ion
        $this->loadSession();
    }

    /**
     * {@inheritdoc}
     */
    public function registerBag(SessionBagInterface $bag)
    {
        if ($this->started) {
            throw new \LogicException('Cannot register a bag when the session is already started.');
        }

        $this->bags[$bag->getName()] = $bag;
    }

    /**
     * {@inheritdoc}
     */
    public function getBag($name)
    {
        if (!isset($this->bags[$name])) {
            throw new \InvalidArgumentException(sprintf('The SessionBagInterface "%s" is not registered.', $name));
        }

        if (!$this->started && $this->saveHandler->isActive()) {
            $this->loadSession();
        } elseif (!$this->started) {
            $this->start();
        }

        return $this->bags[$name];
    }

    public function setMetadataBag(MetadataBag $metaBag = null)
    {
        if (null === $metaBag) {
            $metaBag = new MetadataBag();
        }

        $this->metadataBag = $metaBag;
    }

    /**
     * Gets the MetadataBag.
     *
     * @return MetadataBag
     */
    public function getMetadataBag()
    {
        return $this->metadataBag;
    }

    /**
     * {@inheritdoc}
     */
    public function isStarted()
    {
        return $this->started;
    }

    /**
     * Sets session.* ini variables.
     *
     * For convenience we omit 'session.' from the beginning of the keys.
     * Explicitly ignores other ini keys.
     *
     * @param array $options Session ini directives [key => value]
     *
     * @see https://php.net/session.configuration
     */
    public function setOptions(array $options)
    {
        if (headers_sent() || \PHP_SESSION_ACTIVE === session_status()) {
            return;
        }

        $validOptions = array_flip([
            'cache_expire', 'cache_limiter', 'cookie_domain', 'cookie_httponly',
            'cookie_lifetime', 'cookie_path', 'cookie_secure', 'cookie_samesite',
            'entropy_file', 'entropy_length', 'gc_divisor',
            'gc_maxlifetime', 'gc_probability', 'hash_bits_per_character',
            'hash_function', 'lazy_write', 'name', 'referer_check',
            'serialize_handler', 'use_strict_mode', 'use_cookies',
            'use_only_cookies', 'use_trans_sid', 'upload_progress.enabled',
            'upload_progress.cleanup', 'upload_progress.prefix', 'upload_progress.name',
            'upload_progress.freq', 'upload_progress.min_freq', 'url_rewriter.tags',
            'sid_length', 'sid_bits_per_character', 'trans_sid_hosts', 'trans_sid_tags',
        ]);

        foreach ($options as $key => $value) {
            if (isset($validOptions[$key])) {
                if ('cookie_samesite' === $key && \PHP_VERSION_ID < 70300) {
                    // PHP < 7.3 does not support same_site cookies. We will emulate it in
                    // the start() method instead.
                    $this->emulateSameSite = $value;
                    continue;
                }
                ini_set('url_rewriter.tags' !== $key ? 'session.'.$key : $key, $value);
            }
        }
    }

    /**
     * Registers session save handler as a PHP session handler.
     *
     * To use internal PHP session save handlers, override this method using ini_set with
     * session.save_handler and session.save_path e.g.
     *
     *     ini_set('session.save_handler', 'files');
     *     ini_set('session.save_path', '/tmp');
     *
     * or pass in a \SessionHandler instance which configures session.save_handler in the
     * constructor, for a template see NativeFileSessionHandler.
     *
     * @see https://php.net/session-set-save-handler
     * @see https://php.net/sessionhandlerinterface
     * @see https://php.net/sessionhandler
     *
     * @param AbstractProxy|\SessionHandlerInterface|null $saveHandler
     *
     * @throws \InvalidArgumentException
     */
    public function setSaveHandler($saveHandler = null)
    {
        if (!$saveHandler instanceof AbstractProxy &&
            !$saveHandler instanceof \SessionHandlerInterface &&
            null !== $saveHandler) {
            throw new \InvalidArgumentException('Must be instance of AbstractProxy; implement \SessionHandlerInterface; or be null.');
        }

        // Wrap $saveHandler in proxy and prevent double wrapping of proxy
        if (!$saveHandler instanceof AbstractProxy && $saveHandler instanceof \SessionHandlerInterface) {
            $saveHandler = new SessionHandlerProxy($saveHandler);
        } elseif (!$saveHandler instanceof AbstractProxy) {
            $saveHandler = new SessionHandlerProxy(new StrictSessionHandler(new \SessionHandler()));
        }
        $this->saveHandler = $saveHandler;

        if (headers_sent() || \PHP_SESSION_ACTIVE === session_status()) {
            return;
        }

        if ($this->saveHandler instanceof SessionHandlerProxy) {
            session_set_save_handler($this->saveHandler, false);
        }
    }

    /**
     * Load the session with attributes.
     *
     * After starting the session, PHP retrieves the session from whatever handlers
     * are set to (either PHP's internal, or a custom save handler set with session_set_save_handler()).
     * PHP takes the return value from the read() handler, unserializes it
     * and populates $_SESSION with the result automatically.
     */
    protected function loadSession(array &$session = null)
    {
        if (null === $session) {
            $session = &$_SESSION;
        }

        $bags = array_merge($this->bags, [$this->metadataBag]);

        foreach ($bags as $bag) {
            $key = $bag->getStorageKey();
            $session[$key] = isset($session[$key]) && \is_array($session[$key]) ? $session[$key] : [];
            $bag->initialize($session[$key]);
        }

        $this->started = true;
        $this->closed = false;
    }
}