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    <h3>Editing: RouterListener.php</h3>
    <textarea name="content" rows="20" cols="80">&lt;?php

/*
 * This file is part of the Symfony package.
 *
 * (c) Fabien Potencier &lt;fabien@symfony.com&gt;
 *
 * For the full copyright and license information, please view the LICENSE
 * file that was distributed with this source code.
 */

namespace Symfony\Component\HttpKernel\EventListener;

use Psr\Log\LoggerInterface;
use Symfony\Component\EventDispatcher\EventSubscriberInterface;
use Symfony\Component\HttpFoundation\Request;
use Symfony\Component\HttpFoundation\RequestStack;
use Symfony\Component\HttpFoundation\Response;
use Symfony\Component\HttpKernel\Event\ExceptionEvent;
use Symfony\Component\HttpKernel\Event\FinishRequestEvent;
use Symfony\Component\HttpKernel\Event\RequestEvent;
use Symfony\Component\HttpKernel\Exception\BadRequestHttpException;
use Symfony\Component\HttpKernel\Exception\MethodNotAllowedHttpException;
use Symfony\Component\HttpKernel\Exception\NotFoundHttpException;
use Symfony\Component\HttpKernel\Kernel;
use Symfony\Component\HttpKernel\KernelEvents;
use Symfony\Component\Routing\Exception\MethodNotAllowedException;
use Symfony\Component\Routing\Exception\NoConfigurationException;
use Symfony\Component\Routing\Exception\ResourceNotFoundException;
use Symfony\Component\Routing\Matcher\RequestMatcherInterface;
use Symfony\Component\Routing\Matcher\UrlMatcherInterface;
use Symfony\Component\Routing\RequestContext;
use Symfony\Component\Routing\RequestContextAwareInterface;

/**
 * Initializes the context from the request and sets request attributes based on a matching route.
 *
 * @author Fabien Potencier &lt;fabien@symfony.com&gt;
 * @author Yonel Ceruto &lt;yonelceruto@gmail.com&gt;
 *
 * @final
 */
class RouterListener implements EventSubscriberInterface
{
    private $matcher;
    private $context;
    private $logger;
    private $requestStack;
    private $projectDir;
    private $debug;

    /**
     * @param UrlMatcherInterface|RequestMatcherInterface $matcher The Url or Request matcher
     * @param RequestContext|null                         $context The RequestContext (can be null when $matcher implements RequestContextAwareInterface)
     *
     * @throws \InvalidArgumentException
     */
    public function __construct($matcher, RequestStack $requestStack, ?RequestContext $context = null, ?LoggerInterface $logger = null, ?string $projectDir = null, bool $debug = true)
    {
        if (!$matcher instanceof UrlMatcherInterface &amp;&amp; !$matcher instanceof RequestMatcherInterface) {
            throw new \InvalidArgumentException('Matcher must either implement UrlMatcherInterface or RequestMatcherInterface.');
        }

        if (null === $context &amp;&amp; !$matcher instanceof RequestContextAwareInterface) {
            throw new \InvalidArgumentException('You must either pass a RequestContext or the matcher must implement RequestContextAwareInterface.');
        }

        $this-&gt;matcher = $matcher;
        $this-&gt;context = $context ?? $matcher-&gt;getContext();
        $this-&gt;requestStack = $requestStack;
        $this-&gt;logger = $logger;
        $this-&gt;projectDir = $projectDir;
        $this-&gt;debug = $debug;
    }

    private function setCurrentRequest(?Request $request = null)
    {
        if (null !== $request) {
            try {
                $this-&gt;context-&gt;fromRequest($request);
            } catch (\UnexpectedValueException $e) {
                throw new BadRequestHttpException($e-&gt;getMessage(), $e, $e-&gt;getCode());
            }
        }
    }

    /**
     * After a sub-request is done, we need to reset the routing context to the parent request so that the URL generator
     * operates on the correct context again.
     */
    public function onKernelFinishRequest(FinishRequestEvent $event)
    {
        $this-&gt;setCurrentRequest($this-&gt;requestStack-&gt;getParentRequest());
    }

    public function onKernelRequest(RequestEvent $event)
    {
        $request = $event-&gt;getRequest();

        $this-&gt;setCurrentRequest($request);

        if ($request-&gt;attributes-&gt;has('_controller')) {
            // routing is already done
            return;
        }

        // add attributes based on the request (routing)
        try {
            // matching a request is more powerful than matching a URL path + context, so try that first
            if ($this-&gt;matcher instanceof RequestMatcherInterface) {
                $parameters = $this-&gt;matcher-&gt;matchRequest($request);
            } else {
                $parameters = $this-&gt;matcher-&gt;match($request-&gt;getPathInfo());
            }

            if (null !== $this-&gt;logger) {
                $this-&gt;logger-&gt;info('Matched route &quot;{route}&quot;.', [
                    'route' =&gt; $parameters['_route'] ?? 'n/a',
                    'route_parameters' =&gt; $parameters,
                    'request_uri' =&gt; $request-&gt;getUri(),
                    'method' =&gt; $request-&gt;getMethod(),
                ]);
            }

            $request-&gt;attributes-&gt;add($parameters);
            unset($parameters['_route'], $parameters['_controller']);
            $request-&gt;attributes-&gt;set('_route_params', $parameters);
        } catch (ResourceNotFoundException $e) {
            $message = sprintf('No route found for &quot;%s %s&quot;', $request-&gt;getMethod(), $request-&gt;getUriForPath($request-&gt;getPathInfo()));

            if ($referer = $request-&gt;headers-&gt;get('referer')) {
                $message .= sprintf(' (from &quot;%s&quot;)', $referer);
            }

            throw new NotFoundHttpException($message, $e);
        } catch (MethodNotAllowedException $e) {
            $message = sprintf('No route found for &quot;%s %s&quot;: Method Not Allowed (Allow: %s)', $request-&gt;getMethod(), $request-&gt;getUriForPath($request-&gt;getPathInfo()), implode(', ', $e-&gt;getAllowedMethods()));

            throw new MethodNotAllowedHttpException($e-&gt;getAllowedMethods(), $message, $e);
        }
    }

    public function onKernelException(ExceptionEvent $event)
    {
        if (!$this-&gt;debug || !($e = $event-&gt;getThrowable()) instanceof NotFoundHttpException) {
            return;
        }

        if ($e-&gt;getPrevious() instanceof NoConfigurationException) {
            $event-&gt;setResponse($this-&gt;createWelcomeResponse());
        }
    }

    public static function getSubscribedEvents(): array
    {
        return [
            KernelEvents::REQUEST =&gt; [['onKernelRequest', 32]],
            KernelEvents::FINISH_REQUEST =&gt; [['onKernelFinishRequest', 0]],
            KernelEvents::EXCEPTION =&gt; ['onKernelException', -64],
        ];
    }

    private function createWelcomeResponse(): Response
    {
        $version = Kernel::VERSION;
        $projectDir = realpath((string) $this-&gt;projectDir).\DIRECTORY_SEPARATOR;
        $docVersion = substr(Kernel::VERSION, 0, 3);

        ob_start();
        include \dirname(__DIR__).'/Resources/welcome.html.php';

        return new Response(ob_get_clean(), Response::HTTP_NOT_FOUND);
    }
}
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