import 'health_gateway_fallback.dart'
    if (dart.library.io) 'health_gateway_mobile.dart' as impl;

/// Native health ecosystem backing the current device.
///
/// Kept in `core` (not the health_sync feature) so the platform layer never
/// imports feature code; the biometric controller maps this to the domain's
/// `BiometricSource` enum.
enum NativeHealthPlatform {
  /// Apple HealthKit (iOS).
  appleHealth,

  /// Google Health Connect (Android).
  healthConnect,
}

/// Scalar sample returned by the health gateway.
///
/// Pure value type: [unit] is a display string (`lb`, `kcal`) — unit
/// normalization (kg → lb, joules → kcal) happens inside the gateway so
/// consumers only ever deal in pounds and Calories.
class HealthMetric {
  const HealthMetric({
    required this.timestamp,
    required this.value,
    required this.unit,
  });

  /// When the sample was recorded.
  final DateTime timestamp;

  /// Normalized magnitude (pounds for weight, kilocalories for energy).
  final double value;

  /// Unit of [value] for display (e.g. `lb`, `kcal`).
  final String unit;
}

/// Cross-platform boundary over the OS health ecosystems (architecture rule
/// 2/3: platform-specific packages never leak past this interface).
///
/// * **Android / iOS:** implemented by `health_gateway_mobile.dart`, which
///   wraps the `health` package (Health Connect / HealthKit).
/// * **Windows / macOS / Web:** implemented by `health_gateway_fallback.dart`,
///   a manual-entry mode that never touches platform channels; consumers read
///   the drift-backed cache through `IHealthSyncRepository` instead.
abstract class IHealthGateway {
  /// Whether this device can read/write native health data. `false` on
  /// Web/Windows/macOS, which signals the UI to offer manual entry.
  bool get supportsNativeHealth;

  /// Ecosystem backing [supportsNativeHealth], or `null` in fallback mode.
  NativeHealthPlatform? get nativePlatform;

  /// Requests read permission for weight and active energy; returns whether
  /// access was granted. Always `false` in fallback mode.
  Future<bool> requestPermissions();

  /// Weight samples in pounds for `[start, end)`, newest first.
  ///
  /// Returns an empty list (never throws) in fallback mode or when the OS
  /// denies access.
  Future<List<HealthMetric>> fetchWeightHistory({
    required DateTime start,
    required DateTime end,
  });

  /// Active energy burned (kcal) samples for `[start, end)`, newest first.
  ///
  /// Returns an empty list (never throws) in fallback mode or when the OS
  /// denies access.
  Future<List<HealthMetric>> fetchActiveEnergyBurned({
    required DateTime start,
    required DateTime end,
  });

  /// Writes a weight measurement back to the native store; returns whether
  /// the platform accepted it (always `false` in fallback mode).
  Future<bool> writeWeight({
    required double weightLbs,
    required DateTime timestamp,
  });
}

/// Platform-appropriate factory: native `health`-backed gateway on
/// Android/iOS, manual-entry fallback on Web/Windows/macOS.
IHealthGateway createHealthGateway() => impl.makeHealthGateway();