@@ -0,0 +1,92 @@
+package store.controller;
+
+import store.model.Product;
+import store.model.Receipt;
+import store.model.Store;
+import store.view.InputView;
+import store.view.OutputView;
+
+import java.util.Map;
+
+public class BuyController {
+    private final Store store;
+
+    public BuyController(Store store) {
+        this.store = store;
+    }
+
+    public void buyProduct() {
+        boolean continueShopping = true;
+        while (continueShopping) {
+            Receipt receipt = new Receipt();
+            try {
+                Map<String, Integer> purchasedItems = InputView.purchasedItems();
+                processPurchasedItems(receipt, purchasedItems);
+                applyMembershipDiscount(receipt);
+                receipt.print();
+                OutputView.askForAdditionalPurchase();
+                continueShopping = InputView.yOrN();
+                if (continueShopping) OutputView.printInventoryInformation(store);
+            } catch (IllegalArgumentException e) {
+                System.out.println(e.getMessage());
+            }
+        }
+    }
+
+    private void processPurchasedItems(Receipt receipt, Map<String, Integer> purchasedItems) {
+        for (String key : purchasedItems.keySet()) {
+            int number = purchasedItems.get(key);
+            Product product = checkInventory(key, number);
+            if (product.isPromotion()) {
+                processPromotionalItem(receipt, product, number, purchasedItems, key);
+            } else {
+                addItemToReceipt(receipt, product, number, 0);
+            }
+        }
+    }
+
+    private void processPromotionalItem(Receipt receipt, Product product, int number, Map<String, Integer> purchasedItems, String key) {
+        int eventProduct = product.addPromotions(number);
+        if (eventProduct != 0) {
+            if (product.getQuantity() >= eventProduct + number) {
+                OutputView.printAddEventProduct(eventProduct, product.getName());
+                if (InputView.yOrN()) {
+                    number += eventProduct;
+                    purchasedItems.put(key, number);
+                }
+            }
+            if (product.getQuantity() < eventProduct + number) {
+                OutputView.PromotionNotApplied(product);
+                if (!InputView.yOrN()) {
+                    number -= product.getPromotionBuy();
+                    purchasedItems.put(key, number);
+                }
+            }
+        }
+        store.deductInventory(product.getName(), number);
+        addItemToReceipt(receipt, product, number, product.applyPromotions(number));
+    }
+
+    private void addItemToReceipt(Receipt receipt, Product product, int quantity, int promotionAppliedQuantity) {
+        receipt.addItem(product, quantity, promotionAppliedQuantity);
+    }
+
+    private void applyMembershipDiscount(Receipt receipt) {
+        OutputView.printMemberShipDiscount();
+        if (InputView.yOrN()) {
+            receipt.applyMembershipDiscount();
+        }
+    }
+
+    private Product checkInventory(String productName, int quantity) {
+        if (productName == null || quantity <= 0) {
+            throw new IllegalArgumentException("[ERROR] 잘못된 입력입니다. 다시 입력해 주세요.");
+        }
+        Product product = store.findProductByName(productName)
+                .orElseThrow(() -> new IllegalArgumentException("[ERROR] 존재하지 않는 상품입니다. 다시 입력해 주세요."));
+        if (product.getQuantity() < quantity) {
+            throw new IllegalArgumentException("[ERROR] 재고 수량을 초과하여 구매할 수 없습니다. 다시 입력해 주세요.");
+        }
+        return product;
+    }
+}

리뷰: depth가 3이네요! 메서드를 분리했다면 더 좋았을 것 같아요!:)