class RouteCompiler

class RouteCompiler extends SymfonyRouteCompiler implements RouteCompilerInterface {
    
    /**
     * Utility constant to use for regular expressions against the path.
     */
    const REGEX_DELIMITER = '#';
    
    /**
     * Compiles the current route instance.
     *
     * Because so much of the parent class is private, we need to call the parent
     * class's compile() method and then dissect its return value to build our
     * new compiled object.  If upstream gets refactored so we can subclass more
     * easily then this may not be necessary.
     *
     * @param \Symfony\Component\Routing\Route $route
     *   A Route instance.
     *
     * @return \Drupal\Core\Routing\CompiledRoute
     *   A CompiledRoute instance.
     */
    public static function compile(Route $route) {
        // Symfony 4 requires that all UTF-8 route patterns have the "utf8" option
        // set and Drupal does not support non UTF-8 routes.
        $route->setOption('utf8', TRUE);
        $symfony_compiled = parent::compile($route);
        // The Drupal-specific compiled information.
        $stripped_path = static::getPathWithoutDefaults($route);
        $fit = static::getFit($stripped_path);
        $pattern_outline = static::getPatternOutline($stripped_path);
        // We count the number of parts including any optional trailing parts. This
        // allows the RouteProvider to filter candidate routes more efficiently.
        $num_parts = count(explode('/', trim($route->getPath(), '/')));
        return new CompiledRoute($fit, $pattern_outline, $num_parts, '', $symfony_compiled->getRegex(), $symfony_compiled->getTokens(), $symfony_compiled->getPathVariables(), $symfony_compiled->getHostRegex(), $symfony_compiled->getHostTokens(), $symfony_compiled->getHostVariables(), $symfony_compiled->getVariables());
    }
    
    /**
     * Returns the pattern outline.
     *
     * The pattern outline is the path pattern but normalized so that all
     * placeholders are the string '%'.
     *
     * @param string $path
     *   The path for which we want the normalized outline.
     *
     * @return string
     *   The path pattern outline.
     */
    public static function getPatternOutline($path) {
        return preg_replace('#\\{\\w+\\}#', '%', $path);
    }
    
    /**
     * Determines the fitness of the provided path.
     *
     * @param string $path
     *   The path whose fitness we want.
     *
     * @return int
     *   The fitness of the path, as an integer.
     */
    public static function getFit($path) {
        $parts = explode('/', trim($path, '/'));
        $number_parts = count($parts);
        // We store the highest index of parts here to save some work in the fit
        // calculation loop.
        $slashes = $number_parts - 1;
        // The fit value is a binary number which has 1 at every fixed path
        // position and 0 where there is a wildcard. We keep track of all such
        // patterns that exist so that we can minimize the number of path
        // patterns we need to check in the RouteProvider.
        $fit = 0;
        foreach ($parts as $k => $part) {
            if (strpos($part, '{') === FALSE) {
                $fit |= 1 << $slashes - $k;
            }
        }
        return $fit;
    }
    
    /**
     * Returns the path of the route, without placeholders with a default value.
     *
     * When computing the path outline and fit, we want to skip default-value
     * placeholders.  If we didn't, the path would never match.  Note that this
     * only works for placeholders at the end of the path. Infix placeholders
     * with default values don't make sense anyway, so that should not be a
     * problem.
     *
     * @param \Symfony\Component\Routing\Route $route
     *   The route to have the placeholders removed from.
     *
     * @return string
     *   The path string, stripped of placeholders that have default values.
     */
    public static function getPathWithoutDefaults(Route $route) {
        $path = $route->getPath();
        $defaults = $route->getDefaults();
        // Remove placeholders with default values from the outline, so that they
        // will still match.
        $remove = array_map(function ($a) {
            return '/{' . $a . '}';
        }, array_keys($defaults));
        $path = str_replace($remove, '', $path);
        return $path;
    }

}