app.js

const fs = require('fs');
const Response = require('./lib/response');
const CONTENT_TYPES = require('./lib/mimeTypes');
const { loadTemplate } = require('./lib/viewTemplate');

const STATIC_FOLDER = `${__dirname}/public`;
let visitorCount = 0;

const serveStaticFile = (req) => {
  const path = `${STATIC_FOLDER}${req.url}`;
  const stat = fs.existsSync(path) && fs.statSync(path);
  if (!stat || !stat.isFile()) return new Response();
  const [, extension] = path.match(/.*\.(.*)$/) || [];
  const contentType = CONTENT_TYPES[extension];
  const content = fs.readFileSync(path);
  const res = new Response();
  res.setHeader('Content-Type', contentType);
  res.setHeader('Content-Length', content.length);
  res.statusCode = 200;
  res.body = content;
  return res;
}

const serveHomePage = (req) => {
  visitorCount++;
  const html = loadTemplate('home.html', { visitorCount });
  const res = new Response();
  if (!req.headers['Cookie']) res.setHeader('Set-Cookie', `sessionId=${new Date().getTime()}`);
  res.setHeader('Content-Type', CONTENT_TYPES.html);
  res.setHeader('Content-Length', html.length);
  res.statusCode = 200;
  res.body = html;
  return res;
}
const generateStudentResponse = (student) => {
  const html = loadTemplate('student.html', student);
  const res = new Response();
  res.setHeader('Content-Type', CONTENT_TYPES.html);
  res.setHeader('Content-Length', html.length);
  res.statusCode = 200;
  res.body = html;
  return res;
}
const registerStudent = (req) => {
  return generateStudentResponse(req.query);
}
const registerStudentPost = (req) => {
  return generateStudentResponse(req.body);
}
const serveVisitorCount = (req) => {
  const text = `${visitorCount}`;
  const res = new Response();
  res.setHeader('Content-Type', CONTENT_TYPES.txt);
  res.setHeader('Content-Length', text.length);
  res.statusCode = 200;
  res.body = text;
  return res;
}
const findHandler = (req) => {
  if (req.method === 'GET' && req.url === '/') return serveHomePage;
  if (req.method === 'GET' && req.url === '/visitorCount') return serveVisitorCount;
  if (req.method === 'GET' && req.url === '/registerStudent') return registerStudent;
  if (req.method === 'POST' && req.url === '/registerStudent') return registerStudentPost;
  if (req.method === 'GET') return serveStaticFile;
  return () => new Response();
}
const processRequest = (req) => {
  const handler = findHandler(req);
  return handler(req);
}

module.exports = { processRequest };