second commit

lib/domain/entities/transaction.dart

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+import 'package:equatable/equatable.dart';
+
+import '../../core/utils/extensions.dart';
+import 'cart.dart';
+import 'customer.dart';
+
+enum PaymentMethod {
+  cash('Cash', '💵', true),
+  card('Card', '💳', false),
+  upi('UPI', '📱', false),
+  wallet('Wallet', '👛', false),
+  giftCard('Gift Card', '🎁', false),
+  loyalty('Loyalty Points', '⭐', false);
+
+  const PaymentMethod(this.label, this.emoji, this.needsChange);
+
+  final String label;
+  final String emoji;
+
+  /// Only cash tenders can be over-paid and produce change.
+  final bool needsChange;
+
+  /// Non-cash tenders normally capture a reference number.
+  bool get needsReference =>
+      this == PaymentMethod.card ||
+      this == PaymentMethod.upi ||
+      this == PaymentMethod.giftCard;
+}
+
+/// A single tender against a bill. A split payment holds several of these.
+class PaymentSplit extends Equatable {
+  const PaymentSplit({
+    required this.method,
+    required this.amount,
+    this.tendered,
+    this.reference,
+  });
+
+  final PaymentMethod method;
+
+  /// Amount settled by this tender.
+  final double amount;
+
+  /// Cash handed over — may exceed [amount].
+  final double? tendered;
+
+  /// Card approval code, UPI txn id, gift card number.
+  final String? reference;
+
+  double get change {
+    if (!method.needsChange || tendered == null) return 0;
+    final diff = tendered! - amount;
+    return diff > 0 ? diff.asMoney : 0;
+  }
+
+  @override
+  List<Object?> get props => [method, amount, tendered, reference];
+}
+
+enum TransactionStatus { completed, parked, voided, refunded }
+
+/// An immutable record of a finished sale.
+class SaleTransaction extends Equatable {
+  const SaleTransaction({
+    required this.id,
+    required this.invoiceNumber,
+    required this.cart,
+    required this.payments,
+    required this.createdAt,
+    required this.cashierName,
+    this.status = TransactionStatus.completed,
+    this.terminalId = 'TERM-01',
+  });
+
+  final String id;
+  final String invoiceNumber;
+  final Cart cart;
+  final List<PaymentSplit> payments;
+  final DateTime createdAt;
+  final String cashierName;
+  final TransactionStatus status;
+  final String terminalId;
+
+  Customer? get customer => cart.customer;
+
+  double get total => cart.grandTotal;
+
+  double get amountPaid =>
+      payments.fold(0.0, (sum, p) => sum + p.amount).asMoney;
+
+  double get amountTendered => payments
+      .fold(0.0, (sum, p) => sum + (p.tendered ?? p.amount))
+      .asMoney;
+
+  double get changeDue =>
+      payments.fold(0.0, (sum, p) => sum + p.change).asMoney;
+
+  double get balanceDue => (total - amountPaid).clamp(0, double.infinity);
+
+  bool get isFullySettled => balanceDue <= 0.001;
+
+  bool get isSplit => payments.length > 1;
+
+  int get pointsEarned => cart.pointsEarned;
+  int get pointsRedeemed => cart.pointsRedeemed;
+
+  String get paymentSummary =>
+      payments.map((p) => p.method.label).toSet().join(' + ');
+
+  @override
+  List<Object?> get props => [id, invoiceNumber, createdAt, status];
+}
+
+/// A bill set aside so the cashier can serve the next shopper.
+class ParkedBill extends Equatable {
+  const ParkedBill({
+    required this.id,
+    required this.cart,
+    required this.parkedAt,
+    this.label,
+  });
+
+  final String id;
+  final Cart cart;
+  final DateTime parkedAt;
+  final String? label;
+
+  String get displayLabel =>
+      label ?? cart.customer?.name ?? 'Walk-in #${id.substring(0, 4)}';
+
+  @override
+  List<Object?> get props => [id, parkedAt];
+}