<?php

namespace Drupal\Core\Routing;

use Symfony\Component\EventDispatcher\EventSubscriberInterface;
use Symfony\Component\Routing\RouteCollection;

/**
 * Provides a base implementation for RouteSubscriber.
 */
abstract class RouteSubscriberBase implements EventSubscriberInterface {

  /**
   * Alters existing routes for a specific collection.
   *
   * @param \Symfony\Component\Routing\RouteCollection $collection
   *   The route collection for adding routes.
   */
  abstract protected function alterRoutes(RouteCollection $collection);

  /**
   * {@inheritdoc}
   */
  public static function getSubscribedEvents() {
    $events[RoutingEvents::ALTER] = 'onAlterRoutes';
    return $events;
  }

  /**
   * Delegates the route altering to self::alterRoutes().
   *
   * @param \Drupal\Core\Routing\RouteBuildEvent $event
   *   The route build event.
   */
  public function onAlterRoutes(RouteBuildEvent $event) {
    $collection = $event->getRouteCollection();
    $this->alterRoutes($collection);
  }

}