Add PUT /users/:id endpoint

CLAUDE.md

@@ -0,0 +1,19 @@
+# CLAUDE.md
+
+This file provides guidance to Claude Code (claude.ai/code) when working with code in this repository.
+
+## Commands
+
+- `npm install` — install dependencies
+- `npm run dev` — run the server with auto-restart
+- `npm test` — run tests (Node's built-in test runner)
+- `node --test tests/update-user.test.js` — run a single test file
+- `npm run lint` — run ESLint
+
+## Architecture
+
+Small Express API: `server.js` mounts routers from `routes/` (`/users`, `/health`), which call into `db/store.js` for data. `db/store.js` is an in-memory array, not a real database — data resets on restart.
+
+`server.js` exports `app` without calling `.listen()` when required (only on direct run), so tests use `supertest` against it in-process.
+
+New endpoints follow the same pattern: store functions in `db/store.js`, route handler in `routes/` doing validation (400) and not-found (404) checks, mounted in `server.js`.

NOTES.md

@@ -0,0 +1,9 @@
+# Notes
+
+**Plan:** Task was fully spelled out, so I implemented directly: `updateUser` helper in `db/store.js`, plus a `PUT /:id` route mirroring the existing `POST /` (400 validation) and `GET /:id` (404) patterns. No changes from the initial approach.
+
+**Model:** Claude Sonnet 5 — small CRUD endpoint following existing patterns, no need for anything heavier.
+
+**Commits:** Store helper + route kept as one commit (neither works without the other). `CLAUDE.md` is a separate commit.
+
+**Review:** Checked the non-numeric id case (`PUT /users/abc`) — `Number("abc")` is `NaN`, and strict `===` in `getUserById` correctly falls through to 404. Nothing needed fixing.

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 null;
+  }
+
+  user.name = name;
+  user.email = email;
+  return user;
+}
+
+module.exports = { getAllUsers, getUserById, createUser, updateUser };

routes/users.js

@@ -1,35 +1,53 @@
-const express = require("express");
-const store = require("../db/store");
+const express = require('express');
+const store = require('../db/store');
 
 const router = express.Router();
 
 // GET /users — list every user
-router.get("/", (req, res) => {
+router.get('/', (req, res) => {
   res.json(store.getAllUsers());
 });
 
 // GET /users/:id — fetch a single user, or 404 if it doesn't exist
-router.get("/:id", (req, res) => {
+router.get('/:id', (req, res) => {
   const id = Number(req.params.id);
   const user = store.getUserById(id);
 
   if (!user) {
-    return res.status(404).json({ error: "User not found" });
+    return res.status(404).json({ error: 'User not found' });
   }
 
   res.json(user);
 });
 
 // POST /users — create a user; name and email are required
-router.post("/", (req, res) => {
+router.post('/', (req, res) => {
   const { name, email } = req.body;
 
   if (!name || !email) {
-    return res.status(400).json({ error: "name and email are required" });
+    return res.status(400).json({ error: 'name and email are required' });
   }
 
   const user = store.createUser({ name, email });
   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;