index.js

var express = require('express');
var request = require('superagent');
var bodyParser = require('body-parser');
var app = express();
app.use(bodyParser.json());
app.use(bodyParser.urlencoded({extended: true}));

app.get('/', function (req, res) {
  res.send('Hello World!');
});

app.use(express.static('views'));

var mailchimpInstance   = 'xxx',
    listUniqueId        = 'xxxxxxxxxxxx',
    mailchimpApiKey     = 'xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx-xxx',
    mailchimpClientId   = 'xxxxxxxxxxxx';
    mailchimpSecretKey  = 'xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx';

app.post('/signup', function (req, res) {
    request
        .post('https://' + mailchimpInstance + '.api.mailchimp.com/3.0/lists/' + listUniqueId + '/members/')
        .set('Content-Type', 'application/json;charset=utf-8')
        .set('Authorization', 'Basic ' + new Buffer('any:' + mailchimpApiKey ).toString('base64'))
        .send({
          'email_address': req.body.email,
          'status': 'subscribed',
          'merge_fields': {
            'FNAME': req.body.firstname,
            'LNAME': req.body.lastname
          }
        })
            .end(function(err, response) {
              if (response.status < 300 || (response.status === 400 && response.body.title === "Member Exists")) {
                res.send('Signed Up!');
              } else {
                res.send('Sign Up Failed :(');
              }
          });
});

var querystring = require('querystring');

app.get('/mailchimp/auth/authorize', function(req, res) {
  res.redirect('https://login.mailchimp.com/oauth2/authorize?' +
            querystring.stringify({
                'response_type': 'code',
                'client_id': mailchimpClientId,
                'redirect_uri': 'http://127.0.0.1:3000/mailchimp/auth/callback'
            }));
});

var dataStore = require('./dataStore.js');

app.get('/mailchimp/auth/callback', function(req, res) {
  request.post('https://login.mailchimp.com/oauth2/token')
         .send(querystring.stringify({
            'grant_type': 'authorization_code',
            'client_id': mailchimpClientId,
            'client_secret': mailchimpSecretKey,
            'redirect_uri': 'http://127.0.0.1:3000/mailchimp/auth/callback',
            'code': req.query.code
          }))
            .end((err, result) => {
                if (err) {
                    res.send('An unexpected error occured while trying to perform MailChimp oAuth');
                } else {
                  // we need to get the metadata for the user 
                  request.get('https://login.mailchimp.com/oauth2/metadata')
                    .set('Accept', 'application/json')
                    .set('Authorization', 'OAuth ' + result.body.access_token)
                        .end((err, metaResult) => {
                            if (err) {
                                res.send('An unexpected error occured while trying to get MailChimp meta oAuth');
                            } else {
                                // save the result.body.access_token
                                // save the metadata in result.body
                                // against the current user
                                var mailchimpConf = metaResult.body;
                                console.log(mailchimpConf);
                                mailchimpConf.access_token = result.body.access_token;
                                dataStore.saveMailchimpForUser(mailchimpConf.login.email, mailchimpConf);
                                res.redirect('/pick-a-list.html?email=' + mailchimpConf.login.email);
                            }
                        });
                }
            });
});

app.get('/mailchimp/lists', function(req, res) {
  var mailchimpConf = dataStore.getMailchimpForUser(req.query.email);
  request.get(mailchimpConf.api_endpoint + '/3.0/lists')
                .set('Accept', 'application/json')
                .set('Authorization', 'OAuth ' + mailchimpConf.access_token)
                    .end((err, result) => {
                        if (err) {
                            res.status(500).json(err);
                        } else {
                            res.json(result.body.lists);
                        }
                    });
});

app.get('/mailchimp/list/members/:id', function(req, res) {
  var mailchimpConf = dataStore.getMailchimpForUser(req.query.email);
  request.get(mailchimpConf.api_endpoint + '/3.0/lists/' + req.params.id + '/members')
                .set('Accept', 'application/json')
                .set('Authorization', 'OAuth ' + mailchimpConf.access_token)
                    .end((err, result) => {
                        if (err) {
                            res.status(500).json(err);
                        } else {
                            res.json(result.body.members);
                        }
                    });
});

app.listen(3000, function () {
  console.log('Example app listening on port 3000!');
});