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

using Application.Abstractions.Data;
using Application.Abstractions.Messaging;
using Microsoft.EntityFrameworkCore;
using SharedKernel.Results;

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

internal sealed class Handler(IAppDbContext db) : IQueryHandler<Query, Result<Response>>
{
    public async Task<Result<Response>> Handle(Query request, CancellationToken ct)
    {
        if (request.GameID <= 0)
        {
            return Result.Failure<Response>(Error.Problem("Game.Required", "gameID 는 필수입니다."));
        }

        var game = await db.Game
            .AsNoTracking()
            .Where(c => c.ID == request.GameID)
            .Select(c => new { c.ID, c.KorName })
            .FirstOrDefaultAsync(ct);

        if (game is null)
        {
            return Result.Failure<Response>(Error.NotFound("Game.NotFound", "해당 게임을 찾을 수 없습니다."));
        }

        var page = Math.Max(1, request.Page);
        var limit = Math.Clamp(request.Limit, 1, 500);

        var baseQuery = db.CouponCode
            .AsNoTracking()
            .Where(c => c.Coupon!.GameID == request.GameID);

        if (request.CouponID is int couponID && couponID > 0)
        {
            baseQuery = baseQuery.Where(c => c.CouponID == couponID);
        }

        var total = await baseQuery.CountAsync(ct);

        var items = await baseQuery
            .OrderByDescending(c => c.ID)
            .Skip((page - 1) * limit)
            .Take(limit)
            .Select(c => new Response.Row(
                c.ID,
                c.CouponID,
                c.Coupon!.Name,
                c.Code,
                (int)c.Status,
                c.IssuedAt,
                c.UsedAt
            ))
            .ToListAsync(ct);

        return Result.Success(new Response(game.ID, game.KorName, total, page, limit, items));
    }
}