<?php

/**
 * Session class for Cake.
 *
 * Cake abstracts the handling of sessions.
 * There are several convenient methods to access session information.
 * This class is the implementation of those methods.
 * They are mostly used by the Session Component.
 *
 * PHP 5
 *
 * CakePHP(tm) : Rapid Development Framework (http://cakephp.org)
 * Copyright 2005-2012, Cake Software Foundation, Inc. (http://cakefoundation.org)
 *
 * Licensed under The MIT License
 * Redistributions of files must retain the above copyright notice.
 *
 * @copyright     Copyright 2005-2012, Cake Software Foundation, Inc. (http://cakefoundation.org)
 * @link          http://cakephp.org CakePHP(tm) Project
 * @package       Cake.Model.Datasource
 * @since         CakePHP(tm) v .0.10.0.1222
 * @license       MIT License (http://www.opensource.org/licenses/mit-license.php)
 */
App::uses('Set', 'Utility');
App::uses('Security', 'Utility');

/**
 * Session class for Cake.
 *
 * Cake abstracts the handling of sessions. There are several convenient methods to access session information.
 * This class is the implementation of those methods. They are mostly used by the Session Component.
 *
 * @package       Cake.Model.Datasource
 */
class CakeSession {

    /**
     * True if the Session is still valid
     *
     * @var boolean
     */
    public static $valid = false;

    /**
     * Error messages for this session
     *
     * @var array
     */
    public static $error = false;

    /**
     * User agent string
     *
     * @var string
     */
    protected static $_userAgent = '';

    /**
     * Path to where the session is active.
     *
     * @var string
     */
    public static $path = '/';

    /**
     * Error number of last occurred error
     *
     * @var integer
     */
    public static $lastError = null;

    /**
     * Start time for this session.
     *
     * @var integer
     */
    public static $time = false;

    /**
     * Cookie lifetime
     *
     * @var integer
     */
    public static $cookieLifeTime;

    /**
     * Time when this session becomes invalid.
     *
     * @var integer
     */
    public static $sessionTime = false;

    /**
     * Current Session id
     *
     * @var string
     */
    public static $id = null;

    /**
     * Hostname
     *
     * @var string
     */
    public static $host = null;

    /**
     * Session timeout multiplier factor
     *
     * @var integer
     */
    public static $timeout = null;

    /**
     * Number of requests that can occur during a session time without the session being renewed.
     * This feature is only used when config value `Session.autoRegenerate` is set to true.
     *
     * @var integer
     * @see CakeSession::_checkValid()
     */
    public static $requestCountdown = 10;

    /**
     * Constructor.
     *
     * @param string $base The base path for the Session
     * @return void
     */
    public static function init($base = null) {
        self::$time = time();

        $checkAgent = Configure::read('Session.checkAgent');
        if (($checkAgent === true || $checkAgent === null) && env('HTTP_USER_AGENT') != null) {
            self::$_userAgent = md5(env('HTTP_USER_AGENT') . Configure::read('Security.salt'));
        }
        self::_setPath($base);
        self::_setHost(env('HTTP_HOST'));
    }

    /**
     * Setup the Path variable
     *
     * @param string $base base path
     * @return void
     */
    protected static function _setPath($base = null) {
        if (empty($base)) {
            self::$path = '/';
            return;
        }
        if (strpos($base, 'index.php') !== false) {
            $base = str_replace('index.php', '', $base);
        }
        if (strpos($base, '?') !== false) {
            $base = str_replace('?', '', $base);
        }
        self::$path = $base;
    }

    /**
     * Set the host name
     *
     * @param string $host Hostname
     * @return void
     */
    protected static function _setHost($host) {
        self::$host = $host;
        if (strpos(self::$host, ':') !== false) {
            self::$host = substr(self::$host, 0, strpos(self::$host, ':'));
        }
    }

    /**
     * Starts the Session.
     *
     * @return boolean True if session was started
     */
    public static function start() {
        if (self::started()) {
            return true;
        }
        CakeSession::init();
        $id = self::id();
        session_write_close();
        self::_configureSession();
        self::_startSession();

        if (!$id && self::started()) {
            self::_checkValid();
        }

        self::$error = false;
        return self::started();
    }

    /**
     * Determine if Session has been started.
     *
     * @return boolean True if session has been started.
     */
    public static function started() {
        return isset($_SESSION) && session_id();
    }

