configPassport.js

// DOTENV: Reads environmental variables from .env file
require('dotenv').load();

// PASSPORT: Using Google authentication strategy for OAuth
const GoogleStrategy = require('passport-google-oauth').OAuth2Strategy;

// PASSPORT: Once authenticated, each subsequent request will not contain credentials, but rather the unique cookie that identifies the session.
// In order to support login sessions, Passport will serialize and deserialize user instances to and from the session.
function configPassport(passport) {
  passport.serializeUser((user, done) => {
    done(null, user);
  });
  passport.deserializeUser((user, done) => {
    done(null, user);
  });
  passport.use(new GoogleStrategy({
    clientID: process.env.GOOGLE_CLIENT_ID,
    clientSecret: process.env.GOOGLE_CLIENT_SECRET,
    callbackURL: `${process.env.GOOGLE_CALLBACK_URL}`
  },
  // Requires a `verify` function, which accept credentials (a token, refreshToken, and Google profile), and invoke 'done' callback with a user object and options
    (token, refreshToken, profile, done) => {
      return done(null, {
        profile: profile,
        token: token
      });
    }
  ));
}

module.exports = configPassport;