server.js

var express = require('express');
var session = require('express-session');
var timeout = require('connect-timeout'); //express v4
var oauth2 = require('simple-oauth2');
var path = require('path');
var app = express();

const PORT = YOUR_PORT;										//<<<<<<<<<<<<<<<<<<<<< NEEDS TO BE ADJUSTED!
var redirecturi = 'http://localhost:' + PORT + '/callback';

// __dirname is a global object that contains the name of the root directory 
app.use(express.static(__dirname));

// request will be terminated after this duration [ms]:
app.use(timeout(120000));

// initialize session
app.use(session({
	//secret to sign the session ID cookie
	secret: 'YOUR_SECRET', 									//<<<<<<<<<<<<<<<<<<<<< NEEDS TO BE ADJUSTED!
	resave: true,
	saveUninitialized: true
}));

// Set the OAuth client configuration settings 
var credentials = {
	client: {
		id: 'YOUR OAUTH CLIENT ID',							//<<<<<<<<<<<<<<<<<<<<< NEEDS TO BE ADJUSTED!
		secret: 'YOUR OATH CLIENT SECRET'					//<<<<<<<<<<<<<<<<<<<<< NEEDS TO BE ADJUSTED!
	},
	auth: {
		authorizeHost: 'YOUR AUTHORIZE_HOST',				//<<<<<<<<<<<<<<<<<<<<< NEEDS TO BE ADJUSTED!
		authorizePath: 'YOUR AUTHORIZE_HOST_PATH',			//<<<<<<<<<<<<<<<<<<<<< NEEDS TO BE ADJUSTED!
		tokenHost: 'YOUR TOKEN_HOST',						//<<<<<<<<<<<<<<<<<<<<< NEEDS TO BE ADJUSTED!
		tokenPath: 'YOUR TOKEN_HOST_PATH',					//<<<<<<<<<<<<<<<<<<<<< NEEDS TO BE ADJUSTED!
	},
	options: {
		authorizationMethod: 'body'
	}
}

// Initialize the OAuth2 Library
oauth2 = oauth2.create(credentials);

// Authorization code flow:
// 1. get the authorization code and send it to path /callback:
app.use('/authorizationcode', function (req, res) {
	console.log("inside authorizationcode");

	var authorizationUri = oauth2.authorizationCode.authorizeURL({
		redirect_uri: redirecturi

	});

	console.log("authorizationUri: " + authorizationUri);
	res.redirect(authorizationUri);
});


app.use('/callback', function (req, res) {
	console.log("inside callback");

	// the authorization code is sent to the path /callback. 
	var code = req.query.code;
	console.log("Authorization Code: " + code);

	var tokenConfig = {
		code: code,
		redirect_uri: redirecturi
	};

	// 2. get the access token:
	oauth2.authorizationCode.getToken(tokenConfig)
		.then((result) => {

			const token = oauth2.accessToken.create(result);
			console.log("Access Token: " + token.token.access_token);

			req.session["tokens"] = token;
			res.redirect("logonresponse");
		})
		.catch((error) => {
			console.log('Access Token Error', error.message);
		});
});


app.get('/logonresponse', function (req, res) {
	res.sendFile(path.join(__dirname + '/LogResponse.html'));
});


app.use("/getToken", function (req, res) {
	res.send(JSON.stringify(req.session["tokens"].token));
});

app.listen(PORT);
app.timeout = 7800000;
console.log("Server running on port " + PORT);