ANTOOZA-BACKEND/Application/Features/Api/V1/Coupons/GetCode/Handler.cs

using System.Security.Cryptography;
using System.Text;
using Application.Abstractions.Data;
using Application.Abstractions.Messaging;
using Domain.Entities.Store.ValueObject;
using Microsoft.EntityFrameworkCore;
using SharedKernel.Results;

namespace Application.Features.Api.V1.Coupons.GetCode;

internal sealed class Handler(IAppDbContext db) : IQueryHandler<Query, Result<Response>>
{
    public async Task<Result<Response>> Handle(Query request, CancellationToken ct)
    {
        if (string.IsNullOrWhiteSpace(request.Code))
        {
            return Result.Failure<Response>(Error.Problem("Coupon.CodeRequired", "쿠폰 코드는 필수입니다."));
        }

        var codeHash = ComputeHash(request.Code.Trim());

        var row = await db.CouponCode
            .AsNoTracking()
            .Where(c => c.CodeHash == codeHash)
            .Select(c => new
            {
                c.Code,
                c.CouponID,
                CouponName = c.Coupon!.Name,
                c.Status,
                c.IssuedAt,
                c.UsedAt
            })
            .FirstOrDefaultAsync(ct);

        if (row is null)
        {
            return Result.Failure<Response>(Error.NotFound("Coupon.CodeNotFound", "해당 쿠폰 코드를 찾을 수 없습니다."));
        }

        var label = row.Status switch
        {
            CouponCodeStatus.Available => "미발급",
            CouponCodeStatus.Reserved => "결제 진행 중",
            CouponCodeStatus.Issued => "발급됨",
            CouponCodeStatus.Used => "사용 완료",
            CouponCodeStatus.Expired => "만료",
            _ => row.Status.ToString()
        };

        return Result.Success(new Response(
            row.Code, row.CouponID, row.CouponName,
            (int)row.Status, label, row.IssuedAt, row.UsedAt
        ));
    }

    private static string ComputeHash(string code)
    {
        var bytes = Encoding.UTF8.GetBytes(code);
        var hash = SHA256.HashData(bytes);
        return Convert.ToHexString(hash);
    }
}