class PublicStream

class PublicStream extends LocalStream {
    
    /**
     * {@inheritdoc}
     */
    public static function getType() {
        return StreamWrapperInterface::LOCAL_NORMAL;
    }
    
    /**
     * {@inheritdoc}
     */
    public function getName() {
        return t('Public files');
    }
    
    /**
     * {@inheritdoc}
     */
    public function getDescription() {
        return t('Public local files served by the webserver.');
    }
    
    /**
     * {@inheritdoc}
     */
    public function getDirectoryPath() {
        return static::basePath();
    }
    
    /**
     * {@inheritdoc}
     */
    public function getExternalUrl() {
        $path = str_replace('\\', '/', $this->getTarget());
        return static::baseUrl() . '/' . UrlHelper::encodePath($path);
    }
    
    /**
     * Finds and returns the base URL for public://.
     *
     * Defaults to the current site's base URL plus directory path.
     *
     * Note that this static method is used by \Drupal\system\Form\FileSystemForm
     * so you should alter that form or substitute a different form if you change
     * the class providing the stream_wrapper.public service.
     *
     * @return string
     *   The external base URL for public://
     */
    public static function baseUrl() {
        $settings_base_url = Settings::get('file_public_base_url', '');
        if ($settings_base_url) {
            return (string) $settings_base_url;
        }
        else {
            return $GLOBALS['base_url'] . '/' . static::basePath();
        }
    }
    
    /**
     * Returns the base path for public://.
     *
     * If we have a setting for the public:// scheme's path, we use that.
     * Otherwise we build a reasonable default based on the site.path service if
     * it's available, or a default behavior based on the request.
     *
     * Note that this static method is used by \Drupal\system\Form\FileSystemForm
     * so you should alter that form or substitute a different form if you change
     * the class providing the stream_wrapper.public service.
     *
     * The site path is injectable from the site.path service:
     * @code
     * $base_path = PublicStream::basePath(\Drupal::service('site.path'));
     * @endcode
     *
     * @param string $site_path
     *   (optional) The site.path service parameter, which is typically the path
     *   to sites/ in a Drupal installation. This allows you to inject the site
     *   path using services from the caller. If omitted, this method will use the
     *   global service container or the kernel's default behavior to determine
     *   the site path.
     *
     * @return string
     *   The base path for public:// typically sites/default/files.
     */
    public static function basePath($site_path = NULL) {
        if ($site_path === NULL) {
            // Find the site path. Kernel service is not always available at this
            // point, but is preferred, when available.
            if (\Drupal::hasService('kernel')) {
                $site_path = \Drupal::service('site.path');
            }
            else {
                // If there is no kernel available yet, we call the static
                // findSitePath().
                $site_path = DrupalKernel::findSitePath(Request::createFromGlobals());
            }
        }
        return Settings::get('file_public_path', $site_path . '/files');
    }

}