import 'dart:async';

import 'package:flutter/foundation.dart';

import '../../data/models/jellyfin_library.dart';
import '../../data/models/jellyfin_models.dart';
import '../../data/models/jellyfin_playback.dart';
import '../../data/models/media_playback.dart';
import '../../data/services/jellyfin_library_service.dart';
import '../../data/services/jellyfin_playback_platform.dart';
import '../settings/jellyfin_controller.dart';

/// Owns one Jellyfin album queue and polls the native Media3 state. The native
/// service is independent of this object, so playback continues while the app
/// is backgrounded; [restore] reconnects the UI after an activity restart.
class JellyfinPlaybackController extends ChangeNotifier {
  JellyfinPlaybackController(
    this._platform,
    this._library,
    this._jellyfin, {
    this.pollInterval = const Duration(milliseconds: 700),
  }) {
    _jellyfin.addListener(_onJellyfinChanged);
  }

  final JellyfinPlaybackPlatform _platform;
  final JellyfinLibraryService _library;
  final JellyfinController _jellyfin;
  final Duration pollInterval;

  JellyfinPlaybackQueue? _queue;
  JellyfinAlbum? _album;
  JellyfinPlaybackSnapshot _snapshot = JellyfinPlaybackSnapshot.empty;
  bool _loading = false;
  bool _polling = false;
  bool _disposed = false;
  String? _error;
  int? _pendingIndex;
  int _generation = 0;
  Timer? _timer;

  bool get isActive => _queue != null || _snapshot.available;

  bool get hasQueue => _queue != null;

  bool get loading => _loading;

  bool get playing => _snapshot.playing;

  bool get buffering => _snapshot.buffering;

  bool isCurrentAlbum(JellyfinAlbum album) => _album?.id == album.id;

  JellyfinAlbum? get currentAlbum => _album;

  JellyfinPlaybackSnapshot get snapshot => _snapshot;

  String? get error => _error;

  List<JellyfinQueueItem> get queueItems =>
      _queue?.items ?? const <JellyfinQueueItem>[];

  JellyfinQueueItem? get currentItem {
    final queue = _queue;
    if (queue == null) return null;
    final index = _snapshot.index;
    if (index < 0 || index >= queue.items.length) return null;
    return queue.items[index];
  }

  String? get nowPlayingAlbum =>
      currentItem?.album ?? _snapshot.album ?? _album?.name;

  String? get nowPlayingArtist =>
      currentItem?.artist ?? _snapshot.artist ?? _album?.artist;

  MediaPlayback get mediaPlayback {
    if (!_snapshot.available) return const MediaPlayback();
    return _snapshot.toMediaPlayback(
      fallbackDurationMs: currentItem?.durationMs ?? 0,
    );
  }

  bool get canGoNext => _snapshot.hasNext;

  bool get canGoPrevious => _snapshot.hasPrevious;

  /// Starts an album. The same album is not restarted unless it has ended or
  /// [restart] is true. Returns an error message for the caller, or null.
  Future<String?> playAlbum(JellyfinAlbum album, {bool restart = false}) async {
    if (_disposed) return null;
    if (!_jellyfin.configured) return 'Pair Jellyfin first.';

    final sameAlbum =
        _album?.id == album.id && (_queue != null || _snapshot.available);
    if (sameAlbum && !restart) {
      if (_snapshot.ended) {
        await _platform.seekToIndex(0);
        await _platform.play();
      }
      _startPolling();
      await _poll();
      return null;
    }

    final generation = ++_generation;
    _loading = true;
    _error = null;
    _pendingIndex = null;
    _notify();

    try {
      final queue = await _library.buildQueue(album);
      if (_disposed || generation != _generation) return null;
      if (queue == null || queue.items.isEmpty) {
        throw JellyfinException('No playable tracks in this album.');
      }
      final started = await _platform.setQueue(queue);
      if (_disposed || generation != _generation) return null;
      if (!started) {
        throw JellyfinException('Could not start playback.');
      }
      _queue = queue;
      _album = album;
      _snapshot = await _platform.getState();
      _loading = false;
      _startPolling();
      final pending = _pendingIndex;
      _pendingIndex = null;
      if (pending != null) {
        await playTrackAt(pending);
      }
      _notify();
      return null;
    } on JellyfinException catch (exception) {
      if (_disposed || generation != _generation) return null;
      _loading = false;
      _error = exception.message;
      _notify();
      return exception.message;
    } catch (_) {
      if (_disposed || generation != _generation) return null;
      _loading = false;
      _error = 'Could not play this album.';
      _notify();
      return _error;
    }
  }

