import 'dart:async';

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

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

enum UpdatePhase {
  downloading,
  installing,

  /// Android's installer prompt is open; the app is replaced once the user
  /// confirms it, so there is no "done" state to show.
  waitingForInstaller,
  failed,
}

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

  UpdatePhase _phase = UpdatePhase.downloading;
  double? _progress;
  UpdateFailure? _failure;
  String? _currentVersion;

  StreamSubscription<OtaEvent>? _subscription;
  Timer? _simTimer;

  UpdatePhase get phase => _phase;

  /// Download progress from 0 to 1, or null while it is not known yet.
  double? get progress => _progress;
  UpdateFailure? get failure => _failure;
  String? get currentVersion => _currentVersion;

  bool get isBusy =>
      _phase == UpdatePhase.downloading || _phase == UpdatePhase.installing;

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

  void init() {
    unawaited(_loadCurrentVersion());
    start();
  }

  void start() {
    cancel();
    _phase = UpdatePhase.downloading;
    _progress = null;
    _failure = null;
    notifyListeners();

    if (simulate) {
      _runSimulation();
      return;
    }

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

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

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

  Future<void> _loadCurrentVersion() async {
    try {
      final info = await PackageInfo.fromPlatform();
      _currentVersion = info.version;
      notifyListeners();
    } catch (e) {
      debugPrint('UpdateProgressViewModel: could not read version: $e');
    }
  }

  void _onEvent(OtaEvent event) {
    switch (event.status) {
      case OtaStatus.DOWNLOADING:
        final percent = double.tryParse(event.value ?? '') ?? 0;
        _progress = (percent / 100).clamp(0.0, 1.0);
        _phase = UpdatePhase.downloading;
        notifyListeners();

      case OtaStatus.INSTALLING:
        _progress = 1;
        _phase = UpdatePhase.installing;
        notifyListeners();

      case OtaStatus.INSTALLATION_DONE:
        _phase = UpdatePhase.waitingForInstaller;
        notifyListeners();

      case OtaStatus.DOWNLOAD_ERROR:
        _fail(UpdateFailure.download, event.value);
      case OtaStatus.CHECKSUM_ERROR:
        _fail(UpdateFailure.checksum, event.value);
      case OtaStatus.PERMISSION_NOT_GRANTED_ERROR:
        _fail(UpdateFailure.permission, event.value);
      case OtaStatus.INSTALLATION_ERROR:
        _fail(UpdateFailure.install, event.value);
      case OtaStatus.ALREADY_RUNNING_ERROR:
        _fail(UpdateFailure.alreadyRunning, event.value);
      case OtaStatus.INTERNAL_ERROR:
        _fail(UpdateFailure.unknown, event.value);
      case OtaStatus.CANCELED:
        break;
    }
  }

  /// The plugin closes the stream once it has handed the APK to Android's
  /// installer; closing earlier means it gave up without telling why.
  void _onDone() {
    _subscription = null;

    switch (_phase) {
      case UpdatePhase.installing:
        _phase = UpdatePhase.waitingForInstaller;
        notifyListeners();
      case UpdatePhase.downloading:
        _fail(UpdateFailure.unknown, 'Update stream closed while downloading');
      case UpdatePhase.waitingForInstaller || UpdatePhase.failed:
        break;
    }
  }

  void _onError(Object error, StackTrace stackTrace) {
    debugPrint('UpdateProgressViewModel: stream error: $error');
    unawaited(Sentry.captureException(error, stackTrace: stackTrace));
    _fail(UpdateFailure.unknown, null, report: false);
  }

  void _fail(UpdateFailure failure, String? detail, {bool report = true}) {
    debugPrint('UpdateProgressViewModel: $failure: $detail');
    if (report) {
      unawaited(
        Sentry.captureMessage(
          'OTA update failed ($failure, ${update.version}): $detail',
        ),
      );
    }

    cancel();
    _phase = UpdatePhase.failed;
    _failure = failure;
    notifyListeners();
  }

  void _runSimulation() {
    const totalSteps = 40;
    var step = 0;

    _simTimer = Timer.periodic(const Duration(milliseconds: 150), (timer) {
      step++;

      if (simulateError && step == totalSteps ~/ 2) {
        _phase = UpdatePhase.failed;
        _failure = UpdateFailure.simulated;
        timer.cancel();
        notifyListeners();
        return;
      }

      if (step < totalSteps) {
        _progress = step / totalSteps;
        notifyListeners();
        return;
      }

      timer.cancel();
      _progress = 1;
      _phase = UpdatePhase.installing;
      notifyListeners();

      _simTimer = Timer(const Duration(seconds: 2), () {
        _phase = UpdatePhase.waitingForInstaller;
        notifyListeners();
      });
    });
  }

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