import 'dart:async';

import 'package:flutter/foundation.dart';

import '../../data/models/bluetooth_device_info.dart';
import '../../data/models/bluetooth_power_state.dart';
import '../../data/models/obd_state.dart';
import '../../data/repositories/settings_repository.dart';
import '../../data/services/telemetry_bridge.dart';
import 'obd_economy.dart';

/// Connection lifecycle and rolling economy for the optional ELM327 adapter.
///
/// Bluetooth Classic SPP only; the adapter must already be paired in Android
/// Settings. The native side queues the read-only PID requests.
class ObdController extends ChangeNotifier {
  ObdController(this._platform, this._settings, {DateTime Function()? clock})
    : _clock = clock ?? DateTime.now;

  final TelemetryPlatform _platform;
  final SettingsRepository _settings;
  final DateTime Function() _clock;
  final ObdEconomy _economy = ObdEconomy();

  String? _selectedAddress;
  List<BluetoothDeviceInfo> _devices = const [];
  bool _devicesKnown = false;
  bool _loadingDevices = false;
  String? _devicesError;
  bool _needsBluetoothPermission = false;
  BluetoothPowerState _bluetoothState = BluetoothPowerState.unknown;
  DateTime? _lastDeviceRefreshAt;
  Future<bool>? _deviceRefresh;
  Timer? _bluetoothRetryTimer;
  int _bluetoothRetryAttempts = 0;

  ObdState _state = const ObdState();
  String? _localError;
  Timer? _pollTimer;
  bool _active = false;
  bool _polling = false;
  bool _connectionFailed = false;
  bool _disposed = false;
  int? _lastEconomyTimestamp;

  String? get selectedAddress => _selectedAddress;

  List<BluetoothDeviceInfo> get devices => _devices;

  /// Paired devices that look like Bluetooth Classic OBD-II adapters.
  List<BluetoothDeviceInfo> get obdDevices =>
      List.unmodifiable(_devices.where((device) => device.isLikelyObd));

  /// Paired devices that do not advertise an OBD-II class or name.
  List<BluetoothDeviceInfo> get otherDevices =>
      List.unmodifiable(_devices.where((device) => !device.isLikelyObd));

  bool get loadingDevices => _loadingDevices;

  bool get devicesKnown => _devicesKnown;

  String? get devicesError => _devicesError;

  bool get needsBluetoothPermission => _needsBluetoothPermission;

  BluetoothPowerState get bluetoothState => _bluetoothState;

  bool get bluetoothOff => _bluetoothState.isOff;

  bool get bluetoothTransitioning => _bluetoothState.isTransitioning;

  bool get connected => _state.connected;

  bool get connecting => _state.connecting;

  bool get hasConfiguredAdapter => _selectedAddress != null;

  /// The native worker stopped retrying, or the saved device is not a likely
  /// OBD adapter. Offer an explicit retry action in either case.
  bool get canRetry =>
      _selectedAddress != null &&
      (_connectionFailed || _selectedDeviceIsUnsupported);

  String? get error {
    if (_localError != null) return _localError;
    if (_state.connected) return null;
    return _state.error;
  }

  String get statusLabel {
    if (_loadingDevices) return 'Checking paired devices…';
    if (_needsBluetoothPermission) return 'Bluetooth permission needed';
    if (_bluetoothState == BluetoothPowerState.turningOn) {
      return 'Bluetooth is starting…';
    }
    if (_bluetoothState == BluetoothPowerState.turningOff) {
      return 'Bluetooth is turning off…';
    }
    if (_bluetoothState == BluetoothPowerState.off) return 'Bluetooth is off';
    if (_bluetoothState == BluetoothPowerState.unavailable) {
      return 'Bluetooth is unavailable';
    }
    if (_bluetoothState == BluetoothPowerState.unknown) {
      return 'Bluetooth is not responding';
    }
    if (connecting) return 'Connecting…';
    if (connected) {
      return isFresh ? 'Connected' : 'Connected — waiting for data';
    }
    if (_connectionFailed) return 'Not connected — adapter not responding';
    if (error != null) return 'Not connected — $error';
    if (_selectedAddress == null) return 'Off';
    return 'Not connected';
  }

  bool get isFresh {
    if (!_state.connected || _state.updatedAt <= 0) return false;
    final age = _clock().millisecondsSinceEpoch - _state.updatedAt;
    return age >= 0 && age < 5000;
  }

  bool get hasTelemetry =>
      isFresh && (_state.speedKmh != null || _state.throttlePercent != null);

  double? get speedKmh => isFresh ? _state.speedKmh : null;

  double? get throttlePercent => isFresh ? _state.throttlePercent : null;

  double? get ambientCelsius =>
      _state.connected && isFresh ? _state.ambientCelsius : null;

  double? get economyL100 => isFresh ? _economy.litresPer100Km : null;

  void initialize() {
    _selectedAddress = _settings.obdAdapterAddress;
  }

  Future<void> start() async {
    if (_active) return;
    _active = true;

