ANTOOZA-BACKEND/Domain/Entities/Store/OrderItem.cs

using System.ComponentModel.DataAnnotations;
using System.ComponentModel.DataAnnotations.Schema;

namespace Domain.Entities.Store;

/// <summary>
/// 주문 라인. Order N:1 + Product N:1.
/// Digital 상품인 경우 IssuedCouponCodeID 로 발급된 쿠폰 코드 추적.
/// </summary>
public class OrderItem
{
    [ForeignKey(nameof(OrderID))]
    public virtual Order? Order { get; private set; }

    [ForeignKey(nameof(ProductID))]
    public virtual Product? Product { get; private set; }

    [ForeignKey(nameof(IssuedCouponCodeID))]
    public virtual CouponCode? IssuedCouponCode { get; private set; }

    [Key]
    public int ID { get; private set; }

    public int OrderID { get; private set; }

    public int ProductID { get; private set; }

    public int Quantity { get; private set; }

    /// <summary>주문 시점 상품 단가 (KRW). Product.Price 변경되어도 보존.</summary>
    public int UnitPrice { get; private set; }

    /// <summary>Digital 상품 발급 쿠폰 코드 (Physical 상품은 null).</summary>
    public int? IssuedCouponCodeID { get; private set; }

    public DateTime CreatedAt { get; private set; } = DateTime.UtcNow;

    private OrderItem() { }

    public static OrderItem Create(int productID, int quantity, int unitPrice)
    {
        if (productID <= 0)
        {
            throw new ArgumentOutOfRangeException(nameof(productID));
        }

        if (quantity <= 0)
        {
            throw new ArgumentOutOfRangeException(nameof(quantity), "Quantity must be positive.");
        }

        if (unitPrice < 0)
        {
            throw new ArgumentOutOfRangeException(nameof(unitPrice), "UnitPrice must be non-negative.");
        }

        return new OrderItem
        {
            ProductID = productID,
            Quantity = quantity,
            UnitPrice = unitPrice
        };
    }

    public void AssignCouponCode(int couponCodeID)
    {
        if (couponCodeID <= 0)
        {
            throw new ArgumentOutOfRangeException(nameof(couponCodeID));
        }

        IssuedCouponCodeID = couponCodeID;
    }
}