Proyectos de Subversion Moodle

<?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/>.

/**

 *  Media plugin filtering

 *

 *  This filter will replace any links to a media file with

 *  a media plugin that plays that media inline

 *

 * @package    filter

 * @subpackage mediaplugin

 * @copyright  2004 onwards Martin Dougiamas  {@link http://moodle.com}

 * @license    http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later

 */

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

/**

 * Automatic media embedding filter class.

 *

 * It is highly recommended to configure servers to be compatible with our slasharguments,

 * otherwise the "?d=600x400" may not work.

 *

 * @package    filter

 * @subpackage mediaplugin

 * @copyright  2004 onwards Martin Dougiamas  {@link http://moodle.com}

 * @license    http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later

 */

class filter_mediaplugin extends moodle_text_filter {

    /** @var bool True if currently filtering trusted text */

    private $trusted;

    /**

     * Setup page with filter requirements and other prepare stuff.

     *

     * @param moodle_page $page The page we are going to add requirements to.

     * @param context $context The context which contents are going to be filtered.

     */

    public function setup($page, $context) {

        // This only requires execution once per request.

        static $jsinitialised = false;

        if ($jsinitialised) {

            return;

        }

        $jsinitialised = true;

        // Set up the media manager so that media plugins requiring JS are initialised.

        $mediamanager = core_media_manager::instance($page);

    }

    public function filter($text, array $options = array()) {

        global $CFG, $PAGE;

        if (!is_string($text) or empty($text)) {

            // non string data can not be filtered anyway

            return $text;

        }

        if (stripos($text, '</a>') === false && stripos($text, '</video>') === false && stripos($text, '</audio>') === false) {

            // Performance shortcut - if there are no </a>, </video> or </audio> tags, nothing can match.

            return $text;

        }

        // Check permissions.

        $this->trusted = !empty($options['noclean']) or !empty($CFG->allowobjectembed);

        // Looking for tags.

        $matches = preg_split('/(<[^>]*>)/i', $text, -1, PREG_SPLIT_NO_EMPTY | PREG_SPLIT_DELIM_CAPTURE);

        if (!$matches) {

            return $text;

        }

        // Regex to find media extensions in an <a> tag.

        $embedmarkers = core_media_manager::instance()->get_embeddable_markers();

        $re = '~<a\s[^>]*href="([^"]*(?:' .  $embedmarkers . ')[^"]*)"[^>]*>([^>]*)</a>~is';

        $newtext = '';

        $validtag = '';

        $tagname = '';

        $sizeofmatches = count($matches);

        // We iterate through the given string to find valid <a> tags

        // and build them so that the callback function can check it for

        // embedded content. Then we rebuild the string.

        foreach ($matches as $idx => $tag) {

            if (preg_match('|</'.$tagname.'>|', $tag) && !empty($validtag)) {

                $validtag .= $tag;

                // Given we now have a valid <a> tag to process it's time for

                // ReDoS protection. Stop processing if a word is too large.

                if (strlen($validtag) < 4096) {

                    if ($tagname === 'a') {

                        $processed = preg_replace_callback($re, array($this, 'callback'), $validtag);

                    } else {

                        // For audio and video tags we just process them without precheck for embeddable markers.

                        $processed = $this->process_media_tag($validtag);

                    }

                }

                // Rebuilding the string with our new processed text.

                $newtext .= !empty($processed) ? $processed : $validtag;

                // Wipe it so we can catch any more instances to filter.

                $validtag = '';

                $processed = '';

            } else if (preg_match('/<(a|video|audio)\s[^>]*/', $tag, $tagmatches) && $sizeofmatches > 1 &&

                    (empty($validtag) || $tagname === strtolower($tagmatches[1]))) {

                // Looking for a starting tag. Ignore tags embedded into each other.

