import 'dart:async';

import 'package:flutter/material.dart';

import '../tema/pluriwave_tokens.dart';

/// Timeout applied to the `AudioService.init` MediaBrowser handshake (Design
/// "Timeout without re-init"): the `audio_service` plugin's self-bind has no
/// native timeout and an unhandled `onConnectionSuspended` case, so under
/// bind contention (Android Auto cold start) the handshake can hang forever.
/// Top-level const so tests can reference the production value without
/// duplicating it.
///
/// This doc called the plugin "vendored". It is not: `pubspec.lock` pins the
/// hosted pub.dev `audio_service` 0.18.18 and `pubspec.yaml` declares no
/// `dependency_overrides`. Anyone reading the sentence above would go looking
/// for a local copy to patch, and there is none — the behaviour described is
/// upstream's, so the workaround has to live here.
const timeoutArranqueAudio = Duration(seconds: 8);

/// Outcome of racing an `AudioService.init` future against
/// [timeoutArranqueAudio] (Design "Timeout without re-init"). Sealed so
/// callers exhaustively handle both branches.
sealed class ResultadoArranqueAudio<T> {
  const ResultadoArranqueAudio();
}

/// The handler future completed within the timeout — normal startup path.
class ArranqueAudioListo<T> extends ResultadoArranqueAudio<T> {
  const ArranqueAudioListo(this.handler);

  final T handler;
}

/// The handler future did NOT complete within the timeout. [handlerFuturo]
/// is the SAME original future passed to [esperarArranqueAudio] — the
/// caller must keep awaiting it (e.g. via [ArranqueAudioApp]), never start a
/// second `AudioService.init` call (Design "init must never be called
/// twice").
class ArranqueAudioPendiente<T> extends ResultadoArranqueAudio<T> {
  const ArranqueAudioPendiente(this.handlerFuturo);

  final Future<T> handlerFuturo;
}

/// Races the already-started [handlerFuturo] — a single `AudioService.init`
/// call — against [timeout] (Design "Timeout without re-init"). Returns
/// [ArranqueAudioListo] when [handlerFuturo] resolves in time, otherwise
/// [ArranqueAudioPendiente] wrapping the SAME [handlerFuturo] so it can keep
/// being awaited without ever re-invoking `AudioService.init`.
///
/// [handlerFuturo] and [timeout] are both injected — this function never
/// touches the real `audio_service` plugin, so it is testable with a plain
/// [Future] and short durations.
Future<ResultadoArranqueAudio<T>> esperarArranqueAudio<T>(
  Future<T> handlerFuturo, {
  Duration timeout = timeoutArranqueAudio,
}) async {
  try {
    final handler = await handlerFuturo.timeout(timeout);
    return ArranqueAudioListo<T>(handler);
  } on TimeoutException {
    return ArranqueAudioPendiente<T>(handlerFuturo);
  }
}

/// Subscribes to [errores] — in production `AudioService.asyncError` — and
/// hands every event to [registrar]. Returns the [StreamSubscription] so the
/// caller can cancel it when the handler is torn down.
///
/// Why this exists: `audio_service` funnels EVERY asynchronous failure of its
/// own observers into that stream and nothing else
/// (`_observePlaybackState`/`_observeMediaItem`/`_observeQueue` each wrap
/// their whole body in `catch (e) { _asyncError.add(e); }`, and the artwork
/// path uses `.catchError(_asyncError.add)`), yet this app had ZERO
/// subscribers on it. A `PublishSubject` with no listeners simply drops
/// events, so the platform-side exception behind "the media notification
/// disappeared" — a rejected `setState`, a failed `setMediaItem`, an
/// Android 12+ `ForegroundServiceStartNotAllowedException` surfacing through
/// the plugin — was being discarded without a single log line. This makes
/// that channel audible.
///
/// [errores] and [registrar] are both injected — this function never touches
/// the real `audio_service` plugin, so it is testable with a plain
/// [StreamController] (same seam convention as [esperarArranqueAudio] above,
/// and as `decidirAvanceCola`/`debeReaplicarEcualizador` elsewhere).
StreamSubscription<Object> observarErroresAudio(
  Stream<Object> errores, {
  required void Function(Object error) registrar,
}) {
  return errores.listen(
    registrar,
    // The plugin only ever feeds this subject through `add`, never
    // `addError`, so this branch is purely defensive: a stream-level error
    // would otherwise escape as an unhandled zone error, which is strictly
    // worse than one more log line.
    onError: (Object error, StackTrace _) => registrar(error),
    cancelOnError: false,
  );
}

