class UrlResolver

class UrlResolver implements UrlResolverInterface {
    use UseCacheBackendTrait;
    
    /**
     * The HTTP client.
     *
     * @var \GuzzleHttp\Client
     */
    protected $httpClient;
    
    /**
     * The OEmbed provider repository service.
     *
     * @var \Drupal\media\OEmbed\ProviderRepositoryInterface
     */
    protected $providers;
    
    /**
     * The OEmbed resource fetcher service.
     *
     * @var \Drupal\media\OEmbed\ResourceFetcherInterface
     */
    protected $resourceFetcher;
    
    /**
     * The module handler service.
     *
     * @var \Drupal\Core\Extension\ModuleHandlerInterface
     */
    protected $moduleHandler;
    
    /**
     * Static cache of discovered oEmbed resource URLs, keyed by canonical URL.
     *
     * A discovered resource URL is the actual endpoint URL for a specific media
     * object, fetched from its canonical URL.
     *
     * @var string[]
     */
    protected $urlCache = [];
    
    /**
     * Constructs a UrlResolver object.
     *
     * @param \Drupal\media\OEmbed\ProviderRepositoryInterface $providers
     *   The oEmbed provider repository service.
     * @param \Drupal\media\OEmbed\ResourceFetcherInterface $resource_fetcher
     *   The OEmbed resource fetcher service.
     * @param \GuzzleHttp\ClientInterface $http_client
     *   The HTTP client.
     * @param \Drupal\Core\Extension\ModuleHandlerInterface $module_handler
     *   The module handler service.
     * @param \Drupal\Core\Cache\CacheBackendInterface $cache_backend
     *   (optional) The cache backend.
     */
    public function __construct(ProviderRepositoryInterface $providers, ResourceFetcherInterface $resource_fetcher, ClientInterface $http_client, ModuleHandlerInterface $module_handler, CacheBackendInterface $cache_backend = NULL) {
        $this->providers = $providers;
        $this->resourceFetcher = $resource_fetcher;
        $this->httpClient = $http_client;
        $this->moduleHandler = $module_handler;
        $this->cacheBackend = $cache_backend;
        $this->useCaches = isset($cache_backend);
    }
    
    /**
     * Runs oEmbed discovery and returns the endpoint URL if successful.
     *
     * @param string $url
     *   The resource's URL.
     *
     * @return string|bool
     *   URL of the oEmbed endpoint, or FALSE if the discovery was unsuccessful.
     */
    protected function discoverResourceUrl($url) {
        try {
            $response = $this->httpClient
                ->get($url);
        } catch (RequestException $e) {
            return FALSE;
        }
        $document = Html::load((string) $response->getBody());
        $xpath = new \DOMXpath($document);
        return $this->findUrl($xpath, 'json') ?: $this->findUrl($xpath, 'xml');
    }
    
    /**
     * Tries to find the oEmbed URL in a DOM.
     *
     * @param \DOMXPath $xpath
     *   Page HTML as DOMXPath.
     * @param string $format
     *   Format of oEmbed resource. Possible values are 'json' and 'xml'.
     *
     * @return bool|string
     *   A URL to an oEmbed resource or FALSE if not found.
     */
    protected function findUrl(\DOMXPath $xpath, $format) {
        $result = $xpath->query("//link[@type='application/{$format}+oembed']");
        return $result->length ? $result->item(0)
            ->getAttribute('href') : FALSE;
    }
    
    /**
     * {@inheritdoc}
     */
    public function getProviderByUrl($url) {
        // Check the URL against every scheme of every endpoint of every provider
        // until we find a match.
        foreach ($this->providers
            ->getAll() as $provider_name => $provider_info) {
            foreach ($provider_info->getEndpoints() as $endpoint) {
                if ($endpoint->matchUrl($url)) {
                    return $provider_info;
                }
            }
        }
        $resource_url = $this->discoverResourceUrl($url);
        if ($resource_url) {
            return $this->resourceFetcher
                ->fetchResource($resource_url)
                ->getProvider();
        }
        throw new ResourceException('No matching provider found.', $url);
    }
    
    /**
     * {@inheritdoc}
     */
    public function getResourceUrl($url, $max_width = NULL, $max_height = NULL) {
        // Try to get the resource URL from the static cache.
        if (isset($this->urlCache[$url])) {
            return $this->urlCache[$url];
        }
        // Try to get the resource URL from the persistent cache.
        $cache_id = "media:oembed_resource_url:{$url}:{$max_width}:{$max_height}";
        $cached = $this->cacheGet($cache_id);
        if ($cached) {
            $this->urlCache[$url] = $cached->data;
            return $this->urlCache[$url];
        }
        $provider = $this->getProviderByUrl($url);
        $endpoints = $provider->getEndpoints();
        $endpoint = reset($endpoints);
        $resource_url = $endpoint->buildResourceUrl($url);
        $parsed_url = UrlHelper::parse($resource_url);
        if ($max_width) {
            $parsed_url['query']['maxwidth'] = $max_width;
        }
        if ($max_height) {
            $parsed_url['query']['maxheight'] = $max_height;
        }
        // Let other modules alter the resource URL, because some oEmbed providers
        // provide extra parameters in the query string. For example, Instagram also
        // supports the 'omitscript' parameter.
        $this->moduleHandler
            ->alter('oembed_resource_url', $parsed_url, $provider);
        $resource_url = $parsed_url['path'] . '?' . rawurldecode(UrlHelper::buildQuery($parsed_url['query']));
        $this->urlCache[$url] = $resource_url;
        $this->cacheSet($cache_id, $resource_url);
        return $resource_url;
    }

}