login.js

var async = require('async'),
    https = require('https'),
    querystring = require('querystring'),
    jwt = require('../shared/jwt'),
    crypto = require('crypto'),
    app_secret = 'CH..'; // get it from foursquare
exports.register = function (api) {
    api.post('foursquare', foursquare);
};

function foursquare(request, response) {
    if (request.body.access_token) {
        var decipher = crypto.createDecipher('aes256', app_secret);
        var access_token = null;
        try {
            access_token = decipher.update(request.body.access_token, 'hex', 'utf8') + decipher.final('utf8');
        } catch (err) {
            response.send(statusCodes.UNAUTHORIZED, {
                code: 401,
                error: "Cannot verify the access token."
            });
        }
        if (access_token) {
            var params = {
                oauth_token: access_token,
                v: "20140331"
            };
            https.get('https://api.foursquare.com/v2/users/self?' + querystring.stringify(params), function (res) {
                var msg = '';
                res.on('data', function (chunk) {
                    msg += chunk;
                });
                res.on('end', function () {
                    var _user = JSON.parse(msg);
                    if (_user && _user.response && _user.response.user && _user.response.user.id) {
                        response.send(statusCodes.OK, {
                            "user": {
                                "userId": 'Foursquare:' + _user.response.user.id
                            },
                            "authenticationToken": jwt.createZumoJwt(request.service.config.masterKey, 4, 'Foursquare', 'Foursquare:' + _user.response.user.id, {
                                userId: "Foursquare:" + _user.response.user.id,
                                accessToken: access_token
                            })
                        });
                    } else {
                        response.send(statusCodes.UNAUTHORIZED, {
                            code: 401,
                            error: "Cannot verify the access token."
                        });
                    }
                });
            }).on('error', function (e) {
                response.send(statusCodes.UNAUTHORIZED, {
                    code: 401,
                    error: "Cannot verify the access token."
                });
            });
        }
    } else {
        response.send(statusCodes.UNAUTHORIZED, {
            code: 401,
            error: "An access_token must be provided"
        });
    }
}