How to execute Google Cloud Functions from Firebase Hosting? - firebase-cloud-messaging

Question

I'm trying to create an Android project which can send notifications from one android device to another. For that purpose, I created a node.js file, it's working fine on the local server. But when I hosted it on Google Cloud Platform, it shows Page Not Found. It is not able to call Google Function from hosting. It is looking for or executing index.html but it should execute index.js, which is in functions directory which was created while initializing the project with Firebase.
I took the reference from this video: https://youtu.be/pnysHgQvOiM?list=PLk7v1Z2rk4hjM2NPKqtWQ_ndCuoqUj5Hh
index.js file
const functions = require('firebase-functions');
var {google} = require('googleapis')
var MESSAGING_SCOPE ="https://www.googleapis.com/auth/firebase.messaging"
var SCOPES = [MESSAGING_SCOPE]
var express = require('express')
var app = express();
var bodyParser = require('body-parser');
var router = express.Router();
var request = require('request');
app.use(bodyParser.urlencoded({extended:true}));
app.use(bodyParser.json());
router.post('/send',function(req,res){
getAccessToken().then(function(access_token){
var title = req.body.title;
var body = req.body.body;
var token = req.body.token;
request.post({
headers:{
Authorization: 'Bearer '+ access_token
}, url:
"https://fcm.googleapis.com/v1/projects/my_project_name/messages:send",
body: JSON.stringify(
{
"message":{
"token" : token,
"notification" : {
"body" : body,
"title" : title
}
}
}
)
},function(error,reponse,body){
res.end(body);
console.log(body);
});
});
});
app.use('/api',router);
function getAccessToken()
{
return new Promise(function(resolve,reject){
var key= require("./service-account.json");
var jwtClient = new google.auth.JWT(
key.client_email,
null,
key.private_key,
SCOPES,
null
);
jwtClient.authorize(function(error,tokens){
if(error)
{
reject(error)
}
resolve(tokens.access_token)
// console.log(tokens.access_token)
});
jwtClient.authorize(function(error,tokens){
if(error)
{
reject(error)
}
resolve(tokens.access_token)
console.log(tokens.access_token)
});
});
}
exports.api = functions.https.onRequest(app);
firebase.json
{
"hosting":
{
"public": "public",
"rewrites": [
{
"source": "/api/send",
"functions": "api"
}
],
"ignore": [
"firebase.json",
"**/.*",
"**/node_modules/**"
]
}
}
This code is working fine with using http://localhost:8085/api/send but it is not working as https://my_project_name.firebaseapp.com/api/send