# TT-003 — Domain Models (freezed)

**Type:** Story  
**Priority:** High  
**Labels:** domain, models  
**Depends on:** TT-001  
**Blocks:** TT-004, TT-005, TT-006, TT-007, TT-008

---

## Summary
Define all domain-level models using `freezed`. These are the immutable data
classes used throughout the app's business logic and UI layer — distinct from
the Drift table companion classes.

## Models to implement

### `Project`
```dart
// lib/features/projects/domain/project.dart
@freezed
class Project with _$Project {
  const factory Project({
    required int id,
    required String name,
    required int colorValue,
    String? description,
    DateTime? archivedAt,
    required DateTime createdAt,
  }) = _Project;

  factory Project.fromJson(Map<String, dynamic> json) => _$ProjectFromJson(json);
}
```

### `TimeEntry`
```dart
// lib/features/entries/domain/time_entry.dart
@freezed
class TimeEntry with _$TimeEntry {
  const factory TimeEntry({
    required int id,
    required int projectId,
    required DateTime startTime,
    DateTime? endTime,
    int? durationSeconds,
    String? note,
    @Default([]) List<String> tags,
    required DateTime createdAt,
  }) = _TimeEntry;

  factory TimeEntry.fromJson(Map<String, dynamic> json) => _$TimeEntryFromJson(json);
}
```

### `Tag`
```dart
// lib/features/entries/domain/tag.dart
@freezed
class Tag with _$Tag {
  const factory Tag({
    required int id,
    required String name,
  }) = _Tag;

  factory Tag.fromJson(Map<String, dynamic> json) => _$TagFromJson(json);
}
```

### `TimerState`
```dart
// lib/features/timer/domain/timer_state.dart
@freezed
class TimerState with _$TimerState {
  const factory TimerState.idle() = TimerIdle;
  const factory TimerState.running({
    required int entryId,
    required DateTime startTime,
    required Project project,
    String? note,
  }) = TimerRunning;
}
```

## Acceptance Criteria
- [ ] All models defined with `@freezed`
- [ ] `fromJson` / `toJson` generated via `json_serializable`
- [ ] `dart run build_runner build` generates `*.freezed.dart` and `*.g.dart` without errors
- [ ] Models have no mutable fields
- [ ] `TimerState` is a union type (sealed), not a single class

## Files to create
- `lib/features/projects/domain/project.dart`
- `lib/features/entries/domain/time_entry.dart`
- `lib/features/entries/domain/tag.dart`
- `lib/features/timer/domain/timer_state.dart`

## Notes
- Drift table rows ≠ domain models. Use mapper extension methods to convert between them.
- Add `extension ProjectMapper on ProjectData { Project toDomain() {...} }` in the DAO files.