A "frameworkless" http-server - with separation of concerns

separated-concerns-frameworkless-http-server.js

//code                                                     concern
//-------------------------------------------------------------------
const conf = () => {                                     //config 
  views: {                                               //config
    status: 'i\'m alive',                                //config
    greet:  'hello, %s',                                 //config
    help:   'supports: /greet or /status',               //config
  },                                                     //config
  web: { port: 3000 },                                   //config
};                                                       //config

const log = (...args) => console.log(...args.reverse()); //logging

const { format } = require('util');                      //view
const view = ({ views: { status, greet, help } }) => ({  //view
  status: () => status,                                  //view
  greet: ({ name }) => format(greet, name),              //view
  help: () => help,                                      //view
});                                                      //view

const webCtrl = view => ({                               //controll
  status: () => [view.status()],                         //controll
  greet: ({ req: { url }, log}) => {                     //controll
    const name = url.slice(7);                           //controll
    log({ name }, 'greeting');                           //controll
    return [view.greet({ name })];                       //controll
  },                                                     //controll   
  default: ({ req: { url }, log }) => {                  //controll
    log({ url }, 'no such url');                         //controll
    return [view.help(), 404];                           //controll
  }                                                      //controll
});                                                      //controll

const router = (webCtrl, log) =>                         //route
  (req, res) => {                                        //route
    const [action] = req.url.slice(1).match(/[^\/]+/);   //route
    const handler = webCtrl[action] || webCtrl.default;  //route
    const [body, code = 200] = handler({ req, log });    //route
    res.statusCode = code;                               //route
    res.end(body);                                       //route
  }                                                      //route

const app = () => router(webCtrl(view(conf())), log);    //app
module.exports = { conf, view, webCtrl, router, app };   //app

if (module !== require.main && module.id != '<repl>') {  //binary
  return;                                                //binary
}                                                        //binary
log('starting greeter');                                 //binary
require('http').createServer(app()).listen(              //binary
  conf.web.port,                                         //binary
  err => log(err || `Greeter on port ${conf.web.port}`), //binary
);                                                       //binary