class UriResolver

class UriResolver {
    
    /**
     * Resolves a URI according to a base URI.
     *
     * For example if $uri=/foo/bar and $baseUri=https://symfony.com it will
     * return https://symfony.com/foo/bar
     *
     * If the $uri is not absolute you must pass an absolute $baseUri
     */
    public static function resolve(string $uri, ?string $baseUri) : string {
        $uri = trim($uri);
        // absolute URL?
        if (null !== parse_url(\strlen($uri) !== strcspn($uri, '?#') ? $uri : $uri . '#', \PHP_URL_SCHEME)) {
            return $uri;
        }
        if (null === $baseUri) {
            throw new \InvalidArgumentException('The URI is relative, so you must define its base URI passing an absolute URL.');
        }
        // empty URI
        if (!$uri) {
            return $baseUri;
        }
        // an anchor
        if ('#' === $uri[0]) {
            return self::cleanupAnchor($baseUri) . $uri;
        }
        $baseUriCleaned = self::cleanupUri($baseUri);
        if ('?' === $uri[0]) {
            return $baseUriCleaned . $uri;
        }
        // absolute URL with relative schema
        if (str_starts_with($uri, '//')) {
            return preg_replace('#^([^/]*)//.*$#', '$1', $baseUriCleaned) . $uri;
        }
        $baseUriCleaned = preg_replace('#^(.*?//[^/]*)(?:\\/.*)?$#', '$1', $baseUriCleaned);
        // absolute path
        if ('/' === $uri[0]) {
            return $baseUriCleaned . $uri;
        }
        // relative path
        $path = parse_url(substr($baseUri, \strlen($baseUriCleaned)), \PHP_URL_PATH) ?? '';
        $path = self::canonicalizePath(substr($path, 0, strrpos($path, '/')) . '/' . $uri);
        return $baseUriCleaned . ('' === $path || '/' !== $path[0] ? '/' : '') . $path;
    }
    
    /**
     * Returns the canonicalized URI path (see RFC 3986, section 5.2.4).
     */
    private static function canonicalizePath(string $path) : string {
        if ('' === $path || '/' === $path) {
            return $path;
        }
        if (str_ends_with($path, '.')) {
            $path .= '/';
        }
        $output = [];
        foreach (explode('/', $path) as $segment) {
            if ('..' === $segment) {
                array_pop($output);
            }
            elseif ('.' !== $segment) {
                $output[] = $segment;
            }
        }
        return implode('/', $output);
    }
    
    /**
     * Removes the query string and the anchor from the given uri.
     */
    private static function cleanupUri(string $uri) : string {
        return self::cleanupQuery(self::cleanupAnchor($uri));
    }
    
    /**
     * Removes the query string from the uri.
     */
    private static function cleanupQuery(string $uri) : string {
        if (false !== ($pos = strpos($uri, '?'))) {
            return substr($uri, 0, $pos);
        }
        return $uri;
    }
    
    /**
     * Removes the anchor from the uri.
     */
    private static function cleanupAnchor(string $uri) : string {
        if (false !== ($pos = strpos($uri, '#'))) {
            return substr($uri, 0, $pos);
        }
        return $uri;
    }

}