const Koa = require('koa');
const Router = require('@koa/router');
const bodyParser = require('koa-bodyparser');

const app = new Koa();
const router = new Router();

app.use(bodyParser());

// Basic error handling
app.use(async (ctx, next) => {
  try {
    await next();
  } catch (err) {
    ctx.status = err.status || 500;
    ctx.body = { error: err.message };
  }
});

app.listen(3000, () => {
  console.log('Server running on http://localhost:3000');
});

// In-memory storage for demonstration
let books = [];

// GET all books
router.get('/books', ctx => {
  ctx.body = books;
});

// GET single book
router.get('/books/:id', ctx => {
  const book = books.find(b => b.id === parseInt(ctx.params.id));
  if (book) {
    ctx.body = book;
  } else {
    ctx.status = 404;
    ctx.body = { error: 'Book not found' };
  }
});

// POST new book
router.post('/books', ctx => {
  const book = {
    id: books.length + 1,
    ...ctx.request.body
  };
  books.push(book);
  ctx.status = 201;
  ctx.body = book;
});

// PUT update book
router.put('/books/:id', ctx => {
  const index = books.findIndex(b => b.id === parseInt(ctx.params.id));
  if (index >= 0) {
    books[index] = {
      ...books[index],
      ...ctx.request.body
    };
    ctx.body = books[index];
  } else {
    ctx.status = 404;
    ctx.body = { error: 'Book not found' };
  }
});

// DELETE book
router.delete('/books/:id', ctx => {
  const index = books.findIndex(b => b.id === parseInt(ctx.params.id));
  if (index >= 0) {
    books.splice(index, 1);
    ctx.status = 204;
  } else {
    ctx.status = 404;
    ctx.body = { error: 'Book not found' };
  }
});

app.use(router.routes()).use(router.allowedMethods());

const authMiddleware = async (ctx, next) => {
  const token = ctx.headers.authorization;
  if (!token || token !== 'your-secret-token') {
    ctx.status = 401;
    ctx.body = { error: 'Unauthorized' };
    return;
  }
  await next();
};

// Apply to specific routes
router.use('/books', authMiddleware);