Personal Catalogue: React, Express & MongoDB — Chapter 6, Exercise 1
=====================================================================

TASK
Build the finished /search route (correctly ordered, with escaped
input) plus the global error-handling middleware, then confirm a
search for an author's name returns the correct Book even when that
name never appears in the title, and a search for a nonexistent term
returns an empty array rather than an error.

SOLUTION

routes/items.js (escapeRegex helper plus the search route, registered
before GET /:id):

  function escapeRegex(str) {
    return str.replace(/[.*+?^${}()|[\]\\]/g, '\\$&');
  }

  router.get('/search', async (req, res) => {
    const q = (req.query.q || '').trim();
    if (!q) return res.status(400).json({ error: 'q is required' });
    const regex = new RegExp(escapeRegex(q), 'i');
    const items = await Item.find({
      $or: [{ title: regex }, { author: regex }, { artist: regex }, { director: regex }],
    }).lean();
    res.json(items);
  });

  // GET /:id (Chapter 3) comes after this in the file, not before

server.js (global error-handling middleware, registered last):

  app.use((err, req, res, next) => {
    console.error(err);
    res.status(500).json({ error: 'Server error' });
  });

Setup: create a Book with title "Clean Code" and author
"Robert C. Martin" (the title itself contains neither "Robert" nor
"Martin").

  curl -X POST http://localhost:4000/api/items \
    -H "Content-Type: application/json" \
    -d '{"itemType":"Book","title":"Clean Code","author":"Robert C. Martin"}'

Search by author, not title:

  curl "http://localhost:4000/api/items/search?q=Robert+Martin"

Output:
  [{"_id":"...","title":"Clean Code","itemType":"Book",
    "author":"Robert C. Martin", ...}]

The Book comes back even though "Robert Martin" never appears anywhere
in its title -- the $or condition on author is what matched it.

Search for something that matches nothing:

  curl "http://localhost:4000/api/items/search?q=Nonexistent"

Output:
  []

A clean empty array, with a real 200 status -- not a 404 and not an
error, since "no results" is a completely normal, valid outcome for a
search, not a failure.

WHY THIS WORKS AS AN ANSWER
----------------------------
It builds the route exactly as the chapter finalizes it, then proves
the cross-field matching genuinely works with a real document whose
title alone could never have matched the search term, and confirms the
route treats zero results as a normal response rather than an error
condition, matching real search UX expectations.