<?php
/**
 * Part of the Fuel framework.
 *
 * @package    Fuel
 * @version    1.0
 * @author     Fuel Development Team
 * @license    MIT License
 * @copyright  2010 - 2012 Fuel Development Team
 * @link       http://fuelphp.com
 */

namespace Fuel\Core;



// --------------------------------------------------------------------

class Session_File extends \Session_Driver
{

	/**
	 * array of driver config defaults
	 */
	protected static $_defaults = array(
		'cookie_name'		=> 'fuelfid',				// name of the session cookie for file based sessions
		'path'				=>	'/tmp',					// path where the session files should be stored
		'gc_probability'	=>	5						// probability % (between 0 and 100) for garbage collection
	);

	// --------------------------------------------------------------------

	public function __construct($config = array())
	{
		// merge the driver config with the global config
		$this->config = array_merge($config, is_array($config['file']) ? $config['file'] : static::$_defaults);

		$this->config = $this->_validate_config($this->config);
	}

	// --------------------------------------------------------------------

	/**
	 * create a new session
	 *
	 * @access	public
	 * @return	Fuel\Core\Session_File
	 */
	public function create()
	{
		// create a new session
		$this->keys['session_id']	= $this->_new_session_id();
		$this->keys['previous_id']	= $this->keys['session_id'];	// prevents errors if previous_id has a unique index
		$this->keys['ip_hash']		= md5(\Input::ip().\Input::real_ip());
		$this->keys['user_agent']	= \Input::user_agent();
		$this->keys['created'] 		= $this->time->get_timestamp();
		$this->keys['updated'] 		= $this->keys['created'];

		// create the session record
		$this->_write_file($this->keys['session_id'], serialize(array()));

		// and set the session cookie
		$this->_set_cookie();

		return $this;
	}

	// --------------------------------------------------------------------

	/**
	 * read the session
	 *
	 * @access	public
	 * @param	boolean, set to true if we want to force a new session to be created
	 * @return	Fuel\Core\Session_Driver
	 */
	public function read($force = false)
	{
		// get the session cookie
		$cookie = $this->_get_cookie();

		// if no session cookie was present, initialize a new session
		if ($cookie === false or $force)
		{
			$this->data = array();
			$this->keys = array();
			return $this;
		}

		// read the session file
		$payload = $this->_read_file($this->keys['session_id']);

		if ($payload === false)
		{
			// try to find the previous one
			$payload = $this->_read_file($this->keys['previous_id']);

			if ($payload === false)
			{
				// cookie present, but session record missing. force creation of a new session
				return $this->read(true);
			}
		}

		// unpack the payload
		$payload = $this->_unserialize($payload);

		// session referral?
		if (isset($payload['rotated_session_id']))
		{
			$payload = $this->_read_file($payload['rotated_session_id']);
			if ($payload === false)
			{
				// cookie present, but session record missing. force creation of a new session
				return $this->read(true);
			}
			else
			{
				// update the session
				$this->keys['previous_id'] = $this->keys['session_id'];
				$this->keys['session_id'] = $payload['rotated_session_id'];

				// unpack the payload
				$payload = $this->_unserialize($payload);
			}
		}

		if (isset($payload[0])) $this->data = $payload[0];
		if (isset($payload[1])) $this->flash = $payload[1];

		return parent::read();
	}

	// --------------------------------------------------------------------

	/**
	 * write the session
	 *
	 * @access	public
	 * @return	Fuel\Core\Session_File
	 */
	public function write()
	{
		// do we have something to write?
		if ( ! empty($this->keys) or ! empty($this->data) or ! empty($this->flash))
		{
			// create the session if it doesn't exist
			empty($this->keys) and $this->create();

			parent::write();

			// rotate the session id if needed
			$this->rotate(false);

			// session payload
			$payload = $this->_serialize(array($this->data, $this->flash));

			// create the session file
			$this->_write_file($this->keys['session_id'], $payload);

			// was the session id rotated?
			if ( isset($this->keys['previous_id']) and $this->keys['previous_id'] != $this->keys['session_id'])
			{
				// point the old session file to the new one, we don't want to lose the session
				$payload = $this->_serialize(array('rotated_session_id' => $this->keys['session_id']));
				$this->_write_file($this->keys['previous_id'], $payload);
			}

