import "dart:async";
import "dart:io";

import "package:battery_info/battery_info_plugin.dart";
import "package:battery_info/model/android_battery_info.dart";
import "package:logging/logging.dart";
import "package:photos/core/event_bus.dart";
import "package:photos/events/machine_learning_control_event.dart";

class MachineLearningController {
  MachineLearningController._privateConstructor();

  static final MachineLearningController instance =
      MachineLearningController._privateConstructor();

  final _logger = Logger("MachineLearningController");

  static const kMaximumTemperature = 42; // 42 degree celsius
  static const kMinimumBatteryLevel = 20; // 20%
  static const kInitialInteractionTimeout = Duration(seconds: 10);
  static const kDefaultInteractionTimeout = Duration(seconds: 5);
  static const kUnhealthyStates = ["over_heat", "over_voltage", "dead"];

  bool _isDeviceHealthy = true;
  bool _isUserInteracting = true;
  bool _isRunningML = false;
  late Timer _userInteractionTimer;

  void init() {
    if (Platform.isAndroid) {
      _startInteractionTimer(timeout: kInitialInteractionTimeout);
      BatteryInfoPlugin()
          .androidBatteryInfoStream
          .listen((AndroidBatteryInfo? batteryInfo) {
        _onBatteryStateUpdate(batteryInfo);
      });
    } else {
      // Always run Machine Learning on iOS
      Bus.instance.fire(MachineLearningControlEvent(true));
    }
  }

  void onUserInteraction() {
    if (Platform.isIOS) {
      return;
    }
    if (!_isUserInteracting) {
      _logger.info("User is interacting with the app");
      _isUserInteracting = true;
      _fireControlEvent();
    }
    _resetTimer();
  }

  void _fireControlEvent() {
    final shouldRunML = _isDeviceHealthy && !_isUserInteracting;
    if (shouldRunML != _isRunningML) {
      _isRunningML = shouldRunML;
      _logger.info(
        "Firing event with device health: $_isDeviceHealthy and user interaction: $_isUserInteracting",
      );
      Bus.instance.fire(MachineLearningControlEvent(shouldRunML));
    }
  }

  void _startInteractionTimer({Duration timeout = kDefaultInteractionTimeout}) {
    _userInteractionTimer = Timer(timeout, () {
      _logger.info("User is not interacting with the app");
      _isUserInteracting = false;
      _fireControlEvent();
    });
  }

  void _resetTimer() {
    _userInteractionTimer.cancel();
    _startInteractionTimer();
  }

  void _onBatteryStateUpdate(AndroidBatteryInfo? batteryInfo) {
    _logger.info("Battery info: ${batteryInfo!.toJson()}");
    _isDeviceHealthy = _computeIsDeviceHealthy(batteryInfo);
    _fireControlEvent();
  }

  bool _computeIsDeviceHealthy(AndroidBatteryInfo info) {
    return _hasSufficientBattery(info.batteryLevel ?? kMinimumBatteryLevel) &&
        _isAcceptableTemperature(info.temperature ?? kMaximumTemperature) &&
        _isBatteryHealthy(info.health ?? "");
  }

  bool _hasSufficientBattery(int batteryLevel) {
    return batteryLevel >= kMinimumBatteryLevel;
  }

  bool _isAcceptableTemperature(int temperature) {
    return temperature <= kMaximumTemperature;
  }

  bool _isBatteryHealthy(String health) {
    return !kUnhealthyStates.contains(health);
  }
}