<?php
/**
 * @link http://www.yiiframework.com/
 * @copyright Copyright (c) 2008 Yii Software LLC
 * @license http://www.yiiframework.com/license/
 */

namespace yii\mutex;

use Yii;
use yii\base\InvalidConfigException;

/**
 * MysqlMutex implements mutex "lock" mechanism via MySQL locks.
 *
 * Application configuration example:
 *
 * ```
 * [
 *     'components' => [
 *         'db'=> [
 *             'class' => 'yii\db\Connection',
 *             'dsn' => 'mysql:host=127.0.0.1;dbname=demo',
 *         ]
 *         'mutex'=> [
 *             'class' => 'yii\mutex\MysqlMutex',
 *         ],
 *     ],
 * ]
 * ```
 *
 * GET_LOCK('MySQL',10)返回结果为1，说明成功得到了一个名称为'MySQL'的锁，持续时间为10秒。
 * IS_USED_LOCK('MySQL')返回结果为当前连接ID，表示名称为'MySQL'的锁正在被使用。
 * IS_FREE_LOCK('MySQL')返回结果为0，说明名称为'MySQL'的锁正在被使用。
 * RELEASE_LOCK('MySQL')返回值为1，说明解锁成功。
 *
 * @see Mutex
 *
 * @author resurtm <resurtm@gmail.com>
 * @since 2.0
 */
class MysqlMutex extends DbMutex
{
    /**
     * Initializes MySQL specific mutex component implementation.
     * @throws InvalidConfigException if [[db]] is not MySQL connection.
     */
    public function init()
    {
        parent::init();
        if ($this->db->driverName !== 'mysql') {
            throw new InvalidConfigException('In order to use MysqlMutex connection must be configured to use MySQL database.');
        }
    }

    /**
     * Acquires lock by given name.
     * @param string $name of the lock to be acquired.
     * @param integer $timeout to wait for lock to become released.
     * @return boolean acquiring result.
     * @see http://dev.mysql.com/doc/refman/5.0/en/miscellaneous-functions.html#function_get-lock
     */
    protected function acquireLock($name, $timeout = 0)
    {
        return (bool) $this->db
            ->createCommand('SELECT GET_LOCK(:name, :timeout)', [':name' => $name, ':timeout' => $timeout])
            ->queryScalar();
    }

    /**
     * Releases lock by given name.
     * @param string $name of the lock to be released.
     * @return boolean release result.
     * @see http://dev.mysql.com/doc/refman/5.0/en/miscellaneous-functions.html#function_release-lock
     */
    protected function releaseLock($name)
    {
        return (bool) $this->db
            ->createCommand('SELECT RELEASE_LOCK(:name)', [':name' => $name])
            ->queryScalar();
    }
}
