class UriResolver

class UriResolver implements UriResolverInterface {
    
    /**
     * Parses a URI into five main components
     *
     * @param string $uri
     *
     * @return array
     */
    public function parse($uri) {
        preg_match('|^(([^:/?#]+):)?(//([^/?#]*))?([^?#]*)(\\?([^#]*))?(#(.*))?|', $uri, $match);
        $components = array();
        if (5 < count($match)) {
            $components = array(
                'scheme' => $match[2],
                'authority' => $match[4],
                'path' => $match[5],
            );
        }
        if (7 < count($match)) {
            $components['query'] = $match[7];
        }
        if (9 < count($match)) {
            $components['fragment'] = $match[9];
        }
        return $components;
    }
    
    /**
     * Builds a URI based on n array with the main components
     *
     * @param array $components
     *
     * @return string
     */
    public function generate(array $components) {
        $uri = $components['scheme'] . '://' . $components['authority'] . $components['path'];
        if (array_key_exists('query', $components) && strlen($components['query'])) {
            $uri .= '?' . $components['query'];
        }
        if (array_key_exists('fragment', $components)) {
            $uri .= '#' . $components['fragment'];
        }
        return $uri;
    }
    
    /**
     * {@inheritdoc}
     */
    public function resolve($uri, $baseUri = null) {
        // treat non-uri base as local file path
        if (!is_null($baseUri) && !filter_var($baseUri, \FILTER_VALIDATE_URL) && !preg_match('|^[^/]+://|u', $baseUri)) {
            if (is_file($baseUri)) {
                $baseUri = 'file://' . realpath($baseUri);
            }
            elseif (is_dir($baseUri)) {
                $baseUri = 'file://' . realpath($baseUri) . '/';
            }
            else {
                $baseUri = 'file://' . getcwd() . '/' . $baseUri;
            }
        }
        if ($uri == '') {
            return $baseUri;
        }
        $components = $this->parse($uri);
        $path = $components['path'];
        if (!empty($components['scheme'])) {
            return $uri;
        }
        $baseComponents = $this->parse($baseUri);
        $basePath = $baseComponents['path'];
        $baseComponents['path'] = self::combineRelativePathWithBasePath($path, $basePath);
        if (isset($components['fragment'])) {
            $baseComponents['fragment'] = $components['fragment'];
        }
        return $this->generate($baseComponents);
    }
    
    /**
     * Tries to glue a relative path onto an absolute one
     *
     * @param string $relativePath
     * @param string $basePath
     *
     * @throws UriResolverException
     *
     * @return string Merged path
     */
    public static function combineRelativePathWithBasePath($relativePath, $basePath) {
        $relativePath = self::normalizePath($relativePath);
        if ($relativePath == '') {
            return $basePath;
        }
        if ($relativePath[0] == '/') {
            return $relativePath;
        }
        $basePathSegments = explode('/', $basePath);
        preg_match('|^/?(\\.\\./(?:\\./)*)*|', $relativePath, $match);
        $numLevelUp = strlen($match[0]) / 3 + 1;
        if ($numLevelUp >= count($basePathSegments)) {
            throw new UriResolverException(sprintf("Unable to resolve URI '%s' from base '%s'", $relativePath, $basePath));
        }
        $basePathSegments = array_slice($basePathSegments, 0, -$numLevelUp);
        $path = preg_replace('|^/?(\\.\\./(\\./)*)*|', '', $relativePath);
        return implode('/', $basePathSegments) . '/' . $path;
    }
    
    /**
     * Normalizes a URI path component by removing dot-slash and double slashes
     *
     * @param string $path
     *
     * @return string
     */
    private static function normalizePath($path) {
        $path = preg_replace('|((?<!\\.)\\./)*|', '', $path);
        $path = preg_replace('|//|', '/', $path);
        return $path;
    }
    
    /**
     * @param string $uri
     *
     * @return bool
     */
    public function isValid($uri) {
        $components = $this->parse($uri);
        return !empty($components);
    }

}