server.js

var util = require("util"),
    http = require("http"),
    ejs = require("ejs"),
    static = require("node-static"),
    fs = require("fs"),
    winston = require("winston");

var getIp = function (req) {
  return {
    ip: ( req.headers["X-Forwarded-For"]
      || req.headers["x-forwarded-for"]
      || req.client.remoteAddress )
  };
};

var getAccept = function (req) {
  //I found this regexp on stack overflow.
  //It's no real parser but probably good enough.
  return req.headers.accept.match(/([^()<>@,;:\\"\/[\]?={} \t]+)\/([^()<>@,;:\\"\/[\]?={} \t]+)/)[0];
}

http.createServer(function (req, res) {

  // I bet there's a reasonable way to guess what these should be based on name or mimetype or something. Probably node-static uses it.
var routes = {

  "/index.html": {
    template: "/templates/index.html",
    head: {
      "Content-Type": "text/html"
    }
  },

  "/index.json": {
    template: "/templates/index.json",
    head: {
      "Content-Type": "application/json"
    }
  },

  "/index.txt": {
    template: "/templates/index.txt",
    head: {
      "Content-Type": "text/plain"
    }
  }
}

// Serve template based on accept type
if (req.url === "/") {
  var accept = getAccept(req);

  if (accept === "*/*") {
    req.url = '/index.html';
  }
  else {

    Object.keys(routes).some(function (route) {
      if (routes[route].head["Content-Type"] === accept) {
          req.url = route;
          return true;
      }
      return false;
    });
  }
}

  var handled = Object.keys(routes).some(function(route) {
    if (req.url === route) {
      var ip = getIp(req);

      fs.readFile(__dirname + routes[route].template, function (err, template) {
        if (err) {
          winston.error(JSON.stringify(err, true, 2));
          res.writeHead(200, {"Content-Type": "text/plain"});
          res.end("Whups! Something went wrong.");
        }
        res.writeHead(200, routes[route].head);
        res.end(ejs.render(template.toString(), { locals: ip }));
      });

      return true;
    } else {
      return false;
    }
  });
  
  if (!handled) {
    winston.info("serving static file "+__dirname+"/static"+req.url);
    var server = new static.Server(__dirname+"/static/");
    req.on("end", function () {
      server.serve(req, res);
    });
  }

}).listen(8000);