<?php

/**
 * @file
 * Contains \Drupal\Core\EventSubscriber\SpecialAttributesRouteSubscriber.
 */

namespace Drupal\Core\EventSubscriber;

use Drupal\Component\Utility\String;
use Drupal\Core\Routing\RouteBuildEvent;
use Drupal\Core\Routing\RouteSubscriberBase;
use Symfony\Cmf\Component\Routing\RouteObjectInterface;
use Symfony\Component\Routing\RouteCollection;

/**
 * Provides a route subscriber which checks for invalid pattern variables.
 */
class SpecialAttributesRouteSubscriber extends RouteSubscriberBase {

  /**
   * {@inheritdoc}
   */
  protected function alterRoutes(RouteCollection $collection, $module) {
    $special_variables = array(
      'system_path',
      '_maintenance',
      '_legacy',
      '_authentication_provider',
      '_raw_variables',
      RouteObjectInterface::ROUTE_OBJECT,
      RouteObjectInterface::ROUTE_NAME,
      '_content',
      '_form',
    );

    foreach ($collection->all() as $route) {
      if ($not_allowed_variables = array_intersect($route->compile()->getVariables(), $special_variables)) {
        $placeholders = array('@variables' => implode(', ', $not_allowed_variables));
        drupal_set_message(String::format('The following variables are reserved names by drupal: @variables', $placeholders));
        watchdog('error', 'The following variables are reserved names by drupal: @variables', $placeholders);
        return FALSE;
      }
    }
    return TRUE;
  }

  /**
   * Delegates the route altering to self::alterRoutes().
   *
   * @param \Drupal\Core\Routing\RouteBuildEvent $event
   *   The route build event.
   *
   * @return bool
   *   Returns TRUE if the variables were successfully replaced, otherwise
   *   FALSE.
   */
  public function onAlterRoutes(RouteBuildEvent $event) {
    $collection = $event->getRouteCollection();
    return $this->alterRoutes($collection, $event->getProvider());
  }

}