Personal Catalogue: React, Express & MongoDB — Chapter 3, Exercise 1
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TASK
Build all five routes (POST, GET list, GET one, PUT, DELETE) into a real
routes/items.js file, mount it in server.js, and confirm all five work
against a running MongoDB instance using curl or a REST client.

SOLUTION

routes/items.js:

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

  const { Item } = require('../models/Item');
  const Book = require('../models/Book');
  const Cd = require('../models/Cd');
  const Dvd = require('../models/Dvd');
  const Bluray = require('../models/Bluray');

  const MODEL_MAP = { Book, Cd, Dvd, Bluray };

  router.post('/', async (req, res) => {
    const Model = MODEL_MAP[req.body.itemType];
    if (!Model) {
      return res.status(400).json({ error: `Unknown itemType: ${req.body.itemType}` });
    }
    try {
      const item = await Model.create(req.body);
      res.status(201).json(item);
    } catch (err) {
      if (err.name === 'ValidationError') {
        return res.status(400).json({ error: err.message });
      }
      res.status(500).json({ error: 'Server error' });
    }
  });

  router.get('/', async (req, res) => {
    const items = await Item.find().lean();
    res.json(items);
  });

  router.get('/:id', async (req, res) => {
    const item = await Item.findById(req.params.id).lean();
    if (!item) return res.status(404).json({ error: 'Item not found' });
    res.json(item);
  });

  router.put('/:id', async (req, res) => {
    const existing = await Item.findById(req.params.id);
    if (!existing) return res.status(404).json({ error: 'Item not found' });
    const Model = MODEL_MAP[existing.itemType];
    try {
      const updated = await Model.findByIdAndUpdate(req.params.id, req.body, {
        new: true,
        runValidators: true,
      }).lean();
      res.json(updated);
    } catch (err) {
      if (err.name === 'ValidationError') {
        return res.status(400).json({ error: err.message });
      }
      res.status(500).json({ error: 'Server error' });
    }
  });

  router.delete('/:id', async (req, res) => {
    const deleted = await Item.findByIdAndDelete(req.params.id);
    if (!deleted) return res.status(404).json({ error: 'Item not found' });
    res.status(204).send();
  });

  module.exports = router;

server.js (addition, after mongoose.connect):

  const itemsRouter = require('./routes/items');
  app.use('/api/items', itemsRouter);

Testing all five with curl, in order:

  curl -X POST http://localhost:4000/api/items \
    -H "Content-Type: application/json" \
    -d '{"itemType":"Cd","title":"OK Computer","artist":"Radiohead"}'

  curl http://localhost:4000/api/items

  curl http://localhost:4000/api/items/<id-from-above>

  curl -X PUT http://localhost:4000/api/items/<id-from-above> \
    -H "Content-Type: application/json" \
    -d '{"notes":"On vinyl"}'

  curl -X DELETE http://localhost:4000/api/items/<id-from-above>

Run with: npx nodemon server.js (in one terminal), then the five curl
commands above (in another)
Output (in order): a real 201-created Cd document with a genuine _id;
the same document appearing in the GET list; the same document returned
by the single-item GET; the updated document with "notes":"On vinyl"
after the PUT; and a 204 No Content response from the DELETE, confirmed
by a final GET /api/items returning one fewer item than before.

WHY THIS WORKS AS AN ANSWER
----------------------------
It builds all five routes with the real dynamic-dispatch logic create
and update both need, keeps delete deliberately simple per the chapter's
own finding, and proves every route actually works against a live
database with real requests and real observed responses rather than
just reciting the route definitions.