runable

lib/features/home/domain/usecases/add_to_cart.dart

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+import 'package:dartz/dartz.dart';
+import '../../../../core/errors/failures.dart';
+import '../entities/cart_item.dart';
+import '../repositories/cart_repository.dart';
+
+/// Use case to add item to cart
+class AddToCart {
+  final CartRepository repository;
+
+  AddToCart(this.repository);
+
+  Future<Either<Failure, void>> call(CartItem item) async {
+    return await repository.addToCart(item);
+  }
+}

lib/features/home/domain/usecases/calculate_total.dart

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+import '../entities/cart_item.dart';
+
+/// Use case to calculate cart total
+class CalculateTotal {
+  double call(List<CartItem> items) {
+    return items.fold(0.0, (sum, item) => sum + item.total);
+  }
+}

lib/features/home/domain/usecases/clear_cart.dart

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+import 'package:dartz/dartz.dart';
+import '../../../../core/errors/failures.dart';
+import '../repositories/cart_repository.dart';
+
+/// Use case to clear cart
+class ClearCart {
+  final CartRepository repository;
+
+  ClearCart(this.repository);
+
+  Future<Either<Failure, void>> call() async {
+    return await repository.clearCart();
+  }
+}

lib/features/home/domain/usecases/remove_from_cart.dart

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+import 'package:dartz/dartz.dart';
+import '../../../../core/errors/failures.dart';
+import '../repositories/cart_repository.dart';
+
+/// Use case to remove item from cart
+class RemoveFromCart {
+  final CartRepository repository;
+
+  RemoveFromCart(this.repository);
+
+  Future<Either<Failure, void>> call(String productId) async {
+    return await repository.removeFromCart(productId);
+  }
+}