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<?php
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// This file is part of Moodle - http://moodle.org/
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//
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// Moodle is free software: you can redistribute it and/or modify
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// it under the terms of the GNU General Public License as published by
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// the Free Software Foundation, either version 3 of the License, or
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// (at your option) any later version.
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//
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// Moodle is distributed in the hope that it will be useful,
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// but WITHOUT ANY WARRANTY; without even the implied warranty of
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// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
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// GNU General Public License for more details.
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//
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// You should have received a copy of the GNU General Public License
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// along with Moodle.  If not, see <http://www.gnu.org/licenses/>.
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/**
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 * Cache data source for the lesson overrides.
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 *
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 * @package   mod_lesson
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 * @copyright 2021 Shamim Rezaie <shamim@moodle.com>
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 * @license   http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later
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 */
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declare(strict_types=1);
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namespace mod_lesson\cache;
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use cache_definition;
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/**
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 * Class lesson_overrides
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 *
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 * @package   mod_lesson
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 * @copyright 2021 Shamim Rezaie <shamim@moodle.com>
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 * @license   http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later
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 */
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class overrides implements \cache_data_source {
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    /** @var overrides the singleton instance of this class. */
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    protected static $instance = null;
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    /**
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     * Returns an instance of the data source class that the cache can use for loading data using the other methods
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     * specified by this interface.
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     *
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     * @param cache_definition $definition
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     * @return object
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     */
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    public static function get_instance_for_cache(cache_definition $definition): overrides {
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        if (is_null(self::$instance)) {
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            self::$instance = new overrides();
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        }
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        return self::$instance;
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    }
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    /**
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     * Loads the data for the key provided ready formatted for caching.
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     *
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     * @param string|int $key The key to load.
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     * @return mixed What ever data should be returned, or false if it can't be loaded.
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     * @throws \coding_exception
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     */
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    public function load_for_cache($key) {
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        global $DB;
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        [$lessonid, $ug, $ugid] = explode('_', $key);
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        $lessonid = (int) $lessonid;
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        switch ($ug) {
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            case 'u':
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                $userid = (int) $ugid;
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                $override = $DB->get_record(
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                    'lesson_overrides',
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                    ['lessonid' => $lessonid, 'userid' => $userid],
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                    'available, deadline, timelimit, review, maxattempts, retake, password'
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                );
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                break;
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            case 'g':
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                $groupid = (int) $ugid;
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                $override = $DB->get_record(
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                    'lesson_overrides',
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                    ['lessonid' => $lessonid, 'groupid' => $groupid],
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                    'available, deadline, timelimit, review, maxattempts, retake, password'
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                );
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                break;
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            default:
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                throw new \coding_exception('Invalid cache key');
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        }
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        // Return null instead of false, because false will not be cached.
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        return $override ?: null;
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    }
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    /**
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     * Loads several keys for the cache.
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     *
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     * @param array $keys An array of keys each of which will be string|int.
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     * @return array An array of matching data items.
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     */
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    public function load_many_for_cache(array $keys) {
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        $results = [];
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        foreach ($keys as $key) {
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            $results[] = $this->load_for_cache($key);
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        }
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        return $results;
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    }
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}