OAuth2 app with a Node.js library

oauth2.js

/**
 *
 *  OAuth usage example.
 * 
 **/

var http = require("http");
var Url = require("url");
var querystring = require("querystring");

var Client = require("../index");
var OAuth2 = require("oauth").OAuth2;

var github = new Client({
    version: "3.0.0"
});

var clientId = "e8c434a1c92e9de7ff8d";
var secret = "1d0fcbb060e1dd86a0aa3d12265419c9bb19a333";
var oauth = new OAuth2(clientId, secret, "https://github.com/", "login/oauth/authorize", "login/oauth/access_token");

// for demo purposes use one global access token
// in production this has to be stored in a user session
var accessToken = "";

http.createServer(function(req, res) {
    var url = Url.parse(req.url);
    var path = url.pathname;
    var query = querystring.parse(url.query);
    
    if (path == "/" || path.match(/^\/user\/?$/)) {
        // redirect to github if there is no access token
        if (!accessToken) {
            res.writeHead(303, {
                Location: oauth.getAuthorizeUrl({ 
                    redirect_uri: 'http://localhost:7878/github-callback',
                    scope: "user,repo,gist"
                })
            });
            res.end();
            return;
        }
                
        // use github API            
        github.user.get({}, function(err, user) {
            if (err) {
                res.writeHead(err.code);
                res.end(err + "");
                return;
            }
            res.writeHead(200);
            res.end(JSON.stringify(user));
        });
        return;
    } 
    // URL called by github after authenticating
    else if (path.match(/^\/github-callback\/?$/)) {
        // upgrade the code to an access token
        oauth.getOAuthAccessToken(query.code, {}, function (err, access_token, refresh_token) {
            if (err) {
                console.log(err);
                res.writeHead(500);
                res.end(err + "");
                return;
            }
            
            accessToken = access_token;
            
            // authenticate github API
            github.authenticate({
                type: "oauth",
                token: accessToken
            });
              
            //redirect back
            res.writeHead(303, {
                Location: "/"
            });
            res.end();
        });
        return;
    }

    res.writeHead(404);
    res.end("404 - Not found");
}).listen(7878);

console.log("listening at http://localhost:7878");