import 'dart:async';
import 'dart:typed_data';

import 'package:flutter_bluetooth_serial/flutter_bluetooth_serial.dart';
import 'package:flutter_riverpod/flutter_riverpod.dart';

import '../bluetooth/bt_poller.dart';
import '../bluetooth/bt_service.dart';
import 'settings_provider.dart';

// ─── Connection status enum ──────────────────────────────────────────────────

enum BtStatus { disconnected, connecting, connected, error }

// ─── State ───────────────────────────────────────────────────────────────────

class BtState {
  final BtStatus status;
  final String? deviceName;
  final String? error;
  final int frameCount;
  final int droppedFrames;

  const BtState({
    required this.status,
    this.deviceName,
    this.error,
    this.frameCount = 0,
    this.droppedFrames = 0,
  });

  const BtState.disconnected()
      : this(status: BtStatus.disconnected);

  BtState connecting(String name) =>
      BtState(status: BtStatus.connecting, deviceName: name);

  BtState connected(String name) =>
      BtState(status: BtStatus.connected, deviceName: name);

  BtState withError(String msg) =>
      BtState(status: BtStatus.error, deviceName: deviceName, error: msg);

  BtState withFrameStats(int frames, int dropped) => BtState(
        status: status,
        deviceName: deviceName,
        frameCount: frames,
        droppedFrames: dropped,
      );

  bool get isConnected => status == BtStatus.connected;
  bool get isConnecting => status == BtStatus.connecting;
}

// ─── Notifier ────────────────────────────────────────────────────────────────

class BtNotifier extends StateNotifier<BtState> {
  final Ref _ref;
  BtPoller? _poller;
  StreamSubscription<Uint8List>? _pollSub;
  final StreamController<Uint8List> _frameController =
      StreamController<Uint8List>.broadcast();

  BtNotifier(this._ref) : super(const BtState.disconnected());

  /// Raw validated 128-byte frame stream — consumed by sensorStateProvider.
  Stream<Uint8List> get frameStream => _frameController.stream;

  Future<void> connect(BluetoothDevice device) async {
    state = state.connecting(device.name ?? device.address);
    final service = _ref.read(btServiceProvider);
    final settings = _ref.read(settingsProvider);

    try {
      await service.connect(device);

      _poller = BtPoller(
        service,
        ecuType: settings.ecuType,
        pollingInterval: settings.pollingInterval,
      );

      _pollSub = _poller!.frameStream.listen(
        (frame) {
          _frameController.add(frame);
          state = state.withFrameStats(
              _poller!.validFrames, _poller!.droppedFrames);
        },
        onError: (Object e) {
          _frameController.addError(e);
          state = state.withError(e.toString());
        },
        onDone: () => state = state.withError('BT stream closed'),
      );

      _poller!.start();
      state = state.connected(device.name ?? device.address);
    } catch (e) {
      await service.disconnect();
      state = state.withError(e.toString());
    }
  }

  Future<void> disconnect() async {
    await _pollSub?.cancel();
    _poller?.stop();
    _poller?.dispose();
    _poller = null;
    await _ref.read(btServiceProvider).disconnect();
    state = const BtState.disconnected();
  }

  @override
  void dispose() {
    _pollSub?.cancel();
    _poller?.dispose();
    _frameController.close();
    super.dispose();
  }
}

// ─── Providers ───────────────────────────────────────────────────────────────

/// Singleton BtService — lives as long as the app.
final btServiceProvider = Provider<BtService>((ref) {
  final service = BtService();
  ref.onDispose(service.dispose);
  return service;
});

/// BT connection state notifier.
final btProvider =
    StateNotifierProvider<BtNotifier, BtState>((ref) => BtNotifier(ref));

/// Paired BT devices list (re-fetchable via ref.refresh).
final pairedDevicesProvider = FutureProvider<List<BluetoothDevice>>((ref) {
  return FlutterBluetoothSerial.instance.getBondedDevices();
});