<?php

/*

 * This file is part of the Symfony package.

 *

 * (c) Fabien Potencier <fabien@symfony.com>

 *

 * This code is partially based on the Rack-Cache library by Ryan Tomayko,

 * which is released under the MIT license.

 * (based on commit 02d2b48d75bcb63cf1c0c7149c077ad256542801)

 *

 * For the full copyright and license information, please view the LICENSE

 * file that was distributed with this source code.

 */

namespace Symfony\Component\HttpKernel\HttpCache;

use Symfony\Component\HttpFoundation\Response;

/**

 * EsiResponseCacheStrategy knows how to compute the Response cache HTTP header

 * based on the different ESI response cache headers.

 *

 * This implementation changes the master response TTL to the smallest TTL received

 * or force validation if one of the ESI has validation cache strategy.

 *

 * @author Fabien Potencier <fabien@symfony.com>

 */

class EsiResponseCacheStrategy implements EsiResponseCacheStrategyInterface

{

    private $cacheable = true;

    private $ttls = array();

    private $maxAges = array();

    /**

     * Adds a Response.

     *

     * @param Response $response

     */

    public function add(Response $response)

    {

        if ($response->isValidateable()) {

            $this->cacheable = false;

        } else {

            $this->ttls[] = $response->getTtl();

            $this->maxAges[] = $response->getMaxAge();

        }

    }

    /**

     * Updates the Response HTTP headers based on the embedded Responses.

     *

     * @param Response $response

     */

    public function update(Response $response)

    {

        // if we only have one Response, do nothing

        if (1 === count($this->ttls)) {

            return;

        }

        if (!$this->cacheable) {

            $response->headers->set('Cache-Control', 'no-cache, must-revalidate');

            return;

        }

        if (null !== $maxAge = min($this->maxAges)) {

            $response->setSharedMaxAge($maxAge);

            $response->headers->set('Age', $maxAge - min($this->ttls));

        }

        $response->setMaxAge(0);

    }

}