (!is_array($decoded)) {
            return null;
        }
        return $decoded;
    }

    /**
     * Returns default set of emoticons supported by Moodle
     *
     * @return array of sdtClasses
     */
    public function default_emoticons() {
        return array(
            $this->prepare_emoticon_object(":-)", 's/smiley', 'smiley'),
            $this->prepare_emoticon_object(":)", 's/smiley', 'smiley'),
            $this->prepare_emoticon_object(":-D", 's/biggrin', 'biggrin'),
            $this->prepare_emoticon_object(";-)", 's/wink', 'wink'),
            $this->prepare_emoticon_object(":-/", 's/mixed', 'mixed'),
            $this->prepare_emoticon_object("V-.", 's/thoughtful', 'thoughtful'),
            $this->prepare_emoticon_object(":-P", 's/tongueout', 'tongueout'),
            $this->prepare_emoticon_object(":-p", 's/tongueout', 'tongueout'),
            $this->prepare_emoticon_object("B-)", 's/cool', 'cool'),
            $this->prepare_emoticon_object("^-)", 's/approve', 'approve'),
            $this->prepare_emoticon_object("8-)", 's/wideeyes', 'wideeyes'),
            $this->prepare_emoticon_object(":o)", 's/clown', 'clown'),
            $this->prepare_emoticon_object(":-(", 's/sad', 'sad'),
            $this->prepare_emoticon_object(":(", 's/sad', 'sad'),
            $this->prepare_emoticon_object("8-.", 's/shy', 'shy'),
            $this->prepare_emoticon_object(":-I", 's/blush', 'blush'),
            $this->prepare_emoticon_object(":-X", 's/kiss', 'kiss'),
            $this->prepare_emoticon_object("8-o", 's/surprise', 'surprise'),
            $this->prepare_emoticon_object("P-|", 's/blackeye', 'blackeye'),
            $this->prepare_emoticon_object("8-[", 's/angry', 'angry'),
            $this->prepare_emoticon_object("(grr)", 's/angry', 'angry'),
            $this->prepare_emoticon_object("xx-P", 's/dead', 'dead'),
            $this->prepare_emoticon_object("|-.", 's/sleepy', 'sleepy'),
            $this->prepare_emoticon_object("}-]", 's/evil', 'evil'),
            $this->prepare_emoticon_object("(h)", 's/heart', 'heart'),
            $this->prepare_emoticon_object("(heart)", 's/heart', 'heart'),
            $this->prepare_emoticon_object("(y)", 's/yes', 'yes', 'core'),
            $this->prepare_emoticon_object("(n)", 's/no', 'no', 'core'),
            $this->prepare_emoticon_object("(martin)", 's/martin', 'martin'),
            $this->prepare_emoticon_object("( )", 's/egg', 'egg'),
        );
    }

    /**
     * Helper method preparing the stdClass with the emoticon properties
     *
     * @param string|array $text or array of strings
     * @param string $imagename to be used by {@link pix_emoticon}
     * @param string $altidentifier alternative string identifier, null for no alt
     * @param string $altcomponent where the alternative string is defined
     * @param string $imagecomponent to be used by {@link pix_emoticon}
     * @return stdClass
     */
    protected function prepare_emoticon_object($text, $imagename, $altidentifier = null,
                                               $altcomponent = 'core_pix', $imagecomponent = 'core') {
        return (object)array(
            'text'           => $text,
            'imagename'      => $imagename,
            'imagecomponent' => $imagecomponent,
            'altidentifier'  => $altidentifier,
            'altcomponent'   => $altcomponent,
        );
    }
}

// ENCRYPTION.

/**
 * rc4encrypt
 *
 * @param string $data        Data to encrypt.
 * @return string             The now encrypted data.
 */
function rc4encrypt($data) {
    return endecrypt(get_site_identifier(), $data, '');
}

/**
 * rc4decrypt
 *
 * @param string $data        Data to decrypt.
 * @return string             The now decrypted data.
 */
function rc4decrypt($data) {
    return endecrypt(get_site_identifier(), $data, 'de');
}

/**
 * Based on a class by Mukul Sabharwal [mukulsabharwal @ yahoo.com]
 *
 * @todo Finish documenting this function
 *
 * @param string $pwd The password to use when encrypting or decrypting
 * @param string $data The data to be decrypted/encrypted
 * @param string $case Either 'de' for decrypt or '' for encrypt
 * @return string
 */
function endecrypt ($pwd, $data, $case) {

    if ($case == 'de') {
        $data = urldecode($data);
    }

    $key[] = '';
    $box[] = '';
    $pwdlength = strlen($pwd);

    for ($i = 0; $i <= 255; $i++) {
        $key[$i] = ord(substr($pwd, ($i % $pwdlength), 1));
        $box[$i] = $i;
    }

    $x = 0;

    for ($i = 0; $i <= 255; $i++) {
        $x = ($x + $box[$i] + $key[$i]) % 256;
        $tempswap = $box[$i];
        $box[$i] = $box[$x];
        $box[$x] = $tempswap;
    }

    $cipher = '';

    $a = 0;
    $j = 0;

    for ($i = 0; $i < strlen($data); $i++) {
        $a = ($a + 1) % 256;
        $j = ($j + $box[$a]) % 256;
        $temp = $box[$a];
        $box[$a] = $box[$j];
        $box[$j] = $temp;
        $k = $box[(($box[$a] + $box[$j]) % 256)];
        $cipherby = ord(substr($data, $i, 1)) ^ $k;
        $cipher .= chr($cipherby);
    }

    if ($case == 'de') {
        $cipher = urldecode(urlencode($cipher));
    } else {
        $cipher = urlencode($cipher);
    }

    return $cipher;
}

// ENVIRONMENT CHECKING.

/**
 * This method validates a plug name. It is much faster than calling clean_param.
 *
 * @param string $name a string that might be a plugin name.
 * @return bool if this string is a valid plugin name.
 */
function is_valid_plugin_name($name) {
    // This does not work for 'mod', bad luck, use any other type.
    return core_component::is_valid_plugin_name('tool', $name);
}

/**
 * Get a list of all the plugins of a given type that define a certain API function
 * in a certain file. The plugin component names and function names are returned.
 *
 * @param string $plugintype the type of plugin, e.g. 'mod' or 'report'.
 * @param string $function the part of the name of the function after the
 *      frankenstyle prefix. e.g 'hook' if you are looking for functions with
 *      names like report_courselist_hook.
 * @param string $file the name of file within the plugin that defines the
 *      function. Defaults to lib.php.
 * @return array with frankenstyle plugin names as keys (e.g. 'report_courselist', 'mod_forum')
 *      and the function names as values (e.g. 'report_courselist_hook', 'forum_hook').
 */
function get_plugin_list_with_function($plugintype, $function, $file = 'lib.php') {
    $pluginfunctions = array();
    $pluginswithfile = core_component::get_plugin_list_with_file($plugintype, $file, true);
    foreach ($pluginswithfile as $plugin => $notused) {
        $fullfunction = $plugintype . '_' . $plugin . '_' . $function;

        if (function_exists($fullfunction)) {
            // Function exists with standard name. Store, indexed by frankenstyle name of plugin.
            $pluginfunctions[$plugintype . '_' . $plugin] = $fullfunction;

        } else if ($plugintype === 'mod') {
            // For modules, we also allow plugin without full frankenstyle but just starting with the module name.
            $shortfunction = $plugin . '_' . $function;
            if (function_exists($shortfunction)) {
                $pluginfunctions[$plugintype . '_' . $plugin] = $shortfunction;
            }
        }
    }
    return $pluginfunctions;
}

/**
 * Lists plugin-like directories within specified directory
 *
 * This function was originally used for standard Moodle plugins, please use
 * new core_component::get_plugin_list() now.
 *
 * This function is used for general directory listing and backwards compatility.
 *
 * @param string $directory relative directory from root
 * @param string $exclude dir name to exclude from the list (defaults to none)
 * @param string $basedir full path to the base dir where $plugin resides (defaults to $CFG->dirroot)
 * @return array Sorted array of directory names found under the requested parameters
 */
function get_list_of_plugins($directory='mod', $exclude='', $basedir='') {
    global $CFG;

    $plugins = array();

    if (empty($basedir)) {
        $basedir = $CFG->dirroot .'/'. $directory;

    } else {
        $basedir = $basedir .'/'. $directory;
    }

    if ($CFG->debugdeveloper and empty($exclude)) {
        // Make sure devs do not use this to list normal plugins,
        // this is intended for general directories that are not plugins!

        $subtypes = core_component::get_plugin_types();
        if (in_array($basedir, $subtypes)) {
            debugging('get_list_of_plugins() should not be used to list real plugins, use core_component::get_plugin_list() instead!', DEBUG_DEVELOPER);
        }
        unset($subtypes);
    }

    if (file_exists($basedir) && filetype($basedir) == 'dir') {
        if (!$dirhandle = opendir($basedir)) {
            debugging("Directory permission error for plugin ({$directory}). Directory exists but cannot be read.", DEBUG_DEVELOPER);
            return array();
        }
        while (false !== ($dir = readdir($dirhandle))) {
            // Func: strpos is marginally but reliably faster than substr($dir, 0, 1).
            if (strpos($dir, '.') === 0 or $dir === 'CVS' or $dir === '_vti_cnf' or $dir === 'simpletest' or $dir === 'yui' or
                $dir === 'tests' or $dir === 'classes' or $dir === $exclude) {
                continue;
            }
            if (filetype($basedir .'/'. $dir) != 'dir') {
                continue;
            }
            $plugins[] = $dir;
        }
        closedir($dirhandle);
    }
    if ($plugins) {
        asort($plugins);
    }
    return $plugins;
}

/**
 * Invoke plugin's callback functions
 *
 * @param string $type plugin type e.g. 'mod'
 * @param string $name plugin name
 * @param string $feature feature name
 * @param string $action feature's action
 * @param array $params parameters of callback function, should be an array
 * @param mixed $default default value if callback function hasn't been defined, or if it retursn null.
 * @return mixed
 *
 * @todo Decide about to deprecate and drop plugin_callback() - MDL-30743
 */
function plugin_callback($type, $name, $feature, $action, $params = null, $default = null) {
    return component_callback($type . '_' . $name, $feature . '_' . $action, (array) $params, $default);
}

/**
 * Invoke component's callback functions
 *
 * @param string $component frankenstyle component name, e.g. 'mod_quiz'
 * @param string $function the rest of the function name, e.g. 'cron' will end up calling 'mod_quiz_cron'
 * @param array $params parameters of callback function
 * @param mixed $default default value if callback function hasn't been defined, or if it retursn null.
 * @return mixed
 */
function component_callback($component, $function, array $params = array(), $default = null) {

    $functionname = component_callback_exists($component, $function);

    if ($functionname) {
        // Function exists, so just return function result.
        $ret = call_user_func_array($functionname, $params);
        if (is_null($ret)) {
            return $default;
        } else {
            return $ret;
        }
    }
    return $default;
}

/**
 * Determine if a component callback exists and return the function name to call. Note that this
 * function will include the required library files so that the functioname returned can be
 * called directly.
 *
 * @param string $component frankenstyle component name, e.g. 'mod_quiz'
 * @param string $function the rest of the function name, e.g. 'cron' will end up calling 'mod_quiz_cron'
 * @return mixed Complete function name to call if the callback exists or false if it doesn't.
 * @throws coding_exception if invalid component specfied
 */
function component_callback_exists($component, $function) {
    global $CFG; // This is needed for the inclusions.

