dpot-backend/Application/Features/Api/Studio/Settlement/SaveAccount/Handler.cs

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

namespace Application.Features.Api.Studio.Settlement.SaveAccount;

internal sealed class Handler(IAppDbContext db) : ICommandHandler<Command, Result<Response>>
{
    private const int MaxAccounts = 8;

    public async Task<Result<Response>> Handle(Command request, CancellationToken ct)
    {
        // 유효성 검사
        if (string.IsNullOrWhiteSpace(request.BankCode))
        {
            return Result.Failure<Response>(Error.Problem("BankCode", "은행을 선택해 주세요."));
        }

        if (string.IsNullOrWhiteSpace(request.AccountNumber) || request.AccountNumber.Length is < 7 or > 16 || !request.AccountNumber.All(char.IsDigit))
        {
            return Result.Failure<Response>(Error.Problem("AccountNumber", "올바른 계좌번호를 입력해 주세요. (7~16자리 숫자)"));
        }

        if (string.IsNullOrWhiteSpace(request.AccountHolder) || request.AccountHolder.Trim().Length < 2)
        {
            return Result.Failure<Response>(Error.Problem("AccountHolder", "예금주명을 입력해 주세요. (2자 이상)"));
        }

        var bank = SettlementBankCode.List.FirstOrDefault(b => b.Value == request.BankCode);
        if (bank is null)
        {
            return Result.Failure<Response>(Error.Problem("BankCode", "유효하지 않은 은행 코드입니다."));
        }

        // 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."));
        }

        // 수정
        if (request.AccountID.HasValue)
        {
            var existing = await db.SettlementAccount.FirstOrDefaultAsync(a => a.ID == request.AccountID.Value && a.MemberID == request.MemberID, ct);
            if (existing is null)
            {
                return Result.Failure<Response>(Error.NotFound("Account", "계좌 정보를 찾을 수 없습니다."));
            }

            existing.Update(request.BankCode, bank.Text, request.AccountNumber, request.AccountHolder.Trim());
            await db.SaveChangesAsync(ct);

            return Result.Success(new Response("계좌가 수정되었습니다."));
        }

        // 신규 등록: 개수 제한
        var count = await db.SettlementAccount.CountAsync(a => a.MemberID == request.MemberID, ct);
        if (count >= MaxAccounts)
        {
            return Result.Failure<Response>(Error.Problem("Account", $"계좌는 최대 {MaxAccounts}개까지 등록할 수 있습니다."));
        }

        var account = SettlementAccount.Create(
            channel.ID, request.MemberID,
            request.BankCode, bank.Text,
            request.AccountNumber, request.AccountHolder.Trim()
        );
        db.SettlementAccount.Add(account);
        await db.SaveChangesAsync(ct);

        return Result.Success(new Response("계좌가 등록되었습니다."));
    }
}