claude-ship-a-change-end-to-end

NOTES.md

@@ -0,0 +1,43 @@
+# NOTES
+
+## Plan
+
+The target was defined by the already-written `tests/update-user.test.js`: a
+`PUT /users/:id` endpoint that updates a user (200), 400s on a missing
+`name`/`email` field, and 404s for an unknown id. I read `routes/users.js`
+and `db/store.js` first and planned to mirror the existing patterns exactly
+rather than invent new ones: the same `!name || !email` validation already
+used by `POST /users`, and the same `find`-by-id + `undefined`-means-missing
+approach already used by `getUserById`. No part of the plan needed editing —
+the existing code gave a clear template for the new route and store helper.
+
+## Model
+
+Sonnet 5. This is a small, well-specified CRUD addition to an existing
+codebase with tests already dictating the contract — it doesn't need a
+heavier model's judgment, just careful pattern-matching against the code
+that's already there.
+
+## Commit split
+
+Two commits for the feature, plus this notes file:
+
+1. `db/store.js` — add the `updateUser` helper (data layer).
+2. `routes/users.js` — add the `PUT /:id` route that validates input and
+   wires up the helper (API layer).
+
+Splitting store from route keeps each commit reviewable on its own — the
+data-access change and the HTTP/validation change are different concerns,
+and this mirrors how `createUser`/`POST` and `getUserById`/`GET :id` are
+already split across the two files.
+
+## Review
+
+I ran a self-review of the diff (correctness, cross-file callers, removed
+behavior, reuse/simplification, efficiency) before writing this file. It
+turned up no issues: the new route reuses the existing validation and
+not-found conventions instead of introducing new ones, `express.json()`
+already guarantees `req.body` defaults to `{}` on an empty body (so
+destructuring is safe, matching the existing `POST` handler), and the store
+mutates the same in-memory object reference `getUserById` already returns,
+consistent with how the rest of the store works. `npm test` is green.

db/store.js

@@ -24,4 +24,16 @@ function createUser({ name, email }) {
   return user;
 }
 
-module.exports = { getAllUsers, getUserById, createUser };
+function updateUser(id, { name, email }) {
+  const user = getUserById(id);
+
+  if (!user) {
+    return undefined;
+  }
+
+  user.name = name;
+  user.email = email;
+  return user;
+}
+
+module.exports = { getAllUsers, getUserById, createUser, updateUser };

routes/users.js

@@ -32,4 +32,22 @@ router.post("/", (req, res) => {
   res.status(201).json(user);
 });
 
+// PUT /users/:id — update an existing user; name and email are required
+router.put("/:id", (req, res) => {
+  const id = Number(req.params.id);
+  const { name, email } = req.body;
+
+  if (!name || !email) {
+    return res.status(400).json({ error: "name and email are required" });
+  }
+
+  const user = store.updateUser(id, { name, email });
+
+  if (!user) {
+    return res.status(404).json({ error: "User not found" });
+  }
+
+  res.json(user);
+});
+
 module.exports = router;