dpot-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);

        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));
            }
        }
    }
}