class OEmbedResourceConstraintValidator

class OEmbedResourceConstraintValidator extends ConstraintValidator implements ContainerInjectionInterface {
  
  /**
   * The oEmbed URL resolver service.
   *
   * @var \Drupal\media\OEmbed\UrlResolverInterface
   */
  protected $urlResolver;
  
  /**
   * The resource fetcher service.
   *
   * @var \Drupal\media\OEmbed\ResourceFetcherInterface
   */
  protected $resourceFetcher;
  
  /**
   * The logger service.
   *
   * @var \Drupal\Core\Logger\LoggerChannelInterface
   */
  protected $logger;
  
  /**
   * Constructs a new OEmbedResourceConstraintValidator.
   *
   * @param \Drupal\media\OEmbed\UrlResolverInterface $url_resolver
   *   The oEmbed URL resolver service.
   * @param \Drupal\media\OEmbed\ResourceFetcherInterface $resource_fetcher
   *   The resource fetcher service.
   * @param \Drupal\Core\Logger\LoggerChannelFactoryInterface $logger_factory
   *   The logger service.
   */
  public function __construct(UrlResolverInterface $url_resolver, ResourceFetcherInterface $resource_fetcher, LoggerChannelFactoryInterface $logger_factory) {
    $this->urlResolver = $url_resolver;
    $this->resourceFetcher = $resource_fetcher;
    $this->logger = $logger_factory->get('media');
  }
  
  /**
   * {@inheritdoc}
   */
  public static function create(ContainerInterface $container) {
    return new static($container->get('media.oembed.url_resolver'), $container->get('media.oembed.resource_fetcher'), $container->get('logger.factory'));
  }
  
  /**
   * {@inheritdoc}
   */
  public function validate($value, Constraint $constraint) {
    /** @var \Drupal\media\MediaInterface $media */
    $media = $value->getEntity();
    /** @var \Drupal\media\Plugin\media\Source\OEmbedInterface $source */
    $source = $media->getSource();
    if (!$source instanceof OEmbedInterface) {
      throw new \LogicException('Media source must implement ' . OEmbedInterface::class);
    }
    $url = $source->getSourceFieldValue($media);
    // The URL may be NULL if the source field is empty, which is invalid input.
    if (empty($url)) {
      $this->context
        ->addViolation($constraint->invalidResourceMessage);
      return;
    }
    // Ensure that the URL matches a provider.
    try {
      $provider = $this->urlResolver
        ->getProviderByUrl($url);
    } catch (ResourceException $e) {
      $this->handleException($e, $constraint->unknownProviderMessage);
      return;
    } catch (ProviderException $e) {
      $this->handleException($e, $constraint->providerErrorMessage);
      return;
    }
    // Ensure that the provider is allowed.
    if (!in_array($provider->getName(), $source->getProviders(), TRUE)) {
      $this->context
        ->addViolation($constraint->disallowedProviderMessage, [
        '@name' => $provider->getName(),
      ]);
      return;
    }
    // Verify that resource fetching works, because some URLs might match
    // the schemes but don't support oEmbed.
    try {
      $resource_url = $this->urlResolver
        ->getResourceUrl($url);
      $this->resourceFetcher
        ->fetchResource($resource_url);
    } catch (ResourceException $e) {
      $this->handleException($e, $constraint->invalidResourceMessage);
    }
  }
  
  /**
   * Handles exceptions that occur during validation.
   *
   * @param \Exception $e
   *   The caught exception.
   * @param string $error_message
   *   (optional) The error message to set as a constraint violation.
   */
  protected function handleException(\Exception $e, $error_message = NULL) {
    if ($error_message) {
      $this->context
        ->addViolation($error_message);
    }
    // The oEmbed system makes heavy use of exception wrapping, so log the
    // entire exception chain to help with troubleshooting.
    do {
      // @todo If $e is a ProviderException or ResourceException, log additional
      // debugging information contained in those exceptions in
      // https://www.drupal.org/project/drupal/issues/2972846.
      $this->logger
        ->error($e->getMessage());
      $e = $e->getPrevious();
    } while ($e);
  }

}