<?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 store feature: locking.
 *
 * This is a feature that cache stores can implement if they wish to support locking themselves rather
 * than having the cache loader handle it for them.
 *
 * Can be implemented by classes already implementing store.
 * @package core_cache
 * @copyright Sam Hemelryk
 * @license http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later
 */
interface lockable_cache_interface {
    /**
     * Acquires a lock on the given key for the given identifier.
     *
     * @param string $key The key we are locking.
     * @param string $ownerid The identifier so we can check if we have the lock or if it is someone else.
     *      The use of this property is entirely optional and implementations can act as they like upon it.
     * @return bool True if the lock could be acquired, false otherwise.
     */
    public function acquire_lock($key, $ownerid);

    /**
     * Test if there is already a lock for the given key and if there is whether it belongs to the calling code.
     *
     * @param string $key The key we are locking.
     * @param string $ownerid The identifier so we can check if we have the lock or if it is someone else.
     * @return bool True if this code has the lock, false if there is a lock but this code doesn't have it, null if there
     *      is no lock.
     */
    public function check_lock_state($key, $ownerid);

    /**
     * Releases the lock on the given key.
     *
     * @param string $key The key we are locking.
     * @param string $ownerid The identifier so we can check if we have the lock or if it is someone else.
     *      The use of this property is entirely optional and implementations can act as they like upon it.
     * @return bool True if the lock has been released, false if there was a problem releasing the lock.
     */
    public function release_lock($key, $ownerid);
}

// 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(lockable_cache_interface::class, \cache_is_lockable::class);