Script for making firebase user to user notifications

Question

(Sorry for bad English) I'm looking for a way to make user to user notifications in Android. The system have to catch a new child event in the Database, read the data and send the notification to destination.

The struct of the DB is this:

notificationRequests
    $pushid
      message: "You have a new request! Open the app"
      userId: "sadbijasuobru112u4124u21b"      //user destination id

By doing some researches in the web I've found the possibility to use topic messages. So, i've added this in my LoginActivity befor calling the MainActivity:

    FirebaseMessaging.getInstance().subscribeToTopic("users_topic$uid")
                    .addOnCompleteListener {
                        Log.d("LoginActivity", "User registered")
                    }

The code works. I can send notifications from the console

Like I said before, i need automatic messages. I've found this code on the web, but it doesn't work.

var firebase = require('firebase-admin');
var request = require('request');

var API_KEY = "Firebase Cloud Messaging Server API key"

// Fetch the service account key JSON file contents
var serviceAccount = require("./serviceAccountKey.json");

// Initialize the app with a service account, granting admin privileges
firebase.initializeApp({
  credential: firebase.credential.cert(serviceAccount),
  databaseURL: "https://appname.firebaseio.com/"
});
ref = firebase.database().ref();

function listenForNotificationRequests() {
  var requests = ref.child('notificationRequests');
  requests.on('child_added', (requestSnapshot) => {
    var request = requestSnapshot.val();
    sendNotificationToUser(
      request.userId, 
      request.message,
      () => {
        requestSnapshot.ref.remove();
      }
    );
  }, (error) => {
    console.error(error);
  });
}

function sendNotificationToUser(userID, message, onSuccess) {
  request({
    url: 'https://fcm.googleapis.com/fcm/send',
    method: 'POST',
    headers: {
      'Content-Type' :' application/json',
      'Authorization': 'key='+API_KEY
    },
    body: JSON.stringify({
      notification: {
        title: message
      },
      to : '/topics/users_topic'+userID
    })
  }, (error, response, body) => {
    if (error) { console.error(error); }
    else if (response.statusCode >= 400) { 
      console.error('HTTP Error: '+response.statusCode+' - '+response.statusMessage); 
    }
    else {
      onSuccess();
    }
  });
}

// start listening
listenForNotificationRequests();

I've implemented this code in the index.js for deployng. I've also write the entire file instead of requiring it, but it's always the same.

const functions = require('firebase-functions');

exports.sendNotifications = functions.https.onRequest((request, response) => {
  require('./sendNotifications.js')
})

Any suggestions? Thanks for the kelp!

EDIT

Does this need a billing account configurated? If yes, how can i make it with the free plan?

Answer 1

The problem was that I was calling an external site. I solved it doing this:

const functions = require('firebase-functions');

var firebase = require('firebase-admin');

// Fetch the service account key JSON file contents
var serviceAccount = require("./serviceAccountKey.json");

// Initialize the app with a service account, granting admin privileges
firebase.initializeApp({
  credential: firebase.credential.cert(serviceAccount),
  databaseURL: "https://appname.firebaseio.com/"
});

exports.sendNotifications = functions.database.ref('/notificationRequest/{pushId}')
  .onCreate( (change, context) => {
    var uid = change.child('userId').val()
    var notificationMessage = change.child('message').val()

    var userTopic = 'users_topic'+uid

    var payload = {
      data: {
        message: notificationMessage
      }
    };

    var options = {
      priority: 'high',
      timeToLive: 60 * 60 * 24,
      collapseKey: 'notification'
    };

    firebase.messaging().sendToTopic(userTopic, payload, options)
      // eslint-disable-next-line promise/always-return
      .then((response) => {
        console.log('Done', response);
      })
      .catch((error) => {
        console.log('Error: ', error);
      });

    return change.ref.remove();
  });