public function authenticate(HTTPRequest $request): HTTPRequest
    {
        $requestAdapter = new HttpRequestAdapter();
        $responseAdapter = new HttpResponseAdapter();

        // missing vars (cli)
        $this->addMissingServerVariables($requestAdapter);

        $server = $this->getServer();
        $psrRequest = $requestAdapter->toPsr7($request);
        $psrResponse = new Response();

        try {
            $psrRequest = $server->validateAuthenticatedRequest($psrRequest);
        } catch (OAuthServerException $exception) {
            // convert to authentication exception
            throw new AuthenticationException(
                $exception->getMessage(),
                $exception->getCode(),
                $responseAdapter->fromPsr7($exception->generateHttpResponse($psrResponse))
            );
        } catch (\Exception $exception) {
            // convert to authentication exception
            throw new AuthenticationException(
                $exception->getMessage(),
                $exception->getCode(),
                $responseAdapter->fromPsr7(
                    (new OAuthServerException($exception->getMessage(), 0, 'unknown_error', 500))
                        ->generateHttpResponse($psrResponse)
                )
            );
        }
        // add the request attributes as custom auth headers
        foreach ($psrRequest->getAttributes() as $attribute => $value) {
            $request->addHeader($attribute, $value);
        }

        return $request;
    }