const http = require('http');

module.exports = class SuperMiniKoa {

constructor() {

this.middleware = [];

 }

use(fn) {

  this.middleware.push(fn);

 }

 listen(...args) {

return http.createServer(this.callback.bind(this)).listen(...args);

}

callback(req, res) {

const fn = this.compose(this.middleware);

const handleError = e => { throw new Error(e); };

const handleResponse = () => { res.end(res.body); };

   const ctx = { req, res, app: this, state: {} };

return fn(ctx).then(handleResponse).catch(handleError);

 }

compose(middleware) {

return function(ctx) {

let index = -1;

const dispatch = i => {

index = i;

let fn = middleware[i];

if (i === middleware.length) return Promise.resolve();

try {

return Promise.resolve(fn(ctx, () => dispatch(i + 1)));

} catch (err) {

return Promise.reject(err);

}

}

return dispatch(0);

}

}

}