    $cleancomponent = clean_param($component, PARAM_COMPONENT);
    if (empty($cleancomponent)) {
        throw new coding_exception('Invalid component used in plugin/component_callback():' . $component);
    }
    $component = $cleancomponent;

    list($type, $name) = core_component::normalize_component($component);
    $component = $type . '_' . $name;

    $oldfunction = $name.'_'.$function;
    $function = $component.'_'.$function;

    $dir = core_component::get_component_directory($component);
    if (empty($dir)) {
        throw new coding_exception('Invalid component used in plugin/component_callback():' . $component);
    }

    // Load library and look for function.
    if (file_exists($dir.'/lib.php')) {
        require_once($dir.'/lib.php');
    }

    if (!function_exists($function) and function_exists($oldfunction)) {
        if ($type !== 'mod' and $type !== 'core') {
            debugging("Please use new function name $function instead of legacy $oldfunction", DEBUG_DEVELOPER);
        }
        $function = $oldfunction;
    }

    if (function_exists($function)) {
        return $function;
    }
    return false;
}

/**
 * Checks whether a plugin supports a specified feature.
 *
 * @param string $type Plugin type e.g. 'mod'
 * @param string $name Plugin name e.g. 'forum'
 * @param string $feature Feature code (FEATURE_xx constant)
 * @param mixed $default default value if feature support unknown
 * @return mixed Feature result (false if not supported, null if feature is unknown,
 *         otherwise usually true but may have other feature-specific value such as array)
 * @throws coding_exception
 */
function plugin_supports($type, $name, $feature, $default = null) {
    global $CFG;

    if ($type === 'mod' and $name === 'NEWMODULE') {
        // Somebody forgot to rename the module template.
        return false;
    }

    $component = clean_param($type . '_' . $name, PARAM_COMPONENT);
    if (empty($component)) {
        throw new coding_exception('Invalid component used in plugin_supports():' . $type . '_' . $name);
    }

    $function = null;

    if ($type === 'mod') {
        // We need this special case because we support subplugins in modules,
        // otherwise it would end up in infinite loop.
        if (file_exists("$CFG->dirroot/mod/$name/lib.php")) {
            include_once("$CFG->dirroot/mod/$name/lib.php");
            $function = $component.'_supports';
            if (!function_exists($function)) {
                // Legacy non-frankenstyle function name.
                $function = $name.'_supports';
            }
        }

    } else {
        if (!$path = core_component::get_plugin_directory($type, $name)) {
            // Non existent plugin type.
            return false;
        }
        if (file_exists("$path/lib.php")) {
            include_once("$path/lib.php");
            $function = $component.'_supports';
        }
    }

    if ($function and function_exists($function)) {
        $supports = $function($feature);
        if (is_null($supports)) {
            // Plugin does not know - use default.
            return $default;
        } else {
            return $supports;
        }
    }

    // Plugin does not care, so use default.
    return $default;
}

/**
 * Returns true if the current version of PHP is greater that the specified one.
 *
 * @todo Check PHP version being required here is it too low?
 *
 * @param string $version The version of php being tested.
 * @return bool
 */
function check_php_version($version='5.2.4') {
    return (version_compare(phpversion(), $version) >= 0);
}

/**
 * Determine if moodle installation requires update.
 *
 * Checks version numbers of main code and all plugins to see
 * if there are any mismatches.
 *
 * @return bool
 */
function moodle_needs_upgrading() {
    global $CFG;

    if (empty($CFG->version)) {
        return true;
    }

    // There is no need to purge plugininfo caches here because
    // these caches are not used during upgrade and they are purged after
    // every upgrade.

    if (empty($CFG->allversionshash)) {
        return true;
    }

    $hash = core_component::get_all_versions_hash();

    return ($hash !== $CFG->allversionshash);
}

/**
 * Returns the major version of this site
 *
 * Moodle version numbers consist of three numbers separated by a dot, for
 * example 1.9.11 or 2.0.2. The first two numbers, like 1.9 or 2.0, represent so
 * called major version. This function extracts the major version from either
 * $CFG->release (default) or eventually from the $release variable defined in
 * the main version.php.
 *
 * @param bool $fromdisk should the version if source code files be used
 * @return string|false the major version like '2.3', false if could not be determined
 */
function moodle_major_version($fromdisk = false) {
    global $CFG;

    if ($fromdisk) {
        $release = null;
        require($CFG->dirroot.'/version.php');
        if (empty($release)) {
            return false;
        }

    } else {
        if (empty($CFG->release)) {
            return false;
        }
        $release = $CFG->release;
    }

    if (preg_match('/^[0-9]+\.[0-9]+/', $release, $matches)) {
        return $matches[0];
    } else {
        return false;
    }
}

// MISCELLANEOUS.

/**
 * Sets the system locale
 *
 * @category string
 * @param string $locale Can be used to force a locale
 */
function moodle_setlocale($locale='') {
    global $CFG;

    static $currentlocale = ''; // Last locale caching.

    $oldlocale = $currentlocale;

    // Fetch the correct locale based on ostype.
    if ($CFG->ostype == 'WINDOWS') {
        $stringtofetch = 'localewin';
    } else {
        $stringtofetch = 'locale';
    }

    // The priority is the same as in get_string() - parameter, config, course, session, user, global language.
    if (!empty($locale)) {
        $currentlocale = $locale;
    } else if (!empty($CFG->locale)) { // Override locale for all language packs.
        $currentlocale = $CFG->locale;
    } else {
        $currentlocale = get_string($stringtofetch, 'langconfig');
    }

    // Do nothing if locale already set up.
    if ($oldlocale == $currentlocale) {
        return;
    }

    // Due to some strange BUG we cannot set the LC_TIME directly, so we fetch current values,
    // set LC_ALL and then set values again. Just wondering why we cannot set LC_ALL only??? - stronk7
    // Some day, numeric, monetary and other categories should be set too, I think. :-/.

    // Get current values.
    $monetary= setlocale (LC_MONETARY, 0);
    $numeric = setlocale (LC_NUMERIC, 0);
    $ctype   = setlocale (LC_CTYPE, 0);
    if ($CFG->ostype != 'WINDOWS') {
        $messages= setlocale (LC_MESSAGES, 0);
    }
    // Set locale to all.
    setlocale (LC_ALL, $currentlocale);
    // Set old values.
    setlocale (LC_MONETARY, $monetary);
    setlocale (LC_NUMERIC, $numeric);
    if ($CFG->ostype != 'WINDOWS') {
        setlocale (LC_MESSAGES, $messages);
    }
    if ($currentlocale == 'tr_TR' or $currentlocale == 'tr_TR.UTF-8') {
        // To workaround a well-known PHP problem with Turkish letter Ii.
        setlocale (LC_CTYPE, $ctype);
    }
}

/**
 * Count words in a string.
 *
 * Words are defined as things between whitespace.
 *
 * @category string
 * @param string $string The text to be searched for words.
 * @return int The count of words in the specified string
 */
function count_words($string) {
    $string = strip_tags($string);
    return count(preg_split("/\w\b/", $string)) - 1;
}

/**
 * Count letters in a string.
 *
 * Letters are defined as chars not in tags and different from whitespace.
 *
 * @category string
 * @param string $string The text to be searched for letters.
 * @return int The count of letters in the specified text.
 */
function count_letters($string) {
    $string = strip_tags($string); // Tags are out now.
    $string = preg_replace('/[[:space:]]*/', '', $string); // Whitespace are out now.

    return core_text::strlen($string);
}

/**
 * Generate and return a random string of the specified length.
 *
 * @param int $length The length of the string to be created.
 * @return string
 */
function random_string ($length=15) {
    $pool  = 'ABCDEFGHIJKLMNOPQRSTUVWXYZ';
    $pool .= 'abcdefghijklmnopqrstuvwxyz';
    $pool .= '0123456789';
    $poollen = strlen($pool);
    mt_srand ((double) microtime() * 1000000);
    $string = '';
    for ($i = 0; $i < $length; $i++) {
        $string .= substr($pool, (mt_rand()%($poollen)), 1);
    }
    return $string;
}

/**
 * Generate a complex random string (useful for md5 salts)
 *
 * This function is based on the above {@link random_string()} however it uses a
 * larger pool of characters and generates a string between 24 and 32 characters
 *
 * @param int $length Optional if set generates a string to exactly this length
 * @return string
 */
function complex_random_string($length=null) {
    $pool  = 'ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789';
    $pool .= '`~!@#%^&*()_+-=[];,./<>?:{} ';
    $poollen = strlen($pool);
    mt_srand ((double) microtime() * 1000000);
    if ($length===null) {
        $length = floor(rand(24, 32));
    }
    $string = '';
    for ($i = 0; $i < $length; $i++) {
        $string .= $pool[(mt_rand()%$poollen)];
    }
    return $string;
}

/**
 * Given some text (which may contain HTML) and an ideal length,
 * this function truncates the text neatly on a word boundary if possible
 *
 * @category string
 * @param string $text text to be shortened
 * @param int $ideal ideal string length
 * @param boolean $exact if false, $text will not be cut mid-word
 * @param string $ending The string to append if the passed string is truncated
 * @return string $truncate shortened string
 */
function shorten_text($text, $ideal=30, $exact = false, $ending='...') {
    // If the plain text is shorter than the maximum length, return the whole text.
    if (core_text::strlen(preg_replace('/<.*?>/', '', $text)) <= $ideal) {
        return $text;
    }

    // Splits on HTML tags. Each open/close/empty tag will be the first thing
    // and only tag in its 'line'.
    preg_match_all('/(<.+?>)?([^<>]*)/s', $text, $lines, PREG_SET_ORDER);

    $totallength = core_text::strlen($ending);
    $truncate = '';

