<?php namespace CodeIgniter\Session\Handlers;

/**
 * CodeIgniter
 *
 * An open source application development framework for PHP
 *
 * This content is released under the MIT License (MIT)
 *
 * Copyright (c) 2014 - 2017, British Columbia Institute of Technology
 *
 * Permission is hereby granted, free of charge, to any person obtaining a copy
 * of this software and associated documentation files (the "Software"), to deal
 * in the Software without restriction, including without limitation the rights
 * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
 * copies of the Software, and to permit persons to whom the Software is
 * furnished to do so, subject to the following conditions:
 *
 * The above copyright notice and this permission notice shall be included in
 * all copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
 * THE SOFTWARE.
 *
 * @package	CodeIgniter
 * @author	CodeIgniter Dev Team
 * @copyright	Copyright (c) 2014 - 2017, British Columbia Institute of Technology (http://bcit.ca/)
 * @license	https://opensource.org/licenses/MIT	MIT License
 * @link	https://codeigniter.com
 * @since	Version 3.0.0
 * @filesource
 */

use CodeIgniter\Config\BaseConfig;

/**
 * Session handler using file system for storage
 */
class FileHandler extends BaseHandler implements \SessionHandlerInterface
{
	/**
	 * Where to save the session files to.
	 *
	 * @var string
	 */
	protected $savePath;

	/**
	 * The file handle
	 *
	 * @var resource
	 */
	protected $fileHandle;

	/**
	 * File Name
	 *
	 * @var resource
	 */
	protected $filePath;

	/**
	 * Whether this is a new file.
	 *
	 * @var bool
	 */
	protected $fileNew;

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

	/**
	 * Constructor
	 * @param BaseConfig $config
	 */
	public function __construct($config)
	{
		parent::__construct($config);

		if ( ! empty($config->sessionSavePath))
		{
			$this->savePath = rtrim($config->sessionSavePath, '/\\');
			ini_set('session.save_path', $config->sessionSavePath);
		}
		else
		{
			$this->savePath = rtrim(ini_get('session.save_path'), '/\\');
		}
	}

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

    /**
     * Open
     *
     * Sanitizes the save_path directory.
     *
     * @param    string $savePath Path to session files' directory
     * @param    string $name     Session cookie name
     *
     * @return bool
     * @throws \Exception
     */
	public function open($savePath, $name): bool
	{
		if ( ! is_dir($savePath))
		{
			if ( ! mkdir($savePath, 0700, true))
			{
				throw new \Exception("Session: Configured save path '".$this->savePath.
				                     "' is not a directory, doesn't exist or cannot be created.");
			}
		}
		elseif ( ! is_writable($savePath))
		{
			throw new \Exception("Session: Configured save path '".$this->savePath.
			                    "' is not writable by the PHP process.");
		}

		$this->savePath = $savePath;
		$this->filePath = $this->savePath.'/'
		                  .$name // we'll use the session cookie name as a prefix to avoid collisions
		                  .($this->matchIP ? md5($_SERVER['REMOTE_ADDR']) : '');

		return true;
	}

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

	/**
	 * Read
	 *
	 * Reads session data and acquires a lock
	 *
	 * @param    string $sessionID Session ID
	 *
	 * @return    string    Serialized session data
	 */
	public function read($sessionID)
	{
		// This might seem weird, but PHP 5.6 introduced session_reset(),
		// which re-reads session data
		if ($this->fileHandle === null)
		{
            $this->fileNew = ! file_exists($this->filePath.$sessionID);

			if (($this->fileHandle = fopen($this->filePath.$sessionID, 'c+b')) === false)
			{
				$this->logger->error("Session: Unable to open file '".$this->filePath.$sessionID."'.");

				return false;
			}

			if (flock($this->fileHandle, LOCK_EX) === false)
			{
				$this->logger->error("Session: Unable to obtain lock for file '".$this->filePath.$sessionID."'.");
				fclose($this->fileHandle);
				$this->fileHandle = null;

				return false;
			}

			// Needed by write() to detect session_regenerate_id() calls
			$this->sessionID = $sessionID;

			if ($this->fileNew)
			{
				chmod($this->filePath.$sessionID, 0600);
				$this->fingerprint = md5('');

				return '';
			}
		}
		else
		{
			rewind($this->fileHandle);
		}

		$session_data = '';
		for ($read = 0, $length = filesize($this->filePath.$sessionID); $read < $length; $read += strlen($buffer))
		{
			if (($buffer = fread($this->fileHandle, $length - $read)) === false)
			{
				break;
			}

