passport-setup.js

const passport = require('passport');
const GoogleStrategy = require('passport-google-oauth20').Strategy;
const User = require("./models/user.js")
const ExpressError = require('./utils/expressError');

passport.use(new GoogleStrategy({
    clientID: process.env.GOOGLE_CLIENT_ID,
    clientSecret: process.env.GOOGLE_CLIENT_SECRET,
    callbackURL: process.env.GOOGLE_CALLBACK_URL
},
    async (accessToken, refreshToken, profile, done) => {
        let newUser = {
            googleId: profile.id,
            name: profile.displayName,
            email: profile.emails[0].value
        }
        try {
            var user = await User.findOne({ googleId: profile.id })
            if (user) {
                done(null, user)
            } else {
                user = await User.create(newUser)
                done(null, user)
            }
        } catch (err) {
            console.log(err);
        }
    }

));

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

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