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+# Requirements: GPS Speedometer Restructure
+
+**Defined:** 2026-02-09
+**Core Value:** Reliable, lag-free GPS speed display that coexists politely with other Android apps
+
+## v1 Requirements
+
+Requirements for the restructure milestone. Each maps to roadmap phases.
+
+### Code organization
+
+- [ ] **ORG-01**: Code split into directory structure: `screens/`, `widgets/`, `services/`, `providers/`, `models/`, `config/`
+- [ ] **ORG-02**: `ProcessedGpsData` model extracted to `models/processed_gps_data.dart`
+- [ ] **ORG-03**: `SpeedUnit` and `ColorTheme` moved to `config/` directory
+- [ ] **ORG-04**: Constants file created with all magic numbers (timeouts, thresholds, overlay percentages)
+- [ ] **ORG-05**: Typed `OverlayMessage` class replaces unvalidated Map data for overlay communication
+- [ ] **ORG-06**: All unconditional `print()` replaced with `customDebugPrint()` (debug-only logging)
+- [ ] **ORG-07**: `SpeedometerScreen` extracted from monolithic `main.dart` to `screens/speedometer_screen.dart`
+- [ ] **ORG-08**: `OverlaySpeedometer` extracted to `screens/overlay_screen.dart`
+
+### State management
+
+- [ ] **STATE-01**: `SpeedometerProvider` (ChangeNotifier) manages GPS data stream subscription and speed/heading state
+- [ ] **STATE-02**: `ThemeProvider` (ChangeNotifier) manages theme index and dark/light mode
+- [ ] **STATE-03**: `OverlayProvider` (ChangeNotifier) manages overlay lifecycle and status
+- [ ] **STATE-04**: `MultiProvider` setup in `main.dart` wiring services and providers
+- [ ] **STATE-05**: All `setState()` calls in main screen replaced with Provider Consumer/Selector pattern
+- [ ] **STATE-06**: Selector widgets used for granular rebuilds (speed display does not rebuild on theme change)
+- [ ] **STATE-07**: GPS stream subscription managed by provider, not widget state
+
+### Overlay reliability
+
+- [ ] **OVRL-01**: Overlay receives continuous debounced data updates (not one-shot push + heartbeat)
+- [ ] **OVRL-02**: Overlay errors surfaced to user via snackbar/toast (no silent catch blocks)
+- [ ] **OVRL-03**: Overlay creation verified before setting `isOverlayActive` flag
+- [ ] **OVRL-04**: Messages include timestamp for staleness detection in overlay
+- [ ] **OVRL-05**: Overlay displays "--" when data is stale (no updates for >2 seconds)
+- [ ] **OVRL-06**: `OverlayService` encapsulates all `FlutterOverlayWindow` platform calls
+
+### GPS performance
+
+- [ ] **GPS-01**: GPS data updates display with zero additional lag (stream subscription, no polling intermediary)
+- [ ] **GPS-02**: Speed-adaptive precision: `LocationAccuracy.high` above ~10 km/h, `LocationAccuracy.medium` below
+- [ ] **GPS-03**: Hysteresis on precision switching: up at ~12 km/h, down at ~8 km/h (no thrashing)
+- [ ] **GPS-04**: GPS access is non-exclusive — uses Fused Location Provider, other apps access location normally
+
+### Power & lifecycle
+
+- [ ] **PWR-01**: GPS tracking stops when app backgrounded without overlay visible
+- [ ] **PWR-02**: GPS tracking continues when app backgrounded with overlay visible
+- [ ] **PWR-03**: Heartbeat timer only runs when overlay is active and app is backgrounded
+- [ ] **PWR-04**: Overlay status polling only runs when overlay is active
+- [ ] **PWR-05**: Wake lock only held when actively tracking with overlay visible
+- [ ] **PWR-06**: All timers and stream subscriptions properly canceled in dispose()
+
+### Backward compatibility
+
+- [ ] **COMPAT-01**: All existing features continue to work after restructure (speed display, gauge, theme, units, overlay, haptics)
+- [ ] **COMPAT-02**: App compiles and runs without new dependencies beyond `provider` package
+- [ ] **COMPAT-03**: No changes to Android manifest permissions or service declarations
+
+## v2 Requirements
+
+Deferred to future release. Tracked but not in current roadmap.
