gistfile1.txt

    private Request<Void> registerDevice(JSONObject data) {
        nonNull(data, "data");

        return Requester.call(() -> {

                data.put("deviceToken", FirebaseInstanceId.getInstance().getToken());

                String authHash = getHashedAuth(unifiedPushCredentials.getVariant(),
                    unifiedPushCredentials.getSecret().toCharArray());

                final HttpRequest httpRequest = core.getHttpLayer().newRequest();
                httpRequest.addHeader("Authorization", authHash);

                // Invalidate old on Unified Push Server
                String oldDeviceToken = retrieveOldDeviceToken();
                if (oldDeviceToken != null) {
                    httpRequest.addHeader("x-ag-old-token", oldDeviceToken);
                }

                return httpRequest
                    .post(url + registryDeviceEndpoint, data.toString().getBytes());
            }).map((MapFunction<Request<HttpResponse>, Request<Void>>) value -> value.map(httpResponse -> {
                 switch (httpResponse.getStatus()) {
                     case HTTP_OK:

                         FirebaseMessaging firebaseMessaging =
                             FirebaseMessaging.getInstance();

                         try {
                             JSONArray categories =
                                 data.getJSONArray("categories");
                             for (int i = 0; i < categories.length(); i++) {
                                 String category = categories.getJSONObject(i)
                                     .toString();
                                 firebaseMessaging.subscribeToTopic(category);
                             }
                         } catch (JSONException e) {
                             // ignore
                         }

                         firebaseMessaging.subscribeToTopic(
                             unifiedPushCredentials.getVariant());

                         saveCache(data);

                         return null;
                     default:
                         throw new HttpException(httpResponse.getStatus());
                 }
             })).map(new MapFunction<Request<Void>, Void>() {
            @Override
            public Void map(Request<Void> value) {
                return null;
            }
        });


    }