car-interface-android/lib/data/models/system_status.dart

/// Battery and connectivity snapshot shown on the home screen.
class SystemStatus {
  const SystemStatus({
    this.batteryLevel = 0,
    this.charging = false,
    this.wifi = false,
  });

  final int batteryLevel;
  final bool charging;
  final bool wifi;

  factory SystemStatus.fromMap(Map<dynamic, dynamic> map) {
    return SystemStatus(
      batteryLevel: (map['batteryLevel'] as num?)?.toInt() ?? 0,
      charging: map['charging'] == true,
      wifi: map['wifi'] == true,
    );
  }
}

/// Current media-stream volume and its maximum.
class VolumeInfo {
  const VolumeInfo({this.index = 0, this.max = 15, this.fixed = false});

  final int index;
  final int max;

  /// True when Android delegates volume to a fixed hardware amplifier (common
  /// on car head units). Apps cannot change that volume.
  final bool fixed;

  factory VolumeInfo.fromMap(Map<dynamic, dynamic> map) {
    return VolumeInfo(
      index: (map['index'] as num?)?.toInt() ?? 0,
      max: (map['max'] as num?)?.toInt() ?? 15,
      fixed: map['fixed'] == true,
    );
  }

  double get fraction => max <= 0 ? 0 : (index / max).clamp(0.0, 1.0);

  int get percent => (fraction * 100).round();
}