import '../../../../core/utils/date_time_utils.dart';
import 'pantry_category.dart';

/// Expiration bucket used by the pantry list to render warning badges.
enum ExpirationStatus {
  /// The item has no expiration date recorded.
  none,

  /// Comfortably far from expiring.
  fresh,

  /// Within [PantryItem.expirationWarningDays] of expiring.
  expiringSoon,

  /// Already past its expiration date.
  expired,
}

/// Immutable on-hand inventory record for one ingredient.
///
/// Pure Dart (no framework imports) so the entity can be shared by the delta
/// use case, the drift-backed repository, and the Riverpod presentation
/// layer without leaking infrastructure concerns into the domain.
class PantryItem {
  const PantryItem({
    required this.id,
    required this.name,
    required this.quantityOnHand,
    required this.unit,
    required this.category,
    this.expirationDate,
    required this.lastUpdated,
  });

  /// Days ahead of today that trigger an `expiringSoon` warning badge.
  static const int expirationWarningDays = 3;

  /// UUID primary key assigned when the row is first created.
  final String id;

  /// Canonical, lowercase ingredient key (see
  /// `value_objects/ingredient_name.dart`) used for fuzzy recipe matching,
  /// e.g. `chicken breast`.
  final String name;

  /// Quantity currently on hand, expressed in [unit].
  final double quantityOnHand;

  /// Canonical unit key (e.g. `g`, `oz`, `count`).
  final String unit;

  /// Grocery aisle the item belongs to.
  final PantryCategory category;

  /// Best-by date; `null` when the item does not expire.
  final DateTime? expirationDate;

  /// When the row was last written (drives change tracking).
  final DateTime lastUpdated;

  /// Warning bucket for [now] (defaults to the current instant).
  ExpirationStatus expirationStatus({DateTime? now}) {
    final date = expirationDate;
    if (date == null) return ExpirationStatus.none;
    final today = startOfDay(now ?? DateTime.now());
    final expiry = startOfDay(date);
    if (expiry.isBefore(today)) return ExpirationStatus.expired;
    if (expiry.difference(today).inDays <= expirationWarningDays) {
      return ExpirationStatus.expiringSoon;
    }
    return ExpirationStatus.fresh;
  }

  /// Whole days until expiration (0 = today, negative = overdue); `null`
  /// when no expiration date is recorded.
  int? daysUntilExpiration({DateTime? now}) {
    final date = expirationDate;
    if (date == null) return null;
    return startOfDay(date)
        .difference(startOfDay(now ?? DateTime.now()))
        .inDays;
  }

  PantryItem copyWith({
    String? id,
    String? name,
    double? quantityOnHand,
    String? unit,
    PantryCategory? category,
    DateTime? expirationDate,
    DateTime? lastUpdated,
  }) =>
      PantryItem(
        id: id ?? this.id,
        name: name ?? this.name,
        quantityOnHand: quantityOnHand ?? this.quantityOnHand,
        unit: unit ?? this.unit,
        category: category ?? this.category,
        expirationDate: expirationDate ?? this.expirationDate,
        lastUpdated: lastUpdated ?? this.lastUpdated,
      );

  @override
  String toString() =>
      'PantryItem($id, "$name", $quantityOnHand $unit, ${category.persistenceKey})';
}