Google Authentication using Passport in Node.js

const express = require('express');
const app = express();

app.get('/' , (req , res) => {
    res.send("<h1>GeeksForGeeks</h1>");
});

app.listen(4000 , () => {
    console.log("Server running on port 4000");
});

const passport = require('passport');
const GoogleStrategy = require('passport-google-oauth2').Strategy;

passport.serializeUser((user , done) => {
    done(null , user);
})
passport.deserializeUser(function(user, done) {
    done(null, user);
});

passport.use(new GoogleStrategy({
    clientID:"YOUR ID", // Your Credentials here.
    clientSecret:"YOUR SECRET", // Your Credentials here.
    callbackURL:"http://localhost:4000/auth/callback",
    passReqToCallback:true
  },
  function(request, accessToken, refreshToken, profile, done) {
    return done(null, profile);
  }
));

const express = require('express');
const app = express();
const passport = require('passport');
const cookieSession = require('cookie-session');
require('./passport');

app.use(cookieSession({
    name: 'google-auth-session',
    keys: ['key1', 'key2']
}));
app.use(passport.initialize());
app.use(passport.session());
  

app.get('/', (req, res) => {
    res.send("<button><a href='/auth'>Login With Google</a></button>")
});

// Auth 
app.get('/auth' , passport.authenticate('google', { scope:
    [ 'email', 'profile' ]
}));

// Auth Callback
app.get( '/auth/callback',
    passport.authenticate( 'google', {
        successRedirect: '/auth/callback/success',
        failureRedirect: '/auth/callback/failure'
}));

// Success 
app.get('/auth/callback/success' , (req , res) => {
    if(!req.user)
        res.redirect('/auth/callback/failure');
    res.send("Welcome " + req.user.email);
});

// failure
app.get('/auth/callback/failure' , (req , res) => {
    res.send("Error");
})

app.listen(4000 , () => {
    console.log("Server Running on port 4000");
});