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   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  declare(strict_types=1);
  18  namespace mod_scorm\cache;
  19  use cache_definition;
  20  
  21  /**
  22   * Cache data source for the scorm elements.
  23   *
  24   * @package   mod_scorm
  25   * @copyright 2023 Catalyst IT Ltd
  26   * @author    Dan Marsden <dan@danmarsden.com>
  27   * @license   http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later
  28   */
  29  class elements implements \cache_data_source {
  30  
  31      /** @var elements the singleton instance of this class. */
  32      protected static $instance = null;
  33  
  34      /**
  35       * Returns an instance of the data source class that the cache can use for loading data using the other methods
  36       * specified by this interface.
  37       *
  38       * @param cache_definition $definition
  39       * @return object
  40       */
  41      public static function get_instance_for_cache(cache_definition $definition): elements {
  42          if (is_null(self::$instance)) {
  43              self::$instance = new elements();
  44          }
  45          return self::$instance;
  46      }
  47  
  48      /**
  49       * Loads the data for the key provided ready formatted for caching.
  50       *
  51       * @param string|int $key The key to load.
  52       * @return string What ever data should be returned, or null if it can't be loaded.
  53       * @throws \coding_exception
  54       */
  55      public function load_for_cache($key): ?string {
  56          global $DB;
  57  
  58          $element = $DB->get_field('scorm_element', 'id', ['element' => $key]);
  59          // Return null instead of false, because false will not be cached.
  60          return $element ?: null;
  61      }
  62  
  63      /**
  64       * Loads several keys for the cache.
  65       *
  66       * @param array $keys An array of keys each of which will be string|int.
  67       * @return array An array of matching data items.
  68       */
  69      public function load_many_for_cache(array $keys): array {
  70          global $DB;
  71          list ($elementsql, $params) = $DB->get_in_or_equal($keys);
  72          $sql = "SELECT element, id
  73                    FROM {scorm_element}
  74                   WHERE element ".$elementsql;
  75          return $DB->get_records_sql_menu($sql, $params);
  76      }
  77  }