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   1  <?php
   2  
   3  /*
   4   * This file is part of the Symfony package.
   5   *
   6   * (c) Fabien Potencier <fabien@symfony.com>
   7   *
   8   * This code is partially based on the Rack-Cache library by Ryan Tomayko,
   9   * which is released under the MIT license.
  10   * (based on commit 02d2b48d75bcb63cf1c0c7149c077ad256542801)
  11   *
  12   * For the full copyright and license information, please view the LICENSE
  13   * file that was distributed with this source code.
  14   */
  15  
  16  namespace Symfony\Component\HttpKernel\HttpCache;
  17  
  18  use Symfony\Component\HttpFoundation\Response;
  19  
  20  /**
  21   * EsiResponseCacheStrategy knows how to compute the Response cache HTTP header
  22   * based on the different ESI response cache headers.
  23   *
  24   * This implementation changes the master response TTL to the smallest TTL received
  25   * or force validation if one of the ESI has validation cache strategy.
  26   *
  27   * @author Fabien Potencier <fabien@symfony.com>
  28   */
  29  class EsiResponseCacheStrategy implements EsiResponseCacheStrategyInterface
  30  {
  31      private $cacheable = true;
  32      private $embeddedResponses = 0;
  33      private $ttls = array();
  34      private $maxAges = array();
  35      private $isNotCacheableResponseEmbedded = false;
  36  
  37      /**
  38       * {@inheritdoc}
  39       */
  40      public function add(Response $response)
  41      {
  42          if ($response->isValidateable()) {
  43              $this->cacheable = false;
  44          } else {
  45              $maxAge = $response->getMaxAge();
  46              $this->ttls[] = $response->getTtl();
  47              $this->maxAges[] = $maxAge;
  48  
  49              if (null === $maxAge) {
  50                  $this->isNotCacheableResponseEmbedded = true;
  51              }
  52          }
  53  
  54          ++$this->embeddedResponses;
  55      }
  56  
  57      /**
  58       * {@inheritdoc}
  59       */
  60      public function update(Response $response)
  61      {
  62          // if we have no embedded Response, do nothing
  63          if (0 === $this->embeddedResponses) {
  64              return;
  65          }
  66  
  67          // Remove validation related headers in order to avoid browsers using
  68          // their own cache, because some of the response content comes from
  69          // at least one embedded response (which likely has a different caching strategy).
  70          if ($response->isValidateable()) {
  71              $response->setEtag(null);
  72              $response->setLastModified(null);
  73              $this->cacheable = false;
  74          }
  75  
  76          if (!$this->cacheable) {
  77              $response->headers->set('Cache-Control', 'no-cache, must-revalidate');
  78  
  79              return;
  80          }
  81  
  82          $this->ttls[] = $response->getTtl();
  83          $this->maxAges[] = $response->getMaxAge();
  84  
  85          if ($this->isNotCacheableResponseEmbedded) {
  86              $response->headers->removeCacheControlDirective('s-maxage');
  87          } elseif (null !== $maxAge = min($this->maxAges)) {
  88              $response->setSharedMaxAge($maxAge);
  89              $response->headers->set('Age', $maxAge - min($this->ttls));
  90          }
  91          $response->setMaxAge(0);
  92      }
  93  }