second commit

lib/domain/repositories/transaction_repository.dart

@@ -0,0 +1,20 @@
+import '../entities/transaction.dart';
+
+abstract class TransactionRepository {
+  Future<SaleTransaction> save(SaleTransaction transaction);
+
+  Future<List<SaleTransaction>> history({int limit = 50});
+
+  Future<SaleTransaction?> findByInvoice(String invoiceNumber);
+
+  /// Next invoice sequence for the current month.
+  Future<int> nextInvoiceSequence();
+
+  Future<void> park(ParkedBill bill);
+
+  Future<List<ParkedBill>> parkedBills();
+
+  Future<void> removeParked(String id);
+
+  Future<double> salesTotalForDay(DateTime day);
+}