07_server.js

const fs = require("fs");
const express = require("express");
const exp = require("constants");
const port = process.env.PORT || 1337;
const app = express();
const EventEmitter = require("events");
const chatEmitter = new EventEmitter();
// VERIFY THAT THE CHATEMITTER WORKS
// chatEmitter.on("message", console.log);

// PLAIN-TEXT RESPONSE
function respondText(req, res) {
  res.setHeader("Content-Type", "text/plain");
  res.end("Hello User");
}

// JSON RESPONSE
function respondJson(req, res) {
  res.json({ name: "John Doe" });
}

// DYNAMIC RESPONSE
function respondEcho(req, res) {
  const { input = "" } = req.query;

  res.json({
    normal: input,
    shouty: input.toUpperCase(),
    characterCount: input.length,
    backwards: input.split("").reverse().join(""),
  });
}

// 404 RESPONSE
function respondNotFound(req, res) {
  res.writeHead(404, { "Content-Type": "text/plain" });
  res.end("Not Found");
}

// FILE SERVING
function respondStatic(req, res) {
  const filename = `${__dirname}/public/${req.params[0]}`;
  fs.createReadStream(filename)
    .on("error", () => respondNotFound(req, res))
    .pipe(res);
}

// CHAT
function respondChat(req, res) {
  const { message } = req.query;

  chatEmitter.emit("message", message);
}

// SSE - SERVER SENT EVENTS
function respondSSE(req, res) {
  res.writeHead(200, {
    "Content-Type": "text/event-stream",
    Connection: "keep-alive",
  });

  const onMessage = (msg) => res.write(`data: ${msg}\n\n`);
  chatEmitter.on("message", onMessage);

  res.on("close", function () {
    chatEmitter.off("message", onMessage);
  });
}

app.get("/", respondText);
app.get("/json", respondJson);
app.get("/echo", respondEcho);
app.get("/static/*", respondStatic);
app.get("/chat", respondChat);
app.get("/sse", respondSSE);

app.listen(port, () => console.log(`Server listening on port ${port}`));