public Optional<Tokens> getUserTokens(String code) throws IOException, ParseException {
  final ClientAuthentication basicAuth = new ClientSecretBasic(new ClientID(clientId), new Secret(clientSecret));
  final URI redirectUri = fromUri(redirectUrl).build();
  final AuthorizationCodeGrant authzGrant = new AuthorizationCodeGrant(new AuthorizationCode(code), redirectUri);
  final TokenRequest tokenRequest = new TokenRequest(getTokenUrl(discoveryUrl), basicAuth, authzGrant);
  final TokenResponse response = OIDCTokenResponseParser.parse(tokenRequest.toHTTPRequest().send());

  if (response.indicatesSuccess()) {
    final Tokens tokens = response.toSuccessResponse().getTokens();

    // TODO check if the id is not fake
    return Optional.of(tokens);
  } else {
    LOG.error("Could not retrieve client token: {}", response.toErrorResponse().getErrorObject());
    return Optional.empty();
  }
}
 

@Override
public SsoAuthenticated processLoginResponse() {
	HttpServletRequest request = (HttpServletRequest) RequestCycle.get().getRequest().getContainerRequest();
	try {
		AuthenticationResponse authenticationResponse = AuthenticationResponseParser.parse(
				new URI(request.getRequestURI() + "?" + request.getQueryString()));
		if (authenticationResponse instanceof AuthenticationErrorResponse) {
			throw buildException(((AuthenticationErrorResponse)authenticationResponse).getErrorObject()); 
		} else {
			AuthenticationSuccessResponse authenticationSuccessResponse = 
					(AuthenticationSuccessResponse)authenticationResponse;
			
			String state = (String) Session.get().getAttribute(SESSION_ATTR_STATE);
			
			if (state == null || !state.equals(authenticationSuccessResponse.getState().getValue()))
				throw new AuthenticationException("Unsolicited OIDC authentication response");
			
			AuthorizationGrant codeGrant = new AuthorizationCodeGrant(
					authenticationSuccessResponse.getAuthorizationCode(), getCallbackUri());

			ClientID clientID = new ClientID(getClientId());
			Secret clientSecret = new Secret(getClientSecret());
			ClientAuthentication clientAuth = new ClientSecretBasic(clientID, clientSecret);
			TokenRequest tokenRequest = new TokenRequest(
					new URI(getCachedProviderMetadata().getTokenEndpoint()), clientAuth, codeGrant);
			HTTPResponse httpResponse = tokenRequest.toHTTPRequest().send();
			if (httpResponse.getStatusCode() == HTTPResponse.SC_OK) {
				JSONObject jsonObject = httpResponse.getContentAsJSONObject();
				if (jsonObject.get("error") != null) 
					throw buildException(TokenErrorResponse.parse(jsonObject).getErrorObject());
				else 
					return processTokenResponse(OIDCAccessTokenResponse.parse(jsonObject));
			} else {
				ErrorObject error = TokenErrorResponse.parse(httpResponse).getErrorObject();
				if (error != null) {
					throw buildException(error);
				} else {
					String message = String.format("Error requesting OIDC token: http status: %d", 
							httpResponse.getStatusCode());
					throw new AuthenticationException(message);
				}
			}
		}
	} catch (ParseException | URISyntaxException|SerializeException|IOException e) {
		throw new RuntimeException(e);
	}
}