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;
    }

}