app.js

// book-management-api/index.js

const express = require('express');
const { v4: uuidv4 } = require('uuid');
const fs = require('fs');
const multer = require('multer');
const morgan = require('morgan');
const csv = require('csv-parser');
require('dotenv').config();

const app = express();
const port = process.env.PORT || 3000;

app.use(express.json());
app.use(morgan('dev'));

const upload = multer({ dest: 'uploads/' });

let books = [];

// CRUD ENDPOINTS
app.get('/books', (req, res) => {
  res.json(books);
});

app.get('/books/:id', (req, res) => {
  const book = books.find(b => b.id === req.params.id);
  book ? res.json(book) : res.status(404).json({ message: 'Book not found' });
});

app.post('/books', (req, res) => {
  const { title, author, publishedYear } = req.body;
  if (!title || !author || typeof publishedYear !== 'number') {
    return res.status(400).json({ message: 'Invalid book data' });
  }
  const newBook = { id: uuidv4(), title, author, publishedYear };
  books.push(newBook);
  res.status(201).json(newBook);
});

app.put('/books/:id', (req, res) => {
  const { title, author, publishedYear } = req.body;
  const index = books.findIndex(b => b.id === req.params.id);
  if (index === -1) return res.status(404).json({ message: 'Book not found' });

  books[index] = { ...books[index], title, author, publishedYear };
  res.json(books[index]);
});

app.delete('/books/:id', (req, res) => {
  books = books.filter(b => b.id !== req.params.id);
  res.status(204).send();
});

// CSV IMPORT
app.post('/books/import', upload.single('file'), (req, res) => {
  const errors = [];
  let addedCount = 0;

  fs.createReadStream(req.file.path)
    .pipe(csv())
    .on('data', (data) => {
      const { title, author, publishedYear } = data;
      if (!title || !author || isNaN(Number(publishedYear))) {
        errors.push({ ...data, error: 'Invalid data' });
      } else {
        books.push({ id: uuidv4(), title, author, publishedYear: Number(publishedYear) });
        addedCount++;
      }
    })
    .on('end', () => {
      fs.unlinkSync(req.file.path);
      res.json({ added: addedCount, errors });
    });
});

// ERROR HANDLING MIDDLEWARE
app.use((err, req, res, next) => {
  console.error(err.stack);
  res.status(500).send('Something broke!');
});

app.listen(port, () => {
  console.log(Book API listening at http://localhost:${port});
});