ANTOOZA-BACKEND/Domain/Entities/Common/ValueObject/Money.cs

namespace Domain.Entities.Common.ValueObject;

public sealed record Money
{
    public decimal Value { get; }
    public string Currency { get; }

    private Money(decimal value, string currency)
    {
        if (value < 0)
        {
            throw new ArgumentException("금액은 음수가 될 수 없습니다.");
        }

        Currency = currency;
        Value = Normalize(value, currency);
    }

    public static Money KRW(decimal value) => new(value, "KRW");

    public static Money Zero(string currency) => new(0m, currency);

    public bool IsZero => Value == 0m;

    public static Money operator +(Money a, Money b)
    {
        EnsureSameCurrency(a, b);

        return new Money(a.Value + b.Value, a.Currency);
    }

    public static Money operator -(Money a, Money b)
    {
        EnsureSameCurrency(a, b);

        if (a.Value < b.Value)
        {
            throw new InvalidOperationException("잔액 부족");
        }

        return new Money(a.Value - b.Value, a.Currency);
    }

    public static bool operator >=(Money a, Money b)
    {
        EnsureSameCurrency(a, b);

        return a.Value >= b.Value;
    }

    public static bool operator <=(Money a, Money b)
    {
        EnsureSameCurrency(a, b);

        return a.Value <= b.Value;
    }

    private static void EnsureSameCurrency(Money a, Money b)
    {
        if (a.Currency != b.Currency)
        {
            throw new InvalidOperationException("통화가 다릅니다.");
        }
    }

    private static decimal Normalize(decimal value, string currency)
    {
        var scale = currency == "KRW" ? 0 : 2; // KRW 0자리, 그 외 2자리 같은 정책 예시

        return decimal.Round(value, scale, MidpointRounding.AwayFromZero);
    }
}