    var attempted = false;
    if (_selectedAddress != null && !_connectionFailed) {
      if (!_devicesKnown) {
        await refreshDevices(force: true);
      }
      if (!_active) {
        _notify();
        return;
      }

      final address = _selectedAddress;
      final selected = _deviceFor(address);
      if (address == null) {
        // The user selected None while the device list was loading.
      } else if (selected == null) {
        if (_devicesKnown && _bluetoothState.isOn) {
          _localError = 'Saved adapter is no longer paired.';
        } else if (!_devicesKnown) {
          _localError =
              _devicesError ?? 'Could not read paired Bluetooth devices.';
        }
      } else if (!selected.isLikelyObd) {
        _localError =
            'Saved adapter does not look like an OBD-II adapter. '
            'Use Retry connection to try it anyway.';
      } else {
        attempted = await _connect();
      }
    }

    if (!_active) {
      _notify();
      return;
    }
    if (attempted) {
      _startPolling();
    } else {
      _pollTimer?.cancel();
      _pollTimer = null;
    }
    _notify();
  }

  void stop() {
    _active = false;
    _pollTimer?.cancel();
    _pollTimer = null;
    _bluetoothRetryTimer?.cancel();
    _bluetoothRetryTimer = null;
    _bluetoothRetryAttempts = 0;
    _lastEconomyTimestamp = null;
    _economy.reset();
    _state = const ObdState();
    unawaited(_platform.disconnectObd());
    _notify();
  }

  Future<void> selectAdapter(String? address) async {
    if (_selectedAddress == address) return;
    _selectedAddress = address;
    _localError = null;
    _connectionFailed = false;
    _lastEconomyTimestamp = null;
    _economy.reset();
    _state = const ObdState();
    await _settings.setObdAdapterAddress(address);
    await _platform.disconnectObd();
    if (_active) {
      if (address == null) {
        _pollTimer?.cancel();
        _pollTimer = null;
      } else {
        final started = await _connect();
        if (started && _active) _startPolling();
      }
    }
    _notify();
  }

  /// Explicitly retries the saved adapter after the worker gave up.
  ///
  /// This bypasses the "looks like an OBD-II adapter" guard so an unusual
  /// adapter can still be used after the user deliberately selects Retry.
  Future<void> retryConnection() async {
    if (_selectedAddress == null) return;
    _connectionFailed = false;
    _localError = null;
    _lastEconomyTimestamp = null;
    _economy.reset();
    _state = const ObdState();
    _notify();
    await _platform.disconnectObd();
    if (!_active) return;
    final started = await _connect();
    if (started && _active) _startPolling();
    _notify();
  }

  /// Lists bonded devices. Pass [requestPermission] only when the user asked to
  /// find adapters; the Settings card can show a dedicated allow button.
  ///
  /// [dueToResume] performs a cheap adapter-state check but skips the bonded
  /// list when it is already cached. This keeps the app from querying the
  /// Bluetooth stack on every lifecycle resume.
  Future<bool> refreshDevices({
    bool requestPermission = false,
    bool force = false,
    bool dueToResume = false,
  }) {
    final inFlight = _deviceRefresh;
    if (inFlight != null) return inFlight;

    final future = _refreshDevices(
      requestPermission: requestPermission,
      force: force,
      dueToResume: dueToResume,
    );
    _deviceRefresh = future;
    return future.whenComplete(() {
      if (identical(_deviceRefresh, future)) _deviceRefresh = null;
    });
  }

  Future<bool> _refreshDevices({
    required bool requestPermission,
    required bool force,
    required bool dueToResume,
  }) async {
    final now = _clock();
    final last = _lastDeviceRefreshAt;
    if (!force &&
        last != null &&
        now.difference(last) < const Duration(seconds: 2)) {
      return false;
    }
    _lastDeviceRefreshAt = now;
    _loadingDevices = true;
    _devicesError = null;
    _notify();

    try {
      if (requestPermission) {
        final granted = await _platform.ensureBluetoothPermission();
        if (!granted) {
          _needsBluetoothPermission = true;
          _devicesError = 'Bluetooth permission was denied.';
          return false;
        }
      }

      final previousState = _bluetoothState;
      final state = await _platform.bluetoothState();
      _bluetoothState = state;
      if (!previousState.isOn && state.isOn) {
        // Bluetooth was turned off and on; allow one fresh connection attempt.
        _connectionFailed = false;
      }

      if (state.isOn) {
        if (dueToResume && !force && _devicesKnown) {
          _needsBluetoothPermission = false;
          return true;
        }
        final found = await _platform.listBondedDevices();
        _devices = List.unmodifiable(found);
        _devicesKnown = true;
        _needsBluetoothPermission = false;
        _bluetoothRetryAttempts = 0;
        _bluetoothRetryTimer?.cancel();
        _bluetoothRetryTimer = null;
        return true;
      }

      if (state.isTransitioning) {
        _devicesKnown = false;
        _devicesError = null;
        _needsBluetoothPermission = false;
        _scheduleBluetoothRetry();
        return false;
      }

      if (state.isOff) {
        _devices = const [];
        _devicesKnown = false;
        _devicesError = null;
        _needsBluetoothPermission = false;
        _bluetoothRetryAttempts = 0;
        _bluetoothRetryTimer?.cancel();
        _bluetoothRetryTimer = null;
        return false;
      }

      if (state == BluetoothPowerState.unavailable) {
        _devicesError = 'Bluetooth is not available on this device.';
        _needsBluetoothPermission = false;
        return false;
      }

