index.js

'use strict'

const functions = require('firebase-functions');
const admin = require('firebase-admin');
admin.initializeApp(functions.config().firebase);

exports.sendNotification = functions.database.ref('/notification/chat_notifiation/{rec_user_id}/{sender_user_id}').onWrite((change, context) => {


  const sender_user_id = context.params.sender_user_id;
  const receiver_user_id = context.params.rec_user_id;

  console.log('We have a notification from : '+ sender_user_id+  " | Receiced by " + receiver_user_id);


  if(!change.after.val()){

    return console.log('A Notification has been deleted from the database : ', sender_user_id);

  }
  
  const fromUser = admin.database().ref(`/users/${sender_user_id}/`).once('value');
  
  return fromUser.then(fromUserResult => {
		
		const fromUserName = fromUserResult.val().name;
		
		const deviceTOken = admin.database().ref(`/users/${receiver_user_id}/fcmtoken`).once('value');
  
  return deviceTOken .then(result => {
  
  const token_id = result.val();
		
		const payload = {
	
	notification: {
		title : "Ask Aalim",
		body : `You have new message from ${fromUserName}`,
		icon : "defaulf",
		click_action : "com.zillion.android.AskAalim_Target_Notification"
	},
	data : {
		emailforchat : sender_user_id	
	}
	
  };
  
	return admin.messaging().sendToDevice(token_id, payload).then(response => {
		
		return console.log('this was notification');
		
	});
	
  });
	
  });
  
});

exports.sendNotification = functions.database.ref('/notification/notifications/{rec_user_id}/{notification_Id}').onWrite((change, context) => {


  const notificationID = context.params.notification_Id;
  const receiver_user_id = context.params.rec_user_id;

  console.log('You have a notification : '+  receiver_user_id + ' and ' + notificationID );


  if(!change.after.val()){

    return console.log('A Notification has been deleted from the database : ', sender_user_id);

  }
  const senderUser = admin.database().ref(`/notification/notifications/${receiver_user_id}/${notificationID}`).once('value');
  
  return senderUser.then(senderUserResult => {
  
	const senderUserid = senderUserResult.val().fromUser;
	
	  const fromUser = admin.database().ref(`/users/${senderUserid}/`).once('value');
	  
	  return fromUser.then(fromUserResult => {
			
			const fromUserName = fromUserResult.val().name;
			
			const deviceTOken = admin.database().ref(`/users/${receiver_user_id}/fcmtoken`).once('value');
	  
	  return deviceTOken .then(result => {
	  
	  const token_id = result.val();
			
			const payload = {
		
		notification: {
			title : "Ask Aalim",
			body : `${fromUserName} commentted on your post`,
			icon : "defaulf",
			click_action : "com.zillion.android.AskAalim_Target_Notification"
		},
		data : {
			emailforchat : senderUserid	
		}
		
	  };
	  
		return admin.messaging().sendToDevice(token_id, payload).then(response => {
			
			return console.log('this was notification');
			
		});
		
	  });
		
	  });
		
	  });
	  
	});