    /**
     * Returns true if given variable is set in session.
     *
     * @param string $name Variable name to check for
     * @return boolean True if variable is there
     */
    public static function check($name = null) {
        if (!self::started() && !self::start()) {
            return false;
        }
        if (empty($name)) {
            return false;
        }
        $result = Set::classicExtract($_SESSION, $name);
        return isset($result);
    }

    /**
     * Returns the Session id
     *
     * @param string $id
     * @return string Session id
     */
    public static function id($id = null) {
        if ($id) {
            self::$id = $id;
            session_id(self::$id);
        }
        if (self::started()) {
            return session_id();
        }
        return self::$id;
    }

    /**
     * Removes a variable from session.
     *
     * @param string $name Session variable to remove
     * @return boolean Success
     */
    public static function delete($name) {
        if (self::check($name)) {
            self::_overwrite($_SESSION, Set::remove($_SESSION, $name));
            return (self::check($name) == false);
        }
        self::_setError(2, __d('cake_dev', "%s doesn't exist", $name));
        return false;
    }

    /**
     * Used to write new data to _SESSION, since PHP doesn't like us setting the _SESSION var itself
     *
     * @param array $old Set of old variables => values
     * @param array $new New set of variable => value
     * @return void
     */
    protected static function _overwrite(&$old, $new) {
        if (!empty($old)) {
            foreach ($old as $key => $var) {
                if (!isset($new[$key])) {
                    unset($old[$key]);
                }
            }
        }
        foreach ($new as $key => $var) {
            $old[$key] = $var;
        }
    }

    /**
     * Return error description for given error number.
     *
     * @param integer $errorNumber Error to set
     * @return string Error as string
     */
    protected static function _error($errorNumber) {
        if (!is_array(self::$error) || !array_key_exists($errorNumber, self::$error)) {
            return false;
        } else {
            return self::$error[$errorNumber];
        }
    }

    /**
     * Returns last occurred error as a string, if any.
     *
     * @return mixed Error description as a string, or false.
     */
    public static function error() {
        if (self::$lastError) {
            return self::_error(self::$lastError);
        }
        return false;
    }

    /**
     * Returns true if session is valid.
     *
     * @return boolean Success
     */
    public static function valid() {
        if (self::read('Config')) {
            if (self::_validAgentAndTime() && self::$error === false) {
                self::$valid = true;
            } else {
                self::$valid = false;
                self::_setError(1, 'Session Highjacking Attempted !!!');
            }
        }
        return self::$valid;
    }

    /**
     * Tests that the user agent is valid and that the session hasn't 'timed out'.
     * Since timeouts are implemented in CakeSession it checks the current self::$time
     * against the time the session is set to expire.  The User agent is only checked
     * if Session.checkAgent == true.
     *
     * @return boolean
     */
    protected static function _validAgentAndTime() {
        $config = self::read('Config');
        $validAgent = (
                Configure::read('Session.checkAgent') === false ||
                self::$_userAgent == $config['userAgent']
                );
        return ($validAgent && self::$time <= $config['time']);
    }

    /**
     * Get / Set the userAgent
     *
     * @param string $userAgent Set the userAgent
     * @return void
     */
    public static function userAgent($userAgent = null) {
        if ($userAgent) {
            self::$_userAgent = $userAgent;
        }
        if (empty(self::$_userAgent)) {
            CakeSession::init(self::$path);
        }
        return self::$_userAgent;
    }

    /**
     * Returns given session variable, or all of them, if no parameters given.
     *
     * @param mixed $name The name of the session variable (or a path as sent to Set.extract)
     * @return mixed The value of the session variable
     */
    public static function read($name = null) {
        if (!self::started() && !self::start()) {
            return false;
        }
        if (is_null($name)) {
            return self::_returnSessionVars();
        }
        if (empty($name)) {
            return false;
        }
        $result = Set::classicExtract($_SESSION, $name);

        if (!is_null($result)) {
            return $result;
        }
        self::_setError(2, "$name doesn't exist");
        return null;
    }

    /**
     * Returns all session variables.
     *
     * @return mixed Full $_SESSION array, or false on error.
     */
    protected static function _returnSessionVars() {
        if (!empty($_SESSION)) {
            return $_SESSION;
        }
        self::_setError(2, 'No Session vars set');
        return false;
    }

