P2B-WEB-2026_2025/block-01/week-01-the_web_under_the_hood/demo/server.ts

import express from "express"
import { status } from "http-status"

const app = express()

app.use(express.urlencoded({ extended: true }))
app.use(express.json())

// Log every incoming request to the terminal
app.use((req, res, next) => {
  console.log("\n" + "=".repeat(50))
  console.log(`${req.method} ${req.url}`)
  console.log("\n-- Headers --")
  console.log(req.headers)
  if (Object.keys(req.body || {}).length > 0) {
    console.log("\n-- Body --")
    console.log(req.body)
  }
  if (Object.keys(req.cookies || {}).length > 0) {
    console.log("\n-- Cookies --")
    console.log(req.cookies)
  }
  console.log("=".repeat(50))
  next()
})

// Serve static files from the "public" directory (for CSS, images, etc.)
app.use(express.static("public"))

// Simple GET: echoes request info back as HTML
app.get("/", (req, res) => {
  res.send(`
		<link rel="stylesheet" href="/style.css" />
    <h1>HTTP Echo Server</h1>
    <p>Check your terminal — the server printed everything it received.</p>
    <h2>Try these:</h2>
    <ul>
      <li><a href="/form">POST form demo</a></li>
      <li><a href="/set-cookie">Set a cookie</a></li>
      <li><a href="/show-cookies">Show cookies the server received</a></li>
      <li><a href="/json">JSON response</a></li>
			<li><a href="/delay">Delayed response</a></li>
			<li><a href="/status">HTTP status codes</a></li>
    </ul>
  `)
})

// Form page: allows to submit a POST and see the body
app.get("/form", (req, res) => {
  res.send(`
		<link rel="stylesheet" href="/style.css" />
    <h1>Login Form</h1>
    <form method="POST" action="/login">
      <label>Username: <input name="username" type="text" /></label>
      <label>Password: <input name="password" type="password" /></label>
      <button type="submit">Login</button>
    </form>
    <p>Submit this and watch the terminal. Also check DevTools → Network tab.</p>
  `)
})

// Receives the POST: echoes the body back
app.post("/login", (req, res) => {
  const { username, password } = req.body
  res.send(`
		<link rel="stylesheet" href="/style.css" />
    <h1>Server received your POST</h1>
    <p><strong>Username:</strong> ${username}</p>
    <p><strong>Password:</strong> ${password}</p>
    <p style="color:red">⚠️ Over plain HTTP, anyone between you and the server could read this.</p>
    <a href="/form">Back</a>
  `)
})

// Sets a cookie: shows Set-Cookie header in DevTools
app.get("/set-cookie", (req, res) => {
  res.cookie("session", "abc123xyz", {
    httpOnly: true,
    maxAge: 60 * 60 * 1000, // 1 hour
  })
  res.send(`
		<link rel="stylesheet" href="/style.css" />
    <h1>Cookie Set</h1>
    <p>The server sent a <code>Set-Cookie</code> header. Check DevTools → Network → Response Headers.</p>
    <p>Now visit <a href="/show-cookies">show-cookies</a> — the browser will automatically send it back.</p>
  `)
})

// Shows what cookies the server received
app.get("/show-cookies", (req, res) => {
  const cookieHeader = req.headers["cookie"] || "none"
  res.send(`
		<link rel="stylesheet" href="/style.css" />
    <h1>Cookies the server received</h1>
    <p><code>Cookie: ${cookieHeader}</code></p>
    <p>The browser sent this automatically — you didn't write any JavaScript for that.</p>
  `)
})

// Returns JSON: shows Content-Type in action
app.get("/json", (req, res) => {
  res.json({
    message: "This is a JSON response",
    method: req.method,
    url: req.url,
    headers: req.headers,
  })
})

// Delayed response: simulates a slow server
app.get("/delay", (req, res) => {
  setTimeout(() => {
    res.send(`
			<link rel="stylesheet" href="/style.css" />
			<h1>Delayed Response</h1><p>This response was delayed by 5 seconds.</p>
			`)
  }, 5000)
})

// Show all the different HTTP status codes
app.get("/status", (req, res) => {
  res.send(`
		<link rel="stylesheet" href="/style.css" />
		<h1>HTTP Status Codes</h1>
		<h2>2xx Success</h2>
		<ul>
			${[200, 201, 202, 203, 204, 205, 206, 207, 208, 226]
        .map(
          (code) =>
            `<li><a href="/status/${code}">${code} ${status[code as keyof typeof status]}</a></li>`,
        )
        .join("")}
		</ul>
		<h2>3xx Redirection</h2>
		<ul>
			${[300, 301, 302, 303, 304, 307, 308]
        .map(
          (code) =>
            `<li><a href="/status/${code}">${code} ${status[code as keyof typeof status]}</a></li>`,
        )
        .join("")}
		</ul>
		<h2>4xx Client Errors</h2>
		<ul>
			${[
        400, 401, 403, 404, 405, 406, 407, 408, 409, 410, 411, 412, 413, 414,
        415, 416, 417, 418, 421, 422, 423, 424, 425, 426, 428, 429, 431, 451,
      ]
        .map(
          (code) =>
            `<li><a href="/status/${code}">${code} ${status[code as keyof typeof status]}</a></li>`,
        )
        .join("")}
		</ul>
		<h2>5xx Server Errors</h2>
		<ul>
			${[500, 501, 502, 503, 504, 505, 506, 507, 508, 510, 511]
        .map(
          (code) =>
            `<li><a href="/status/${code}">${code} ${status[code as keyof typeof status]}</a></li>`,
        )
        .join("")}
		</ul>
		`)
})

// Demonstrates different status codes
app.get("/status/:code", (req, res) => {
  const code = parseInt(req.params.code)
  res.status(code).send(`
			<link rel="stylesheet" href="/style.css" />
			<h1>Status ${code}</h1><p>This response was sent with HTTP status ${code} (${status[code as keyof typeof status]}).</p>
			`)
})

app.listen(3000, () => {
  console.log("Echo server running on http://localhost:3000")
  console.log("Watching for requests...\n")
})