EsiResponseCacheStrategy.php

<?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 $embeddedResponses = 0;
  private $ttls = array();
  private $maxAges = array();

  /**
   * {@inheritdoc}
   */
  public function add(Response $response) {
    if ($response
      ->isValidateable()) {
      $this->cacheable = false;
    }
    else {
      $this->ttls[] = $response
        ->getTtl();
      $this->maxAges[] = $response
        ->getMaxAge();
    }
    $this->embeddedResponses++;
  }

  /**
   * {@inheritdoc}
   */
  public function update(Response $response) {

    // if we have no embedded Response, do nothing
    if (0 === $this->embeddedResponses) {
      return;
    }

    // Remove validation related headers in order to avoid browsers using
    // their own cache, because some of the response content comes from
    // at least one embedded response (which likely has a different caching strategy).
    if ($response
      ->isValidateable()) {
      $response
        ->setEtag(null);
      $response
        ->setLastModified(null);
      $this->cacheable = false;
    }
    if (!$this->cacheable) {
      $response->headers
        ->set('Cache-Control', 'no-cache, must-revalidate');
      return;
    }
    $this->ttls[] = $response
      ->getTtl();
    $this->maxAges[] = $response
      ->getMaxAge();
    if (null !== ($maxAge = min($this->maxAges))) {
      $response
        ->setSharedMaxAge($maxAge);
      $response->headers
        ->set('Age', $maxAge - min($this->ttls));
    }
    $response
      ->setMaxAge(0);
  }

}