    /**
     * Writes value to given session variable name.
     *
     * @param mixed $name Name of variable
     * @param string $value Value to write
     * @return boolean True if the write was successful, false if the write failed
     */
    public static function write($name, $value = null) {
        if (!self::started() && !self::start()) {
            return false;
        }
        if (empty($name)) {
            return false;
        }
        $write = $name;
        if (!is_array($name)) {
            $write = array($name => $value);
        }
        foreach ($write as $key => $val) {
            self::_overwrite($_SESSION, Set::insert($_SESSION, $key, $val));
            if (Set::classicExtract($_SESSION, $key) !== $val) {
                return false;
            }
        }
        return true;
    }

    /**
     * Helper method to destroy invalid sessions.
     *
     * @return void
     */
    public static function destroy() {
        if (self::started()) {
            session_destroy();
        }
        self::clear();
    }

    /**
     * Clears the session, the session id, and renew's the session.
     *
     * @return void
     */
    public static function clear() {
        $_SESSION = null;
        self::$id = null;
        self::start();
        self::renew();
    }

    /**
     * Helper method to initialize a session, based on Cake core settings.
     *
     * Sessions can be configured with a few shortcut names as well as have any number of ini settings declared.
     *
     * @return void
     * @throws CakeSessionException Throws exceptions when ini_set() fails.
     */
    protected static function _configureSession() {
        $sessionConfig = Configure::read('Session');
        $iniSet = function_exists('ini_set');

        if (isset($sessionConfig['defaults'])) {
            $defaults = self::_defaultConfig($sessionConfig['defaults']);
            if ($defaults) {
                $sessionConfig = Set::merge($defaults, $sessionConfig);
            }
        }
        if (!isset($sessionConfig['ini']['session.cookie_secure']) && env('HTTPS')) {
            $sessionConfig['ini']['session.cookie_secure'] = 1;
        }
        if (isset($sessionConfig['timeout']) && !isset($sessionConfig['cookieTimeout'])) {
            $sessionConfig['cookieTimeout'] = $sessionConfig['timeout'];
        }
        if (!isset($sessionConfig['ini']['session.cookie_lifetime'])) {
            $sessionConfig['ini']['session.cookie_lifetime'] = $sessionConfig['cookieTimeout'] * 60;
        }
        if (!isset($sessionConfig['ini']['session.name'])) {
            $sessionConfig['ini']['session.name'] = $sessionConfig['cookie'];
        }
        if (!empty($sessionConfig['handler'])) {
            $sessionConfig['ini']['session.save_handler'] = 'user';
        }
        if (!isset($sessionConfig['ini']['session.gc_maxlifetime'])) {
            $sessionConfig['ini']['session.gc_maxlifetime'] = $sessionConfig['timeout'] * 60;
        }

        if (empty($_SESSION)) {
            if (!empty($sessionConfig['ini']) && is_array($sessionConfig['ini'])) {
                foreach ($sessionConfig['ini'] as $setting => $value) {
                    if (ini_set($setting, $value) === false) {
                        throw new CakeSessionException(sprintf(
                                __d('cake_dev', 'Unable to configure the session, setting %s failed.'), $setting
                        ));
                    }
                }
            }
        }
        if (!empty($sessionConfig['handler']) && !isset($sessionConfig['handler']['engine'])) {
            call_user_func_array('session_set_save_handler', $sessionConfig['handler']);
        }
        if (!empty($sessionConfig['handler']['engine'])) {
            $handler = self::_getHandler($sessionConfig['handler']['engine']);
            session_set_save_handler(
                    array($handler, 'open'), array($handler, 'close'), array($handler, 'read'), array($handler, 'write'), array($handler, 'destroy'), array($handler, 'gc')
            );
        }
        Configure::write('Session', $sessionConfig);
        self::$sessionTime = self::$time + ($sessionConfig['timeout'] * 60);
    }

    /**
     * Find the handler class and make sure it implements the correct interface.
     *
     * @param string $handler
     * @return void
     * @throws CakeSessionException
     */
    protected static function _getHandler($handler) {
        list($plugin, $class) = pluginSplit($handler, true);
        App::uses($class, $plugin . 'Model/Datasource/Session');
        if (!class_exists($class)) {
            throw new CakeSessionException(__d('cake_dev', 'Could not load %s to handle the session.', $class));
        }
        $handler = new $class();
        if ($handler instanceof CakeSessionHandlerInterface) {
            return $handler;
        }
        throw new CakeSessionException(__d('cake_dev', 'Chosen SessionHandler does not implement CakeSessionHandlerInterface it cannot be used with an engine key.'));
    }

