import 'dart:async';
import 'dart:developer' as developer;

import 'package:audio_session/audio_session.dart';
import 'package:flutter/foundation.dart';

/// Minimal playback contract this service needs from the audio handler
/// (Design 3.1). `PluriWaveAudioHandler` implements it; tests use a fake.
abstract class ObjetivoAudioInterrumpible {
  /// Intent-to-play flag (Designs 3.1/7.2): true while the user wants audio
  /// playing. The S7 reconnect logic reads the same flag, so an interruption
  /// pause also disarms reconnection attempts.
  bool get intencionReproducir;

  bool get estaReproduciendo;

  Future<void> pausar();

  Future<void> reanudar();

  /// Temporarily lowers ("ducks") the output volume without pausing.
  Future<void> setAtenuado(bool atenuado);
}

/// Wrapper around `package:audio_session` (S3-R1): configures the session
/// for music playback and translates interruption / becoming-noisy events
/// into pause, duck and auto-resume calls on the audio handler.
class ServicioAudioSession {
  ServicioAudioSession({
    required ObjetivoAudioInterrumpible objetivo,
    Future<AudioSession> Function()? obtenerSesion,
  }) : _objetivo = objetivo,
       _obtenerSesion = obtenerSesion ?? (() => AudioSession.instance);

  final ObjetivoAudioInterrumpible _objetivo;
  final Future<AudioSession> Function() _obtenerSesion;
  StreamSubscription<AudioInterruptionEvent>? _interrupcionesSub;
  StreamSubscription<void>? _ruidoSub;

  /// True when WE paused because of an interruption; only then does an
  /// interruption end with shouldResume restart playback.
  bool _pausadoPorInterrupcion = false;

  Future<void> configurar() async {
    try {
      final sesion = await _obtenerSesion();
      await sesion.configure(
        const AudioSessionConfiguration.music().copyWith(
          androidWillPauseWhenDucked: true,
        ),
      );
      await _interrupcionesSub?.cancel();
      await _ruidoSub?.cancel();
      _interrupcionesSub = sesion.interruptionEventStream.listen(
        (evento) => unawaited(manejarInterrupcion(evento)),
      );
      _ruidoSub = sesion.becomingNoisyEventStream.listen(
        (_) => unawaited(manejarDesconexionSalida()),
      );
    } catch (e) {
      developer.log(
        '[PluriWave] No se pudo configurar la sesion de audio: $e',
        name: 'ServicioAudioSession',
        level: 900,
      );
    }
  }

  @visibleForTesting
  Future<void> manejarInterrupcion(AudioInterruptionEvent evento) async {
    if (evento.begin) {
      switch (evento.type) {
        case AudioInterruptionType.duck:
          await _objetivo.setAtenuado(true);
        case AudioInterruptionType.pause:
        case AudioInterruptionType.unknown:
          if (_objetivo.estaReproduciendo || _objetivo.intencionReproducir) {
            _pausadoPorInterrupcion = true;
            await _objetivo.pausar();
          }
      }
      return;
    }
    switch (evento.type) {
      case AudioInterruptionType.duck:
        await _objetivo.setAtenuado(false);
      case AudioInterruptionType.pause:
        // Transient loss ended and the OS says we may resume.
        if (_pausadoPorInterrupcion) {
          _pausadoPorInterrupcion = false;
          await _objetivo.reanudar();
        }
      case AudioInterruptionType.unknown:
        // Permanent focus loss: never auto-resume.
        _pausadoPorInterrupcion = false;
    }
  }

  @visibleForTesting
  Future<void> manejarDesconexionSalida() async {
    // Headphones unplugged: hard pause, never auto-resume afterwards.
    _pausadoPorInterrupcion = false;
    if (_objetivo.estaReproduciendo) {
      await _objetivo.pausar();
    }
  }

  Future<void> dispose() async {
    await _interrupcionesSub?.cancel();
    await _ruidoSub?.cancel();
  }
}