class UpdateFetcher

class UpdateFetcher implements UpdateFetcherInterface {
    use DependencySerializationTrait;
    
    /**
     * URL to check for updates, if a given project doesn't define its own.
     */
    const UPDATE_DEFAULT_URL = 'https://updates.drupal.org/release-history';
    
    /**
     * The fetch URL configured in the update settings.
     *
     * @var string
     */
    protected $fetchUrl;
    
    /**
     * The update settings.
     *
     * @var \Drupal\Core\Config\Config
     */
    protected $updateSettings;
    
    /**
     * The HTTP client to fetch the feed data with.
     *
     * @var \GuzzleHttp\ClientInterface
     */
    protected $httpClient;
    
    /**
     * Whether to use HTTP fallback if HTTPS fails.
     *
     * @var bool
     */
    protected $withHttpFallback;
    
    /**
     * Constructs an UpdateFetcher.
     *
     * @param \Drupal\Core\Config\ConfigFactoryInterface $config_factory
     *   The config factory.
     * @param \GuzzleHttp\ClientInterface $http_client
     *   A Guzzle client object.
     * @param \Drupal\Core\Site\Settings|null $settings
     *   The settings instance.
     */
    public function __construct(ConfigFactoryInterface $config_factory, ClientInterface $http_client, Settings $settings = NULL) {
        $this->fetchUrl = $config_factory->get('update.settings')
            ->get('fetch.url');
        $this->httpClient = $http_client;
        $this->updateSettings = $config_factory->get('update.settings');
        if (is_null($settings)) {
            @trigger_error('The settings service should be passed to UpdateFetcher::__construct() since 9.1.0. This will be required in Drupal 10.0.0. See https://www.drupal.org/node/3179315', E_USER_DEPRECATED);
            $settings = \Drupal::service('settings');
        }
        $this->withHttpFallback = $settings->get('update_fetch_with_http_fallback', FALSE);
    }
    
    /**
     * {@inheritdoc}
     */
    public function fetchProjectData(array $project, $site_key = '') {
        $url = $this->buildFetchUrl($project, $site_key);
        return $this->doRequest($url, [
            'headers' => [
                'Accept' => 'text/xml',
            ],
        ], $this->withHttpFallback);
    }
    
    /**
     * Applies a GET request with a possible HTTP fallback.
     *
     * This method falls back to HTTP in case there was some certificate
     * problem.
     *
     * @param string $url
     *   The URL.
     * @param array $options
     *   The guzzle client options.
     * @param bool $with_http_fallback
     *   Should the function fall back to HTTP.
     *
     * @return string
     *   The body of the HTTP(S) request, or an empty string on failure.
     */
    protected function doRequest(string $url, array $options, bool $with_http_fallback) : string {
        $data = '';
        try {
            $data = (string) $this->httpClient
                ->get($url, [
                'headers' => [
                    'Accept' => 'text/xml',
                ],
            ])
                ->getBody();
        } catch (TransferException $exception) {
            watchdog_exception('update', $exception);
            if ($with_http_fallback && strpos($url, "http://") === FALSE) {
                $url = str_replace('https://', 'http://', $url);
                return $this->doRequest($url, $options, FALSE);
            }
        }
        return $data;
    }
    
    /**
     * {@inheritdoc}
     */
    public function buildFetchUrl(array $project, $site_key = '') {
        $name = $project['name'];
        $url = $this->getFetchBaseUrl($project);
        $url .= '/' . $name . '/current';
        // Only append usage information if we have a site key and the project is
        // enabled. We do not want to record usage statistics for disabled projects.
        if (!empty($site_key) && strpos($project['project_type'], 'disabled') === FALSE) {
            // Append the site key.
            $url .= strpos($url, '?') !== FALSE ? '&' : '?';
            $url .= 'site_key=';
            $url .= rawurlencode($site_key);
            // Append the version.
            if (!empty($project['info']['version'])) {
                $url .= '&version=';
                $url .= rawurlencode($project['info']['version']);
            }
            // Append the list of modules or themes enabled.
            $list = array_keys($project['includes']);
            $url .= '&list=';
            $url .= rawurlencode(implode(',', $list));
        }
        return $url;
    }
    
    /**
     * {@inheritdoc}
     */
    public function getFetchBaseUrl($project) {
        if (isset($project['info']['project status url'])) {
            $url = $project['info']['project status url'];
        }
        else {
            $url = $this->fetchUrl;
            if (empty($url)) {
                $url = static::UPDATE_DEFAULT_URL;
            }
        }
        return $url;
    }

}