    // This array stores information about open and close tags and their position
    // in the truncated string. Each item in the array is an object with fields
    // ->open (true if open), ->tag (tag name in lower case), and ->pos
    // (byte position in truncated text).
    $tagdetails = array();

    foreach ($lines as $linematchings) {
        // If there is any html-tag in this line, handle it and add it (uncounted) to the output.
        if (!empty($linematchings[1])) {
            // If it's an "empty element" with or without xhtml-conform closing slash (f.e. <br/>).
            if (!preg_match('/^<(\s*.+?\/\s*|\s*(img|br|input|hr|area|base|basefont|col|frame|isindex|link|meta|param)(\s.+?)?)>$/is', $linematchings[1])) {
                if (preg_match('/^<\s*\/([^\s]+?)\s*>$/s', $linematchings[1], $tagmatchings)) {
                    // Record closing tag.
                    $tagdetails[] = (object) array(
                            'open' => false,
                            'tag'  => core_text::strtolower($tagmatchings[1]),
                            'pos'  => core_text::strlen($truncate),
                        );

                } else if (preg_match('/^<\s*([^\s>!]+).*?>$/s', $linematchings[1], $tagmatchings)) {
                    // Record opening tag.
                    $tagdetails[] = (object) array(
                            'open' => true,
                            'tag'  => core_text::strtolower($tagmatchings[1]),
                            'pos'  => core_text::strlen($truncate),
                        );
                }
            }
            // Add html-tag to $truncate'd text.
            $truncate .= $linematchings[1];
        }

        // Calculate the length of the plain text part of the line; handle entities as one character.
        $contentlength = core_text::strlen(preg_replace('/&[0-9a-z]{2,8};|&#[0-9]{1,7};|&#x[0-9a-f]{1,6};/i', ' ', $linematchings[2]));
        if ($totallength + $contentlength > $ideal) {
            // The number of characters which are left.
            $left = $ideal - $totallength;
            $entitieslength = 0;
            // Search for html entities.
            if (preg_match_all('/&[0-9a-z]{2,8};|&#[0-9]{1,7};|&#x[0-9a-f]{1,6};/i', $linematchings[2], $entities, PREG_OFFSET_CAPTURE)) {
                // Calculate the real length of all entities in the legal range.
                foreach ($entities[0] as $entity) {
                    if ($entity[1]+1-$entitieslength <= $left) {
                        $left--;
                        $entitieslength += core_text::strlen($entity[0]);
                    } else {
                        // No more characters left.
                        break;
                    }
                }
            }
            $breakpos = $left + $entitieslength;

            // If the words shouldn't be cut in the middle...
            if (!$exact) {
                // Search the last occurence of a space.
                for (; $breakpos > 0; $breakpos--) {
                    if ($char = core_text::substr($linematchings[2], $breakpos, 1)) {
                        if ($char === '.' or $char === ' ') {
                            $breakpos += 1;
                            break;
                        } else if (strlen($char) > 2) {
                            // Chinese/Japanese/Korean text can be truncated at any UTF-8 character boundary.
                            $breakpos += 1;
                            break;
                        }
                    }
                }
            }
            if ($breakpos == 0) {
                // This deals with the test_shorten_text_no_spaces case.
                $breakpos = $left + $entitieslength;
            } else if ($breakpos > $left + $entitieslength) {
                // This deals with the previous for loop breaking on the first char.
                $breakpos = $left + $entitieslength;
            }

            $truncate .= core_text::substr($linematchings[2], 0, $breakpos);
            // Maximum length is reached, so get off the loop.
            break;
        } else {
            $truncate .= $linematchings[2];
            $totallength += $contentlength;
        }

        // If the maximum length is reached, get off the loop.
        if ($totallength >= $ideal) {
            break;
        }
    }

    // Add the defined ending to the text.
    $truncate .= $ending;

    // Now calculate the list of open html tags based on the truncate position.
    $opentags = array();
    foreach ($tagdetails as $taginfo) {
        if ($taginfo->open) {
            // Add tag to the beginning of $opentags list.
            array_unshift($opentags, $taginfo->tag);
        } else {
            // Can have multiple exact same open tags, close the last one.
            $pos = array_search($taginfo->tag, array_reverse($opentags, true));
            if ($pos !== false) {
                unset($opentags[$pos]);
            }
        }
    }

    // Close all unclosed html-tags.
    foreach ($opentags as $tag) {
        $truncate .= '</' . $tag . '>';
    }

    return $truncate;
}


/**
 * Given dates in seconds, how many weeks is the date from startdate
 * The first week is 1, the second 2 etc ...
 *
 * @param int $startdate Timestamp for the start date
 * @param int $thedate Timestamp for the end date
 * @return string
 */
function getweek ($startdate, $thedate) {
    if ($thedate < $startdate) {
        return 0;
    }

    return floor(($thedate - $startdate) / WEEKSECS) + 1;
}

/**
 * Returns a randomly generated password of length $maxlen.  inspired by
 *
 * {@link http://www.phpbuilder.com/columns/jesus19990502.php3} and
 * {@link http://es2.php.net/manual/en/function.str-shuffle.php#73254}
 *
 * @param int $maxlen  The maximum size of the password being generated.
 * @return string
 */
function generate_password($maxlen=10) {
    global $CFG;

    if (empty($CFG->passwordpolicy)) {
        $fillers = PASSWORD_DIGITS;
        $wordlist = file($CFG->wordlist);
        $word1 = trim($wordlist[rand(0, count($wordlist) - 1)]);
        $word2 = trim($wordlist[rand(0, count($wordlist) - 1)]);
        $filler1 = $fillers[rand(0, strlen($fillers) - 1)];
        $password = $word1 . $filler1 . $word2;
    } else {
        $minlen = !empty($CFG->minpasswordlength) ? $CFG->minpasswordlength : 0;
        $digits = $CFG->minpassworddigits;
        $lower = $CFG->minpasswordlower;
        $upper = $CFG->minpasswordupper;
        $nonalphanum = $CFG->minpasswordnonalphanum;
        $total = $lower + $upper + $digits + $nonalphanum;
        // Var minlength should be the greater one of the two ( $minlen and $total ).
        $minlen = $minlen < $total ? $total : $minlen;
        // Var maxlen can never be smaller than minlen.
        $maxlen = $minlen > $maxlen ? $minlen : $maxlen;
        $additional = $maxlen - $total;

        // Make sure we have enough characters to fulfill
        // complexity requirements.
        $passworddigits = PASSWORD_DIGITS;
        while ($digits > strlen($passworddigits)) {
            $passworddigits .= PASSWORD_DIGITS;
        }
        $passwordlower = PASSWORD_LOWER;
        while ($lower > strlen($passwordlower)) {
            $passwordlower .= PASSWORD_LOWER;
        }
        $passwordupper = PASSWORD_UPPER;
        while ($upper > strlen($passwordupper)) {
            $passwordupper .= PASSWORD_UPPER;
        }
        $passwordnonalphanum = PASSWORD_NONALPHANUM;
        while ($nonalphanum > strlen($passwordnonalphanum)) {
            $passwordnonalphanum .= PASSWORD_NONALPHANUM;
        }

        // Now mix and shuffle it all.
        $password = str_shuffle (substr(str_shuffle ($passwordlower), 0, $lower) .
                                 substr(str_shuffle ($passwordupper), 0, $upper) .
                                 substr(str_shuffle ($passworddigits), 0, $digits) .
                                 substr(str_shuffle ($passwordnonalphanum), 0 , $nonalphanum) .
                                 substr(str_shuffle ($passwordlower .
                                                     $passwordupper .
                                                     $passworddigits .
                                                     $passwordnonalphanum), 0 , $additional));
    }

    return substr ($password, 0, $maxlen);
}

/**
 * Given a float, prints it nicely.
 * Localized floats must not be used in calculations!
 *
 * The stripzeros feature is intended for making numbers look nicer in small
 * areas where it is not necessary to indicate the degree of accuracy by showing
 * ending zeros. If you turn it on with $decimalpoints set to 3, for example,
 * then it will display '5.4' instead of '5.400' or '5' instead of '5.000'.
 *
 * @param float $float The float to print
 * @param int $decimalpoints The number of decimal places to print.
 * @param bool $localized use localized decimal separator
 * @param bool $stripzeros If true, removes final zeros after decimal point
 * @return string locale float
 */
function format_float($float, $decimalpoints=1, $localized=true, $stripzeros=false) {
    if (is_null($float)) {
        return '';
    }
    if ($localized) {
        $separator = get_string('decsep', 'langconfig');
    } else {
        $separator = '.';
    }
    $result = number_format($float, $decimalpoints, $separator, '');
    if ($stripzeros) {
        // Remove zeros and final dot if not needed.
        $result = preg_replace('~(' . preg_quote($separator) . ')?0+$~', '', $result);
    }
    return $result;
}

/**
 * Converts locale specific floating point/comma number back to standard PHP float value
 * Do NOT try to do any math operations before this conversion on any user submitted floats!
 *
 * @param string $localefloat locale aware float representation
 * @param bool $strict If true, then check the input and return false if it is not a valid number.
 * @return mixed float|bool - false or the parsed float.
 */
function unformat_float($localefloat, $strict = false) {
    $localefloat = trim($localefloat);

    if ($localefloat == '') {
        return null;
    }

    $localefloat = str_replace(' ', '', $localefloat); // No spaces - those might be used as thousand separators.
    $localefloat = str_replace(get_string('decsep', 'langconfig'), '.', $localefloat);

    if ($strict && !is_numeric($localefloat)) {
        return false;
    }

    return (float)$localefloat;
}

/**
 * Given a simple array, this shuffles it up just like shuffle()
 * Unlike PHP's shuffle() this function works on any machine.
 *
 * @param array $array The array to be rearranged
 * @return array
 */
function swapshuffle($array) {

    srand ((double) microtime() * 10000000);
    $last = count($array) - 1;
    for ($i = 0; $i <= $last; $i++) {
        $from = rand(0, $last);
        $curr = $array[$i];
        $array[$i] = $array[$from];
        $array[$from] = $curr;
    }
    return $array;
}

/**
 * Like {@link swapshuffle()}, but works on associative arrays
 *
 * @param array $array The associative array to be rearranged
 * @return array
 */
function swapshuffle_assoc($array) {

    $newarray = array();
    $newkeys = swapshuffle(array_keys($array));

    foreach ($newkeys as $newkey) {
        $newarray[$newkey] = $array[$newkey];
    }
    return $newarray;
}

/**
 * Given an arbitrary array, and a number of draws,
 * this function returns an array with that amount
 * of items.  The indexes are retained.
 *
 * @todo Finish documenting this function
 *
 * @param array $array
 * @param int $draws
 * @return array
 */
function draw_rand_array($array, $draws) {
    srand ((double) microtime() * 10000000);

    $return = array();

    $last = count($array);

    if ($draws > $last) {
        $draws = $last;
    }

    while ($draws > 0) {
        $last--;

