lnet_tutor/docs/stack-architecture.md

Minimal Architecture (Django + Angular)

Goals

• Read exam JSON from input/, render online, autosave progress, submit, and write bundled JSON to output/.
• Keep logic simple, deterministic, and file-backed.

Components

• Frontend: Angular SPA (exam UI, autosave, timer, resume)
• Backend: Django REST API (file I/O, attempt state, publish/finish checks)
• Storage: File system folders (input/, attempts/, output/, progress/, manifest.json)
• Web: Nginx (serve Angular, proxy /api/ to Django)

Data Flow

1. Angular requests /api/exams → Django lists published exams by reading manifest.json + input/.
2. Start/resume attempt: /api/exams/{examId}/attempt → Django reads/writes attempts/ and returns current attempt JSON.
3. Autosave: PUT /api/attempts/{attemptId} → backend persists answers and updates progress/.
4. Submit: POST /api/attempts/{attemptId}/submit → backend writes output/{examId}_{attemptId}.json with { exam, attempt } and marks finished.

Minimal State Machine

• draft → published → in_progress → submitted → finished

Files & Folders

• input/ — source exam JSON files
• attempts/{userId}/{examId}/{attemptId}.json — current attempt
• output/{examId}_{attemptId}.json — final bundle { exam, attempt }
• progress/{userId}.json — per-user progress snapshot
• manifest.json — registry of exams (published flags) and per-user finished set

Security (minimal)

• Auth: simple token cookie, userId in session
• CORS/CSRF configured for Angular origin
• No external services required

Observability

• Request logs, error logs
• Autosave frequency metric (client)