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/>.

/**

 * This filter provides automatic support for MathJax

 *

 * @package    filter_mathjaxloader

 * @copyright  2013 Damyon Wiese (damyon@moodle.com)

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

 */

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

/**

 * Mathjax filtering

 */

class filter_mathjaxloader extends moodle_text_filter {

    /*

     * Perform a mapping of the moodle language code to the equivalent for MathJax.

     *

     * @param string $moodlelangcode - The moodle language code - e.g. en_pirate

     * @return string The MathJax language code.

     */

    public function map_language_code($moodlelangcode) {

        // List of language codes found in the MathJax/localization/ directory.

        $mathjaxlangcodes = [

            'ar', 'ast', 'bcc', 'bg', 'br', 'ca', 'cdo', 'ce', 'cs', 'cy', 'da', 'de', 'diq', 'en', 'eo', 'es', 'fa',

            'fi', 'fr', 'gl', 'he', 'ia', 'it', 'ja', 'kn', 'ko', 'lb', 'lki', 'lt', 'mk', 'nl', 'oc', 'pl', 'pt',

            'pt-br', 'qqq', 'ru', 'scn', 'sco', 'sk', 'sl', 'sv', 'th', 'tr', 'uk', 'vi', 'zh-hans', 'zh-hant'

        ];

        // List of explicit mappings and known exceptions (moodle => mathjax).

        $explicit = [

            'cz' => 'cs',

            'pt_br' => 'pt-br',

            'zh_tw' => 'zh-hant',

            'zh_cn' => 'zh-hans',

        ];

        // If defined, explicit mapping takes the highest precedence.

        if (isset($explicit[$moodlelangcode])) {

            return $explicit[$moodlelangcode];

        }

        // If there is exact match, it will be probably right.

        if (in_array($moodlelangcode, $mathjaxlangcodes)) {

            return $moodlelangcode;

        }

        // Finally try to find the best matching mathjax pack.

        $parts = explode('_', $moodlelangcode, 2);

        if (in_array($parts[0], $mathjaxlangcodes)) {

            return $parts[0];

        }

        // No more guessing, use English.

        return 'en';

    }

    /*

     * Add the javascript to enable mathjax processing on this page.

     *

     * @param moodle_page $page The current page.

     * @param context $context The current context.

     */

    public function setup($page, $context) {

        if ($page->requires->should_create_one_time_item_now('filter_mathjaxloader-scripts')) {

            $url = get_config('filter_mathjaxloader', 'httpsurl');

            $lang = $this->map_language_code(current_language());

            $url = new moodle_url($url, array('delayStartupUntil' => 'configured'));

            $page->requires->js($url);

            $config = get_config('filter_mathjaxloader', 'mathjaxconfig');

            $wwwroot = new moodle_url('/');

            $config = str_replace('{wwwroot}', $wwwroot->out(true), $config);

            $params = array('mathjaxconfig' => $config, 'lang' => $lang);

            $page->requires->js_call_amd('filter_mathjaxloader/loader', 'configure', [$params]);

        }

    }

    /*

     * This function wraps the filtered text in a span, that mathjaxloader is configured to process.

     *

     * @param string $text The text to filter.

     * @param array $options The filter options.

     */

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

        global $PAGE;

        $legacy = get_config('filter_mathjaxloader', 'texfiltercompatibility');

        $extradelimiters = explode(',', get_config('filter_mathjaxloader', 'additionaldelimiters'));

        if ($legacy) {

            // This replaces any of the tex filter maths delimiters with the default for inline maths in MathJAX "\( blah \)".

            // E.g. "<tex.*> blah </tex>".

            $text = preg_replace('|<(/?) *tex( [^>]*)?>|u', '[\1tex]', $text);

            // E.g. "[tex.*] blah [/tex]".

            $text = str_replace('[tex]', '\\(', $text);

            $text = str_replace('[/tex]', '\\)', $text);

            // E.g. "$$ blah $$".

            $text = preg_replace('|\$\$([\S\s]*?)\$\$|u', '\\(\1\\)', $text);

            // E.g. "\[ blah \]".

            $text = str_replace('\\[', '\\(', $text);

            $text = str_replace('\\]', '\\)', $text);

        }

        $hasextra = false;

        foreach ($extradelimiters as $extra) {

            if ($extra && strpos($text, $extra) !== false) {

                $hasextra = true;

                break;

            }

        }

        $hasdisplayorinline = false;

        if ($hasextra) {

            // Convert the HTML tag wrapper inside the equation to entities.

            $text = $this->escape_html_tag_wrapper($text);

            // If custom dilimeters are used, wrap whole text to prevent autolinking.