+
+### Testing
+
+- **TEST-01**: Unit tests for ProcessedGpsData model and speed unit conversions
+- **TEST-02**: Widget tests for extracted widgets with mocked providers
+- **TEST-03**: Integration tests for GPS → Provider → Widget data flow
+- **TEST-04**: Manual test checklist for overlay lifecycle edge cases
+
+### Persistence
+
+- **PERSIST-01**: Speed unit preference persisted via SharedPreferences
+- **PERSIST-02**: Theme preference persisted via SharedPreferences
+- **PERSIST-03**: Settings load on app startup
+
+### Error recovery
+
+- **ERR-01**: Permission re-request button when GPS shows 'NO PERM'
+- **ERR-02**: Permission re-check on app resume (handle runtime revocation)
+
+## Out of scope
+
+| Feature | Reason |
+|---------|--------|
+| New UI features | This is a restructure, not a feature release |
+| Dedicated settings screen | Inline toggles sufficient for current scope |
+| GPS interpolation between fixes | Display what hardware gives, instantly |
+| iOS testing or optimization | Android primary |
+| Riverpod migration | Provider sufficient for single-screen app complexity |
+| Dependency version upgrades | Keep current versions stable during restructure |
+| BLoC pattern | Over-engineered for this app's complexity |
+| Feature-first directory structure | Layer-first appropriate for single-screen app |
+
+## Traceability
+
+| Requirement | Phase | Status |
+|-------------|-------|--------|
+| ORG-01 | Phase 1 | Pending |
+| ORG-02 | Phase 1 | Pending |
+| ORG-03 | Phase 1 | Pending |
+| ORG-04 | Phase 1 | Pending |
+| ORG-05 | Phase 1 | Pending |
+| ORG-06 | Phase 1 | Pending |
+| ORG-07 | Phase 1 | Pending |
+| ORG-08 | Phase 1 | Pending |
+| STATE-01 | Phase 2 | Pending |
+| STATE-02 | Phase 2 | Pending |
+| STATE-03 | Phase 2 | Pending |
+| STATE-04 | Phase 2 | Pending |
+| STATE-05 | Phase 2 | Pending |
+| STATE-06 | Phase 2 | Pending |
+| STATE-07 | Phase 2 | Pending |
+| OVRL-01 | Phase 3 | Pending |
+| OVRL-02 | Phase 3 | Pending |
+| OVRL-03 | Phase 3 | Pending |
+| OVRL-04 | Phase 3 | Pending |
+| OVRL-05 | Phase 3 | Pending |
+| OVRL-06 | Phase 3 | Pending |
+| GPS-01 | Phase 4 | Pending |
+| GPS-02 | Phase 4 | Pending |
+| GPS-03 | Phase 4 | Pending |
+| GPS-04 | Phase 4 | Pending |
+| PWR-01 | Phase 4 | Pending |
+| PWR-02 | Phase 4 | Pending |
+| PWR-03 | Phase 4 | Pending |
+| PWR-04 | Phase 4 | Pending |
+| PWR-05 | Phase 4 | Pending |
+| PWR-06 | Phase 4 | Pending |
+| COMPAT-01 | All | Pending |
+| COMPAT-02 | All | Pending |
+| COMPAT-03 | All | Pending |
+
+**Coverage:**
+- v1 requirements: 30 total
+- Mapped to phases: 30
+- Unmapped: 0
+
+---
+*Requirements defined: 2026-02-09*
+*Last updated: 2026-02-09 after initial definition*