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) : void {
        
        /** @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);
    }

}