  Future<void> toggle() async {
    if (!_snapshot.available && _queue == null) return;
    if (_snapshot.playing) {
      await _platform.pause();
      _snapshot = _snapshot.copyWith(playing: false);
      _notify();
    } else {
      if (_snapshot.ended) {
        await _platform.seekToIndex(0);
      }
      await _platform.play();
      _snapshot = _snapshot.copyWith(playing: true);
      _notify();
    }
    _startPolling();
    await _poll();
  }

  Future<void> next() async {
    if (!_snapshot.hasNext) return;
    await _platform.next();
    await _poll();
  }

  Future<void> previous() async {
    if (!_snapshot.hasPrevious) return;
    await _platform.previous();
    await _poll();
  }

  /// Selects an album track. If the queue is still being built, the index is
  /// applied as soon as it is ready.
  Future<void> playTrackAt(int index) async {
    if (_queue == null) {
      _pendingIndex = index;
      return;
    }
    if (index < 0 || index >= _queue!.items.length) return;
    final selected = await _platform.seekToIndex(index);
    if (!selected) {
      _error = 'Could not play that track.';
      _notify();
      return;
    }
    await _platform.play();
    _startPolling();
    await _poll();
  }

  Future<void> seek(Duration position) async {
    if (!_snapshot.available) return;
    await _platform.seek(position);
    await _poll();
  }

  Future<bool> notificationPermissionGranted() {
    return _platform.notificationPermissionGranted();
  }

  Future<bool> requestNotificationPermission() {
    return _platform.requestNotificationPermission();
  }

  Future<void> stop() async {
    _generation++;
    await _platform.stop();
    _queue = null;
    _album = null;
    _snapshot = JellyfinPlaybackSnapshot.empty;
    _loading = false;
    _error = null;
    _pendingIndex = null;
    _stopPolling();
    _notify();
  }

  /// Reconnects to a service that was already playing when the activity was
  /// recreated. The queue itself is not persisted; the snapshot still drives
  /// the Home media card.
  Future<void> restore() async {
    if (_disposed) return;
    final snapshot = await _platform.getState();
    if (_disposed || !snapshot.available) return;
    _snapshot = snapshot;
    _startPolling();
    _notify();
  }

  void onAppPaused() {
    _stopPolling();
  }

  void onAppResumed() {
    if (!isActive) return;
    _startPolling();
    unawaited(_poll());
  }

  Future<void> _poll() async {
    if (_disposed || _polling) return;
    _polling = true;
    try {
      final next = await _platform.getState();
      if (_disposed) return;
      final changed = next != _snapshot;
      _snapshot = next;
      final nextError = next.error;
      if (nextError != null && nextError != _error) {
        _error = nextError;
      }
      if (changed) _notify();
    } catch (_) {
      // Keep the last known state; the next poll retries.
    } finally {
      _polling = false;
    }
  }

  void _startPolling() {
    if (_disposed || _timer != null) return;
    _timer = Timer.periodic(pollInterval, (_) => unawaited(_poll()));
  }

  void _stopPolling() {
    _timer?.cancel();
    _timer = null;
  }

  void _onJellyfinChanged() {
    if (!_jellyfin.configured && (_queue != null || _snapshot.available)) {
      unawaited(stop());
    }
  }

  void _notify() {
    if (!_disposed) notifyListeners();
  }

  @override
  void dispose() {
    _disposed = true;
    _jellyfin.removeListener(_onJellyfinChanged);
    _stopPolling();
    _platform.dispose();
    super.dispose();
  }
}