Add completed task filtering

sample-app/README.md

@@ -22,7 +22,7 @@ npm start        # run the compiled server
 | Method | Path | Description |
 | --- | --- | --- |
 | `GET` | `/health` | Liveness check → `{ "status": "ok" }` |
-| `GET` | `/tasks` | List all tasks |
+| `GET` | `/tasks` | List all tasks; use `?completed=true` or `?completed=false` to filter |
 | `POST` | `/tasks` | Create a task from `{ "title": "..." }` |
 | `GET` | `/tasks/:id` | Get one task (404 if missing) |
 | `PATCH` | `/tasks/:id` | Set `{ "completed": true \| false }` |
@@ -36,7 +36,6 @@ These are the hooks for the [exercises](../exercises/README.md). Don't "fix" the
 1. `POST /tasks` does **no input validation**.
 2. There is **no `DELETE /tasks/:id`** (and `TaskStore.remove()` is missing).
 3. `setCompleted` never refreshes `updatedAt` — a subtle bug.
-4. `GET /tasks` has **no `?completed=` filter**.
 
 ## Layout
 

sample-app/src/app.test.ts

@@ -35,6 +35,26 @@ describe('Task API', () => {
     expect(patched.body.completed).toBe(true);
   });
 
+  it('lists only completed tasks when filtered', async () => {
+    const app = createApp();
+    const completed = await request(app).post('/tasks').send({ title: 'Done' });
+    await request(app).post('/tasks').send({ title: 'Not done' });
+    await request(app).patch(`/tasks/${completed.body.id}`).send({ completed: true });
+
+    const res = await request(app).get('/tasks?completed=true');
+
+    expect(res.status).toBe(200);
+    expect(res.body).toHaveLength(1);
+    expect(res.body[0].title).toBe('Done');
+  });
+
+  it('rejects an invalid completed filter', async () => {
+    const res = await request(createApp()).get('/tasks?completed=maybe');
+
+    expect(res.status).toBe(400);
+    expect(res.body.error).toBe("completed must be 'true' or 'false'");
+  });
+
   it('returns 404 for an unknown task', async () => {
     const res = await request(createApp()).get('/tasks/does-not-exist');
     expect(res.status).toBe(404);

sample-app/src/tasks/routes.ts

@@ -4,9 +4,14 @@ import type { TaskStore } from './store.js';
 export function createTaskRouter(store: TaskStore): Router {
   const router = Router();
 
-  // Exercise 4: support filtering with GET /tasks?completed=true|false
-  router.get('/', (_req, res) => {
-    res.json(store.list());
+  router.get('/', (req, res) => {
+    const { completed } = req.query;
+    if (completed === undefined) return res.json(store.list());
+    if (completed !== 'true' && completed !== 'false') {
+      return res.status(400).json({ error: "completed must be 'true' or 'false'" });
+    }
+    const want = completed === 'true';
+    res.json(store.list().filter((task) => task.completed === want));
   });
 
   router.post('/', (req, res) => {