<?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\Component;

/**
 * @author resurtm <resurtm@gmail.com>
 * @since 2.0
 */
abstract class Mutex extends Component
{
	/**
	 * @var boolean whether all locks acquired in this process (i.e. local locks) must be released automagically
	 * before finishing script execution. Defaults to true. Setting this property to true means that all locks
	 * acquire in this process must be released in any case (regardless any kind of errors or exceptions).
	 */
	public $autoRelease = true;
	/**
	 * @var string[] names of the locks acquired in the current PHP process.
	 */
	private $_locks = array();


	/**
	 * Initializes the mutex component.
	 */
	public function init()
	{
		if ($this->autoRelease) {
			$mutex = $this;
			$locks = &$this->_locks;
			register_shutdown_function(function () use ($mutex, &$locks) {
				foreach ($locks as $lock) {
					$mutex->release($lock);
				}
			});
		}
	}

	/**
	 * @param string $name of the lock to be acquired. Must be unique.
	 * @param integer $timeout to wait for lock to be released. Defaults to zero meaning that method will return
	 * false immediately in case lock was already acquired.
	 * @return boolean lock acquiring result.
	 */
	public function acquire($name, $timeout = 0)
	{
		if ($this->acquireLock($name, $timeout)) {
			$this->_locks[] = $name;
			return true;
		} else {
			return false;
		}
	}

	/**
	 * Release acquired lock. This method will return false in case named lock was not found.
	 * @param string $name of the lock to be released. This lock must be already created.
	 * @return boolean lock release result: false in case named lock was not found..
	 */
	public function release($name)
	{
		if ($this->releaseLock($name)) {
			$index = array_search($name, $this->_locks);
			if ($index !== false) {
				unset($this->_locks[$index]);
			}
			return true;
		} else {
			return false;
		}
	}

	/**
	 * This method should be extended by concrete mutex implementations. Acquires lock by given name.
	 * @param string $name of the lock to be acquired.
	 * @param integer $timeout to wait for lock to become released.
	 * @return boolean acquiring result.
	 */
	abstract protected function acquireLock($name, $timeout = 0);

	/**
	 * This method should be extended by concrete mutex implementations. Releases lock by given name.
	 * @param string $name of the lock to be released.
	 * @return boolean release result.
	 */
	abstract protected function releaseLock($name);
}
