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

/**
 * A driver that use plain filesystem as data store
 */
class AJAX_Locking_Driver_File extends AJAX_Locking_Driver
{
	var $dir;

	/**
	 * Constructor
	 *
	 * @return AJAX_Locking_Driver
	 */
	function AJAX_Locking_Driver_File($dir = '/tmp', $timeout = false)
	{
		parent::AJAX_Locking_Driver($timeout);

		$this->dir = realpath($dir);
	}

	/**
	 * 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 = $this->_get($key);
		if (empty($value)) {
			// object is unlocked: lock it
			$value = $this->_getValue($user, $type, $id);
			$this->_set($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
				$this->_rm($key);
				$this->_set($key, $value);
				return true;
			} else {
				// object properly locked by (another?) user
				return ($owner == $user);
			}
		}

	}

	/**
	 * 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 = $this->_get($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
				$this->_rm($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 = $this->_get($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
					$this->_rm($key);
					return AJAX_LOCKING_TIMEOUT . '~' . $owner;
				} else {
					return AJAX_LOCKING_OWNED . '~' . $owner;
				}
			} else {
				if ($timeout) {
					// lock expired: remove it
					$this->_rm($key);
					return AJAX_LOCKING_UNLOCKED . '~' . 'nobody';
				} else {
					return AJAX_LOCKING_LOCKED . '~' . $owner;
				}
			}
		}
	}

	/**
	 * Returns the list of all active locks for administration purpose
	 *
	 * @return array of locks (owner, type, id), false if not implemented
	 */
	function getLocks()
	{
	    $files = array();
        $dh  = opendir($this->dir);
        while (false !== ($filename = readdir($dh))) {
            if (strstr($filename, AJAX_LOCKING_PREFIX) == $filename) {
                $files[] = $filename;
            }
        }

        $locks = array();
        foreach ($files as $f) {
            $value = file_get_contents($this->dir . DIRECTORY_SEPARATOR . $f);
            if ($value) {
                list($owner, $type, $id, $time) = $this->_parseValue($value);
                $timeout = (time() - $time > $this->timeout);
                if (!$timeout) {
                    $locks[] = array(
                        'owner' => $owner,
                        'type' => $type,
                        'id' => $id
                    );
                }
            }
        }

        return $locks;
	}

	/**
	 * Administrately delete lock
	 *
	 * @param string $type
	 * @param mixed $id
	 *
	 * @return true if the lock is deleted successfully, false otherwise
	 */
    function deleteLock($type, $id)
    {
        $key = $this->_getKey($type, $id);
        $this->_rm($key);
    }


	/**
	 * Returns the values stored in file $key
	 *
	 * @param string $key
	 * @return string
	 */
	function _get($key)
	{
	    $value = '';
	    $filename = $this->dir . DIRECTORY_SEPARATOR . $key;
	    if (file_exists($filename)) {
	        $value = file_get_contents($filename);
	    }
	    return $value;
	}

	/**
	 * Puts the value $value into file $key
	 *
	 * @param string $key
	 * @param string $value
	 */
	function _set($key, $value)
	{
	    $filename = $this->dir . DIRECTORY_SEPARATOR . $key;
	    $fp = fopen($filename, 'w');
	    fwrite($fp, $value);
	    fclose($fp);
	}

	/**
	 * Remove the file $key
	 *
	 * @param string $key
	 */
	function _rm($key)
	{
	    $filename = $this->dir . DIRECTORY_SEPARATOR . $key;
	    return @unlink($filename);
	}

}
?>