dpot-backend/Application/Features/Api/Studio/Wallet/RequestWithdraw/Handler.cs

using Application.Abstractions.Data;
using Application.Abstractions.Messaging;
using Domain.Entities.Common.ValueObject;
using Domain.Entities.Donations;
using Domain.Entities.Donations.ValueObject;
using Domain.Entities.Wallets;
using Domain.Entities.Wallets.ValueObject;
using Microsoft.EntityFrameworkCore;
using SharedKernel.Results;

namespace Application.Features.Api.Studio.Wallet.RequestWithdraw;

internal sealed class Handler(IAppDbContext db) : ICommandHandler<Command, Result<Response>>
{
    private const int MinWithdrawAmount = 40000;

    public async Task<Result<Response>> Handle(Command request, CancellationToken ct)
    {
        // 금액 검증
        if (request.Amount < MinWithdrawAmount)
        {
            return Result.Failure<Response>(Error.Problem("Amount", $"최소 출금 금액은 {MinWithdrawAmount:N0}원입니다."));
        }

        // 채널 확인
        var channel = await db.Channel.AsNoTracking().FirstOrDefaultAsync(c => c.MemberID == request.MemberID && c.IsActive, ct);
        if (channel is null)
        {
            return Result.Failure<Response>(Error.NotFound("Channel", "채널 정보를 찾을 수 없습니다."));
        }

        // 계좌 확인
        var account = await db.SettlementAccount.AsNoTracking().FirstOrDefaultAsync(a => a.ID == request.AccountID && a.MemberID == request.MemberID, ct);
        if (account is null)
        {
            return Result.Failure<Response>(Error.Problem("Account", "정산 계좌를 선택해 주세요."));
        }

        // Wallet 조회 (Tracked — 잔액 변경 필요)
        var wallet = await db.Wallet
            .Include(w => w.Balances)
            .FirstOrDefaultAsync(w => w.MemberID == request.MemberID, ct);

        if (wallet is null)
        {
            return Result.Failure<Response>(Error.Problem("Wallet", "지갑 정보를 찾을 수 없습니다."));
        }

        var donationBal = wallet.Balances.FirstOrDefault(b => b.Type == WalletBalanceType.Donation);
        if (donationBal is null || (int)donationBal.Amount.Value < request.Amount)
        {
            return Result.Failure<Response>(Error.Problem("Amount", "출금 가능 잔액이 부족합니다."));
        }

        // 이미 대기 중인 출금이 있는지 확인
        var hasPending = await db.WithdrawalRequest.AnyAsync(
            w => w.MemberID == request.MemberID && (w.Status == WithdrawalStatus.Pending || w.Status == WithdrawalStatus.Processing), ct);
        if (hasPending)
        {
            return Result.Failure<Response>(Error.Problem("Withdrawal", "이미 처리 중인 출금 요청이 있습니다."));
        }

        // Wallet 잔액 Lock
        wallet.LockForWithdrawal(Money.KRW(request.Amount));

        // 출금 요청 생성
        var withdrawal = WithdrawalRequest.Create(
            channel.ID, request.MemberID, request.Amount,
            account.BankCode, account.BankName, account.AccountNumber, account.AccountHolder
        );
        db.WithdrawalRequest.Add(withdrawal);

        await db.SaveChangesAsync(ct);

        return Result.Success(new Response("출금 신청이 완료되었습니다."));
    }
}