Firebase-Messaging-Service-(Push-Messaging).md

+Reve SaaS usages firebase messaging for receiving call and message when not registered with server. 
+
+To receive call and message you must integrate fire base messaging to your app.
+
+For that case there can be 2 case : 
+1. You need firebase messaging for your core application. 
+2. You actually do not need firebase messaging for your core application but need it for Reve Saas. 
+
+In both case you need to integrate the firebase service in your app according to the [official documentation](https://firebase.google.com/docs/android/setup).  
+
+After you set up the firebase messaging  in your app, you handle the following cases. 
+
+**1. You need firebase messaging for your core application:**
+
+Reve Saas has its own Firebase messaging service in the package. So, if you need firebase messaging in your core app, you have created a `Service `in your app that extends `FirebaseMessagingService`.
+
+To get fire base to work in Reve SaaS, you just extend `ReveFirebaseMessagingService` instead of `FirebaseMessagingService` in your app. 
+
+**Sample code:**
+
+```
+public class AppFirebaseMessagingService extends ReveFirebaseMessagingService {
+    @Override
+    public void onNewToken(String refreshedToken) {
+        super.onNewToken(refreshedToken);
+        //your code below
+    }
+
+    @Override
+    public void onMessageReceived(RemoteMessage remoteMessage) {
+        super.onMessageReceived(remoteMessage);
+        //your code below
+    }
+}
+```
+
+
+**2. You actually do not need firebase messaging for your core application but need it for Reve SaaS**
+
+In that case, you do **NOT** need to do the following:
+1. Declare firebase dependency in gradle file
+2. Declare any firebase service in your app
+
+But, you must **NOT FORGET** to declare google service plugin at the end gradle file. 
+
+`apply plugin: 'com.google.gms.google-services'`
+