        $keys = array_keys($array);
        $rand = rand(0, $last);

        $return[$keys[$rand]] = $array[$keys[$rand]];
        unset($array[$keys[$rand]]);

        $draws--;
    }

    return $return;
}

/**
 * Calculate the difference between two microtimes
 *
 * @param string $a The first Microtime
 * @param string $b The second Microtime
 * @return string
 */
function microtime_diff($a, $b) {
    list($adec, $asec) = explode(' ', $a);
    list($bdec, $bsec) = explode(' ', $b);
    return $bsec - $asec + $bdec - $adec;
}

/**
 * Given a list (eg a,b,c,d,e) this function returns
 * an array of 1->a, 2->b, 3->c etc
 *
 * @param string $list The string to explode into array bits
 * @param string $separator The separator used within the list string
 * @return array The now assembled array
 */
function make_menu_from_list($list, $separator=',') {

    $array = array_reverse(explode($separator, $list), true);
    foreach ($array as $key => $item) {
        $outarray[$key+1] = trim($item);
    }
    return $outarray;
}

/**
 * Creates an array that represents all the current grades that
 * can be chosen using the given grading type.
 *
 * Negative numbers
 * are scales, zero is no grade, and positive numbers are maximum
 * grades.
 *
 * @todo Finish documenting this function or better deprecated this completely!
 *
 * @param int $gradingtype
 * @return array
 */
function make_grades_menu($gradingtype) {
    global $DB;

    $grades = array();
    if ($gradingtype < 0) {
        if ($scale = $DB->get_record('scale', array('id'=> (-$gradingtype)))) {
            return make_menu_from_list($scale->scale);
        }
    } else if ($gradingtype > 0) {
        for ($i=$gradingtype; $i>=0; $i--) {
            $grades[$i] = $i .' / '. $gradingtype;
        }
        return $grades;
    }
    return $grades;
}

/**
 * This function returns the number of activities using the given scale in the given course.
 *
 * @param int $courseid The course ID to check.
 * @param int $scaleid The scale ID to check
 * @return int
 */
function course_scale_used($courseid, $scaleid) {
    global $CFG, $DB;

    $return = 0;

    if (!empty($scaleid)) {
        if ($cms = get_course_mods($courseid)) {
            foreach ($cms as $cm) {
                // Check cm->name/lib.php exists.
                if (file_exists($CFG->dirroot.'/mod/'.$cm->modname.'/lib.php')) {
                    include_once($CFG->dirroot.'/mod/'.$cm->modname.'/lib.php');
                    $functionname = $cm->modname.'_scale_used';
                    if (function_exists($functionname)) {
                        if ($functionname($cm->instance, $scaleid)) {
                            $return++;
                        }
                    }
                }
            }
        }

        // Check if any course grade item makes use of the scale.
        $return += $DB->count_records('grade_items', array('courseid' => $courseid, 'scaleid' => $scaleid));

        // Check if any outcome in the course makes use of the scale.
        $return += $DB->count_records_sql("SELECT COUNT('x')
                                             FROM {grade_outcomes_courses} goc,
                                                  {grade_outcomes} go
                                            WHERE go.id = goc.outcomeid
                                                  AND go.scaleid = ? AND goc.courseid = ?",
                                          array($scaleid, $courseid));
    }
    return $return;
}

/**
 * This function returns the number of activities using scaleid in the entire site
 *
 * @param int $scaleid
 * @param array $courses
 * @return int
 */
function site_scale_used($scaleid, &$courses) {
    $return = 0;

    if (!is_array($courses) || count($courses) == 0) {
        $courses = get_courses("all", false, "c.id, c.shortname");
    }

    if (!empty($scaleid)) {
        if (is_array($courses) && count($courses) > 0) {
            foreach ($courses as $course) {
                $return += course_scale_used($course->id, $scaleid);
            }
        }
    }
    return $return;
}

/**
 * make_unique_id_code
 *
 * @todo Finish documenting this function
 *
 * @uses $_SERVER
 * @param string $extra Extra string to append to the end of the code
 * @return string
 */
function make_unique_id_code($extra = '') {

    $hostname = 'unknownhost';
    if (!empty($_SERVER['HTTP_HOST'])) {
        $hostname = $_SERVER['HTTP_HOST'];
    } else if (!empty($_ENV['HTTP_HOST'])) {
        $hostname = $_ENV['HTTP_HOST'];
    } else if (!empty($_SERVER['SERVER_NAME'])) {
        $hostname = $_SERVER['SERVER_NAME'];
    } else if (!empty($_ENV['SERVER_NAME'])) {
        $hostname = $_ENV['SERVER_NAME'];
    }

    $date = gmdate("ymdHis");

    $random =  random_string(6);

    if ($extra) {
        return $hostname .'+'. $date .'+'. $random .'+'. $extra;
    } else {
        return $hostname .'+'. $date .'+'. $random;
    }
}


/**
 * Function to check the passed address is within the passed subnet
 *
 * The parameter is a comma separated string of subnet definitions.
 * Subnet strings can be in one of three formats:
 *   1: xxx.xxx.xxx.xxx/nn or xxxx:xxxx:xxxx:xxxx:xxxx:xxxx:xxxx/nnn          (number of bits in net mask)
 *   2: xxx.xxx.xxx.xxx-yyy or  xxxx:xxxx:xxxx:xxxx:xxxx:xxxx:xxxx::xxxx-yyyy (a range of IP addresses in the last group)
 *   3: xxx.xxx or xxx.xxx. or xxx:xxx:xxxx or xxx:xxx:xxxx.                  (incomplete address, a bit non-technical ;-)
 * Code for type 1 modified from user posted comments by mediator at
 * {@link http://au.php.net/manual/en/function.ip2long.php}
 *
 * @param string $addr    The address you are checking
 * @param string $subnetstr    The string of subnet addresses
 * @return bool
 */
function address_in_subnet($addr, $subnetstr) {

    if ($addr == '0.0.0.0') {
        return false;
    }
    $subnets = explode(',', $subnetstr);
    $found = false;
    $addr = trim($addr);
    $addr = cleanremoteaddr($addr, false); // Normalise.
    if ($addr === null) {
        return false;
    }
    $addrparts = explode(':', $addr);

    $ipv6 = strpos($addr, ':');

    foreach ($subnets as $subnet) {
        $subnet = trim($subnet);
        if ($subnet === '') {
            continue;
        }

        if (strpos($subnet, '/') !== false) {
            // 1: xxx.xxx.xxx.xxx/nn or xxxx:xxxx:xxxx:xxxx:xxxx:xxxx:xxxx/nnn.
            list($ip, $mask) = explode('/', $subnet);
            $mask = trim($mask);
            if (!is_number($mask)) {
                continue; // Incorect mask number, eh?
            }
            $ip = cleanremoteaddr($ip, false); // Normalise.
            if ($ip === null) {
                continue;
            }
            if (strpos($ip, ':') !== false) {
                // IPv6.
                if (!$ipv6) {
                    continue;
                }
                if ($mask > 128 or $mask < 0) {
                    continue; // Nonsense.
                }
                if ($mask == 0) {
                    return true; // Any address.
                }
                if ($mask == 128) {
                    if ($ip === $addr) {
                        return true;
                    }
                    continue;
                }
                $ipparts = explode(':', $ip);
                $modulo  = $mask % 16;
                $ipnet   = array_slice($ipparts, 0, ($mask-$modulo)/16);
                $addrnet = array_slice($addrparts, 0, ($mask-$modulo)/16);
                if (implode(':', $ipnet) === implode(':', $addrnet)) {
                    if ($modulo == 0) {
                        return true;
                    }
                    $pos     = ($mask-$modulo)/16;
                    $ipnet   = hexdec($ipparts[$pos]);
                    $addrnet = hexdec($addrparts[$pos]);
                    $mask    = 0xffff << (16 - $modulo);
                    if (($addrnet & $mask) == ($ipnet & $mask)) {
                        return true;
                    }
                }

            } else {
                // IPv4.
                if ($ipv6) {
                    continue;
                }
                if ($mask > 32 or $mask < 0) {
                    continue; // Nonsense.
                }
                if ($mask == 0) {
                    return true;
                }
                if ($mask == 32) {
                    if ($ip === $addr) {
                        return true;
                    }
                    continue;
                }
                $mask = 0xffffffff << (32 - $mask);
                if (((ip2long($addr) & $mask) == (ip2long($ip) & $mask))) {
                    return true;
                }
            }

        } else if (strpos($subnet, '-') !== false) {
            // 2: xxx.xxx.xxx.xxx-yyy or  xxxx:xxxx:xxxx:xxxx:xxxx:xxxx:xxxx::xxxx-yyyy. A range of IP addresses in the last group.
            $parts = explode('-', $subnet);
            if (count($parts) != 2) {
                continue;
            }

            if (strpos($subnet, ':') !== false) {
                // IPv6.
                if (!$ipv6) {
                    continue;
                }
                $ipstart = cleanremoteaddr(trim($parts[0]), false); // Normalise.
                if ($ipstart === null) {
                    continue;
                }
                $ipparts = explode(':', $ipstart);
                $start = hexdec(array_pop($ipparts));
                $ipparts[] = trim($parts[1]);
                $ipend = cleanremoteaddr(implode(':', $ipparts), false); // Normalise.
                if ($ipend === null) {
                    continue;
                }
                $ipparts[7] = '';
                $ipnet = implode(':', $ipparts);
                if (strpos($addr, $ipnet) !== 0) {
                    continue;
                }
                $ipparts = explode(':', $ipend);
                $end = hexdec($ipparts[7]);

                $addrend = hexdec($addrparts[7]);

                if (($addrend >= $start) and ($addrend <= $end)) {
                    return true;
                }

            } else {
                // IPv4.
                if ($ipv6) {
                    continue;
                }
                $ipstart = cleanremoteaddr(trim($parts[0]), false); // Normalise.
                if ($ipstart === null) {
                    continue;
                }
                $ipparts = explode('.', $ipstart);
                $ipparts[3] = trim($parts[1]);
                $ipend = cleanremoteaddr(implode('.', $ipparts), false); // Normalise.
                if ($ipend === null) {
                    continue;
                }

                if ((ip2long($addr) >= ip2long($ipstart)) and (ip2long($addr) <= ip2long($ipend))) {
                    return true;
                }
            }

