public function httpGet(RequestInterface $request, ResponseInterface $response)
    {
        $path = $request->getPath();

        try {
            $node = $this->server->tree->getNodeForPath($path);
        } catch (DAV\Exception\NotFound $e) {
            return;
        }

        if (!$node instanceof INode) {
            return;
        }

        $writer = $this->server->xml->getWriter();
        $writer->contextUri = $this->server->getBaseUri();
        $writer->openMemory();
        $writer->startDocument('1.0', 'UTF-8');
        $writer->startElement('{http://calendarserver.org/ns/}notification');
        $node->getNotificationType()->xmlSerializeFull($writer);
        $writer->endElement();

        $response->setHeader('Content-Type', 'application/xml');
        $response->setHeader('ETag', $node->getETag());
        $response->setStatus(200);
        $response->setBody($writer->outputMemory());

        // Return false to break the event chain.
        return false;
    }