ANTOOZA-BACKEND/Application/Features/Admin/Payment/Danal/Confirm/Cancel/Handler.cs

using Application.Abstractions.Data;
using Application.Abstractions.Messaging;
using Application.Abstractions.Payment;
using Domain.Entities.Common.ValueObject;
using Domain.Entities.Payments.Danal;
using Domain.Entities.Payments.Danal.ValueObject;
using Domain.Entities.Payments.ValueObject;
using Microsoft.EntityFrameworkCore;
using SharedKernel.Results;

namespace Application.Features.Admin.Payment.Danal.Confirm.Cancel;

public sealed class Handler(
    IAppDbContext db,
    IDanalPayService danalPay
) : ICommandHandler<Command, Result>
{
    public async Task<Result> Handle(Command request, CancellationToken ct)
    {
        var confirm = await db.DanalConfirm.FirstOrDefaultAsync(x => x.ID == request.ID, ct);
        if (confirm is null)
        {
            return Result.Failure(Error.NotFound("Danal.ConfirmNotFound", "결제 내역을 찾을 수 없습니다."));
        }

        var order = await db.PaymentOrder.FirstOrDefaultAsync(o => o.ID == confirm.PaymentOrderID, ct);
        if (order is null)
        {
            return Result.Failure(Error.NotFound("Payment.OrderNotFound", "주문을 찾을 수 없습니다."));
        }

        // 진실의 근원은 PaymentOrder.Status — DanalConfirm.ResponseCode 가 비어있거나 "0000" 이 아니어도
        // PG 측에 실제 결제가 잡혀있다면(=Paid) 운영자 강제 환불이 필요. confirm.IsSuccess 단독 가드는 너무 엄격.
        if (order.Status != PaymentStatus.Paid)
        {
            return Result.Failure(Error.Problem("Payment.InvalidStatusForCancel", "취소할 수 없는 주문 상태입니다."));
        }

        // 이미 성공 취소된 경우 방지
        var hasSuccessfulCancel = await db.DanalCancel.AnyAsync(
            c => c.PaymentOrderID == order.ID && c.ResponseCode == "0000", ct);
        if (hasSuccessfulCancel)
        {
            return Result.Failure(Error.Problem("Danal.AlreadyCancelled", "이미 결제가 취소되었습니다."));
        }

        // 다날 결제수단 코드 매핑
        var methodCode = order.PaymentMethod switch
        {
            PaymentMethod.Integrated => "INTEGRATED",
            PaymentMethod.Card => "CARD",
            PaymentMethod.VirtualAccount => "VACCOUNT",
            PaymentMethod.Mobile => "MOBILE",
            PaymentMethod.Transfer => "TRANSFER",
            PaymentMethod.NaverPay => "NAVERPAY",
            PaymentMethod.KakaoPay => "KAKAOPAY",
            PaymentMethod.Payco => "PAYCO",
            _ => "CARD"
        };

        // 취소 요청 기록 저장 (전체 취소)
        var cancel = DanalCancel.CreateRequest(
            memberID: order.MemberID,
            paymentOrderID: order.ID,
            method: order.PaymentMethod,
            transactionID: order.TransactionID!,
            orderID: order.OrderID,
            amount: order.Amount,
            merchantID: order.MerchantID,
            cancelType: DanalCancelType.Full,
            cancelRequester: request.CancelRequester,
            cancelReason: request.CancelReason
        );

        await db.DanalCancel.AddAsync(cancel, ct);
        await db.SaveChangesAsync(ct);

        // 다날 API 호출
        var result = await danalPay.CancelAsync(methodCode, order.TransactionID!, order.Amount, "C", ct);
        if (!result.Success)
        {
            cancel.SetResponse(result.Code ?? "", result.Message ?? "취소 실패");
            await db.DanalLog.AddAsync(DanalLog.Create(
                order.MemberID,
                DanalLogType.Failed,
                result.Code ?? "FAIL",
                result.Message ?? "취소 실패",
                order.TransactionID,
                order.OrderID), ct);
            await db.SaveChangesAsync(ct);

            return Result.Failure(Error.Problem("Danal.CancelFailed", result.Message ?? "결제 취소에 실패했습니다."));
        }

        // 취소 응답 저장
        cancel.SetResponse(
            result.Code ?? "",
            result.Message ?? "",
            result.OriginalTransactionID,
            result.CancelledAmount,
            result.TransDate,
            result.TransTime,
            int.TryParse(result.Balance, out var balanceVal) ? balanceVal : null,
            int.TryParse(result.RemainedAmount, out var remainedVal) ? remainedVal : null,
            result.ApprovalDateTime
        );

        order.MarkCancelled();

        // 지갑에서 환불 처리 (잔액 부족 시 음수 방지 위해 예외 흡수)
        var wallet = await db.Wallet.Include(w => w.Balances)
            .FirstOrDefaultAsync(w => w.MemberID == order.MemberID, ct);
        if (wallet is not null)
        {
            try
            {
                wallet.AdjustDecrease(Money.KRW(order.PointAmount), "결제 취소 환불", order.OrderID);
            }
            catch (InvalidOperationException)
            {
                // 잔액 부족 — 음수 방지 (0 처리)
            }
        }

        await db.SaveChangesAsync(ct);

        return Result.Success();
    }
}