        } else {
            // 3: xxx.xxx or xxx.xxx. or xxx:xxx:xxxx or xxx:xxx:xxxx.
            if (strpos($subnet, ':') !== false) {
                // IPv6.
                if (!$ipv6) {
                    continue;
                }
                $parts = explode(':', $subnet);
                $count = count($parts);
                if ($parts[$count-1] === '') {
                    unset($parts[$count-1]); // Trim trailing :'s.
                    $count--;
                    $subnet = implode('.', $parts);
                }
                $isip = cleanremoteaddr($subnet, false); // Normalise.
                if ($isip !== null) {
                    if ($isip === $addr) {
                        return true;
                    }
                    continue;
                } else if ($count > 8) {
                    continue;
                }
                $zeros = array_fill(0, 8-$count, '0');
                $subnet = $subnet.':'.implode(':', $zeros).'/'.($count*16);
                if (address_in_subnet($addr, $subnet)) {
                    return true;
                }

            } else {
                // IPv4.
                if ($ipv6) {
                    continue;
                }
                $parts = explode('.', $subnet);
                $count = count($parts);
                if ($parts[$count-1] === '') {
                    unset($parts[$count-1]); // Trim trailing .
                    $count--;
                    $subnet = implode('.', $parts);
                }
                if ($count == 4) {
                    $subnet = cleanremoteaddr($subnet, false); // Normalise.
                    if ($subnet === $addr) {
                        return true;
                    }
                    continue;
                } else if ($count > 4) {
                    continue;
                }
                $zeros = array_fill(0, 4-$count, '0');
                $subnet = $subnet.'.'.implode('.', $zeros).'/'.($count*8);
                if (address_in_subnet($addr, $subnet)) {
                    return true;
                }
            }
        }
    }

    return false;
}

/**
 * For outputting debugging info
 *
 * @param string $string The string to write
 * @param string $eol The end of line char(s) to use
 * @param string $sleep Period to make the application sleep
 *                      This ensures any messages have time to display before redirect
 */
function mtrace($string, $eol="\n", $sleep=0) {

    if (defined('STDOUT') and !PHPUNIT_TEST) {
        fwrite(STDOUT, $string.$eol);
    } else {
        echo $string . $eol;
    }

    flush();

    // Delay to keep message on user's screen in case of subsequent redirect.
    if ($sleep) {
        sleep($sleep);
    }
}

/**
 * Replace 1 or more slashes or backslashes to 1 slash
 *
 * @param string $path The path to strip
 * @return string the path with double slashes removed
 */
function cleardoubleslashes ($path) {
    return preg_replace('/(\/|\\\){1,}/', '/', $path);
}

/**
 * Is current ip in give list?
 *
 * @param string $list
 * @return bool
 */
function remoteip_in_list($list) {
    $inlist = false;
    $clientip = getremoteaddr(null);

    if (!$clientip) {
        // Ensure access on cli.
        return true;
    }

    $list = explode("\n", $list);
    foreach ($list as $subnet) {
        $subnet = trim($subnet);
        if (address_in_subnet($clientip, $subnet)) {
            $inlist = true;
            break;
        }
    }
    return $inlist;
}

/**
 * Returns most reliable client address
 *
 * @param string $default If an address can't be determined, then return this
 * @return string The remote IP address
 */
function getremoteaddr($default='0.0.0.0') {
    global $CFG;

    if (empty($CFG->getremoteaddrconf)) {
        // This will happen, for example, before just after the upgrade, as the
        // user is redirected to the admin screen.
        $variablestoskip = 0;
    } else {
        $variablestoskip = $CFG->getremoteaddrconf;
    }
    if (!($variablestoskip & GETREMOTEADDR_SKIP_HTTP_CLIENT_IP)) {
        if (!empty($_SERVER['HTTP_CLIENT_IP'])) {
            $address = cleanremoteaddr($_SERVER['HTTP_CLIENT_IP']);
            return $address ? $address : $default;
        }
    }
    if (!($variablestoskip & GETREMOTEADDR_SKIP_HTTP_X_FORWARDED_FOR)) {
        if (!empty($_SERVER['HTTP_X_FORWARDED_FOR'])) {
            $address = cleanremoteaddr($_SERVER['HTTP_X_FORWARDED_FOR']);
            return $address ? $address : $default;
        }
    }
    if (!empty($_SERVER['REMOTE_ADDR'])) {
        $address = cleanremoteaddr($_SERVER['REMOTE_ADDR']);
        return $address ? $address : $default;
    } else {
        return $default;
    }
}

/**
 * Cleans an ip address. Internal addresses are now allowed.
 * (Originally local addresses were not allowed.)
 *
 * @param string $addr IPv4 or IPv6 address
 * @param bool $compress use IPv6 address compression
 * @return string normalised ip address string, null if error
 */
function cleanremoteaddr($addr, $compress=false) {
    $addr = trim($addr);

    // TODO: maybe add a separate function is_addr_public() or something like this.

    if (strpos($addr, ':') !== false) {
        // Can be only IPv6.
        $parts = explode(':', $addr);
        $count = count($parts);

        if (strpos($parts[$count-1], '.') !== false) {
            // Legacy ipv4 notation.
            $last = array_pop($parts);
            $ipv4 = cleanremoteaddr($last, true);
            if ($ipv4 === null) {
                return null;
            }
            $bits = explode('.', $ipv4);
            $parts[] = dechex($bits[0]).dechex($bits[1]);
            $parts[] = dechex($bits[2]).dechex($bits[3]);
            $count = count($parts);
            $addr = implode(':', $parts);
        }

        if ($count < 3 or $count > 8) {
            return null; // Severly malformed.
        }

        if ($count != 8) {
            if (strpos($addr, '::') === false) {
                return null; // Malformed.
            }
            // Uncompress.
            $insertat = array_search('', $parts, true);
            $missing = array_fill(0, 1 + 8 - $count, '0');
            array_splice($parts, $insertat, 1, $missing);
            foreach ($parts as $key => $part) {
                if ($part === '') {
                    $parts[$key] = '0';
                }
            }
        }

        $adr = implode(':', $parts);
        if (!preg_match('/^([0-9a-f]{1,4})(:[0-9a-f]{1,4})*$/i', $adr)) {
            return null; // Incorrect format - sorry.
        }

        // Normalise 0s and case.
        $parts = array_map('hexdec', $parts);
        $parts = array_map('dechex', $parts);

        $result = implode(':', $parts);

        if (!$compress) {
            return $result;
        }

        if ($result === '0:0:0:0:0:0:0:0') {
            return '::'; // All addresses.
        }

        $compressed = preg_replace('/(:0)+:0$/', '::', $result, 1);
        if ($compressed !== $result) {
            return $compressed;
        }

        $compressed = preg_replace('/^(0:){2,7}/', '::', $result, 1);
        if ($compressed !== $result) {
            return $compressed;
        }

        $compressed = preg_replace('/(:0){2,6}:/', '::', $result, 1);
        if ($compressed !== $result) {
            return $compressed;
        }

        return $result;
    }

    // First get all things that look like IPv4 addresses.
    $parts = array();
    if (!preg_match('/^(\d{1,3})\.(\d{1,3})\.(\d{1,3})\.(\d{1,3})$/', $addr, $parts)) {
        return null;
    }
    unset($parts[0]);

    foreach ($parts as $key => $match) {
        if ($match > 255) {
            return null;
        }
        $parts[$key] = (int)$match; // Normalise 0s.
    }

    return implode('.', $parts);
}

/**
 * This function will make a complete copy of anything it's given,
 * regardless of whether it's an object or not.
 *
 * @param mixed $thing Something you want cloned
 * @return mixed What ever it is you passed it
 */
function fullclone($thing) {
    return unserialize(serialize($thing));
}

 /**
  * If new messages are waiting for the current user, then insert
  * JavaScript to pop up the messaging window into the page
  *
  * @return void
  */
function message_popup_window() {
    global $USER, $DB, $PAGE, $CFG;

    if (!$PAGE->get_popup_notification_allowed() || empty($CFG->messaging)) {
        return;
    }

    if (!isloggedin() || isguestuser()) {
        return;
    }

    if (!isset($USER->message_lastpopup)) {
        $USER->message_lastpopup = 0;
    } else if ($USER->message_lastpopup > (time()-120)) {
        // Don't run the query to check whether to display a popup if its been run in the last 2 minutes.
        return;
    }

    // A quick query to check whether the user has new messages.
    $messagecount = $DB->count_records('message', array('useridto' => $USER->id));
    if ($messagecount<1) {
        return;
    }

    // Got unread messages so now do another query that joins with the user table.
    $messagesql = "SELECT m.id, m.smallmessage, m.fullmessageformat, m.notification, u.firstname, u.lastname
                     FROM {message} m
                     JOIN {message_working} mw ON m.id=mw.unreadmessageid
                     JOIN {message_processors} p ON mw.processorid=p.id
                     JOIN {user} u ON m.useridfrom=u.id
                    WHERE m.useridto = :userid
                      AND p.name='popup'";

    // If the user was last notified over an hour ago we can re-notify them of old messages
    // so don't worry about when the new message was sent.
    $lastnotifiedlongago = $USER->message_lastpopup < (time()-3600);
    if (!$lastnotifiedlongago) {
        $messagesql .= 'AND m.timecreated > :lastpopuptime';
    }

    $messageusers = $DB->get_records_sql($messagesql, array('userid' => $USER->id, 'lastpopuptime' => $USER->message_lastpopup));

    // If we have new messages to notify the user about.
    if (!empty($messageusers)) {

        $strmessages = '';
        if (count($messageusers)>1) {
            $strmessages = get_string('unreadnewmessages', 'message', count($messageusers));
        } else {
            $messageusers = reset($messageusers);

            // Show who the message is from if its not a notification.
            if (!$messageusers->notification) {
                $strmessages = get_string('unreadnewmessage', 'message', fullname($messageusers) );
            }

            // Try to display the small version of the message.
            $smallmessage = null;
            if (!empty($messageusers->smallmessage)) {
                // Display the first 200 chars of the message in the popup.
                $smallmessage = null;
                if (core_text::strlen($messageusers->smallmessage) > 200) {
                    $smallmessage = core_text::substr($messageusers->smallmessage, 0, 200).'...';
                } else {
                    $smallmessage = $messageusers->smallmessage;
                }

                // Prevent html symbols being displayed.
                if ($messageusers->fullmessageformat == FORMAT_HTML) {
                    $smallmessage = html_to_text($smallmessage);
                } else {
                    $smallmessage = s($smallmessage);
                }
            } else if ($messageusers->notification) {
                // Its a notification with no smallmessage so just say they have a notification.
                $smallmessage = get_string('unreadnewnotification', 'message');
            }
            if (!empty($smallmessage)) {
                $strmessages .= '<div id="usermessage">'.s($smallmessage).'</div>';
            }
        }

        $strgomessage = get_string('gotomessages', 'message');
        $strstaymessage = get_string('ignore', 'admin');

        $notificationsound = null;
        $beep = get_user_preferences('message_beepnewmessage', '');
        if (!empty($beep)) {
            // Browsers will work down this list until they find something they support.
            $sourcetags =  html_writer::empty_tag('source', array('src' => $CFG->wwwroot.'/message/bell.wav', 'type' => 'audio/wav'));
            $sourcetags .= html_writer::empty_tag('source', array('src' => $CFG->wwwroot.'/message/bell.ogg', 'type' => 'audio/ogg'));
            $sourcetags .= html_writer::empty_tag('source', array('src' => $CFG->wwwroot.'/message/bell.mp3', 'type' => 'audio/mpeg'));
            $sourcetags .= html_writer::empty_tag('embed',  array('src' => $CFG->wwwroot.'/message/bell.wav', 'autostart' => 'true', 'hidden' => 'true'));

            $notificationsound = html_writer::tag('audio', $sourcetags, array('preload' => 'auto', 'autoplay' => 'autoplay'));
        }

        $url = $CFG->wwwroot.'/message/index.php';
        $content =  html_writer::start_tag('div', array('id' => 'newmessageoverlay', 'class' => 'mdl-align')).
                        html_writer::start_tag('div', array('id' => 'newmessagetext')).
                            $strmessages.
                        html_writer::end_tag('div').

