group/classes/visibility.php

   1 <?php
   2 // This file is part of Moodle - http://moodle.org/
   3 //
   4 // Moodle is free software: you can redistribute it and/or modify
   5 // it under the terms of the GNU General Public License as published by
   6 // the Free Software Foundation, either version 3 of the License, or
   7 // (at your option) any later version.
   8 //
   9 // Moodle is distributed in the hope that it will be useful,
  10 // but WITHOUT ANY WARRANTY; without even the implied warranty of
  11 // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  12 // GNU General Public License for more details.
  13 //
  14 // You should have received a copy of the GNU General Public License
  15 // along with Moodle.  If not, see <http://www.gnu.org/licenses/>.
  16
  17 /**
  18  * Group visibility methods
  19  *
  20  * @package   core_group
  21  * @copyright 2022 onwards Catalyst IT EU {@link https://catalyst-eu.net}
  22  * @author    Mark Johnson <mark.johnson@catalyst-eu.net>
  23  * @license   http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later
  24  */
  25
  26 namespace core_group;
  27
  28 /**
  29  * Group visibility methods.
  30  */
  31 class visibility {
  32
  33     /**
  34      * Store the number groups with visibility other than ALL on the course.
  35      *
  36      * @param int $courseid Course ID to update the cache for.
  37      * @param \cache|null $cache Existing cache instance. If null, once will be created.
  38      * @return void
  39      * @throws \dml_exception
  40      */
  41     public static function update_hiddengroups_cache(int $courseid, ?\cache $cache = null): void {
  42         global $DB;
  43         if (!$cache) {
  44             $cache = \cache::make('core', 'coursehiddengroups');
  45         }
  46         $hiddengroups = $DB->count_records_select('groups', 'courseid = ? AND visibility != ?',
  47                 [$courseid, GROUPS_VISIBILITY_ALL]);
  48         $cache->set($courseid, $hiddengroups);
  49     }
  50
  51     /**
  52      * Return whether a course currently had hidden groups.
  53      *
  54      * This can be used as a shortcut to decide whether visibility restrictions need to be applied. If this returns false,
  55      * we may be able to use cached data, or do a much simpler query.
  56      *
  57      * @param int $courseid
  58      * @return bool
  59      * @throws \coding_exception
  60      * @throws \dml_exception
  61      */
  62     public static function course_has_hidden_groups(int $courseid): bool {
  63         $cache = \cache::make('core', 'coursehiddengroups');
  64         $hiddengroups = $cache->get($courseid);
  65         if ($hiddengroups === false) {
  66             self::update_hiddengroups_cache($courseid, $cache);
  67             $cache->get($courseid);
  68         }
  69         return $hiddengroups > 0;
  70     }
  71
  72     /**
  73      * Can the current user view all the groups on the course?
  74      *
  75      * Returns true if there are no groups on the course with visibility != ALL,
  76      * or if the user has viewhiddengroups.
  77      *
  78      * This is useful for deciding whether we need to perform additional visibility checkes
  79      * such as the sql_* methods of this class.
  80      *
  81      * @param int $courseid
  82      * @return bool
  83      */
  84     public static function can_view_all_groups(int $courseid): bool {
  85         $viewhidden = has_capability('moodle/course:viewhiddengroups', \context_course::instance($courseid));
  86         $hashidden = self::course_has_hidden_groups($courseid);
  87         return $viewhidden || !$hashidden;
  88     }
  89
  90     /**
  91      * Return SQL conditions for determining whether a user can see a group and its memberships.
  92      *
  93      * @param int $userid
  94      * @param string $groupsalias The SQL alias being used for the groups table.
  95      * @param string $groupsmembersalias The SQL alias being used for the groups_members table.
  96      * @return array [$where, $params]
  97      */
  98     public static function sql_group_visibility_where(int $userid,
  99             string $groupsalias = 'g', string $groupsmembersalias = 'gm'): array {
 100         global $USER;
 101         // Apply visibility restrictions.
 102         // Everyone can see who is in groups with ALL visibility.
 103         $where = "({$groupsalias}.visibility = :all";
 104         $params['all'] = GROUPS_VISIBILITY_ALL;
 105         if ($userid == $USER->id) {
 106             // If the user is looking at their own groups, they can see those with MEMBERS or OWN visibility.
 107             $where .= " OR {$groupsalias}.visibility IN (:members, :own)";
 108             $params['members'] = GROUPS_VISIBILITY_MEMBERS;
 109             $params['own'] = GROUPS_VISIBILITY_OWN;
 110         } else {
 111             list($memberssql, $membersparams) = self::sql_members_visibility_condition($groupsalias, $groupsmembersalias);
 112             // If someone else's groups, they can see those with MEMBERS visibilty, only if they are a member too.
 113             $where .= " OR ($memberssql)";
 114             $params = array_merge($params, $membersparams);
 115         }
 116         $where .= ")";
 117         return [$where, $params];
 118     }
 119
 120     /**
 121      * Return SQL conditions for determining whether a user can see a group's members.
 122      *
 123      * @param string $groupsalias The SQL alias being used for the groups table.
 124      * @param string $groupsmembersalias The SQL alias being used for the groups_members table.
 125      * @param string $useralias The SQL alias being used for the user table.
 126      * @param string $paramprefix Prefix for the parameter names.
 127      * @return array [$where, $params]
 128      */
 129     public static function sql_member_visibility_where(
 130         string $groupsalias = 'g',
 131         string $groupsmembersalias = 'gm',
 132         string $useralias = 'u',
 133         string $paramprefix = '',
 134     ): array {
 135         global $USER;
 136
 137         list($memberssql, $membersparams) = self::sql_members_visibility_condition($groupsalias, $groupsmembersalias, $paramprefix);
 138
 139         $where = "(
 140             {$groupsalias}.visibility = :{$paramprefix}all
 141             OR ($memberssql)
 142             OR ({$groupsalias}.visibility = :{$paramprefix}own AND {$useralias}.id = :{$paramprefix}currentuser2)
 143         )";
 144         $params = [
 145             "{$paramprefix}all" => GROUPS_VISIBILITY_ALL,
 146             "{$paramprefix}own" => GROUPS_VISIBILITY_OWN,
 147             "{$paramprefix}currentuser2" => $USER->id,
 148         ];
 149         $params = array_merge($params, $membersparams);
 150         return [$where, $params];
 151     }
 152
 153     /**
 154      * Return a condition to check if a user can view a group because it has MEMBERS visibility and they are a member.
 155      *
 156      * @param string $groupsalias The SQL alias being used for the groups table.
 157      * @param string $groupsmembersalias The SQL alias being used for the groups_members table.
 158      * @param string $paramprefix Prefix for the parameter names.
 159      * @return array [$sql, $params]
 160      */
 161     protected static function sql_members_visibility_condition(
 162         string $groupsalias = 'g',
 163         string $groupsmembersalias = 'gm',
 164         string $paramprefix = '',
 165     ): array {
 166         global $USER;
 167         $sql = "{$groupsalias}.visibility = :{$paramprefix}members
 168                     AND (
 169                         SELECT gm2.id
 170                           FROM {groups_members} gm2
 171                          WHERE gm2.groupid = {$groupsmembersalias}.groupid
 172                                AND gm2.userid = :{$paramprefix}currentuser
 173                     ) IS NOT NULL";
 174         $params = [
 175             "{$paramprefix}members" => GROUPS_VISIBILITY_MEMBERS,
 176             "{$paramprefix}currentuser" => $USER->id
 177         ];
 178
 179         return [$sql, $params];
 180     }
 181 }