            $text = '<span class="nolink">' . $text . '</span>';

        } else if (preg_match('/\\\\[[(]/', $text) || preg_match('/\$\$/', $text)) {

            // Convert the HTML tag wrapper inside the equation to entities.

            $text = $this->escape_html_tag_wrapper($text);

            // Only parse the text if there are mathjax symbols in it. The recognized

            // math environments are \[ \] and $$ $$ for display mathematics and \( \)

            // for inline mathematics.

            // Note: 2 separate regexes seems to perform better here than using a single

            // regex with groupings.

            // Wrap display and inline math environments in nolink spans.

            // Do not wrap nested environments, i.e., if inline math is nested

            // inside display math, only the outer display math is wrapped in

            // a span. The span HTML inside a LaTex math environment would break

            // MathJax. See MDL-61981.

            list($text, $hasdisplayorinline) = $this->wrap_math_in_nolink($text);

        }

        if ($hasdisplayorinline || $hasextra) {

            $PAGE->requires->js_call_amd('filter_mathjaxloader/loader', 'typeset');

            return '<span class="filter_mathjaxloader_equation">' . $text . '</span>';

        }

        return $text;

    }

    /**

     * Find math environments in the $text and wrap them in no link spans

     * (<span class="nolink"></span>). If math environments are nested, only

     * the outer environment is wrapped in the span.

     *

     * The recognized math environments are \[ \] and $$ $$ for display

     * mathematics and \( \) for inline mathematics.

     *

     * @param string $text The text to filter.

     * @return array An array containing the potentially modified text and

     * a boolean that is true if any changes were made to the text.

     */

    protected function wrap_math_in_nolink($text) {

        $i = 1;

        $len = strlen($text);

        $displaystart = -1;

        $displaybracket = false;

        $displaydollar = false;

        $inlinestart = -1;

        $changesdone = false;

        // Loop over the $text once.

        while ($i < $len) {

            if ($displaystart === -1) {

                // No display math has started yet.

                if ($text[$i - 1] === '\\' && $text[$i] === '[') {

                    // Display mode \[ begins.

                    $displaystart = $i - 1;

                    $displaybracket = true;

                } else if ($text[$i - 1] === '$' && $text[$i] === '$') {

                    // Display mode $$ begins.

                    $displaystart = $i - 1;

                    $displaydollar = true;

                } else if ($text[$i - 1] === '\\' && $text[$i] === '(') {

                    // Inline math \( begins, not nested inside display math.

                    $inlinestart = $i - 1;

                } else if ($text[$i - 1] === '\\' && $text[$i] === ')' && $inlinestart > -1) {

                    // Inline math ends, not nested inside display math.

                    // Wrap the span around it.

                    $text = $this->insert_span($text, $inlinestart, $i);

                    $inlinestart = -1; // Reset.

                    $i += 28; // The $text length changed due to the <span>.

                    $len += 28;

                    $changesdone = true;

                }

            } else {

                // Display math open.

                if (($text[$i - 1] === '\\' && $text[$i] === ']' && $displaybracket) ||

                        ($text[$i - 1] === '$' && $text[$i] === '$' && $displaydollar)) {

                    // Display math ends, wrap the span around it.

                    $text = $this->insert_span($text, $displaystart, $i);

                    $displaystart = -1; // Reset.

                    $displaybracket = false;

                    $displaydollar = false;

                    $i += 28; // The $text length changed due to the <span>.

                    $len += 28;

                    $changesdone = true;

                }

            }

            ++$i;

        }

        return array($text, $changesdone);

    }

    /**

     * Wrap a portion of the $text inside a no link span

     * (<span class="nolink"></span>). The whole text is then returned.

     *

     * @param string $text The text to modify.

     * @param int $start The start index of the substring in $text that should

     * be wrapped in the span.

     * @param int $end The end index of the substring in $text that should be

     * wrapped in the span.

     * @return string The whole $text with the span inserted around

     * the defined substring.

     */

    protected function insert_span($text, $start, $end) {

        return substr_replace($text,

                '<span class="nolink">'. substr($text, $start, $end - $start + 1) .'</span>',

                $start,

                $end - $start + 1);

    }

    /**

     * Escapes HTML tags within a string.

     *

     * This function replaces HTML tags enclosed in curly brackets with their respective HTML entities.

     *

     * @param string $text The input string containing HTML tags.

     * @return string Returns the input string with HTML tags escaped.

     */

    private function escape_html_tag_wrapper(string $text): string {

        return preg_replace_callback('/\{([^}]+)\}/', function(array $matches): string {

            $search = ['<', '>'];

            $replace = ['<', '>'];

            return str_replace($search, $replace, $matches[0]);

        }, $text);

    }

}