                        $notificationsound.
                        html_writer::start_tag('div', array('id' => 'newmessagelinks')).
                        html_writer::link($url, $strgomessage, array('id' => 'notificationyes')).'&nbsp;&nbsp;&nbsp;'.
                        html_writer::link('', $strstaymessage, array('id' => 'notificationno')).
                        html_writer::end_tag('div');
                    html_writer::end_tag('div');

        $PAGE->requires->js_init_call('M.core_message.init_notification', array('', $content, $url));

        $USER->message_lastpopup = time();
    }
}

/**
 * Used to make sure that $min <= $value <= $max
 *
 * Make sure that value is between min, and max
 *
 * @param int $min The minimum value
 * @param int $value The value to check
 * @param int $max The maximum value
 * @return int
 */
function bounded_number($min, $value, $max) {
    if ($value < $min) {
        return $min;
    }
    if ($value > $max) {
        return $max;
    }
    return $value;
}

/**
 * Check if there is a nested array within the passed array
 *
 * @param array $array
 * @return bool true if there is a nested array false otherwise
 */
function array_is_nested($array) {
    foreach ($array as $value) {
        if (is_array($value)) {
            return true;
        }
    }
    return false;
}

/**
 * get_performance_info() pairs up with init_performance_info()
 * loaded in setup.php. Returns an array with 'html' and 'txt'
 * values ready for use, and each of the individual stats provided
 * separately as well.
 *
 * @return array
 */
function get_performance_info() {
    global $CFG, $PERF, $DB, $PAGE;

    $info = array();
    $info['html'] = '';         // Holds userfriendly HTML representation.
    $info['txt']  = me() . ' '; // Holds log-friendly representation.

    $info['realtime'] = microtime_diff($PERF->starttime, microtime());

    $info['html'] .= '<span class="timeused">'.$info['realtime'].' secs</span> ';
    $info['txt'] .= 'time: '.$info['realtime'].'s ';

    if (function_exists('memory_get_usage')) {
        $info['memory_total'] = memory_get_usage();
        $info['memory_growth'] = memory_get_usage() - $PERF->startmemory;
        $info['html'] .= '<span class="memoryused">RAM: '.display_size($info['memory_total']).'</span> ';
        $info['txt']  .= 'memory_total: '.$info['memory_total'].'B (' . display_size($info['memory_total']).') memory_growth: '.
            $info['memory_growth'].'B ('.display_size($info['memory_growth']).') ';
    }

    if (function_exists('memory_get_peak_usage')) {
        $info['memory_peak'] = memory_get_peak_usage();
        $info['html'] .= '<span class="memoryused">RAM peak: '.display_size($info['memory_peak']).'</span> ';
        $info['txt']  .= 'memory_peak: '.$info['memory_peak'].'B (' . display_size($info['memory_peak']).') ';
    }

    $inc = get_included_files();
    $info['includecount'] = count($inc);
    $info['html'] .= '<span class="included">Included '.$info['includecount'].' files</span> ';
    $info['txt']  .= 'includecount: '.$info['includecount'].' ';

    if (!empty($CFG->early_install_lang) or empty($PAGE)) {
        // We can not track more performance before installation or before PAGE init, sorry.
        return $info;
    }

    $filtermanager = filter_manager::instance();
    if (method_exists($filtermanager, 'get_performance_summary')) {
        list($filterinfo, $nicenames) = $filtermanager->get_performance_summary();
        $info = array_merge($filterinfo, $info);
        foreach ($filterinfo as $key => $value) {
            $info['html'] .= "<span class='$key'>$nicenames[$key]: $value </span> ";
            $info['txt'] .= "$key: $value ";
        }
    }

    $stringmanager = get_string_manager();
    if (method_exists($stringmanager, 'get_performance_summary')) {
        list($filterinfo, $nicenames) = $stringmanager->get_performance_summary();
        $info = array_merge($filterinfo, $info);
        foreach ($filterinfo as $key => $value) {
            $info['html'] .= "<span class='$key'>$nicenames[$key]: $value </span> ";
            $info['txt'] .= "$key: $value ";
        }
    }

    $jsmodules = $PAGE->requires->get_loaded_modules();
    if ($jsmodules) {
        $yuicount = 0;
        $othercount = 0;
        $details = '';
        foreach ($jsmodules as $module => $backtraces) {
            if (strpos($module, 'yui') === 0) {
                $yuicount += 1;
            } else {
                $othercount += 1;
            }
            if (!empty($CFG->yuimoduledebug)) {
                // Hidden feature for developers working on YUI module infrastructure.
                $details .= "<div class='yui-module'><p>$module</p>";
                foreach ($backtraces as $backtrace) {
                    $details .= "<div class='backtrace'>$backtrace</div>";
                }
                $details .= '</div>';
            }
        }
        $info['html'] .= "<span class='includedyuimodules'>Included YUI modules: $yuicount</span> ";
        $info['txt'] .= "includedyuimodules: $yuicount ";
        $info['html'] .= "<span class='includedjsmodules'>Other JavaScript modules: $othercount</span> ";
        $info['txt'] .= "includedjsmodules: $othercount ";
        if ($details) {
            $info['html'] .= '<div id="yui-module-debug" class="notifytiny">'.$details.'</div>';
        }
    }

    if (!empty($PERF->logwrites)) {
        $info['logwrites'] = $PERF->logwrites;
        $info['html'] .= '<span class="logwrites">Log DB writes '.$info['logwrites'].'</span> ';
        $info['txt'] .= 'logwrites: '.$info['logwrites'].' ';
    }

    $info['dbqueries'] = $DB->perf_get_reads().'/'.($DB->perf_get_writes() - $PERF->logwrites);
    $info['html'] .= '<span class="dbqueries">DB reads/writes: '.$info['dbqueries'].'</span> ';
    $info['txt'] .= 'db reads/writes: '.$info['dbqueries'].' ';

    if (function_exists('posix_times')) {
        $ptimes = posix_times();
        if (is_array($ptimes)) {
            foreach ($ptimes as $key => $val) {
                $info[$key] = $ptimes[$key] -  $PERF->startposixtimes[$key];
            }
            $info['html'] .= "<span class=\"posixtimes\">ticks: $info[ticks] user: $info[utime] sys: $info[stime] cuser: $info[cutime] csys: $info[cstime]</span> ";
            $info['txt'] .= "ticks: $info[ticks] user: $info[utime] sys: $info[stime] cuser: $info[cutime] csys: $info[cstime] ";
        }
    }

    // Grab the load average for the last minute.
    // /proc will only work under some linux configurations
    // while uptime is there under MacOSX/Darwin and other unices.
    if (is_readable('/proc/loadavg') && $loadavg = @file('/proc/loadavg')) {
        list($serverload) = explode(' ', $loadavg[0]);
        unset($loadavg);
    } else if ( function_exists('is_executable') && is_executable('/usr/bin/uptime') && $loadavg = `/usr/bin/uptime` ) {
        if (preg_match('/load averages?: (\d+[\.,:]\d+)/', $loadavg, $matches)) {
            $serverload = $matches[1];
        } else {
            trigger_error('Could not parse uptime output!');
        }
    }
    if (!empty($serverload)) {
        $info['serverload'] = $serverload;
        $info['html'] .= '<span class="serverload">Load average: '.$info['serverload'].'</span> ';
        $info['txt'] .= "serverload: {$info['serverload']} ";
    }

    // Display size of session if session started.
    if ($si = \core\session\manager::get_performance_info()) {
        $info['sessionsize'] = $si['size'];
        $info['html'] .= $si['html'];
        $info['txt'] .= $si['txt'];
    }

    if ($stats = cache_helper::get_stats()) {
        $html = '<span class="cachesused">';
        $html .= '<span class="cache-stats-heading">Caches used (hits/misses/sets)</span>';
        $text = 'Caches used (hits/misses/sets): ';
        $hits = 0;
        $misses = 0;
        $sets = 0;
        foreach ($stats as $definition => $stores) {
            $html .= '<span class="cache-definition-stats">';
            $html .= '<span class="cache-definition-stats-heading">'.$definition.'</span>';
            $text .= "$definition {";
            foreach ($stores as $store => $data) {
                $hits += $data['hits'];
                $misses += $data['misses'];
                $sets += $data['sets'];
                if ($data['hits'] == 0 and $data['misses'] > 0) {
                    $cachestoreclass = 'nohits';
                } else if ($data['hits'] < $data['misses']) {
                    $cachestoreclass = 'lowhits';
                } else {
                    $cachestoreclass = 'hihits';
                }
                $text .= "$store($data[hits]/$data[misses]/$data[sets]) ";
                $html .= "<span class=\"cache-store-stats $cachestoreclass\">$store: $data[hits] / $data[misses] / $data[sets]</span>";
            }
            $html .= '</span>';
            $text .= '} ';
        }
        $html .= "<span class='cache-total-stats'>Total: $hits / $misses / $sets</span>";
        $html .= '</span> ';
        $info['cachesused'] = "$hits / $misses / $sets";
        $info['html'] .= $html;
        $info['txt'] .= $text.'. ';
    } else {
        $info['cachesused'] = '0 / 0 / 0';
        $info['html'] .= '<span class="cachesused">Caches used (hits/misses/sets): 0/0/0</span>';
        $info['txt'] .= 'Caches used (hits/misses/sets): 0/0/0 ';
    }

    $info['html'] = '<div class="performanceinfo siteinfo">'.$info['html'].'</div>';
    return $info;
}

