index.js

const {stringify} = require('querystring');
const google = require('googleapis');
const co = require('co');
const fetch = require('node-fetch');
// eslint-disable-next-line import/no-extraneous-dependencies
//const {BrowserWindow} = require('electron');
const electron = require('electron')

var BrowserWindow =  electron.BrowserWindow;


const OAuth2 = google.auth.OAuth2;

/* eslint-disable camelcase */

function getAuthenticationUrl(scopes, clientId, clientSecret, redirectUri = 'urn:ietf:wg:oauth:2.0:oob') {
	const oauth2Client = new OAuth2(
		clientId,
		clientSecret,
		redirectUri
	);
	const url = oauth2Client.generateAuthUrl({
		access_type: 'offline', // 'online' (default) or 'offline' (gets refresh_token)
		scope: scopes // If you only need one scope you can pass it as string
	});
	return url;
}

function authorizeApp(url, browserWindowParams) {
	return new Promise((resolve, reject) => {
		const win = new BrowserWindow(browserWindowParams || {'use-content-size': true});

		win.loadURL(url);

		win.on('closed', () => {
			reject(new Error('User closed the window'));
		});

		win.on('page-title-updated', () => {
			setImmediate(() => {
				const title = win.getTitle();
				if (title.startsWith('Denied')) {
					reject(new Error(title.split(/[ =]/)[2]));
					win.removeAllListeners('closed');
					win.close();
				} else if (title.startsWith('Success')) {
					resolve(title.split(/[ =]/)[2]);
					win.removeAllListeners('closed');
					win.close();
				}
			});
		});
	});
}

module.exports = function electronGoogleOauth(browserWindowParams, httpAgent) {
	function getAuthorizationCode(scopes, clientId, clientSecret, redirectUri = 'urn:ietf:wg:oauth:2.0:oob') {
		const url = getAuthenticationUrl(scopes, clientId, clientSecret, redirectUri);
		return authorizeApp(url, browserWindowParams);
	}

	const getAccessToken = co.wrap(function * (scopes, clientId, clientSecret, redirectUri = 'urn:ietf:wg:oauth:2.0:oob') {
		const authorizationCode = yield getAuthorizationCode(scopes, clientId, clientSecret, redirectUri);

		const data = stringify({
			code: authorizationCode,
			client_id: clientId,
			client_secret: clientSecret,
			grant_type: 'authorization_code',
			redirect_uri: redirectUri
		});

		const res = yield fetch('https://accounts.google.com/o/oauth2/token', {
			method: 'post',
			headers: {
				'Accept': 'application/json',
				'Content-Type': 'application/x-www-form-urlencoded'
			},
			body: data,
			agent: httpAgent
		});
		return yield res.json();
	});

	return {getAuthorizationCode, getAccessToken};
};