Express Routing

const express = require('express');
const app = express();

// Route parameters — capture dynamic segments
app.get('/users/:id', (req, res) => {
  const id = Number(req.params.id);   // req.params.id is the STRING '42'
  if (!Number.isInteger(id) || id < 1) {
    return res.status(400).json({ error: 'id must be a positive integer' });
  }
  res.json({ message: `User ${id} details` });
});
// GET /users/42 → { message: "User 42 details" }

// Multiple parameters
app.get('/posts/:year/:month', (req, res) => {
  res.json({
    year: req.params.year,
    month: req.params.month
  });
});
// GET /posts/2025/03 → { year: "2025", month: "03" }

// Query strings — parsed automatically, but every value is a string
app.get('/search', (req, res) => {
  const q = req.query.q;

  // A repeated key becomes an ARRAY: ?tag=node&tag=api -> ['node','api']
  const tags = [].concat(req.query.tag || []);

  // Defaults are not validation. Clamp anything that costs you memory.
  const page  = Math.max(1, Number(req.query.page) || 1);
  const limit = Math.min(100, Math.max(1, Number(req.query.limit) || 10));

  res.json({ query: q, tags, page, limit });
});
// GET /search?q=nodejs&page=2 -> { query: "nodejs", tags: [], page: 2, limit: 10 }

const express = require('express');
const app = express();

// WRONG ORDER — /users/new never reaches its own handler
app.get('/users/:id', (req, res) => res.json({ id: req.params.id }));
app.get('/users/new', (req, res) => res.json({ form: true }));
// GET /users/new  ->  { "id": "new" }   ...then a database error about "new"

// RIGHT ORDER — specific paths above parametrised ones
app.get('/users/new', (req, res) => res.json({ form: true }));
app.get('/users/:id', (req, res) => res.json({ id: req.params.id }));

// The method matters as much as the path
app.get('/books', listBooks);
// POST /books  ->  404, because no POST route for /books was ever defined

// The 404 catch-all goes LAST. Anything registered below it is unreachable.
app.use((req, res) => {
  res.status(404).json({ error: `Cannot ${req.method} ${req.originalUrl}` });
});

// The error handler (four arguments) comes after even that — see lesson 10
app.use((err, req, res, next) => {
  res.status(500).json({ error: 'Something went wrong' });
});

// routes/users.js
const express = require('express');
const router = express.Router();

// Applies to EVERY route in this file — impossible to forget on a new one
// router.use(requireAuth);

// Paths here are RELATIVE to the mount point: '/' becomes /api/users
router.get('/', (req, res) => {
  res.json([{ id: 1, name: 'Alice' }]);
});

router.get('/:id', (req, res) => {
  res.json({ id: req.params.id, name: 'Alice' });
});

router.post('/', (req, res) => {
  res.status(201).json({ message: 'User created', data: req.body });
});

module.exports = router;

// app.js — Mount the router
const express = require('express');
const userRoutes = require('./routes/users');
const app = express();

app.use(express.json());
app.use('/api/users', userRoutes);   // every route above gains this prefix

// Versioning is nothing more than a second mount point
// app.use('/api/v2/users', userRoutesV2);

// A nested router needs mergeParams to see the parent's :userId
// const postRoutes = express.Router({ mergeParams: true });
// app.use('/api/users/:userId/posts', postRoutes);

app.listen(process.env.PORT || 3000);

const express = require('express');
const router = express.Router();

// Small, named, reusable checks
function requireAuth(req, res, next) {
  if (!req.headers.authorization) {
    return res.status(401).json({ error: 'Login required' });
  }
  req.user = { id: 7, role: 'admin' };   // decoded from a token in lesson 16
  return next();
}

function requireAdmin(req, res, next) {
  if (req.user.role !== 'admin') {
    return res.status(403).json({ error: 'Admin only' });
  }
  return next();
}

// A chain, read left to right
router.get('/stats', requireAuth, requireAdmin, (req, res) => {
  res.json({ books: 120 });
});

// Keep one path's methods together
router.route('/')
  .get(listBooks)
  .post(requireAuth, createBook);

// Runs for every route in this router that has an :id
router.param('id', async (req, res, next, value) => {
  try {
    const book = await Book.findById(value);
    if (!book) return res.status(404).json({ error: 'Book not found' });
    req.book = book;        // handlers below can now assume it exists
    return next();
  } catch (err) {
    return next(err);
  }
});

router.get('/:id', (req, res) => res.json(req.book));
router.delete('/:id', requireAuth, async (req, res) => {
  await req.book.deleteOne();
  res.status(204).send();
});

module.exports = router;