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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  /**
  18   * Cache data source for the time of the last message between users.
  19   *
  20   * @package    core_message
  21   * @category   cache
  22   * @copyright  2016 Ryan Wyllie <ryan@moodle.com>
  23   * @license    http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later
  24   */
  25  
  26  namespace core_message;
  27  
  28  defined('MOODLE_INTERNAL') || die();
  29  
  30  /**
  31   * Cache data source for the time of the last message in a conversation.
  32   *
  33   * @package    core_message
  34   * @category   cache
  35   * @copyright  2016 Ryan Wyllie <ryan@moodle.com>
  36   * @license    http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later
  37   */
  38  class time_last_message_between_users implements \cache_data_source {
  39  
  40      /** @var time_last_message_between_users the singleton instance of this class. */
  41      protected static $instance = null;
  42  
  43      /**
  44       * Returns an instance of the data source class that the cache can use for loading data using the other methods
  45       * specified by the cache_data_source interface.
  46       *
  47       * @param \cache_definition $definition
  48       * @return object
  49       */
  50      public static function get_instance_for_cache(\cache_definition $definition) {
  51          if (is_null(self::$instance)) {
  52              self::$instance = new time_last_message_between_users();
  53          }
  54          return self::$instance;
  55      }
  56  
  57      /**
  58       * Loads the data for the key provided ready formatted for caching.
  59       *
  60       * @param string|int $key The key to load.
  61       * @return mixed What ever data should be returned, or false if it can't be loaded.
  62       */
  63      public function load_for_cache($key) {
  64          $message = api::get_most_recent_conversation_message($key);
  65  
  66          if ($message) {
  67              return $message->timecreated;
  68          } else {
  69              return null;
  70          }
  71      }
  72  
  73      /**
  74       * Loads several keys for the cache.
  75       *
  76       * @param array $keys An array of keys each of which will be string|int.
  77       * @return array An array of matching data items.
  78       */
  79      public function load_many_for_cache(array $keys) {
  80          $results = [];
  81  
  82          foreach ($keys as $key) {
  83              $results[] = $this->load_for_cache($key);
  84          }
  85  
  86          return $results;
  87      }
  88  }