<?php
require_once('Driver.php');
require_once('System/SharedMemory.php');

/**
 * A driver that use System_SharedMemory as data store
 */
class AJAX_Locking_Driver_SharedMemory extends AJAX_Locking_Driver
{
	var $shared;

	/**
	 * Constructor
	 *
	 * @return AJAX_Locking_Driver
	 */
	function AJAX_Locking_Driver_SharedMemory($type = false, $options = false, $timeout = false)
	{
		parent::AJAX_Locking_Driver($timeout);

		$this->shared = &System_SharedMemory::factory($type, $options);
	}

	/**
	 * Locks an object
	 *
	 * @param mixed $user	id of the user who wants to lock
	 * @param string $type	type/classname of the object
	 * @param mixed $id		id of the object
	 * @return boolean true if the unlock was successfull, false otherwise
	 */
	function lock($user, $type, $id)
	{
		$key = $this->_getKey($type, $id);
		$value = $this->shared->get($key);
		if (empty($value)) {
			// object is unlocked: lock it
			$value = $this->_getValue($user, $type, $id);
			$this->shared->set($key, $value);
			return true;
		} else {
			// object is locked: check if lock expired
			list($owner, $type, $id, $time) = $this->_parseValue($value);
			if (time() - $time > $this->timeout) {
				// lock expired: remove it and lock
				$this->shared->rm($key);
				$this->shared->set($key, $value);
				return true;
			} else {
				// object properly locked by another user
				return false;
			}
		}

	}

	/**
	 * Unlocks an object
	 *
	 * @param mixed $user	id of the user who wants to unlock
	 * @param string $type	type/classname of the object
	 * @param mixed $id		id of the object
	 * @return boolean true if the unlock was successfull, false otherwise
	 */
	function unlock($user, $type, $id)
	{
		$key = $this->_getKey($type, $id);
		$value = $this->shared->get($key);
		if (empty($value)) {
			// object was not locked
			return false;
		} else {
			// check if user is owner of the lock
			list($owner, $type, $id, $time) = $this->_parseValue($value);
			if ($user == $owner) {
				// unlock it
				$this->shared->rm($key);
				return true;
			} else {
				// user cannot unlock it
				return false;
			}
		}
	}

	/**
	 * Returns the status of the object (lock or unlocked)
	 *
	 * @param mixed $user	id of the user who wants to know the object's status
	 * @param string $type	type/classname of the object
	 * @param mixed $id		id of the object
	 * @return string the status and the owner of the object
	 */
	function status($user, $type, $id)
	{
		$key = $this->_getKey($type, $id);
		$value = $this->shared->get($key);
		if (empty($value)) {
			// object is unlocked
			return AJAX_LOCKING_UNLOCKED . '~' . 'noboby';
		} else {
			// object is locked:
			// 1. check if current user is owner of the lock
			// 2. check if lock expired
			list($owner, $type, $id, $time) = $this->_parseValue($value);
			$timeout = (time() - $time > $this->timeout);
			if ($owner == $user) {
				if ($timeout) {
					// lock expired: remove it and inform it's ower
					$this->shared->rm($key);
					return AJAX_LOCKING_TIMEOUT . '~' . $owner;
				} else {
					return AJAX_LOCKING_OWNED . '~' . $owner;
				}
			} else {
				if ($timeout) {
					// lock expired: remove it
					$this->shared->rm($key);
					return AJAX_LOCKING_UNLOCKED . '~' . 'nobody';
				} else {
					return AJAX_LOCKING_LOCKED . '~' . $owner;
				}
			}
		}
	}
}
?>