@@ -0,0 +1,94 @@
+package controller;
+
+import java.util.Objects;
+import model.Inventory;
+import model.Order;
+import model.Orders;
+import model.Product;
+import model.Purchase;
+import model.Receipts;
+import view.InputView;
+
+public final class PurchaseController {
+    public static void purchaseExec() {
+        for (Order order : Orders.getOrders()) {
+            purchaseProduct(order);
+        }
+    }
+
+    public static void purchaseProduct(final Order order) {
+        Product product = Inventory.getProduct(order.orderProductName());
+        if (product.getPromotion() != null) {
+            purchasePromotion(product, order);
+        } else {
+            processPurchase(product, order.purchaseCount(), 0, 0);
+        }
+    }
+
+    private static void purchasePromotion(final Product product, final Order order) {
+        if (order.purchaseCount() > product.getPromotionQuantity()) {
+            purchasePartialPromotion(product, order);
+            return;
+        }
+        purchaseAllPromotion(product, order);
+    }
+
+    private static void purchaseAllPromotion(final Product product, final Order order) {
+        int buyPlusGet = product.getPromotion().buyPlusGet();
+        int promotionGet = order.purchaseCount() / buyPlusGet * buyPlusGet;
+        if (shouldOfferAdditionalPromotion(order, product, buyPlusGet)) {
+            handleAdditionalPromotionOption(product, order, buyPlusGet);
+            return;
+        }
+        processPurchase(product, 0, order.purchaseCount(), promotionGet / buyPlusGet);
+    }
+
+    private static boolean shouldOfferAdditionalPromotion(final Order order, final Product product,
+                                                          final int buyPlusGet) {
+        return order.purchaseCount() % buyPlusGet == product.getPromotion().buy() &&
+                product.getPromotionQuantity() >= (order.purchaseCount() + 1);
+    }
+
+    private static void handleAdditionalPromotionOption(final Product product, final Order order,
+                                                        final int buyPlusGet) {
+        String inputValue = InputView.additionalPromotionQuantity(product.getProductName());
+        int newQuantity = order.purchaseCount();
+        if (Objects.equals(inputValue, "Y")) {
+            newQuantity = order.purchaseCount() + 1;
+        }
+        processPurchase(product, 0, newQuantity, newQuantity / buyPlusGet);
+    }
+
+    private static void purchasePartialPromotion(final Product product, final Order order) {
+        int buyPlusGet = product.getPromotion().buyPlusGet();
+        int promotionGet = product.getPromotionQuantity() / buyPlusGet * buyPlusGet;
+        String inputValue = InputView.partialPromotion(product.getProductName(), order.purchaseCount() - promotionGet);
+        if (Objects.equals(inputValue, "Y")) {
+            yPartialPromotion(product, order, buyPlusGet);
+            return;
+        }
+        nPartialPromotion(product, buyPlusGet, promotionGet);
+    }
+
+    private static void yPartialPromotion(final Product product, final Order order, final int buyPlusGet) {
+        processPurchase(product, order.purchaseCount() - product.getPromotionQuantity(),
+                product.getPromotionQuantity(), product.getPromotionQuantity() / buyPlusGet);
+    }
+
+    private static void nPartialPromotion(final Product product, final int buyPlusGet, final int promotionGet) {
+        if (promotionGet != 0) {
+            processPurchase(product, 0, promotionGet, promotionGet / buyPlusGet);
+        }
+    }
+
+    private static void processPurchase(final Product product, final int quantity, final int promotionQuantity,
+                                        final int giftQuantity) {
+        product.purchaseProduct(quantity, promotionQuantity);
+        int buyPlusGet = 0;
+        if (product.getPromotion() != null) {
+            buyPlusGet = product.getPromotion().buyPlusGet();
+        }
+        Receipts.add(new Purchase(product.getProductName(), quantity + promotionQuantity,
+                giftQuantity, product.getPrice(), buyPlusGet));
+    }
+}

리뷰: 이 부분에서는 Promotion 상품을 구매한다면 purchasePromotion함수 실행 아니면 processPurchase 함수 실행이라 else를 사용하는 것이 더 깔끔해 보인다고 생각해서 else를 사용하였습니다.

하지만 확장성과 유지보수를 위해서는 여기서 사용하지 않는 것이 더 좋을 것 같네요. 감사합니다!!