NODE.JS DEVELOPMENT:Day 6: Building a REST API with Express

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

// In-memory data store (replace with database in production)
let books = [
  { id: 1, title: 'Clean Code', author: 'Robert Martin', year: 2008 },
  { id: 2, title: 'You Don't Know JS', author: 'Kyle Simpson', year: 2015 },
];
let nextId = 3;

// GET /api/books — list all books (with optional filter)
router.get('/', (req, res) => {
  const { author, year } = req.query;
  let result = books;
  
  if (author) result = result.filter(b => b.author.toLowerCase().includes(author.toLowerCase()));
  if (year) result = result.filter(b => b.year === parseInt(year));
  
  res.json({ data: result, count: result.length });
});

// GET /api/books/:id — get single book
router.get('/:id', (req, res) => {
  const book = books.find(b => b.id === parseInt(req.params.id));
  if (!book) return res.status(404).json({ error: 'Book not found' });
  res.json({ data: book });
});

// POST /api/books — create book
router.post('/', (req, res) => {
  const { title, author, year } = req.body;
  
  // Validation
  if (!title || !author) {
    return res.status(422).json({ error: 'title and author are required' });
  }
  
  const book = { id: nextId++, title, author, year: year || null };
  books.push(book);
  res.status(201).json({ data: book });
});

// PATCH /api/books/:id — partial update
router.patch('/:id', (req, res) => {
  const index = books.findIndex(b => b.id === parseInt(req.params.id));
  if (index === -1) return res.status(404).json({ error: 'Book not found' });
  
  books[index] = { ...books[index], ...req.body, id: books[index].id }; // id immutable
  res.json({ data: books[index] });
});

// DELETE /api/books/:id — delete book
router.delete('/:id', (req, res) => {
  const index = books.findIndex(b => b.id === parseInt(req.params.id));
  if (index === -1) return res.status(404).json({ error: 'Book not found' });
  
  books.splice(index, 1);
  res.status(204).send();  // 204 No Content
});

module.exports = router;

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

app.use(express.json());
app.use('/api/books', require('./routes/books'));

app.listen(3000);

const { body, param, validationResult } = require('express-validator');

const bookValidation = [
  body('title').trim().notEmpty().withMessage('Title is required').isLength({ max: 200 }),
  body('author').trim().notEmpty().withMessage('Author is required'),
  body('year').optional().isInt({ min: 1000, max: 2100 }).withMessage('Invalid year'),
];

router.post('/', bookValidation, (req, res) => {
  const errors = validationResult(req);
  if (!errors.isEmpty()) {
    return res.status(422).json({ errors: errors.array() });
  }
  // Process valid request...
});

// Catch-all error handler — must have 4 parameters
app.use((err, req, res, next) => {
  console.error(err.stack);
  
  // Handle specific error types
  if (err.name === 'ValidationError') {
    return res.status(422).json({ error: err.message });
  }
  if (err.name === 'CastError') {
    return res.status(400).json({ error: 'Invalid ID format' });
  }
  
  // Default error response
  const status = err.status || 500;
  res.status(status).json({
    error: process.env.NODE_ENV === 'production' ? 'Internal server error' : err.message
  });
});

// 404 handler — after all routes
app.use((req, res) => {
  res.status(404).json({ error: `Route ${req.method} ${req.path} not found` });
});