			$session_data .= $buffer;
		}

		$this->fingerprint = md5($session_data);

		return $session_data;
	}

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

	/**
	 * Write
	 *
	 * Writes (create / update) session data
	 *
	 * @param    string $sessionID   Session ID
	 * @param    string $sessionData Serialized session data
	 *
	 * @return    bool
	 */
	public function write($sessionID, $sessionData): bool
	{
		// If the two IDs don't match, we have a session_regenerate_id() call
		// and we need to close the old handle and open a new one
		if ($sessionID !== $this->sessionID && (! $this->close() || $this->read($sessionID) === false))
		{
			return false;
		}

		if ( ! is_resource($this->fileHandle))
		{
			return false;
		}
		elseif ($this->fingerprint === md5($sessionData))
		{
			return ($this->fileNew)
				? true
				: touch($this->filePath.$sessionID);
		}

		if ( ! $this->fileNew)
		{
			ftruncate($this->fileHandle, 0);
			rewind($this->fileHandle);
		}

		if (($length = strlen($sessionData)) > 0)
		{
			for ($written = 0; $written < $length; $written += $result)
			{
				if (($result = fwrite($this->fileHandle, substr($sessionData, $written))) === false)
				{
					break;
				}
			}

			if ( ! is_int($result))
			{
				$this->fingerprint = md5(substr($sessionData, 0, $written));
				$this->logger->error('Session: Unable to write data.');

				return false;
			}
		}

		$this->fingerprint = md5($sessionData);

		return true;
	}

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

	/**
	 * Close
	 *
	 * Releases locks and closes file descriptor.
	 *
	 * @return    bool
	 */
	public function close(): bool
	{
		if (is_resource($this->fileHandle))
		{
			flock($this->fileHandle, LOCK_UN);
			fclose($this->fileHandle);

			$this->fileHandle = $this->fileNew = $this->sessionID = null;

			return true;
		}

		return true;
	}

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

	/**
	 * Destroy
	 *
	 * Destroys the current session.
	 *
	 * @param    string $session_id Session ID
	 *
	 * @return    bool
	 */
	public function destroy($session_id): bool
	{
		if ($this->close())
		{
			return file_exists($this->filePath.$session_id)
				? (unlink($this->filePath.$session_id) && $this->destroyCookie())
				: true;
		}
		elseif ($this->filePath !== null)
		{
			clearstatcache();

			return file_exists($this->filePath.$session_id)
				? (unlink($this->filePath.$session_id) && $this->destroyCookie())
				: true;
		}

		return false;
	}

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

	/**
	 * Garbage Collector
	 *
	 * Deletes expired sessions
	 *
	 * @param    int $maxlifetime Maximum lifetime of sessions
	 *
	 * @return    bool
	 */
	public function gc($maxlifetime): bool
	{
		if ( ! is_dir($this->savePath) || ($directory = opendir($this->savePath)) === false)
		{
			$this->logger->debug("Session: Garbage collector couldn't list files under directory '".$this->savePath."'.");

			return false;
		}

		$ts = time() - $maxlifetime;

		$pattern = sprintf(
			'/^%s[0-9a-f]{%d}$/',
			preg_quote($this->cookieName, '/'),
			($this->matchIP === true ? 72 : 40)
		);

		while (($file = readdir($directory)) !== false)
		{
			// If the filename doesn't match this pattern, it's either not a session file or is not ours
			if ( ! preg_match($pattern, $file)
			     || ! is_file($this->savePath.'/'.$file)
			     || ($mtime = filemtime($this->savePath.'/'.$file)) === false
			     || $mtime > $ts
			)
			{
				continue;
			}

			unlink($this->savePath.'/'.$file);
		}

		closedir($directory);

		return true;
	}

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

}
