# Tracking Feature Implementation Summary

## ✅ Implementation Complete

All acceptance criteria from [feat-tracking.md](.github/specs/active/feat-dynamic-points/feat-tracking.md) have been implemented and tested.

---

## 📦 What Was Delivered

### Backend

1. **Data Model** ([tracking_event.py](backend/models/tracking_event.py))
   - `TrackingEvent` dataclass with full type safety
   - Factory method `create_event()` for server-side timestamp generation
   - Delta invariant validation (`delta == points_after - points_before`)

2. **Database Layer** ([tracking.py](backend/db/tracking.py))
   - New TinyDB table: `tracking_events.json`
   - Helper functions: `insert_tracking_event`, `get_tracking_events_by_child`, `get_tracking_events_by_user`, `anonymize_tracking_events_for_user`
   - Offset-based pagination with sorting by `occurred_at` (desc)

3. **Audit Logging** ([tracking_logger.py](backend/utils/tracking_logger.py))
   - Per-user rotating file handlers (`logs/tracking_user_<user_id>.log`)
   - 10MB max file size, 5 backups
   - Structured log format with all event metadata

4. **API Integration** ([child_api.py](backend/api/child_api.py))
   - Tracking added to:
     - `POST /child/<id>/trigger-task` → action: `activated`
     - `POST /child/<id>/request-reward` → action: `requested`
     - `POST /child/<id>/trigger-reward` → action: `redeemed`
     - `POST /child/<id>/cancel-request-reward` → action: `cancelled`

5. **Admin API** ([tracking_api.py](backend/api/tracking_api.py))
   - `GET /admin/tracking` with filters:
     - `child_id` (required if no `user_id`)
     - `user_id` (admin only)
     - `entity_type` (task|reward|penalty)
     - `action` (activated|requested|redeemed|cancelled)
     - `limit` (default 50, max 500)
     - `offset` (default 0)
   - Returns total count for future pagination UI

6. **SSE Events** ([event_types.py](backend/events/types/event_types.py), [tracking_event_created.py](backend/events/types/tracking_event_created.py))
   - New event type: `TRACKING_EVENT_CREATED`
   - Payload: `tracking_event_id`, `child_id`, `entity_type`, `action`
   - Emitted on every tracking event creation

---

### Frontend

1. **TypeScript Models** ([models.ts](frontend/vue-app/src/common/models.ts))
   - `TrackingEvent` interface (1:1 parity with Python)
   - Type aliases: `EntityType`, `ActionType`
   - `TrackingEventCreatedPayload` for SSE events

2. **API Helpers** ([api.ts](frontend/vue-app/src/common/api.ts))
   - `getTrackingEventsForChild()` function with all filter params

3. **SSE Registration**
   - Event type registered in type union
   - Ready for future UI components

---

### Tests

**Backend Unit Tests** ([test_tracking.py](backend/tests/test_tracking.py)):

- ✅ Tracking event creation with factory method
- ✅ Delta invariant validation
- ✅ Insert and query tracking events
- ✅ Filtering by `entity_type` and `action`
- ✅ Offset-based pagination
- ✅ User anonymization on deletion
- ✅ Points change correctness (positive/negative/zero delta)
- ✅ No points change for request/cancel actions

---

## 🔑 Key Design Decisions

1. **Append-only tracking table** - No deletions, only anonymization on user deletion
2. **Server timestamps** - `occurred_at` always uses server time (UTC) to avoid client clock drift
3. **Separate logging** - Per-user audit logs independent of database
4. **Offset pagination** - Simpler than cursors, sufficient for expected scale
5. **No UI (yet)** - API/models/SSE only; UI deferred to future phase

---

## 🚀 Usage Examples

### Backend: Create a tracking event

```python
from models.tracking_event import TrackingEvent
from db.tracking import insert_tracking_event
from utils.tracking_logger import log_tracking_event

event = TrackingEvent.create_event(
    user_id='user123',
    child_id='child456',
    entity_type='task',
    entity_id='task789',
    action='activated',
    points_before=50,
    points_after=60,
    metadata={'task_name': 'Homework'}
)

insert_tracking_event(event)
log_tracking_event(event)
```

### Frontend: Query tracking events

```typescript
import { getTrackingEventsForChild } from "@/common/api";

const res = await getTrackingEventsForChild({
  childId: "child456",
  entityType: "task",
  limit: 20,
  offset: 0,
});

const data = await res.json();
// { tracking_events: [...], total: 42, count: 20, limit: 20, offset: 0 }
```

---

## 📋 Migration Notes

1. **New database file**: `backend/data/db/tracking_events.json` will be created automatically on first tracking event.
2. **New log directory**: `backend/logs/tracking_user_<user_id>.log` files will be created per user.
3. **No breaking changes** to existing APIs or data models.

---

## 🔮 Future Enhancements (Not in This Phase)

- Admin/parent UI for viewing tracking history
- Badges and certificates based on tracking data
- Analytics and reporting dashboards
- Export tracking data (CSV, JSON)
- Time-based filters (date range queries)
