# Design: Freemium unlock via one-time in-app purchase

## Technical Approach

One cross-cutting `EstadoEntitlement` notifier (idiomatic `EstadoIdioma` shape) plus a top-level prefs-lazy reader for headless callers. Gating is hybrid: UI CTAs open the paywall, state-layer choke points hold the authoritative check. Ads are a port + AdMob adapter; the banner is a layout sibling (never an overlay), the interstitial fires on a CTA's natural transition behind a frequency cap.

## Architecture Decisions

### ADR-1: Entitlement is a notifier plus a free function, not a singleton

**Choice**: `lib/estado/estado_entitlement.dart` exports `EstadoEntitlement extends ChangeNotifier` (optional injected `SharedPreferences`, key `compra_premium_v1`, `bool get esPremium`) **and** a top-level `Future<bool> esPremiumPersistido({SharedPreferences? prefs})` that reads the same key directly.
**Alternatives**: global singleton; passing the notifier into `PluriWaveAudioHandler`.
**Rationale**: `PluriWaveAudioHandler` registers before `runApp`, so no `BuildContext`/`Provider` exists. The free function mirrors `FuenteMusicaLocalAutoImpl._resolverPrefs()` (`musica_local_auto.dart:163`) — same convention, testable via `setMockInitialValues`, no lifecycle to leak.

### ADR-2: Purchase I/O behind a port

**Choice**: `PuertoCompras` abstraction (`comprar`, `restaurar`, `Stream<EventoCompra>`) with `ServicioComprasPlayBilling` as the only `in_app_purchase` call site; `EstadoEntitlement` takes `PuertoCompras?`.
**Alternatives**: calling `InAppPurchase.instance` from the notifier.
**Rationale**: matches `EstadoAlarmas(android: PuertoAlarmasAndroid)`; keeps Strict TDD viable with zero plugin channels in unit tests.
**Fail-open**: only `purchased`/`restored` writes `true`. Errors, timeouts and offline never write `false`; the persisted flag is the source of truth at cold start.

### ADR-3: Gate placement (4 gates)

| Gate | Authoritative check | UI paywall entry |
|---|---|---|
| Alarm cap > 5 | `EstadoAlarmas.guardarAlarma` (`estado_alarmas.dart:104`) | `_EditorAlarmaSheet` save + the add CTA in `pantalla_alarmas.dart` |
| Alarm vacations | `EstadoAlarmas.crearRangoVacaciones` (`:510`) | `pantalla_vacaciones.dart` — `vacation-add-header` + `_CtaAnadirRango` |
| Recording | `EstadoGrabacion.iniciar` (`estado_grabacion.dart:90`) | 3 call sites in `pantalla_reproductor.dart` |
| Android Auto | `getChildren` / `playFromMediaId` / `playFromSearch` / `skipToNext-Previous` in `servicio_audio.dart` | none (car never shows a purchase flow) |

The phone equalizer is **not** gated.

### ADR-4: Auto reduced mode = real root labels, locked children, locked switching

**Choice**: `ConstructorArbolAuto.raiz({required bool incluirMusicaLocal, required bool premium})` keeps the same visible folder labels for free users; `getChildren` resolves entitlement once via `esPremiumPersistido()` and, when free, returns exactly `[itemPremiumBloqueado()]` (non-playable, id `premium:info`, hardcoded Spanish label like every other car label) for **any** non-root `parentMediaId`. Station switching is additionally blocked at `playFromMediaId`, `playFromSearch`, `skipToNext`/`skipToPrevious` (no-op returns).
**Alternatives**: empty root; omitting the folders entirely.
**Rationale**: head units cache browse trees, so a stale `emisora:<uuid>` tap would bypass `getChildren` — the play-path gates are mandatory, not belt-and-braces. Keeping labels + one explicit locked item guarantees no blank list. Play/pause/stop of the already-playing station are untouched.

### ADR-5: Distinct alarm-limit signal

**Choice**: `guardarAlarma` returns `ResultadoGuardarAlarma { guardada, limiteAlcanzado }`; `_error` stays reserved for native scheduling failures. Pure query `bool puedeCrearAlarma` (count = `_alarmas.length`, enabled or not; edits of an existing id always pass).
**Rationale**: overloading `_error` would surface a limit as a scheduling failure in `app.dart`'s snackbar path. Grandfathering falls out for free — nothing is deleted, only new creation past 5 is refused.

### ADR-6: Banner reserves layout; interstitial is cap-checked first

**Choice**: In `_PaginaPrincipalState.build`, `body:` becomes `Column[ SafeArea(bottom:false, child: BannerAnuncioSuperior), Expanded(existing SafeArea+AnimatedSwitcher) ]`. Premium or unloaded ⇒ `SizedBox.shrink()` (zero layout impact). Never a `Stack`/overlay.
**Interstitial ordering (add-alarm)**: `puedeCrearAlarma` → if false, show the limit message and **no ad**; if true, maybe-interstitial, then open the editor. Add-station: interstitial on the CTA tap, before `FormularioEmisoraPersonalizada` opens.
**Frequency cap**: in-memory in `ServicioAnuncios` — max 2 interstitials per process lifetime and ≥3 min apart; over cap ⇒ silent no-op.
**Rationale**: an ad followed by "you can't create this" is both hostile and an AdMob disruptive-ad policy risk.

