how to create movable tree interface with sonata

Category - tree

<?php

/*
 * This file is part of the Sonata package.
 *
 * (c) Thomas Rabaix <thomas.rabaix@sonata-project.org>
 *
 * For the full copyright and license information, please view the LICENSE
 * file that was distributed with this source code.
 */

namespace Luxodo\Bundle\ProductionBundle\Controller;


class CategoryController extends Controller {

    public function upAction($id) {
        $em = $this->getDoctrine()->getEntityManager();
        $repo = $em->getRepository('LuxodoProductionBundle:Category');
        $category = $repo->findOneById($id);
        if ($category->getParent()) {
            $repo->moveUp($category);
        }
        return $this->redirect($this->getRequest()->headers->get('referer'));
    }


    public function downAction($id) {
        $em = $this->getDoctrine()->getEntityManager();
        $repo = $em->getRepository('LuxodoProductionBundle:Category');
        $category = $repo->findOneById($id);
        if ($category->getParent()) {
            $repo->moveDown($category);
        }
        return $this->redirect($this->getRequest()->headers->get('referer'));
    }
    
    public function childrenAction($id) {
     
        // the key used to lookup the template
        $templateKey = 'edit';

        if (false === $this->admin->isGranted('CREATE')) {
            throw new AccessDeniedException();
        }

        $object = $this->admin->getNewInstance();

        $em = $this->getDoctrine()->getEntityManager();
        $repo = $em->getRepository('LuxodoProductionBundle:Category');
        $category = $repo->findOneById($id);
        
        if(!$category) {
            $this->createNotFoundException("Parent category with id {$id} was not found");
        }
        
        $object->setParent($category);
        
        $this->admin->setSubject($object);

        /** @var $form \Symfony\Component\Form\Form */
        $form = $this->admin->getForm();
        $form->setData($object);

        if ($this->get('request')->getMethod() == 'POST') {
            $form->bind($this->get('request'));

            $isFormValid = $form->isValid();

            // persist if the form was valid and if in preview mode the preview was approved
            if ($isFormValid && (!$this->isInPreviewMode() || $this->isPreviewApproved())) {
                $this->admin->create($object);

                if ($this->isXmlHttpRequest()) {
                    return $this->renderJson(array(
                        'result' => 'ok',
                        'objectId' => $this->admin->getNormalizedIdentifier($object)
                    ));
                }

                $this->get('session')->setFlash('sonata_flash_success','flash_create_success');
                // redirect to edit mode
                return $this->redirectTo($object);
            }

            // show an error message if the form failed validation
            if (!$isFormValid) {
                if (!$this->isXmlHttpRequest()) {
                    $this->get('session')->setFlash('sonata_flash_error', 'flash_create_error');
                }
            } elseif ($this->isPreviewRequested()) {
                // pick the preview template if the form was valid and preview was requested
                $templateKey = 'preview';
            }
        }

        $view = $form->createView();

        // set the theme for the current Admin Form
        $this->get('twig')->getExtension('form')->renderer->setTheme($view, $this->admin->getFormTheme());

        return $this->render($this->admin->getTemplate($templateKey), array(
            'action' => 'create',
            'form'   => $view,
            'object' => $object,
        ));
        
    }

}