Exercise: Pagination, Filtering, Validation & Error Handling

Goal

Improve the API for real-world use: list endpoints with pagination, filtering (completed, search by title), and strong input validation + proper HTTP errors.

Tasks

1. List endpoint with query params

   • GET /todos?limit=20&offset=0&completed=true&search=read

   • Return metadata: total, limit, offset and items.

2. Validation

   • Enforce limit [1..100], offset ≥ 0.

   • Title length validated in creation/update.

3. Error handling

   • Return 400 for invalid query params.

   • 404 for missing resource with consistent error structure: { "detail": "...", "code": "NOT_FOUND" }.

4. Sorting

   • Support sort=-created_at or sort=title.

5. OpenAPI docs

   • Describe each query param with examples.

Acceptance Criteria

• Pagination and filters work and are documented in /docs.

• Errors are consistent with status codes.

Deliverables

• Updated source + docs.

• Sample curl calls demonstrating pagination + filters.

Rubric (50 pts)

• Pagination

• Filtering & sorting

• Validation & error handling

• Docs clarity