import 'dart:async';

import 'package:flutter/foundation.dart';
import 'package:ota_update/ota_update.dart';
import 'package:sentry_flutter/sentry_flutter.dart';

import '../utils/app_config.dart';
import '../utils/app_update_util.dart';

enum OtaPhase { downloading, installing, done, error }

class UpdateProgressViewModel extends ChangeNotifier {
  final UpdateInfo update;
  final bool simulate;
  final bool simulateError;

  OtaPhase _phase = OtaPhase.downloading;
  double _progress = 0;
  String _statusText = 'Preparing download…';
  String? _errorMessage;
  bool _done = false;

  StreamSubscription? _subscription;
  Timer? _simTimer;

  OtaPhase get phase => _phase;
  double get progress => _progress;
  String get statusText => _statusText;
  String? get errorMessage => _errorMessage;

  UpdateProgressViewModel({
    required this.update,
    this.simulate = false,
    this.simulateError = false,
  });

  Future<void> start() async {
    if (simulate) {
      _runSimulation();
      return;
    }

    final url = update.download.startsWith('http')
        ? update.download
        : '$kUpdateServerUrl${update.download}';

    debugPrint('UpdateProgressViewModel: starting download from $url');

    _subscription = OtaUpdate()
        .execute(
          url,
          destinationFilename: 'update.apk',
          sha256checksum: update.sha256,
        )
        .listen(
          _onEvent,
          onError: _onError,
          onDone: _onDone,
        );
  }

  void _runSimulation() {
    debugPrint('UpdateProgressViewModel: running simulated download');

    int step = 0;
    const totalSteps = 20;
    const stepDuration = Duration(milliseconds: 500);

    _simTimer = Timer.periodic(stepDuration, (timer) {
      step++;

      if (simulateError && step == 10) {
        timer.cancel();
        _phase = OtaPhase.error;
        _errorMessage = 'Simulated download error (network timeout)';
        _statusText = 'Download failed';
        notifyListeners();
        return;
      }

      if (step < totalSteps) {
        _progress = step / totalSteps;
        _statusText = 'Downloading ${(_progress * 100).toStringAsFixed(0)}%';
        _phase = OtaPhase.downloading;
        notifyListeners();
      } else {
        timer.cancel();
        _startInstallPhase();
      }
    });
  }

  void _startInstallPhase() {
    _phase = OtaPhase.installing;
    _progress = 1.0;
    _statusText = 'Installing update…';
    notifyListeners();

    _simTimer = Timer(const Duration(seconds: 3), () {
      _phase = OtaPhase.done;
      _progress = 1.0;
      _statusText = 'Update installed! Restarting…';
      notifyListeners();
    });
  }

  void _onDone() {
    if (_done) return;
    _done = true;
    _phase = OtaPhase.done;
    _progress = 1.0;
    _statusText = 'Update installed! Restarting…';
    notifyListeners();
  }

  void _onEvent(OtaEvent event) {
    switch (event.status) {
      case OtaStatus.DOWNLOADING:
        final raw = double.tryParse(event.value ?? '0') ?? 0;
        _progress = (raw / 100).clamp(0.0, 1.0);
        _statusText = 'Downloading ${_progress.toStringAsFixed(0)}%';
        _phase = OtaPhase.downloading;
        notifyListeners();

      case OtaStatus.INSTALLING:
        _phase = OtaPhase.installing;
        _progress = 1.0;
        _statusText = 'Installing update…';
        notifyListeners();

      case OtaStatus.INSTALLATION_DONE:
        _onDone();
        return;

      case OtaStatus.DOWNLOAD_ERROR:
        _phase = OtaPhase.error;
        _errorMessage = 'Download failed: ${event.value}';
        _statusText = 'Download failed';
        Sentry.captureMessage('OTA download error: ${event.value}');
        notifyListeners();

      case OtaStatus.INSTALLATION_ERROR:
        _phase = OtaPhase.error;
        _errorMessage = 'Installation failed: ${event.value}';
        _statusText = 'Installation failed';
        Sentry.captureMessage('OTA installation error: ${event.value}');
        notifyListeners();

      case OtaStatus.ALREADY_RUNNING_ERROR:
        _phase = OtaPhase.error;
        _errorMessage = 'Update already in progress';
        _statusText = 'Update already running';
        notifyListeners();

      default:
        break;
    }
  }

  void _onError(Object error, StackTrace stack) {
    debugPrint('UpdateProgressViewModel: stream error: $error');
    _phase = OtaPhase.error;
    _errorMessage = error.toString();
    _statusText = 'Update failed';
    Sentry.captureException(error, stackTrace: stack);
    notifyListeners();
  }

  void cancel() {
    _simTimer?.cancel();
    _simTimer = null;
    _subscription?.cancel();
    _subscription = null;
  }

  @override
  void dispose() {
    cancel();
    super.dispose();
  }
}