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\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;
  }
  
  /**
   * 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 = $request->request
      ->all('menus')) {
      foreach ($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(),
    ];
  }

}