Chris@0: <?php
Chris@0: 
Chris@0: namespace Drupal\Core\EventSubscriber;
Chris@0: 
Chris@0: use Drupal\Core\Render\HtmlResponse;
Chris@0: use Drupal\Core\Render\Placeholder\PlaceholderStrategyInterface;
Chris@0: use Symfony\Component\HttpKernel\Event\FilterResponseEvent;
Chris@0: use Symfony\Component\HttpKernel\KernelEvents;
Chris@0: use Symfony\Component\EventDispatcher\EventSubscriberInterface;
Chris@0: 
Chris@0: /**
Chris@0:  * HTML response subscriber to allow for different placeholder strategies.
Chris@0:  *
Chris@0:  * This allows core and contrib to coordinate how to render placeholders;
Chris@0:  * e.g. an EsiRenderStrategy could replace the placeholders with ESI tags,
Chris@0:  * while e.g. a BigPipeRenderStrategy could store the placeholders in a
Chris@0:  * BigPipe service and render them after the main content has been sent to
Chris@0:  * the client.
Chris@0:  */
Chris@0: class HtmlResponsePlaceholderStrategySubscriber implements EventSubscriberInterface {
Chris@0: 
Chris@0:   /**
Chris@0:    * The placeholder strategy to use.
Chris@0:    *
Chris@0:    * @var \Drupal\Core\Render\Placeholder\PlaceholderStrategyInterface
Chris@0:    */
Chris@0:   protected $placeholderStrategy;
Chris@0: 
Chris@0:   /**
Chris@0:    * Constructs a HtmlResponsePlaceholderStrategySubscriber object.
Chris@0:    *
Chris@0:    * @param \Drupal\Core\Render\Placeholder\PlaceholderStrategyInterface $placeholder_strategy
Chris@0:    *   The placeholder strategy to use.
Chris@0:    */
Chris@0:   public function __construct(PlaceholderStrategyInterface $placeholder_strategy) {
Chris@0:     $this->placeholderStrategy = $placeholder_strategy;
Chris@0:   }
Chris@0: 
Chris@0:   /**
Chris@0:    * Processes placeholders for HTML responses.
Chris@0:    *
Chris@0:    * @param \Symfony\Component\HttpKernel\Event\FilterResponseEvent $event
Chris@0:    *   The event to process.
Chris@0:    */
Chris@0:   public function onRespond(FilterResponseEvent $event) {
Chris@0:     $response = $event->getResponse();
Chris@0:     if (!$response instanceof HtmlResponse) {
Chris@0:       return;
Chris@0:     }
Chris@0: 
Chris@0:     $attachments = $response->getAttachments();
Chris@0:     if (empty($attachments['placeholders'])) {
Chris@0:       return;
Chris@0:     }
Chris@0: 
Chris@0:     $attachments['placeholders'] = $this->placeholderStrategy->processPlaceholders($attachments['placeholders']);
Chris@0: 
Chris@0:     $response->setAttachments($attachments);
Chris@0:   }
Chris@0: 
Chris@0:   /**
Chris@0:    * {@inheritdoc}
Chris@0:    */
Chris@0:   public static function getSubscribedEvents() {
Chris@0:     // Run shortly before HtmlResponseSubscriber.
Chris@0:     $events[KernelEvents::RESPONSE][] = ['onRespond', 5];
Chris@0:     return $events;
Chris@0:   }
Chris@0: 
Chris@0: }