3 Leg POC.

package.json

{
  "name": "gists",
  "version": "1.0.0",
  "main": "index.js",
  "license": "MIT",
  "dependencies": {
    "@request/headers": "request/headers",
    "consolidate": "^0.14.5",
    "cookie-parser": "^1.4.3",
    "express": "^4.15.3",
    "hogan": "^1.0.2",
    "node-fetch": "^1.7.1",
    "oauth": "^0.9.15",
    "twit": "^2.2.9",
    "url-search-params": "^0.9.0"
  },
  "scripts": {
    "start": "node twitter.js"
  }
}

twitter_oauth.js

const express = require('express');
const engines = require('consolidate');
const OAuth = require('oauth');
const Twit = require('twit');
const cookieParser = require('cookie-parser')

const app = express();
app.use(cookieParser());


const oauth = new OAuth.OAuth(
  'https://api.twitter.com/oauth/request_token',
  'https://api.twitter.com/oauth/access_token',
  '<consumer_key>',
  '<consumer_secret>',
  '1.0',
  'http://localhost:3000/post_auth',
  'HMAC-SHA1',
);


const createT = (oAuthAccessToken, oAuthAccessTokenSecret) => new Twit({
	  consumer_key: '<consumer_key>',
    consumer_secret: '<consumer_secret>',
    access_token: oAuthAccessToken,
    access_token_secret: oAuthAccessTokenSecret
});


app.get('/', (req, res) => {
	oauth.getOAuthRequestToken((err, OAuthToken, OAuthTokenSecret, results) => {
		app.locals.oAuthTokenSecret = OAuthTokenSecret;
		res.send([
			'<a href="https://api.twitter.com/oauth/authenticate?oauth_token=',
			OAuthToken,
			'">',
			'Sign in with twitter</a>'
		].join(''));
	});
});

app.get('/post_auth', (req, res) => {
	console.log(app.locals.oAuthTokenSecret);
	oauth.getOAuthAccessToken(
		req.query.oauth_token,
		app.locals.oAuthTokenSecret,
        req.query.oauth_verifier,
        (err, oAuthAccessToken, oAuthAccessTokenSecret, results) => {
        	console.log(oAuthAccessToken, oAuthAccessTokenSecret);
        	let T = createT(oAuthAccessToken, oAuthAccessTokenSecret);
        	T.post('statuses/update', { status: 'testing 3 Legs auth' }, (err, data, response) => {
			  console.log(data);
			});        
    });
});

app.listen(3000);