filter/mediaplugin/filter.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  *  Media plugin filtering
  19  *
  20  *  This filter will replace any links to a media file with
  21  *  a media plugin that plays that media inline
  22  *
  23  * @package    filter
  24  * @subpackage mediaplugin
  25  * @copyright  2004 onwards Martin Dougiamas  {@link http://moodle.com}
  26  * @license    http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later
  27  */
  28
  29 defined('MOODLE_INTERNAL') || die();
  30
  31 /**
  32  * Automatic media embedding filter class.
  33  *
  34  * It is highly recommended to configure servers to be compatible with our slasharguments,
  35  * otherwise the "?d=600x400" may not work.
  36  *
  37  * @package    filter
  38  * @subpackage mediaplugin
  39  * @copyright  2004 onwards Martin Dougiamas  {@link http://moodle.com}
  40  * @license    http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later
  41  */
  42 class filter_mediaplugin extends moodle_text_filter {
  43     /** @var bool True if currently filtering trusted text */
  44     private $trusted;
  45
  46     /**
  47      * Setup page with filter requirements and other prepare stuff.
  48      *
  49      * @param moodle_page $page The page we are going to add requirements to.
  50      * @param context $context The context which contents are going to be filtered.
  51      */
  52     public function setup($page, $context) {
  53         // This only requires execution once per request.
  54         static $jsinitialised = false;
  55         if ($jsinitialised) {
  56             return;
  57         }
  58         $jsinitialised = true;
  59
  60         // Set up the media manager so that media plugins requiring JS are initialised.
  61         $mediamanager = core_media_manager::instance($page);
  62     }
  63
  64     public function filter($text, array $options = array()) {
  65         global $CFG, $PAGE;
  66
  67         if (!is_string($text) or empty($text)) {
  68             // non string data can not be filtered anyway
  69             return $text;
  70         }
  71
  72         if (stripos($text, '</a>') === false && stripos($text, '</video>') === false && stripos($text, '</audio>') === false) {
  73             // Performance shortcut - if there are no </a>, </video> or </audio> tags, nothing can match.
  74             return $text;
  75         }
  76
  77         // Check SWF permissions.
  78         $this->trusted = !empty($options['noclean']) or !empty($CFG->allowobjectembed);
  79
  80         // Looking for tags.
  81         $matches = preg_split('/(<[^>]*>)/i', $text, -1, PREG_SPLIT_NO_EMPTY | PREG_SPLIT_DELIM_CAPTURE);
  82
  83         if (!$matches) {
  84             return $text;
  85         }
  86
  87         // Regex to find media extensions in an <a> tag.
  88         $embedmarkers = core_media_manager::instance()->get_embeddable_markers();
  89         $re = '~<a\s[^>]*href="([^"]*(?:' .  $embedmarkers . ')[^"]*)"[^>]*>([^>]*)</a>~is';
  90
  91         $newtext = '';
  92         $validtag = '';
  93         $tagname = '';
  94         $sizeofmatches = count($matches);
  95
  96         // We iterate through the given string to find valid <a> tags
  97         // and build them so that the callback function can check it for
  98         // embedded content. Then we rebuild the string.
  99         foreach ($matches as $idx => $tag) {
 100             if (preg_match('|</'.$tagname.'>|', $tag) && !empty($validtag)) {
 101                 $validtag .= $tag;
 102
 103                 // Given we now have a valid <a> tag to process it's time for
 104                 // ReDoS protection. Stop processing if a word is too large.
 105                 if (strlen($validtag) < 4096) {
 106                     if ($tagname === 'a') {
 107                         $processed = preg_replace_callback($re, array($this, 'callback'), $validtag);
 108                     } else {
 109                         // For audio and video tags we just process them without precheck for embeddable markers.
 110                         $processed = $this->process_media_tag($validtag);
 111                     }
 112                 }
 113                 // Rebuilding the string with our new processed text.
 114                 $newtext .= !empty($processed) ? $processed : $validtag;
 115                 // Wipe it so we can catch any more instances to filter.
 116                 $validtag = '';
 117                 $processed = '';
 118             } else if (preg_match('/<(a|video|audio)\s[^>]*/', $tag, $tagmatches) && $sizeofmatches > 1 &&
 119                     (empty($validtag) || $tagname === strtolower($tagmatches[1]))) {
 120                 // Looking for a starting tag. Ignore tags embedded into each other.
 121                 $validtag = $tag;
 122                 $tagname = strtolower($tagmatches[1]);
 123             } else {
 124                 // If we have a validtag add to that to process later,
 125                 // else add straight onto our newtext string.
