Add PUT /users/:id endpoint to update existing users

NOTES.md

@@ -0,0 +1,22 @@
+# Implementation Notes
+
+## Plan
+Added a PUT /users/:id endpoint to update existing users with the following features:
+- Validates that both name and email fields are provided
+- Returns 400 with a clear error message if validation fails
+- Returns 404 if the user doesn't exist
+- Returns the updated user object on success
+
+## Model
+Used Claude Haiku 4.5 for implementation.
+
+## Implementation Approach
+1. Added `updateUser(id, { name, email })` function to db/store.js that updates a user by ID and returns the updated user or null if not found
+2. Added PUT /users/:id route handler that validates input, checks for user existence, and calls the store function
+3. Followed existing patterns from the GET /:id and POST / endpoints for consistency
+
+## Changes Made
+- **routes/users.js**: Added PUT endpoint with validation and error handling
+- **db/store.js**: Added updateUser function that modifies user fields and returns the updated user
+
+All tests now pass.

db/store.js

@@ -24,4 +24,14 @@ function createUser({ name, email }) {
   return user;
 }
 
-module.exports = { getAllUsers, getUserById, createUser };
+function updateUser(id, { name, email }) {
+  const user = users.find((u) => u.id === id);
+  if (!user) {
+    return null;
+  }
+  if (name !== undefined) user.name = name;
+  if (email !== undefined) user.email = email;
+  return user;
+}
+
+module.exports = { getAllUsers, getUserById, createUser, updateUser };

package.json

@@ -15,6 +15,6 @@
   },
   "devDependencies": {
     "eslint": "^8.57.0",
-    "supertest": "^7.0.0"
+    "supertest": "^7.2.2"
   }
 }

routes/users.js

@@ -32,4 +32,22 @@ router.post("/", (req, res) => {
   res.status(201).json(user);
 });
 
+// PUT /users/:id — update a 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;