/**
 * Legacy function.
 *
 * @todo Document this function linux people
 */
function apd_get_profiling() {
    return shell_exec('pprofp -u ' . ini_get('apd.dumpdir') . '/pprof.' . getmypid() . '.*');
}

/**
 * Delete directory or only its content
 *
 * @param string $dir directory path
 * @param bool $contentonly
 * @return bool success, true also if dir does not exist
 */
function remove_dir($dir, $contentonly=false) {
    if (!file_exists($dir)) {
        // Nothing to do.
        return true;
    }
    if (!$handle = opendir($dir)) {
        return false;
    }
    $result = true;
    while (false!==($item = readdir($handle))) {
        if ($item != '.' && $item != '..') {
            if (is_dir($dir.'/'.$item)) {
                $result = remove_dir($dir.'/'.$item) && $result;
            } else {
                $result = unlink($dir.'/'.$item) && $result;
            }
        }
    }
    closedir($handle);
    if ($contentonly) {
        clearstatcache(); // Make sure file stat cache is properly invalidated.
        return $result;
    }
    $result = rmdir($dir); // If anything left the result will be false, no need for && $result.
    clearstatcache(); // Make sure file stat cache is properly invalidated.
    return $result;
}

/**
 * Detect if an object or a class contains a given property
 * will take an actual object or the name of a class
 *
 * @param mix $obj Name of class or real object to test
 * @param string $property name of property to find
 * @return bool true if property exists
 */
function object_property_exists( $obj, $property ) {
    if (is_string( $obj )) {
        $properties = get_class_vars( $obj );
    } else {
        $properties = get_object_vars( $obj );
    }
    return array_key_exists( $property, $properties );
}

/**
 * Converts an object into an associative array
 *
 * This function converts an object into an associative array by iterating
 * over its public properties. Because this function uses the foreach
 * construct, Iterators are respected. It works recursively on arrays of objects.
 * Arrays and simple values are returned as is.
 *
 * If class has magic properties, it can implement IteratorAggregate
 * and return all available properties in getIterator()
 *
 * @param mixed $var
 * @return array
 */
function convert_to_array($var) {
    $result = array();

    // Loop over elements/properties.
    foreach ($var as $key => $value) {
        // Recursively convert objects.
        if (is_object($value) || is_array($value)) {
            $result[$key] = convert_to_array($value);
        } else {
            // Simple values are untouched.
            $result[$key] = $value;
        }
    }
    return $result;
}

/**
 * Detect a custom script replacement in the data directory that will
 * replace an existing moodle script
 *
 * @return string|bool full path name if a custom script exists, false if no custom script exists
 */
function custom_script_path() {
    global $CFG, $SCRIPT;

    if ($SCRIPT === null) {
        // Probably some weird external script.
        return false;
    }

    $scriptpath = $CFG->customscripts . $SCRIPT;

    // Check the custom script exists.
    if (file_exists($scriptpath) and is_file($scriptpath)) {
        return $scriptpath;
    } else {
        return false;
    }
}

/**
 * Returns whether or not the user object is a remote MNET user. This function
 * is in moodlelib because it does not rely on loading any of the MNET code.
 *
 * @param object $user A valid user object
 * @return bool        True if the user is from a remote Moodle.
 */
function is_mnet_remote_user($user) {
    global $CFG;

    if (!isset($CFG->mnet_localhost_id)) {
        include_once($CFG->dirroot . '/mnet/lib.php');
        $env = new mnet_environment();
        $env->init();
        unset($env);
    }

    return (!empty($user->mnethostid) && $user->mnethostid != $CFG->mnet_localhost_id);
}

/**
 * This function will search for browser prefereed languages, setting Moodle
 * to use the best one available if $SESSION->lang is undefined
 */
function setup_lang_from_browser() {
    global $CFG, $SESSION, $USER;

    if (!empty($SESSION->lang) or !empty($USER->lang) or empty($CFG->autolang)) {
        // Lang is defined in session or user profile, nothing to do.
        return;
    }

    if (!isset($_SERVER['HTTP_ACCEPT_LANGUAGE'])) { // There isn't list of browser langs, nothing to do.
        return;
    }

    // Extract and clean langs from headers.
    $rawlangs = $_SERVER['HTTP_ACCEPT_LANGUAGE'];
    $rawlangs = str_replace('-', '_', $rawlangs);         // We are using underscores.
    $rawlangs = explode(',', $rawlangs);                  // Convert to array.
    $langs = array();

    $order = 1.0;
    foreach ($rawlangs as $lang) {
        if (strpos($lang, ';') === false) {
            $langs[(string)$order] = $lang;
            $order = $order-0.01;
        } else {
            $parts = explode(';', $lang);
            $pos = strpos($parts[1], '=');
            $langs[substr($parts[1], $pos+1)] = $parts[0];
        }
    }
    krsort($langs, SORT_NUMERIC);

    // Look for such langs under standard locations.
    foreach ($langs as $lang) {
        // Clean it properly for include.
        $lang = strtolower(clean_param($lang, PARAM_SAFEDIR));
        if (get_string_manager()->translation_exists($lang, false)) {
            // Lang exists, set it in session.
            $SESSION->lang = $lang;
            // We have finished. Go out.
            break;
        }
    }
    return;
}

/**
 * Check if $url matches anything in proxybypass list
 *
 * Any errors just result in the proxy being used (least bad)
 *
 * @param string $url url to check
 * @return boolean true if we should bypass the proxy
 */
function is_proxybypass( $url ) {
    global $CFG;

    // Sanity check.
    if (empty($CFG->proxyhost) or empty($CFG->proxybypass)) {
        return false;
    }

    // Get the host part out of the url.
    if (!$host = parse_url( $url, PHP_URL_HOST )) {
        return false;
    }

    // Get the possible bypass hosts into an array.
    $matches = explode( ',', $CFG->proxybypass );

    // Check for a match.
    // (IPs need to match the left hand side and hosts the right of the url,
    // but we can recklessly check both as there can't be a false +ve).
    foreach ($matches as $match) {
        $match = trim($match);

        // Try for IP match (Left side).
        $lhs = substr($host, 0, strlen($match));
        if (strcasecmp($match, $lhs)==0) {
            return true;
        }

        // Try for host match (Right side).
        $rhs = substr($host, -strlen($match));
        if (strcasecmp($match, $rhs)==0) {
            return true;
        }
    }

    // Nothing matched.
    return false;
}

/**
 * Check if the passed navigation is of the new style
 *
 * @param mixed $navigation
 * @return bool true for yes false for no
 */
function is_newnav($navigation) {
    if (is_array($navigation) && !empty($navigation['newnav'])) {
        return true;
    } else {
        return false;
    }
}

/**
 * Checks whether the given variable name is defined as a variable within the given object.
 *
 * This will NOT work with stdClass objects, which have no class variables.
 *
 * @param string $var The variable name
 * @param object $object The object to check
 * @return boolean
 */
function in_object_vars($var, $object) {
    $classvars = get_class_vars(get_class($object));
    $classvars = array_keys($classvars);
    return in_array($var, $classvars);
}

/**
 * Returns an array without repeated objects.
 * This function is similar to array_unique, but for arrays that have objects as values
 *
 * @param array $array
 * @param bool $keepkeyassoc
 * @return array
 */
function object_array_unique($array, $keepkeyassoc = true) {
    $duplicatekeys = array();
    $tmp         = array();

    foreach ($array as $key => $val) {
        // Convert objects to arrays, in_array() does not support objects.
        if (is_object($val)) {
            $val = (array)$val;
        }

        if (!in_array($val, $tmp)) {
            $tmp[] = $val;
        } else {
            $duplicatekeys[] = $key;
        }
    }

    foreach ($duplicatekeys as $key) {
        unset($array[$key]);
    }

    return $keepkeyassoc ? $array : array_values($array);
}

/**
 * Is a userid the primary administrator?
 *
 * @param int $userid int id of user to check
 * @return boolean
 */
function is_primary_admin($userid) {
    $primaryadmin =  get_admin();

    if ($userid == $primaryadmin->id) {
        return true;
    } else {
        return false;
    }
}

/**
 * Returns the site identifier
 *
 * @return string $CFG->siteidentifier, first making sure it is properly initialised.
 */
function get_site_identifier() {
    global $CFG;
    // Check to see if it is missing. If so, initialise it.
    if (empty($CFG->siteidentifier)) {
        set_config('siteidentifier', random_string(32) . $_SERVER['HTTP_HOST']);
    }
    // Return it.
    return $CFG->siteidentifier;
}

/**
 * Check whether the given password has no more than the specified
 * number of consecutive identical characters.
 *
 * @param string $password   password to be checked against the password policy
 * @param integer $maxchars  maximum number of consecutive identical characters
 * @return bool
 */
function check_consecutive_identical_characters($password, $maxchars) {

    if ($maxchars < 1) {
        return true; // Zero 0 is to disable this check.
    }
    if (strlen($password) <= $maxchars) {
        return true; // Too short to fail this test.
    }

    $previouschar = '';
    $consecutivecount = 1;
    foreach (str_split($password) as $char) {
        if ($char != $previouschar) {
            $consecutivecount = 1;
        } else {
            $consecutivecount++;
            if ($consecutivecount > $maxchars) {
                return false; // Check failed already.
            }
        }

        $previouschar = $char;
    }

    return true;
}

/**
 * Helper function to do partial function binding.
 * so we can use it for preg_replace_callback, for example
 * this works with php functions, user functions, static methods and class methods
 * it returns you a callback that you can pass on like so:
 *
 * $callback = partial('somefunction', $arg1, $arg2);
 *     or
 * $callback = partial(array('someclass', 'somestaticmethod'), $arg1, $arg2);
 *     or even
 * $obj = new someclass();
 * $callback = partial(array($obj, 'somemethod'), $arg1, $arg2);
 *
 * and then the arguments that are passed through at calltime are appended to the argument list.
 *
 * @param mixed $function a php callback
 * @param mixed $arg1,... $argv arguments to partially bind with
 * @return array Array callback
 */
function partial() {
    if (!class_exists('partial')) {
        /**
         * Used to manage function binding.
         * @copyright  2009 Penny Leach
         * @license    http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later
         */
        class partial{
            /** @var array */
            public $values = array();
            /** @var string The function to call as a callback. */
            public $func;
            /**
             * Constructor
             * @param string $func
             * @param array $args
             */
            public function __construct($func, $args) {
                $this->values = $args;
                $this->func = $func;
            }
            /**
             * Calls the callback function.
             * @return mixed
             */
            public function method() {
                $args = func_get_args();
                return call_user_func_array($this->func, array_merge($this->values, $args));
            }
        }
    }
    $args = func_get_args();
    $func = array_shift($args);
    $p = new partial($func, $args);
    return array($p, 'method');
}

