@@ -0,0 +1,136 @@
+package store.domain;
+
+import static store.constants.ProductConstants.OUT_OF_STOCK;
+import static store.constants.ProductConstants.PRODUCT_DESCRIPTION_PREFIX;
+import static store.constants.ProductConstants.UNIT_QUANTITY;
+import static store.constants.ProductConstants.UNIT_WON;
+import static store.message.ErrorMessage.NOT_FOUND_PROMOTION;
+
+import java.text.NumberFormat;
+import java.util.Locale;
+import java.util.Optional;
+import store.dto.ProductDto;
+import store.validation.ProductValidator;
+
+public class Product {
+    private String name;
+    private int price;
+    private int quantity;
+    private Optional<Promotion> promotion;
+
+    private Product() {
+    }
+
+    public Product(ProductDto productDto, Optional<Promotion> promotion) {
+        ProductValidator.validate(productDto);
+        this.name = productDto.name();
+        this.price = Integer.parseInt(productDto.price());
+        this.quantity = Integer.parseInt(productDto.quantity());
+        this.promotion = promotion;
+    }
+
+    /**
+     * 프로모션을 적용 여부 검증
+     */
+    public boolean isEligibleForStandardPromotion(int orderedQuantity) {
+        if (promotion.isEmpty()) {
+            return false;
+        }
+        Promotion promotionInfo = promotion.get();
+        return orderedQuantity <= quantity
+                && getRemainingItemsForPromotion(orderedQuantity, promotionInfo) + promotionInfo.getGet() <= quantity;
+    }
+
+    /**
+     * 보너스 상품이 적용 여부 검증
+     */
+    public boolean isEligibleForBonusProduct(int orderedQuantity) {
+        if (promotion.isEmpty()) {
+            return false;
+        }
+        Promotion promotionInfo = promotion.get();
+        return getRemainingItemsForPromotion(orderedQuantity, promotionInfo) >= promotionInfo.getBuy()
+                && orderedQuantity + promotionInfo.getGet() <= quantity;
+    }
+
+    /**
+     * 프로모션 조건을 만족하는 남은 수량을 계산
+     */
+    public int getRemainingItemsForPromotion(int orderedQuantity, Promotion promotionInfo) {
+        return orderedQuantity % promotionInfo.getTotalRequiredQuantity();
+    }
+
+    /**
+     * 보너스 상품의 수량을 계산
+     */
+    public int calculateBonusQuantity(int orderedQuantity, Promotion promotion) {
+        return (orderedQuantity / promotion.getTotalRequiredQuantity()) * promotion.getGet();
+    }
+
+    /**
+     * 프로모션이 적용된 후, 실제 주문 가능한 수량을 계산
+     */
+    public int calculateQuantityAfterPromotion(int orderedQuantity) {
+        Promotion promotionInfo = getPromotionOrElseThrow();
+        int requiredQuantity = promotionInfo.getTotalRequiredQuantity();
+        return (orderedQuantity - quantity) + (quantity % requiredQuantity);
+    }
+
+    /**
+     * 프로모션이 존재하지 않으면 예외 발생
+     */
+    public Promotion getPromotionOrElseThrow() {
+        return promotion.orElseThrow(() -> new IllegalArgumentException(NOT_FOUND_PROMOTION.getMessage()));
+    }
+
+    /**
+     * 값을 가지고 있는 주체이기 때문에 상품 리스트를 포맷을 합니다.
+     */
+    @Override
+    public String toString() {
+        return PRODUCT_DESCRIPTION_PREFIX
+                + name + " "
+                + getFormatKoreanLocale(price) + UNIT_WON
+                + getFormattedQuantity()
+                + getFormattedPromotion();
+    }
+
+    public String getFormattedQuantity() {
+        if (quantity < 1) {
+            return OUT_OF_STOCK;
+        }
+        return getFormatKoreanLocale(quantity) + UNIT_QUANTITY;
+    }
+
+    public String getFormatKoreanLocale(int number) {
+        return NumberFormat.getInstance(Locale.KOREA).format(number);
+    }
+
+    public String getFormattedPromotion() {
+        return promotion.map(Promotion::getName).orElse("");
+    }
+
+    public String getName() {
+        return name;
+    }
+
+    public int getPrice() {
+        return price;
+    }
+
+    public int getQuantity() {
+        return quantity;
+    }
+
+    public Optional<Promotion> getPromotion() {
+        return promotion;
+    }
+
+    public boolean isPromotionalProduct() {
+        return promotion.isPresent();
+    }
+
+    public void decreaseQuantity(int orderQuantity) {
+        this.quantity -= orderQuantity;
+    }
+}

리뷰: Optional 좋네요 👍