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   1  <?php
   2  
   3  /*
   4   * This file is part of the Symfony package.
   5   *
   6   * (c) Fabien Potencier <[email protected]>
   7   *
   8   * For the full copyright and license information, please view the LICENSE
   9   * file that was distributed with this source code.
  10   */
  11  
  12  namespace Symfony\Component\WebLink\EventListener;
  13  
  14  use Psr\Link\LinkProviderInterface;
  15  use Symfony\Component\EventDispatcher\EventSubscriberInterface;
  16  use Symfony\Component\HttpKernel\Event\ResponseEvent;
  17  use Symfony\Component\HttpKernel\KernelEvents;
  18  use Symfony\Component\WebLink\HttpHeaderSerializer;
  19  
  20  // Help opcache.preload discover always-needed symbols
  21  class_exists(HttpHeaderSerializer::class);
  22  
  23  /**
  24   * Adds the Link HTTP header to the response.
  25   *
  26   * @author Kévin Dunglas <[email protected]>
  27   *
  28   * @final
  29   */
  30  class AddLinkHeaderListener implements EventSubscriberInterface
  31  {
  32      private $serializer;
  33  
  34      public function __construct()
  35      {
  36          $this->serializer = new HttpHeaderSerializer();
  37      }
  38  
  39      public function onKernelResponse(ResponseEvent $event)
  40      {
  41          if (!$event->isMainRequest()) {
  42              return;
  43          }
  44  
  45          $linkProvider = $event->getRequest()->attributes->get('_links');
  46          if (!$linkProvider instanceof LinkProviderInterface || !$links = $linkProvider->getLinks()) {
  47              return;
  48          }
  49  
  50          $event->getResponse()->headers->set('Link', $this->serializer->serialize($links), false);
  51      }
  52  
  53      /**
  54       * {@inheritdoc}
  55       */
  56      public static function getSubscribedEvents(): array
  57      {
  58          return [KernelEvents::RESPONSE => 'onKernelResponse'];
  59      }
  60  }