/**
 * helper function to load up and initialise the mnet environment
 * this must be called before you use mnet functions.
 *
 * @return mnet_environment the equivalent of old $MNET global
 */
function get_mnet_environment() {
    global $CFG;
    require_once($CFG->dirroot . '/mnet/lib.php');
    static $instance = null;
    if (empty($instance)) {
        $instance = new mnet_environment();
        $instance->init();
    }
    return $instance;
}

/**
 * during xmlrpc server code execution, any code wishing to access
 * information about the remote peer must use this to get it.
 *
 * @return mnet_remote_client the equivalent of old $MNETREMOTE_CLIENT global
 */
function get_mnet_remote_client() {
    if (!defined('MNET_SERVER')) {
        debugging(get_string('notinxmlrpcserver', 'mnet'));
        return false;
    }
    global $MNET_REMOTE_CLIENT;
    if (isset($MNET_REMOTE_CLIENT)) {
        return $MNET_REMOTE_CLIENT;
    }
    return false;
}

/**
 * during the xmlrpc server code execution, this will be called
 * to setup the object returned by {@link get_mnet_remote_client}
 *
 * @param mnet_remote_client $client the client to set up
 * @throws moodle_exception
 */
function set_mnet_remote_client($client) {
    if (!defined('MNET_SERVER')) {
        throw new moodle_exception('notinxmlrpcserver', 'mnet');
    }
    global $MNET_REMOTE_CLIENT;
    $MNET_REMOTE_CLIENT = $client;
}

/**
 * return the jump url for a given remote user
 * this is used for rewriting forum post links in emails, etc
 *
 * @param stdclass $user the user to get the idp url for
 */
function mnet_get_idp_jump_url($user) {
    global $CFG;

    static $mnetjumps = array();
    if (!array_key_exists($user->mnethostid, $mnetjumps)) {
        $idp = mnet_get_peer_host($user->mnethostid);
        $idpjumppath = mnet_get_app_jumppath($idp->applicationid);
        $mnetjumps[$user->mnethostid] = $idp->wwwroot . $idpjumppath . '?hostwwwroot=' . $CFG->wwwroot . '&wantsurl=';
    }
    return $mnetjumps[$user->mnethostid];
}

/**
 * Gets the homepage to use for the current user
 *
 * @return int One of HOMEPAGE_*
 */
function get_home_page() {
    global $CFG;

    if (isloggedin() && !isguestuser() && !empty($CFG->defaulthomepage)) {
        if ($CFG->defaulthomepage == HOMEPAGE_MY) {
            return HOMEPAGE_MY;
        } else {
            return (int)get_user_preferences('user_home_page_preference', HOMEPAGE_MY);
        }
    }
    return HOMEPAGE_SITE;
}

/**
 * Gets the name of a course to be displayed when showing a list of courses.
 * By default this is just $course->fullname but user can configure it. The
 * result of this function should be passed through print_string.
 * @param stdClass|course_in_list $course Moodle course object
 * @return string Display name of course (either fullname or short + fullname)
 */
function get_course_display_name_for_list($course) {
    global $CFG;
    if (!empty($CFG->courselistshortnames)) {
        if (!($course instanceof stdClass)) {
            $course = (object)convert_to_array($course);
        }
        return get_string('courseextendednamedisplay', '', $course);
    } else {
        return $course->fullname;
    }
}

/**
 * The lang_string class
 *
 * This special class is used to create an object representation of a string request.
 * It is special because processing doesn't occur until the object is first used.
 * The class was created especially to aid performance in areas where strings were
 * required to be generated but were not necessarily used.
 * As an example the admin tree when generated uses over 1500 strings, of which
 * normally only 1/3 are ever actually printed at any time.
 * The performance advantage is achieved by not actually processing strings that
 * arn't being used, as such reducing the processing required for the page.
 *
 * How to use the lang_string class?
 *     There are two methods of using the lang_string class, first through the
 *     forth argument of the get_string function, and secondly directly.
 *     The following are examples of both.
 * 1. Through get_string calls e.g.
 *     $string = get_string($identifier, $component, $a, true);
 *     $string = get_string('yes', 'moodle', null, true);
 * 2. Direct instantiation
 *     $string = new lang_string($identifier, $component, $a, $lang);
 *     $string = new lang_string('yes');
 *
 * How do I use a lang_string object?
 *     The lang_string object makes use of a magic __toString method so that you
 *     are able to use the object exactly as you would use a string in most cases.
 *     This means you are able to collect it into a variable and then directly
 *     echo it, or concatenate it into another string, or similar.
 *     The other thing you can do is manually get the string by calling the
 *     lang_strings out method e.g.
 *         $string = new lang_string('yes');
 *         $string->out();
 *     Also worth noting is that the out method can take one argument, $lang which
 *     allows the developer to change the language on the fly.
 *
 * When should I use a lang_string object?
 *     The lang_string object is designed to be used in any situation where a
 *     string may not be needed, but needs to be generated.
 *     The admin tree is a good example of where lang_string objects should be
 *     used.
 *     A more practical example would be any class that requries strings that may
 *     not be printed (after all classes get renderer by renderers and who knows
 *     what they will do ;))
 *
 * When should I not use a lang_string object?
 *     Don't use lang_strings when you are going to use a string immediately.
 *     There is no need as it will be processed immediately and there will be no
 *     advantage, and in fact perhaps a negative hit as a class has to be
 *     instantiated for a lang_string object, however get_string won't require
 *     that.
 *
 * Limitations:
 * 1. You cannot use a lang_string object as an array offset. Doing so will
 *     result in PHP throwing an error. (You can use it as an object property!)
 *
 * @package    core
 * @category   string
 * @copyright  2011 Sam Hemelryk
 * @license    http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later
 */
class lang_string {

    /** @var string The strings identifier */
    protected $identifier;
    /** @var string The strings component. Default '' */
    protected $component = '';
    /** @var array|stdClass Any arguments required for the string. Default null */
    protected $a = null;
    /** @var string The language to use when processing the string. Default null */
    protected $lang = null;

    /** @var string The processed string (once processed) */
    protected $string = null;

    /**
     * A special boolean. If set to true then the object has been woken up and
     * cannot be regenerated. If this is set then $this->string MUST be used.
     * @var bool
     */
    protected $forcedstring = false;

    /**
     * Constructs a lang_string object
     *
     * This function should do as little processing as possible to ensure the best
     * performance for strings that won't be used.
     *
     * @param string $identifier The strings identifier
     * @param string $component The strings component
     * @param stdClass|array $a Any arguments the string requires
     * @param string $lang The language to use when processing the string.
     * @throws coding_exception
     */
    public function __construct($identifier, $component = '', $a = null, $lang = null) {
        if (empty($component)) {
            $component = 'moodle';
        }

        $this->identifier = $identifier;
        $this->component = $component;
        $this->lang = $lang;

        // We MUST duplicate $a to ensure that it if it changes by reference those
        // changes are not carried across.
        // To do this we always ensure $a or its properties/values are strings
        // and that any properties/values that arn't convertable are forgotten.
        if (!empty($a)) {
            if (is_scalar($a)) {
                $this->a = $a;
            } else if ($a instanceof lang_string) {
                $this->a = $a->out();
            } else if (is_object($a) or is_array($a)) {
                $a = (array)$a;
                $this->a = array();
                foreach ($a as $key => $value) {
                    // Make sure conversion errors don't get displayed (results in '').
                    if (is_array($value)) {
                        $this->a[$key] = '';
                    } else if (is_object($value)) {
                        if (method_exists($value, '__toString')) {
                            $this->a[$key] = $value->__toString();
                        } else {
                            $this->a[$key] = '';
                        }
                    } else {
                        $this->a[$key] = (string)$value;
                    }
                }
            }
        }

        if (debugging(false, DEBUG_DEVELOPER)) {
            if (clean_param($this->identifier, PARAM_STRINGID) == '') {
                throw new coding_exception('Invalid string identifier. Most probably some illegal character is part of the string identifier. Please check your string definition');
            }
            if (!empty($this->component) && clean_param($this->component, PARAM_COMPONENT) == '') {
                throw new coding_exception('Invalid string compontent. Please check your string definition');
            }
            if (!get_string_manager()->string_exists($this->identifier, $this->component)) {
                debugging('String does not exist. Please check your string definition for '.$this->identifier.'/'.$this->component, DEBUG_DEVELOPER);
            }
        }
    }

    /**
     * Processes the string.
     *
     * This function actually processes the string, stores it in the string property
     * and then returns it.
     * You will notice that this function is VERY similar to the get_string method.
     * That is because it is pretty much doing the same thing.
     * However as this function is an upgrade it isn't as tolerant to backwards
     * compatibility.
     *
     * @return string
     * @throws coding_exception
     */
    protected function get_string() {
        global $CFG;

        // Check if we need to process the string.
        if ($this->string === null) {
            // Check the quality of the identifier.
            if ($CFG->debugdeveloper && clean_param($this->identifier, PARAM_STRINGID) === '') {
                throw new coding_exception('Invalid string identifier. Most probably some illegal character is part of the string identifier. Please check your string definition', DEBUG_DEVELOPER);
            }

            // Process the string.
            $this->string = get_string_manager()->get_string($this->identifier, $this->component, $this->a, $this->lang);
            // Debugging feature lets you display string identifier and component.
            if (isset($CFG->debugstringids) && $CFG->debugstringids && optional_param('strings', 0, PARAM_INT)) {
                $this->string .= ' {' . $this->identifier . '/' . $this->component . '}';
            }
        }
        // Return the string.
        return $this->string;
    }

    /**
     * Returns the string
     *
     * @param string $lang The langauge to use when processing the string
     * @return string
     */
    public function out($lang = null) {
        if ($lang !== null && $lang != $this->lang && ($this->lang == null && $lang != current_language())) {
            if ($this->forcedstring) {
                debugging('lang_string objects that have been used cannot be printed in another language. ('.$this->lang.' used)', DEBUG_DEVELOPER);
                return $this->get_string();
            }
            $translatedstring = new lang_string($this->identifier, $this->component, $this->a, $lang);
            return $translatedstring->out();
        }
        return $this->get_string();
    }

    /**
     * Magic __toString method for printing a string
     *
     * @return string
     */
    public function __toString() {
        return $this->get_string();
    }

    /**
     * Magic __set_state method used for var_export
     *
     * @return string
     */
    public function __set_state() {
        return $this->get_string();
    }

    /**
     * Prepares the lang_string for sleep and stores only the forcedstring and
     * string properties... the string cannot be regenerated so we need to ensure
     * it is generated for this.
     *
     * @return string
     */
    public function __sleep() {
        $this->get_string();
        $this->forcedstring = true;
        return array('forcedstring', 'string', 'lang');
    }
}