ANTOOZA-BACKEND/Application/Features/Api/Forum/StockBoard/GetPrediction/Handler.cs

using Application.Abstractions.Data;
using Application.Abstractions.Messaging;
using Domain.Entities.Forum.Posts.ValueObject;
using Microsoft.EntityFrameworkCore;
using SharedKernel.Results;

namespace Application.Features.Api.Forum.StockBoard.GetPrediction;

/// <summary>글의 예측 메타 + 채점 상태 (d2 §④ M2, 익명). 예측이 없으면 NotFound.</summary>
internal sealed class Handler(IAppDbContext db) : IQueryHandler<Query, Result<Response>>
{
    public async Task<Result<Response>> Handle(Query request, CancellationToken ct)
    {
        var prediction = await db.PostPrediction.AsNoTracking()
            .Where(c => c.PostID == request.PostID)
            .Select(c => new
            {
                c.PostID,
                c.MemberID,
                c.StockCode,
                c.Direction,
                c.BasePrice,
                c.TargetPrice,
                c.HorizonDays,
                c.DueDate,
                c.Status,
                c.SettledPrice,
                c.SettledAt,
                c.CreatedAt
            })
            .FirstOrDefaultAsync(ct);

        if (prediction is null)
        {
            return Result.Failure<Response>(Error.NotFound("Prediction.NotFound", "예측 정보를 찾을 수 없습니다."));
        }

        var stockName = await db.Stock.AsNoTracking().Where(c => c.Code == prediction.StockCode).Select(c => c.Name).FirstOrDefaultAsync(ct);

        return new Response(
            prediction.PostID,
            prediction.MemberID,
            prediction.StockCode,
            stockName,
            (byte)prediction.Direction,
            DirectionLabel(prediction.Direction),
            prediction.BasePrice,
            prediction.TargetPrice,
            prediction.HorizonDays,
            prediction.DueDate,
            (byte)prediction.Status,
            StatusLabel(prediction.Status),
            prediction.SettledPrice,
            prediction.SettledAt,
            prediction.CreatedAt);
    }

    private static string DirectionLabel(PredictionDirection direction) => direction switch
    {
        PredictionDirection.Up => "상승",
        PredictionDirection.Down => "하락",
        _ => "알수없음"
    };

    private static string StatusLabel(PredictionStatus status) => status switch
    {
        PredictionStatus.Pending => "채점대기",
        PredictionStatus.Hit => "적중",
        PredictionStatus.Miss => "실패",
        PredictionStatus.Void => "무효",
        _ => "알수없음"
    };
}