 126                 if (!empty($validtag)) {
 127                     $validtag .= $tag;
 128                 } else {
 129                     $newtext .= $tag;
 130                 }
 131             }
 132         }
 133
 134         // Return the same string except processed by the above.
 135         return $newtext;
 136     }
 137
 138     /**
 139      * Replace link with embedded content, if supported.
 140      *
 141      * @param array $matches
 142      * @return string
 143      */
 144     private function callback(array $matches) {
 145         $mediamanager = core_media_manager::instance();
 146
 147         global $CFG, $PAGE;
 148         // Check if we ignore it.
 149         if (preg_match('/class="[^"]*nomediaplugin/i', $matches[0])) {
 150             return $matches[0];
 151         }
 152
 153         // Get name.
 154         $name = trim($matches[2]);
 155         if (empty($name) or strpos($name, 'http') === 0) {
 156             $name = ''; // Use default name.
 157         }
 158
 159         // Split provided URL into alternatives.
 160         $urls = $mediamanager->split_alternatives($matches[1], $width, $height);
 161
 162         $options = [core_media_manager::OPTION_ORIGINAL_TEXT => $matches[0]];
 163         return $this->embed_alternatives($urls, $name, $width, $height, $options);
 164     }
 165
 166     /**
 167      * Renders media files (audio or video) using suitable embedded player.
 168      *
 169      * Wrapper for {@link core_media_manager::embed_alternatives()}
 170      *
 171      * @param array $urls Array of moodle_url to media files
 172      * @param string $name Optional user-readable name to display in download link
 173      * @param int $width Width in pixels (optional)
 174      * @param int $height Height in pixels (optional)
 175      * @param array $options Array of key/value pairs
 176      * @return string HTML content of embed
 177      */
 178     protected function embed_alternatives($urls, $name, $width, $height, $options) {
 179
 180         // Allow SWF (or not).
 181         if ($this->trusted) {
 182             $options[core_media_manager::OPTION_TRUSTED] = true;
 183         }
 184
 185         // We could test whether embed is possible using can_embed, but to save
 186         // time, let's just embed it with the 'fallback to blank' option which
 187         // does most of the same stuff anyhow.
 188         $options[core_media_manager::OPTION_FALLBACK_TO_BLANK] = true;
 189
 190         // NOTE: Options are not passed through from filter because the 'embed'
 191         // code does not recognise filter options (it's a different kind of
 192         // option-space) as it can be used in non-filter situations.
 193         $result = core_media_manager::instance()->embed_alternatives($urls, $name, $width, $height, $options);
 194
 195         // If something was embedded, return it, otherwise return original.
 196         if ($result !== '') {
 197             return $result;
 198         } else {
 199             return $options[core_media_manager::OPTION_ORIGINAL_TEXT];
 200         }
 201     }
 202
 203     /**
 204      * Replaces <video> or <audio> tag with processed contents
 205      *
 206      * @param string $fulltext complete HTML snipped "<video ...>...</video>" or "<audio ...>....</audio>"
 207      * @return string
 208      */
 209     protected function process_media_tag($fulltext) {
 210         // Check if we ignore it.
 211         if (preg_match('/^<[^>]*class="[^"]*nomediaplugin/im', $fulltext)) {
 212             return $fulltext;
 213         }
 214
 215         // Find all sources both as <video src=""> and as embedded <source> tags.
 216         $urls = [];
 217         if (preg_match('/^<[^>]*\bsrc="(.*?)"/im', $fulltext, $matches)) {
 218             $urls[] = new moodle_url($matches[1]);
 219         }
 220         if (preg_match_all('/<source\b[^>]*\bsrc="(.*?)"/im', $fulltext, $matches)) {
 221             foreach ($matches[1] as $url) {
 222                 $urls[] = new moodle_url($url);
 223             }
 224         }
 225         // Extract width/height/title attributes and call embed_alternatives to find a suitable media player.
 226         if ($urls) {
 227             $options = [core_media_manager::OPTION_ORIGINAL_TEXT => $fulltext];
 228             $width = core_media_player_native::get_attribute($fulltext, 'width', PARAM_INT);
 229             $height = core_media_player_native::get_attribute($fulltext, 'height', PARAM_INT);
 230             $name = core_media_player_native::get_attribute($fulltext, 'title');
 231             return $this->embed_alternatives($urls, $name, $width, $height, $options);
 232         }
 233         return $fulltext;
 234     }
 235 }