# TT-002 — Drift Database Schema

**Type:** Story  
**Priority:** Highest  
**Labels:** database, infrastructure  
**Depends on:** TT-001  
**Blocks:** TT-004, TT-005

---

## Summary
Implement the full Drift database schema in `lib/core/database/app_database.dart`
including all table definitions, DAOs, and the database connection provider.

## Background
The Drift schema is documented in `.ai/database.md`. The placeholder file
`lib/core/database/app_database.dart` exists but contains no implementation.

## Data Model
### Tables
| Table             | Key columns                                              |
|-------------------|----------------------------------------------------------|
| `projects`        | id, name, color_value, description, archived_at, created_at |
| `time_entries`    | id, project_id (FK), start_time, end_time, duration_s, note, created_at |
| `tags`            | id, name                                                 |
| `time_entry_tags` | time_entry_id (FK), tag_id (FK) — composite PK           |

## Acceptance Criteria
- [ ] All 4 tables defined as Drift `Table` classes
- [ ] Foreign key constraints declared and enforced
- [ ] `AppDatabase` annotated with `@DriftDatabase(tables: [...])`
- [ ] `_openConnection()` uses `getApplicationDocumentsDirectory()` + `NativeDatabase.createInBackground`
- [ ] `schemaVersion` = 1, empty `MigrationStrategy` scaffold in place
- [ ] Three DAOs created: `ProjectsDao`, `TimeEntriesDao`, `TagsDao`
- [ ] Each DAO has at minimum: `watchAll()`, `insert()`, `update()`, `delete()`
- [ ] `TimeEntriesDao.getActiveEntry()` returns entry where `end_time IS NULL`
- [ ] Riverpod `@Riverpod(keepAlive: true)` provider for `AppDatabase`
- [ ] `dart run build_runner build` generates schema without errors
- [ ] Unit test: insert + read a `Project` using in-memory DB

## Files to create / modify
- `lib/core/database/app_database.dart` — full implementation
- `lib/core/database/daos/projects_dao.dart`
- `lib/core/database/daos/time_entries_dao.dart`
- `lib/core/database/daos/tags_dao.dart`
- `test/core/database/app_database_test.dart`

## Notes
- See `.ai/database.md` for full schema details
- Use `NativeDatabase.memory()` in tests — never the real file DB