<?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/>.

namespace core_cache;

/**
 * Cache Data Source.
 *
 * The cache data source interface can be implemented by any class within Moodle.
 * If implemented then the class can be reference in a cache definition and will be used to load information that cannot be
 * retrieved from the cache. As part of its retrieval that information will also be loaded into the cache.
 *
 * This allows developers to created a complete cache solution that can be used through code ensuring consistent cache
 * interaction and loading. Allowing them in turn to centralise code and help keeps things more easily maintainable.
 *
 * Can be implemented by any class.
 *
 * @package    core_cache
 * @category   cache
 * @copyright  2012 Sam Hemelryk
 * @license    http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later
 */
interface data_source_interface {
    /**
     * Returns an instance of the data source class that the cache can use for loading data using the other methods
     * specified by this interface.
     *
     * @param definition $definition
     * @return object
     */
    public static function get_instance_for_cache(definition $definition);

    /**
     * Loads the data for the key provided ready formatted for caching.
     *
     * @param string|int $key The key to load.
     * @return mixed What ever data should be returned, or false if it can't be loaded.
     */
    public function load_for_cache($key);

    /**
     * Loads several keys for the cache.
     *
     * @param array $keys An array of keys each of which will be string|int.
     * @return array An array of matching data items.
     */
    public function load_many_for_cache(array $keys);
}

// Alias this class to the old name.
// This file will be autoloaded by the legacyclasses autoload system.
// In future all uses of this class will be corrected and the legacy references will be removed.
class_alias(data_source_interface::class, \cache_data_source::class);