			$this->_set_cookie();

			// do some garbage collection
			if (mt_rand(0,100) < $this->config['gc_probability'])
			{
				if ($handle = opendir($this->config['path']))
				{
					$expire = $this->time->get_timestamp() - $this->config['expiration_time'];

					while (($file = readdir($handle)) !== false)
					{
						if (filetype($this->config['path'] . $file) == 'file' and
							strpos($file, $this->config['cookie_name'].'_') === 0 and
							filemtime($this->config['path'] . $file) < $expire)
						{
							@unlink($this->config['path'] . $file);
						}
					}
					closedir($handle);
				}
			}
		}

		return $this;
	}

	// --------------------------------------------------------------------

	/**
	 * destroy the current session
	 *
	 * @access	public
	 * @return	Fuel\Core\Session_File
	 */
	public function destroy()
	{
		// do we have something to destroy?
		if ( ! empty($this->keys))
		{
			// delete the session file
			$file = $this->config['path'].$this->config['cookie_name'].'_'.$this->keys['session_id'];
			if (file_exists($file))
			{
				unlink($file);
			}
		}

		// reset the stored session data
		$this->keys = $this->flash = $this->data = array();

		return $this;
	}

	// --------------------------------------------------------------------

	/**
	 * Writes the session file
	 *
	 * @access	private
	 * @return  boolean, true if it was an existing session, false if not
	 */
	protected function _write_file($session_id, $payload)
	{
		// create the session file
		$file = $this->config['path'].$this->config['cookie_name'].'_'.$session_id;
		$exists = file_exists($file);
		$handle = fopen($file,'c');
		if ($handle)
		{
			// wait for a lock
			while(!flock($handle, LOCK_EX));

			// erase existing contents
			ftruncate($handle, 0);

			// write the session data
			fwrite($handle, $payload);

			//release the lock
			flock($handle, LOCK_UN);

			// close the file
			fclose($handle);
		}

		return $exists;
	}

	// --------------------------------------------------------------------

	/**
	 * Reads the session file
	 *
	 * @access	private
	 * @return  mixed, the payload if the file exists, or false if not
	 */
	protected function _read_file($session_id)
	{
		$payload = false;

		$file = $this->config['path'].$this->config['cookie_name'].'_'.$session_id;
		if (file_exists($file))
		{
			$handle = fopen($file,'r');
			if ($handle)
			{
				// wait for a lock
				while(!flock($handle, LOCK_EX));

				// read the session data
				$payload = fread($handle, filesize($file));

				//release the lock
				flock($handle, LOCK_UN);

				// close the file
				fclose($handle);

			}
		}
		return $payload;
	}

	// --------------------------------------------------------------------

	/**
	 * validate a driver config value
	 *
	 * @param	array	array with configuration values
	 * @access	public
	 * @return  array	validated and consolidated config
	 */
	public function _validate_config($config)
	{
		$validated = array();

		foreach ($config as $name => $item)
		{
			// filter out any driver config
			if (!is_array($item))
			{
				switch ($name)
				{
					case 'cookie_name':
						if ( empty($item) OR ! is_string($item))
						{
							$item = 'fuelfid';
						}
					break;

					case 'path':
						// do we have a path?
						if ( empty($item) OR ! is_dir($item))
						{
							throw new \FuelException('You have specify a valid path to store the session data files.');
						}
						// and can we write to it?
						if ( ! is_writable($item))
						{
							throw new \FuelException('The webserver doesn\'t have write access to the path to store the session data files.');
						}
						// update the path, and add the trailing slash
						$item = realpath($item).'/';
					break;

					case 'gc_probability':
						// do we have a path?
						if ( ! is_numeric($item) OR $item < 0 OR $item > 100)
						{
							// default value: 5%
							$item = 5;
						}
					break;

					default:
						// no config item for this driver
					break;
				}

				// global config, was validated in the driver
				$validated[$name] = $item;
			}
		}

		// validate all global settings as well
		return parent::_validate_config($validated);
	}

}