MenuController.php

<?php

namespace Drupal\menu_ui\Controller;

use Drupal\Component\Utility\Xss;
use Drupal\Core\Controller\ControllerBase;
use Drupal\Core\Menu\MenuParentFormSelectorInterface;
use Drupal\system\MenuInterface;
use Symfony\Component\DependencyInjection\ContainerInterface;
use Symfony\Component\HttpFoundation\JsonResponse;
use Symfony\Component\HttpFoundation\Request;

/**
 * Returns responses for Menu routes.
 */
class MenuController extends ControllerBase {
    
    /**
     * The menu parent form service.
     *
     * @var \Drupal\Core\Menu\MenuParentFormSelectorInterface
     */
    protected $menuParentSelector;
    
    /**
     * Creates a new MenuController object.
     *
     * @param \Drupal\Core\Menu\MenuParentFormSelectorInterface $menu_parent_form
     *   The menu parent form service.
     */
    public function __construct(MenuParentFormSelectorInterface $menu_parent_form) {
        $this->menuParentSelector = $menu_parent_form;
    }
    
    /**
     * {@inheritdoc}
     */
    public static function create(ContainerInterface $container) {
        return new static($container->get('menu.parent_form_selector'));
    }
    
    /**
     * Gets all the available menus and menu items as a JavaScript array.
     *
     * @param \Symfony\Component\HttpFoundation\Request $request
     *   The request of the page.
     *
     * @return \Symfony\Component\HttpFoundation\JsonResponse
     *   The available menu and menu items.
     */
    public function getParentOptions(Request $request) {
        $available_menus = [];
        if ($menus = $request->request
            ->get('menus')) {
            foreach ($menus as $menu) {
                $available_menus[$menu] = $menu;
            }
        }
        // @todo Update this to use the optional $cacheability parameter, so that
        //   a cacheable JSON response can be sent.
        $options = $this->menuParentSelector
            ->getParentSelectOptions('', $available_menus);
        return new JsonResponse($options);
    }
    
    /**
     * Route title callback.
     *
     * @param \Drupal\system\MenuInterface $menu
     *   The menu entity.
     *
     * @return array
     *   The menu label as a render array.
     */
    public function menuTitle(MenuInterface $menu) {
        return [
            '#markup' => $menu->label(),
            '#allowed_tags' => Xss::getHtmlTagList(),
        ];
    }

}