first working version

docs/stack-architecture.md

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+# 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)