ANTOOZA-BACKEND/Domain/Entities/Wallets/WalletBalance.cs

using System.ComponentModel.DataAnnotations;
using Domain.Entities.Common.ValueObject;
using Domain.Entities.Wallets.ValueObject;

namespace Domain.Entities.Wallets;

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

    public Guid WalletKey { get; private set; }

    public WalletBalanceType Type { get; private set; }

    public Money Amount { get; private set; } = Money.KRW(0);

    /// <summary>동시 갱신 감지용 rowversion — 이중 지출 방지 (last-write-wins 차단)</summary>
    public byte[] RowVersion { get; private set; } = [];

    private WalletBalance() { }

    private WalletBalance(Guid walletKey, WalletBalanceType type, Money initial)
    {
        if (walletKey == Guid.Empty)
        {
            throw new ArgumentException("WalletKey is required.", nameof(walletKey));
        }

        WalletKey = walletKey;
        Type = type;
        Amount = initial;
    }

    public static WalletBalance Create(Guid walletKey, WalletBalanceType type, string currency = "KRW")
    {
        return new(walletKey, type, Money.Zero(currency));
    }

    public void Increase(Money amount)
    {
        EnsurePositive(amount);

        Amount = Amount + amount;
    }

    public void Decrease(Money amount)
    {
        EnsurePositive(amount);

        if (Amount.Value < amount.Value)
        {
            throw new InvalidOperationException("Insufficient balance.");
        }

        Amount = Amount - amount;
    }

    private static void EnsurePositive(Money amount)
    {
        if (amount.IsZero || amount.Value <= 0)
        {
            throw new ArgumentException("Amount must be positive.", nameof(amount));
        }
    }
}