/// Default [observarErroresAudio] logger: one line per swallowed plugin
/// exception.
///
/// Uses [debugPrint], NOT `dart:developer`'s `log`. That distinction is the
/// whole reason this channel existed for weeks without ever producing a
/// single line of evidence: `log()` writes to the VM service, which a
/// RELEASE build does not have, so every exception this was built to catch
/// was still being thrown away — just one layer further down than before.
/// `debugPrint` reaches logcat in release, which is the only build that ever
/// runs in the car.
void registrarErrorAudioService(Object error) {
  debugPrint('[PluriWave][ArranqueAudio] AudioService.asyncError: $error');
}

/// Minimal branded bootstrap widget for the degraded path (Design "still
/// call runApp, but with a minimal bootstrap widget that keeps waiting on
/// the SAME original future"). Shows [_CargandoArranqueAudio] while
/// [handlerFuturo] is pending; once it settles, swaps to [construirApp]'s
/// result. On success, [alListo] is called exactly once (handler wiring:
/// `registrarHandler` + `ServicioAudioSession`) before the swap. On an
/// error, [alListo] is never called — the app shell still renders (an
/// infinite spinner is strictly worse) and the error is reported via
/// `FlutterError.reportError` instead of becoming an unhandled exception.
class ArranqueAudioApp<T> extends StatefulWidget {
  const ArranqueAudioApp({
    super.key,
    required this.handlerFuturo,
    required this.alListo,
    required this.construirApp,
  });

  /// The SAME future returned by the original `AudioService.init` call —
  /// never a new one.
  final Future<T> handlerFuturo;

  /// Handler-wiring callback (Design "same handler wiring" as the
  /// on-time path). Invoked exactly once, when [handlerFuturo] resolves.
  final void Function(T handler) alListo;

  /// Builds the real app widget once [handlerFuturo] has settled — with the
  /// resolved handler on success, or `null` if [handlerFuturo] completed
  /// with an error (Design "error path": an infinite spinner is strictly
  /// worse than an app shell without the handler wired).
  final Widget Function(T? handler) construirApp;

  @override
  State<ArranqueAudioApp<T>> createState() => _ArranqueAudioAppState<T>();
}

class _ArranqueAudioAppState<T> extends State<ArranqueAudioApp<T>> {
  @override
  void initState() {
    super.initState();
    // Attached once in initState (not in build) so alListo runs exactly
    // once regardless of how many times FutureBuilder rebuilds below.
    unawaited(
      widget.handlerFuturo.then(
        widget.alListo,
        // Design "error path": a post-timeout handler failure must never
        // become an unhandled async exception. alListo is deliberately NOT
        // called here — it only wires a real handler; build() below still
        // swaps away from the spinner via `connectionState == done`
        // regardless of hasError, so the app shell renders either way.
        onError: (Object error, StackTrace stackTrace) {
          FlutterError.reportError(
            FlutterErrorDetails(
              exception: error,
              stack: stackTrace,
              library: 'arranque_audio',
              context: ErrorDescription(
                'esperando handlerFuturo tras el timeout de arranque de audio',
              ),
            ),
          );
        },
      ),
    );
  }

  @override
  Widget build(BuildContext context) {
    return FutureBuilder<T>(
      future: widget.handlerFuturo,
      builder: (context, snapshot) {
        // `done` covers BOTH hasData and hasError — an errored handshake
        // still swaps to the app shell instead of spinning forever (Design
        // "error path").
        if (snapshot.connectionState == ConnectionState.done) {
          return widget.construirApp(snapshot.data);
        }
        return const _CargandoArranqueAudio();
      },
    );
  }
}

/// Standalone loading screen shown while [ArranqueAudioApp] waits (Design
/// "minimal branded loading view"): centered `CircularProgressIndicator`,
/// no text — `AppLocalizations` is not available at this point in startup.
/// Self-contained (its own `MaterialApp`) since this can be the direct
/// `runApp()` root.
class _CargandoArranqueAudio extends StatelessWidget {
  const _CargandoArranqueAudio();

  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      debugShowCheckedModeBanner: false,
      home: Scaffold(
        backgroundColor: PluriWaveTokens.dark.deepViolet,
        body: const Center(
          child: CircularProgressIndicator(color: PluriWaveTokens.brand),
        ),
      ),
    );
  }
}