import 'sensor_def.dart';
import 'sensor_defs.dart';

enum SpeedUnit { kmh, mph }

enum TempUnit { celsius, fahrenheit }

enum PressureUnit { kpa, bar, psi }

/// User's display units. Values are always stored and logged in the base
/// (metric) units of [sensorDefs]; conversion happens only for display.
class UnitPrefs {
  final SpeedUnit speed;
  final TempUnit temp;
  final PressureUnit pressure;

  const UnitPrefs({
    this.speed = SpeedUnit.kmh,
    this.temp = TempUnit.celsius,
    this.pressure = PressureUnit.kpa,
  });

  UnitPrefs copyWith({
    SpeedUnit? speed,
    TempUnit? temp,
    PressureUnit? pressure,
  }) =>
      UnitPrefs(
        speed: speed ?? this.speed,
        temp: temp ?? this.temp,
        pressure: pressure ?? this.pressure,
      );

  @override
  bool operator ==(Object other) =>
      other is UnitPrefs &&
      other.speed == speed &&
      other.temp == temp &&
      other.pressure == pressure;

  @override
  int get hashCode => Object.hash(speed, temp, pressure);
}

/// How one sensor is displayed under the current [UnitPrefs]: unit label,
/// converted range, and value conversion/formatting.
class SensorView {
  final SensorDef def;
  final String unit;
  final double min;
  final double max;
  final int decimals;
  final double Function(double base) _convert;

  const SensorView._(
      this.def, this.unit, this.min, this.max, this.decimals, this._convert);

  String get name => def.displayName;

  /// Converts a base-unit value to the display unit.
  double convert(double base) => _convert(base);

  /// Converted and formatted, without unit.
  String format(double base) => convert(base).toStringAsFixed(decimals);

  /// 0..1 position of [base] within the sensor's range.
  double fraction(double base) =>
      ((convert(base) - min) / (max - min)).clamp(0.0, 1.0);
}

double _id(double v) => v;

SensorView sensorView(String id, UnitPrefs u) {
  final d = sensorDef(id);
  SensorView view(String unit, double Function(double) f, {int? decimals}) =>
      SensorView._(d, unit, f(d.min), f(d.max), decimals ?? d.decimals, f);

  switch (id) {
    case 'vss':
      return u.speed == SpeedUnit.mph
          ? view('mph', (v) => v * 0.621371)
          : view(d.unit, _id);
    case 'ect':
    case 'iat':
      return u.temp == TempUnit.fahrenheit
          ? view('°F', (v) => v * 9 / 5 + 32)
          : view(d.unit, _id);
    case 'map':
    case 'pa':
      switch (u.pressure) {
        case PressureUnit.bar:
          return view('bar', (v) => v / 100, decimals: 2);
        case PressureUnit.psi:
          return view('psi', (v) => v * 0.145038);
        case PressureUnit.kpa:
          return view(d.unit, _id);
      }
    default:
      return view(d.unit, _id);
  }
}