<?php

/*
 * This file is part of the Symfony package.
 *
 * (c) Fabien Potencier <fabien@symfony.com>
 *
 * For the full copyright and license information, please view the LICENSE
 * file that was distributed with this source code.
 */

namespace Symfony\Component\HttpKernel\EventListener;

use Symfony\Component\EventDispatcher\EventSubscriberInterface;
use Symfony\Component\HttpFoundation\Session\SessionInterface;
use Symfony\Component\HttpKernel\Event\GetResponseEvent;
use Symfony\Component\HttpKernel\KernelEvents;

/**
 * Sets the session in the request.
 *
 * @author Johannes M. Schmitt <schmittjoh@gmail.com>
 */
abstract class SessionListener implements EventSubscriberInterface
{
    public function onKernelRequest(GetResponseEvent $event)
    {
        if (!$event->isMasterRequest()) {
            return;
        }

        $request = $event->getRequest();
        $session = $this->getSession();
        if (null === $session || $request->hasSession()) {
            return;
        }

        $request->setSession($session);
    }

    public static function getSubscribedEvents()
    {
        return array(
            KernelEvents::REQUEST => array('onKernelRequest', 128),
        );
    }

    /**
     * Gets the session object.
     *
     * @return SessionInterface|null A SessionInterface instance or null if no session is available
     */
    abstract protected function getSession();
}