Controller as a listener

HttpFacade.php

<?php

use Symfony\Component\HttpFoundation\RequestStack;

class HttpFacade
{
    /**
     * @var RequestStack
     */
    private $requestStack;

    public function __construct(RequestStack $requestStack)
    {
        $this->requestStack = $requestStack;
    }

    public function setTemplate($template)
    {
        $this->getRequest()->attributes->set('_template', $template);
    }

    public function setTemplateVars(array $vars)
    {
        $this->getRequest()->attributes->set('_template_vars', array_keys($vars));

        foreach ($vars as $name => $value) {
            $this->getRequest()->attributes->set($name, $value);
        }
    }

    private function getRequest()
    {
        return $this->requestStack->getCurrentRequest();
    }
} 

SearchController.php

<?php

class SearchController implements SearchListener
{
    private $searchInteractor;

    private $httpFacade;

    private $response;

    public function __construct(SearchInteractor $searchInteractor, HttpFacade $httpFacade)
    {
        $this->searchInteractor = $searchInteractor;
        $this->searchInteractor->attach($this);

        $this->httpFacade = $httpFacade;
    }

    /**
     * @Route("/search", name="search")
     * @Template
     */
    public function searchAction(Request $request)
    {
        $this->searchInteractor->search($request->query->get('query'));

        return $this->response;
    }

    public function onSearchResults(array $products)
    {
        $this->httpFacade->setTemplate('AcmeSearchBundle:search:results.html.twig');
        $this->httpFacade->setTemplateVars(['products' => $products]);
    }

    public function onNoKeywords()
    {
        $this->httpFacade->setTemplate('AcmeSearchBundle:search:noResults.html.twig');
    }

    public function onSearchUnavailable($keywords)
    {
        $this->response = new RedirectResponse('/search-fallback?query='.$keywords);
    }
}

SearchInteractor.php

<?php

class SearchInteractor
{
    private $repository;

    private $listener;

    public function __construct($repository)
    {
        $this->repository = $repository;
    }

    public function attach(SearchListener $listener)
    {
        $this->listener = $listener;
    }

    public function search($keywords)
    {
        if ($this->isDown()) {
            $this->getListener()->onSearchUnavailable($keywords);

            return;
        }

        if (empty($keywords)) {
            $this->getListener()->onNoKeywords();
 
            return;
        }

        $products = $this->repository->search($keywords);

        $this->getListener()->onSearchResults($products);
    }

    private function getListener()
    {
        if (null === $this->listener) {
            throw new \UnexpectedException();
        }

        return $this->listener;
    }

    private function isDown()
    {
        // some piece of logic deciding if the service is available
        return false;
    }
}

SearchListener.php

<?php

interface SearchListener
{
    /**
     * @param array $products
     * 
     * @return null
     */
    public function onSearchResults(array $products);

    /**
     * @return null
     */
    public function onNoKeywords();

    /**
     * @param string $keywords
     *
     * @return null
     */
    public function onSearchUnavailable($keywords);
}