class RouteSubscriber

class RouteSubscriber extends RouteSubscriberBase {
  
  /**
   * The entity type manager service.
   *
   * @var \Drupal\Core\Entity\EntityTypeManagerInterface
   */
  protected $entityTypeManager;
  
  /**
   * The router service.
   *
   * @var \Symfony\Component\Routing\RouterInterface
   */
  protected $routeProvider;
  
  /**
   * Constructs a new RouteSubscriber object.
   *
   * @param \Drupal\Core\Entity\EntityTypeManagerInterface $entity_manager
   *   The entity type manager.
   * @param \Drupal\Core\Routing\RouteProviderInterface $router_provider
   *   The router service.
   */
  public function __construct(EntityTypeManagerInterface $entity_manager, RouteProviderInterface $router_provider) {
    $this->entityTypeManager = $entity_manager;
    $this->routeProvider = $router_provider;
  }
  
  /**
   * {@inheritdoc}
   */
  protected function alterRoutes(RouteCollection $collection) {
    foreach ($this->entityTypeManager
      ->getDefinitions() as $entity_type_id => $entity_type) {
      if ($route = $this->getEntityLoadRoute($entity_type)) {
        $collection->add("entity.{$entity_type_id}.devel_load", $route);
      }
      if ($route = $this->getEntityRenderRoute($entity_type)) {
        $collection->add("entity.{$entity_type_id}.devel_render", $route);
      }
      if ($route = $this->getEntityTypeDefinitionRoute($entity_type)) {
        $collection->add("entity.{$entity_type_id}.devel_definition", $route);
      }
    }
  }
  
  /**
   * Gets the entity load route.
   *
   * @param \Drupal\Core\Entity\EntityTypeInterface $entity_type
   *   The entity type.
   *
   * @return \Symfony\Component\Routing\Route|null
   *   The generated route, if available.
   */
  protected function getEntityLoadRoute(EntityTypeInterface $entity_type) {
    if ($devel_load = $entity_type->getLinkTemplate('devel-load')) {
      $route = (new Route($devel_load))->addDefaults([
        '_controller' => '\\Drupal\\devel\\Controller\\EntityDebugController::entityLoad',
        '_title' => 'Devel Load',
      ])
        ->addRequirements([
        '_permission' => 'access devel information',
      ])
        ->setOption('_admin_route', TRUE)
        ->setOption('_devel_entity_type_id', $entity_type->id());
      if ($parameters = $this->getRouteParameters($entity_type, 'edit-form')) {
        $route->setOption('parameters', $parameters);
      }
      return $route;
    }
    return NULL;
  }
  
  /**
   * Gets the entity render route.
   *
   * @param \Drupal\Core\Entity\EntityTypeInterface $entity_type
   *   The entity type.
   *
   * @return \Symfony\Component\Routing\Route|null
   *   The generated route, if available.
   */
  protected function getEntityRenderRoute(EntityTypeInterface $entity_type) {
    if ($devel_render = $entity_type->getLinkTemplate('devel-render')) {
      $route = (new Route($devel_render))->addDefaults([
        '_controller' => '\\Drupal\\devel\\Controller\\EntityDebugController::entityRender',
        '_title' => 'Devel Render',
      ])
        ->addRequirements([
        '_permission' => 'access devel information',
      ])
        ->setOption('_admin_route', TRUE)
        ->setOption('_devel_entity_type_id', $entity_type->id());
      if ($parameters = $this->getRouteParameters($entity_type, 'canonical')) {
        $route->setOption('parameters', $parameters);
      }
      return $route;
    }
    return NULL;
  }
  
  /**
   * Gets the entity type definition route.
   *
   * @param \Drupal\Core\Entity\EntityTypeInterface $entity_type
   *   The entity type.
   *
   * @return \Symfony\Component\Routing\Route|null
   *   The generated route, if available.
   */
  protected function getEntityTypeDefinitionRoute(EntityTypeInterface $entity_type) {
    if ($devel_definition = $entity_type->getLinkTemplate('devel-definition')) {
      $route = (new Route($devel_definition))->addDefaults([
        '_controller' => '\\Drupal\\devel\\Controller\\EntityDebugController::entityTypeDefinition',
        '_title' => 'Entity type definition',
      ])
        ->addRequirements([
        '_permission' => 'access devel information',
      ])
        ->setOption('_admin_route', TRUE)
        ->setOption('_devel_entity_type_id', $entity_type->id());
      $link_template = $entity_type->getLinkTemplate('edit-form') ? 'edit-form' : 'canonical';
      if ($parameters = $this->getRouteParameters($entity_type, $link_template)) {
        $route->setOption('parameters', $parameters);
      }
      return $route;
    }
  }
  
  /**
   * Gets the route parameters from the template.
   *
   * @param \Drupal\Core\Entity\EntityTypeInterface $entity_type
   *   The entity type definition.
   * @param string $link_template
   *   The link template.
   *
   * @return array[]
   *   A list of route of parameters.
   */
  protected function getRouteParameters(EntityTypeInterface $entity_type, string $link_template) : array {
    $parameters = [];
    if (!($path = $entity_type->getLinkTemplate($link_template))) {
      return $parameters;
    }
    $original_route_parameters = [];
    $candidate_routes = $this->routeProvider
      ->getRoutesByPattern($path);
    if ($candidate_routes->count()) {
      // Guess the best match. There could be more than one route sharing the
      // same path. Try first an educated guess based on the route name. If we
      // can't find one, pick-up the first from the list.
      $name = 'entity.' . $entity_type->id() . '.' . str_replace('-', '_', $link_template);
      if (!($original_route = $candidate_routes->get($name))) {
        $iterator = $candidate_routes->getIterator();
        $iterator->rewind();
        $original_route = $iterator->current();
      }
      $original_route_parameters = $original_route->getOption('parameters') ?? [];
    }
    if (preg_match_all('/{\\w*}/', $path, $matches)) {
      foreach ($matches[0] as $match) {
        $match = str_replace([
          '{',
          '}',
        ], '', $match);
        // This match has an original route parameter definition.
        if (isset($original_route_parameters[$match])) {
          $parameters[$match] = $original_route_parameters[$match];
        }
        elseif ($this->entityTypeManager
          ->hasDefinition($match)) {
          $parameters[$match] = [
            'type' => "entity:{$match}",
          ];
        }
      }
    }
    return $parameters;
  }
  
  /**
   * {@inheritdoc}
   */
  public static function getSubscribedEvents() {
    $events = parent::getSubscribedEvents();
    $events[RoutingEvents::ALTER] = [
      'onAlterRoutes',
      100,
    ];
    return $events;
  }

}