parcer/server/src/routes/auth.ts

import { Router } from 'express';;
import { google } from "googleapis";
import { OAuth2Client } from 'google-auth-library'

export const router = Router()

const oauth2Client = new OAuth2Client(
    '_CLIENT_ID',
    '_CLIENT_SECRET',
    '_REDIRECT_URI'
);

// initialize Google OAuth 2.0 flow
router.get('/auth/google', (req, res) => {
  const url = oauth2Client.generateAuthUrl({
    access_type: 'offline',
    scope: [
      'https://www.googleapis.com/auth/userinfo.profile',
      'https://www.googleapis.com/auth/drive.file',
      'https://www.googleapis.com/auth/spreadsheets'
    ]
  });
  res.redirect(url);
});