      _devicesKnown = false;
      _devicesError = 'Bluetooth is not responding.';
      _needsBluetoothPermission = false;
      _scheduleBluetoothRetry();
      return false;
    } on TelemetryException catch (problem) {
      if (problem.code == 'turning_on') {
        _bluetoothState = BluetoothPowerState.turningOn;
        _devicesKnown = false;
        _devicesError = null;
        _needsBluetoothPermission = false;
        _scheduleBluetoothRetry();
      } else if (problem.code == 'turning_off') {
        _bluetoothState = BluetoothPowerState.turningOff;
        _devicesKnown = false;
        _devicesError = null;
        _needsBluetoothPermission = false;
        _scheduleBluetoothRetry();
      } else if (problem.code == 'disabled') {
        _bluetoothState = BluetoothPowerState.off;
        _devices = const [];
        _devicesKnown = false;
        _devicesError = null;
        _needsBluetoothPermission = false;
      } else if (problem.code == 'permission') {
        _needsBluetoothPermission = true;
        _devicesKnown = false;
        _devicesError = problem.message;
      } else if (problem.code == 'unavailable') {
        _bluetoothState = BluetoothPowerState.unavailable;
        _devicesKnown = false;
        _devicesError = problem.message;
        _needsBluetoothPermission = false;
      } else {
        _needsBluetoothPermission = problem.message.toLowerCase().contains(
          'permission',
        );
        _devicesKnown = false;
        _devicesError = problem.message;
      }
      return false;
    } finally {
      _loadingDevices = false;
      _notify();
    }
  }

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

  Future<bool> _connect() async {
    final address = _selectedAddress;
    if (address == null) return false;
    _pollTimer?.cancel();
    _pollTimer = null;
    _localError = null;
    _connectionFailed = false;
    var started = false;
    try {
      await _platform.connectObd(address);
      started = true;
    } on TelemetryException catch (problem) {
      _localError = problem.message;
      _needsBluetoothPermission = problem.code == 'permission';
      if (problem.code == 'timeout' ||
          problem.code == 'permission' ||
          problem.code == 'disabled' ||
          problem.code == 'unavailable') {
        _connectionFailed = problem.code == 'timeout';
        _pollTimer?.cancel();
        _pollTimer = null;
      }
    } catch (_) {
      _localError = 'Could not connect to the OBD adapter.';
    }
    _notify();
    return started;
  }

  void _startPolling() {
    _pollTimer?.cancel();
    _pollTimer = Timer.periodic(const Duration(seconds: 1), (_) => _poll());
  }

  Future<void> _poll() async {
    if (!_active || _polling) return;
    _polling = true;
    try {
      final next = await _platform.getObdState();
      final lostConnection = _state.connected && !next.connected;
      if (lostConnection) {
        _economy.reset();
        _lastEconomyTimestamp = null;
      }
      _state = next;
      if (next.connected) {
        _connectionFailed = false;
      }
      if (next.retryExhausted) {
        _connectionFailed = true;
        _pollTimer?.cancel();
        _pollTimer = null;
      }
      if (next.connected && next.updatedAt > 0) {
        if (_lastEconomyTimestamp != next.updatedAt) {
          _lastEconomyTimestamp = next.updatedAt;
          _economy.add(
            at: _clock(),
            speedKmh: next.speedKmh,
            mafGps: next.mafGramsPerSecond,
            throttlePercent: next.throttlePercent,
          );
        }
      }
    } catch (_) {
      // Keep the last known state; the next poll may recover.
    } finally {
      _polling = false;
      _notify();
    }
  }

  BluetoothDeviceInfo? _deviceFor(String? address) {
    if (address == null) return null;
    for (final device in _devices) {
      if (device.address == address) return device;
    }
    return null;
  }

  bool get _selectedDeviceIsUnsupported {
    final device = _deviceFor(_selectedAddress);
    return device != null && !device.isLikelyObd;
  }

  void _scheduleBluetoothRetry() {
    _bluetoothRetryTimer?.cancel();
    if (_disposed || _bluetoothRetryAttempts >= 3) return;
    _bluetoothRetryAttempts++;
    _bluetoothRetryTimer = Timer(const Duration(seconds: 2), () {
      _bluetoothRetryTimer = null;
      if (_disposed || !_active) return;
      unawaited(refreshDevices(force: true));
    });
  }

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

  @override
  void dispose() {
    _disposed = true;
    _pollTimer?.cancel();
    _bluetoothRetryTimer?.cancel();
    unawaited(_platform.disconnectObd());
    super.dispose();
  }
}