                $validtag = $tag;

                $tagname = strtolower($tagmatches[1]);

            } else {

                // If we have a validtag add to that to process later,

                // else add straight onto our newtext string.

                if (!empty($validtag)) {

                    $validtag .= $tag;

                } else {

                    $newtext .= $tag;

                }

            }

        }

        // Return the same string except processed by the above.

        return $newtext;

    }

    /**

     * Replace link with embedded content, if supported.

     *

     * @param array $matches

     * @return string

     */

    private function callback(array $matches) {

        $mediamanager = core_media_manager::instance();

        global $CFG, $PAGE;

        // Check if we ignore it.

        if (preg_match('/class="[^"]*nomediaplugin/i', $matches[0])) {

            return $matches[0];

        }

        // Get name.

        $name = trim($matches[2]);

        if (empty($name) or strpos($name, 'http') === 0) {

            $name = ''; // Use default name.

        }

        // Split provided URL into alternatives.

        $urls = $mediamanager->split_alternatives($matches[1], $width, $height);

        $options = [core_media_manager::OPTION_ORIGINAL_TEXT => $matches[0]];

        return $this->embed_alternatives($urls, $name, $width, $height, $options);

    }

    /**

     * Renders media files (audio or video) using suitable embedded player.

     *

     * Wrapper for {@link core_media_manager::embed_alternatives()}

     *

     * @param array $urls Array of moodle_url to media files

     * @param string $name Optional user-readable name to display in download link

     * @param int $width Width in pixels (optional)

     * @param int $height Height in pixels (optional)

     * @param array $options Array of key/value pairs

     * @return string HTML content of embed

     */

    protected function embed_alternatives($urls, $name, $width, $height, $options) {

        // Allow trusted content (or not).

        if ($this->trusted) {

            $options[core_media_manager::OPTION_TRUSTED] = true;

        }

        // We could test whether embed is possible using can_embed, but to save

        // time, let's just embed it with the 'fallback to blank' option which

        // does most of the same stuff anyhow.

        $options[core_media_manager::OPTION_FALLBACK_TO_BLANK] = true;

        // NOTE: Options are not passed through from filter because the 'embed'

        // code does not recognise filter options (it's a different kind of

        // option-space) as it can be used in non-filter situations.

        $result = core_media_manager::instance()->embed_alternatives($urls, $name, $width, $height, $options);

        // If something was embedded, return it, otherwise return original.

        if ($result !== '') {

            return $result;

        } else {

            return $options[core_media_manager::OPTION_ORIGINAL_TEXT];

        }

    }

    /**

     * Replaces <video> or <audio> tag with processed contents

     *

     * @param string $fulltext complete HTML snipped "<video ...>...</video>" or "<audio ...>....</audio>"

     * @return string

     */

    protected function process_media_tag($fulltext) {

        // Check if we ignore it.

        if (preg_match('/^<[^>]*class="[^"]*nomediaplugin/im', $fulltext)) {

            return $fulltext;

        }

        // Find all sources both as <video src=""> and as embedded <source> tags.

        $urls = [];

        if (preg_match('/^<[^>]*\bsrc="(.*?)"/im', $fulltext, $matches)) {

            $urls[] = new moodle_url($matches[1]);

        }

        if (preg_match_all('/<source\b[^>]*\bsrc="(.*?)"/im', $fulltext, $matches)) {

            foreach ($matches[1] as $url) {

                $urls[] = new moodle_url($url);

            }

        }

        // Extract width/height/title attributes and call embed_alternatives to find a suitable media player.

        if ($urls) {

            $options = [core_media_manager::OPTION_ORIGINAL_TEXT => $fulltext];

            $width = core_media_player_native::get_attribute($fulltext, 'width', PARAM_INT);

            $height = core_media_player_native::get_attribute($fulltext, 'height', PARAM_INT);

            $name = core_media_player_native::get_attribute($fulltext, 'title');

            return $this->embed_alternatives($urls, $name, $width, $height, $options);

        }

        return $fulltext;

    }

}