## Data Flow

    Play Billing ──→ PuertoCompras ──→ EstadoEntitlement ──→ prefs(compra_premium_v1)
                                             │                        │
                          UI (Provider.watch)┘                        │
                                                                      ▼
    PluriWaveAudioHandler.getChildren ──→ esPremiumPersistido() ──────┘   (no Provider)

## File Changes

| File | Action | Description |
|---|---|---|
| `lib/estado/estado_entitlement.dart` | Create | Notifier + `esPremiumPersistido()` |
| `lib/servicios/servicio_compras.dart` | Create | `PuertoCompras` + Play Billing adapter |
| `lib/servicios/servicio_anuncios.dart` | Create | Banner/interstitial port + AdMob adapter + frequency cap |
| `lib/widgets/banner_anuncio_superior.dart` | Create | Entitlement-aware banner slot |
| `lib/widgets/hoja_premium.dart` | Create | Paywall sheet, reused by every gate |
| `lib/app.dart` | Modify | Provider registration + banner Column |
| `lib/estado/estado_alarmas.dart` | Modify | `puedeCrearAlarma`, `ResultadoGuardarAlarma`, vacation gate |
| `lib/estado/estado_grabacion.dart` | Modify | Recording gate in `iniciar` |
| `lib/servicios/navegacion_auto.dart` | Modify | `raiz(premium:)`, `itemPremiumBloqueado()` |
| `lib/servicios/servicio_audio.dart` | Modify | Entitlement gate in browse + play paths |
| `lib/pantallas/pantalla_ajustes.dart` | Modify | Purchase + restore rows |
| `lib/pantallas/pantalla_alarmas.dart`, `pantalla_vacaciones.dart`, `pantalla_reproductor.dart`, `pantalla_favoritos.dart`, `ajustes/pantalla_ajustes_emisoras_personalizadas.dart` | Modify | Contextual upsell / interstitial trigger |
| `pubspec.yaml` | Modify | Activate `in_app_purchase`, `google_mobile_ads` |
| `lib/l10n/app_*.arb` | Modify | Paywall, limit message, restore strings |

## Interfaces / Contracts

```dart
class EstadoEntitlement extends ChangeNotifier {
  EstadoEntitlement({SharedPreferences? prefs, PuertoCompras? compras});
  static const idProducto = 'pluriwave_premium';
  bool get esPremium;
  bool get compraEnCurso;
  Future<void> comprar();
  Future<void> restaurar();
}
Future<bool> esPremiumPersistido({SharedPreferences? prefs});
enum ResultadoGuardarAlarma { guardada, limiteAlcanzado }
```

## Testing Strategy

| Layer | What to Test | Approach |
|---|---|---|
| Unit | Entitlement persistence, fail-open on error, restore | Fake `PuertoCompras` + `setMockInitialValues` |
| Unit | `puedeCrearAlarma` at 4/5/6, edit-at-cap, vacations, recording | `EstadoAlarmas(prefs:)`/`EstadoGrabacion` directly |
| Unit | `raiz(premium:false)`, locked-child for every parent id, play-path no-ops | Pure `ConstructorArbolAuto` + handler fakes |
| Unit | Interstitial cap (2/session, 3 min) and cap-before-ad ordering | Fake clock in `ServicioAnuncios` |
| Widget | Banner absent when premium; no overlap on all 5 tabs | `pumpWidget(PluriWaveApp(prefs:))` + golden-free layout asserts |
| Widget | Limit message with secondary unlock action, paywall from each gate | Existing `pantalla_*_test.dart` conventions |

## Threat Matrix

N/A — no routing, shell, subprocess, VCS/PR automation, executable-file classification, or process-integration boundary. Android Auto media-id dispatch is pre-existing in-process routing, not shell/process execution.

## Migration / Rollout

No migration. Additive and prefs-backed; absent key = free. Revert by re-commenting both plugins and reverting the gate commits. Versioned key (`compra_premium_v1`) is ignored by older builds.

## Open Questions

- [ ] Price point (Play Console decision).
- [ ] AdMob ad unit IDs (banner + interstitial) not yet provisioned; test IDs until then.
- [x] ~~Should a cached head-unit tree be actively invalidated (`notifyChildrenChanged`) at purchase time, or is the next browse refresh enough?~~ **RESOLVED (orchestrator): actively invalidate.** On the entitlement transition to premium, call `notifyChildrenChanged` for the affected parent ids. Rationale: the same head-unit caching that forces the `playFromMediaId` guard in ADR-4 also means a purchaser would otherwise keep seeing the locked tree until the unit re-binds — plausibly the rest of the drive. A user who just paid and still sees "Premium feature" in the car reads that as a broken purchase, which is a refund and a one-star review. Relying on the next browse refresh trades a cheap, bounded call for a highly visible failure. The invalidation is one-directional and only fires on the free → premium transition; there is no premium → free transition to handle (the purchase is permanent and entitlement never writes `false`, per ADR-2).