    /**
     * Get one of the prebaked default session configurations.
     *
     * @param string $name
     * @return boolean|array
     */
    protected static function _defaultConfig($name) {
        $defaults = array(
            'php' => array(
                'cookie' => 'CAKEPHP',
                'timeout' => 240,
                'ini' => array(
                    'session.use_trans_sid' => 0,
                    'session.cookie_path' => self::$path
                )
            ),
            'cake' => array(
                'cookie' => 'CAKEPHP',
                'timeout' => 240,
                'ini' => array(
                    'session.use_trans_sid' => 0,
                    'url_rewriter.tags' => '',
                    'session.serialize_handler' => 'php',
                    'session.use_cookies' => 1,
                    'session.cookie_path' => self::$path,
                    //'session.auto_start' => 0,
                    'session.save_path' => TMP . 'sessions',
                    'session.save_handler' => 'files'
                )
            ),
            'cache' => array(
                'cookie' => 'CAKEPHP',
                'timeout' => 240,
                'ini' => array(
                    'session.use_trans_sid' => 0,
                    'url_rewriter.tags' => '',
                    'session.auto_start' => 0,
                    'session.use_cookies' => 1,
                    'session.cookie_path' => self::$path,
                    'session.save_handler' => 'user',
                ),
                'handler' => array(
                    'engine' => 'CacheSession',
                    'config' => 'default'
                )
            ),
            'database' => array(
                'cookie' => 'CAKEPHP',
                'timeout' => 240,
                'ini' => array(
                    'session.use_trans_sid' => 0,
                    'url_rewriter.tags' => '',
                    'session.auto_start' => 0,
                    'session.use_cookies' => 1,
                    'session.cookie_path' => self::$path,
                    'session.save_handler' => 'user',
                    'session.serialize_handler' => 'php',
                ),
                'handler' => array(
                    'engine' => 'DatabaseSession',
                    'model' => 'Session'
                )
            )
        );
        if (isset($defaults[$name])) {
            return $defaults[$name];
        }
        return false;
    }

    /**
     * Helper method to start a session
     *
     * @return boolean Success
     */
    protected static function _startSession() {
        if (headers_sent()) {
            if (empty($_SESSION)) {
                $_SESSION = array();
            }
        } else {
            // For IE<=8
            session_cache_limiter("must-revalidate");
            session_start();
        }
        return true;
    }

    /**
     * Helper method to create a new session.
     *
     * @return void
     */
    protected static function _checkValid() {
        if (!self::started() && !self::start()) {
            self::$valid = false;
            return false;
        }
        if ($config = self::read('Config')) {
            $sessionConfig = Configure::read('Session');

            if (self::_validAgentAndTime()) {
                self::write('Config.time', self::$sessionTime);
                if (isset($sessionConfig['autoRegenerate']) && $sessionConfig['autoRegenerate'] === true) {
                    $check = $config['countdown'];
                    $check -= 1;
                    self::write('Config.countdown', $check);

                    if ($check < 1) {
                        self::renew();
                        self::write('Config.countdown', self::$requestCountdown);
                    }
                }
                self::$valid = true;
            } else {
                self::destroy();
                self::$valid = false;
                self::_setError(1, 'Session Highjacking Attempted !!!');
            }
        } else {
            self::write('Config.userAgent', self::$_userAgent);
            self::write('Config.time', self::$sessionTime);
            self::write('Config.countdown', self::$requestCountdown);
            self::$valid = true;
        }
    }

    /**
     * Restarts this session.
     *
     * @return void
     */
    public static function renew() {
        if (session_id()) {
            if (session_id() != '' || isset($_COOKIE[session_name()])) {
                setcookie(Configure::read('Session.cookie'), '', time() - 42000, self::$path);
            }
            session_regenerate_id(true);
        }
    }

    /**
     * Helper method to set an internal error message.
     *
     * @param integer $errorNumber Number of the error
     * @param string $errorMessage Description of the error
     * @return void
     */
    protected static function _setError($errorNumber, $errorMessage) {
        if (self::$error === false) {
            self::$error = array();
        }
        self::$error[$errorNumber] = $errorMessage;
        self::$lastError = $errorNumber;
    }

}
