class UnroutedUrlAssembler

class UnroutedUrlAssembler implements UnroutedUrlAssemblerInterface {
    
    /**
     * A request stack object.
     *
     * @var \Symfony\Component\HttpFoundation\RequestStack
     */
    protected $requestStack;
    
    /**
     * The outbound path processor.
     *
     * @var \Drupal\Core\PathProcessor\OutboundPathProcessorInterface
     */
    protected $pathProcessor;
    
    /**
     * Constructs a new unroutedUrlAssembler object.
     *
     * @param \Symfony\Component\HttpFoundation\RequestStack $request_stack
     *   A request stack object.
     * @param \Drupal\Core\PathProcessor\OutboundPathProcessorInterface $path_processor
     *   The output path processor.
     * @param string[] $filter_protocols
     *   (optional) An array of protocols allowed for URL generation.
     */
    public function __construct(RequestStack $request_stack, OutboundPathProcessorInterface $path_processor, array $filter_protocols = [
        'http',
        'https',
    ]) {
        UrlHelper::setAllowedProtocols($filter_protocols);
        $this->requestStack = $request_stack;
        $this->pathProcessor = $path_processor;
    }
    
    /**
     * {@inheritdoc}
     *
     * This is a helper function that calls buildExternalUrl() or buildLocalUrl()
     * based on a check of whether the path is a valid external URL.
     */
    public function assemble($uri, array $options = [], $collect_bubbleable_metadata = FALSE) {
        // Note that UrlHelper::isExternal will return FALSE if the $uri has a
        // disallowed protocol.  This is later made safe since we always add at
        // least a leading slash.
        if (parse_url($uri, PHP_URL_SCHEME) === 'base') {
            return $this->buildLocalUrl($uri, $options, $collect_bubbleable_metadata);
        }
        elseif (UrlHelper::isExternal($uri)) {
            // UrlHelper::isExternal() only returns true for safe protocols.
            return $this->buildExternalUrl($uri, $options, $collect_bubbleable_metadata);
        }
        throw new \InvalidArgumentException("The URI '{$uri}' is invalid. You must use a valid URI scheme. Use base: for a path, e.g., to a Drupal file that needs the base path. Do not use this for internal paths controlled by Drupal.");
    }
    
    /**
     * {@inheritdoc}
     */
    protected function buildExternalUrl($uri, array $options = [], $collect_bubbleable_metadata = FALSE) {
        $this->addOptionDefaults($options);
        // Split off the query & fragment.
        $parsed = UrlHelper::parse($uri);
        $uri = $parsed['path'];
        $parsed += [
            'query' => [],
        ];
        $options += [
            'query' => [],
        ];
        $options['query'] = NestedArray::mergeDeepArray([
            $parsed['query'],
            $options['query'],
        ], TRUE);
        if ($parsed['fragment'] && !$options['fragment']) {
            $options['fragment'] = '#' . $parsed['fragment'];
        }
        if (isset($options['https'])) {
            if ($options['https'] === TRUE) {
                $uri = str_replace('http://', 'https://', $uri);
            }
            elseif ($options['https'] === FALSE) {
                $uri = str_replace('https://', 'http://', $uri);
            }
        }
        // Append the query.
        if ($options['query']) {
            $uri .= '?' . UrlHelper::buildQuery($options['query']);
        }
        // Reassemble.
        $url = $uri . $options['fragment'];
        return $collect_bubbleable_metadata ? (new GeneratedUrl())->setGeneratedUrl($url) : $url;
    }
    
    /**
     * {@inheritdoc}
     */
    protected function buildLocalUrl($uri, array $options = [], $collect_bubbleable_metadata = FALSE) {
        $generated_url = $collect_bubbleable_metadata ? new GeneratedUrl() : NULL;
        $this->addOptionDefaults($options);
        $request = $this->requestStack
            ->getCurrentRequest();
        // Remove the base: scheme.
        // @todo Consider using a class constant for this in
        //   https://www.drupal.org/node/2417459
        $uri = substr($uri, 5);
        // Allow (outbound) path processing, if needed. A valid use case is the path
        // alias overview form:
        // @see \Drupal\path\Controller\PathController::adminOverview().
        if (!empty($options['path_processing'])) {
            // Do not pass the request, since this is a special case and we do not
            // want to include e.g. the request language in the processing.
            $uri = $this->pathProcessor
                ->processOutbound($uri, $options, NULL, $generated_url);
        }
        // Strip leading slashes from internal paths to prevent them becoming
        // external URLs without protocol. /example.com should not be turned into
        // //example.com.
        $uri = ltrim($uri, '/');
        // Add any subdirectory where Drupal is installed.
        $current_base_path = $request->getBasePath() . '/';
        if ($options['absolute']) {
            $current_base_url = $request->getSchemeAndHttpHost() . $current_base_path;
            if (isset($options['https'])) {
                if (!empty($options['https'])) {
                    $base = str_replace('http://', 'https://', $current_base_url);
                    $options['absolute'] = TRUE;
                }
                else {
                    $base = str_replace('https://', 'http://', $current_base_url);
                    $options['absolute'] = TRUE;
                }
            }
            else {
                $base = $current_base_url;
            }
            if ($collect_bubbleable_metadata) {
                $generated_url->addCacheContexts([
                    'url.site',
                ]);
            }
        }
        else {
            $base = $current_base_path;
        }
        $prefix = empty($uri) ? rtrim($options['prefix'], '/') : $options['prefix'];
        $uri = str_replace('%2F', '/', rawurlencode($prefix . $uri));
        $query = $options['query'] ? '?' . UrlHelper::buildQuery($options['query']) : '';
        $url = $base . $options['script'] . $uri . $query . $options['fragment'];
        return $collect_bubbleable_metadata ? $generated_url->setGeneratedUrl($url) : $url;
    }
    
    /**
     * Merges in default defaults.
     *
     * @param array $options
     *   The options to merge in the defaults.
     */
    protected function addOptionDefaults(array &$options) {
        $request = $this->requestStack
            ->getCurrentRequest();
        $current_base_path = $request->getBasePath() . '/';
        $current_script_path = '';
        $base_path_with_script = $request->getBaseUrl();
        // If the current request was made with the script name (eg, index.php) in
        // it, then extract it, making sure the leading / is gone, and a trailing /
        // is added, to allow simple string concatenation with other parts.
        if (!empty($base_path_with_script)) {
            $script_name = $request->getScriptName();
            if (strpos($base_path_with_script, $script_name) !== FALSE) {
                $current_script_path = ltrim(substr($script_name, strlen($current_base_path)), '/') . '/';
            }
        }
        // Merge in defaults.
        $options += [
            'fragment' => '',
            'query' => [],
            'absolute' => FALSE,
            'prefix' => '',
            'script' => $current_script_path,
        ];
        if (isset($options['fragment']) && $options['fragment'] !== '') {
            $options['fragment'] = '#' . $options['fragment'];
        }
    }

}