ANTOOZA-BACKEND/Application/Features/Api/Chat/GetHistory/Handler.cs

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

namespace Application.Features.Api.Chat.GetHistory;

/// <summary>
/// 룸 최근 메시지 히스토리 (D2 M1) — 익명 허용 (게스트 읽기 — d0 §5-④).
/// main 은 항상 조회 가능, 종목방은 ChatRoomConfig row 존재 + IsActive 시에만 (단계 오픈).
/// </summary>
internal sealed class Handler(IAppDbContext db, IChatMessageStore messageStore) : IQueryHandler<Query, Result<Response>>
{
    public const int DefaultCount = 50;

    public async Task<Result<Response>> Handle(Query request, CancellationToken ct)
    {
        var roomKey = request.RoomKey?.Trim() ?? string.Empty;

        if (!ChatRoomKeys.IsValid(roomKey))
        {
            return Result.Failure<Response>(Error.NotFound("Chat.RoomNotFound", "존재하지 않는 채팅방입니다."));
        }

        var row = await db.ChatRoomConfig.AsNoTracking().Where(c => c.RoomKey == roomKey).Select(c => new { c.IsActive, c.SlowModeSeconds, c.Notice }).FirstOrDefaultAsync(ct);

        var config = row is null
            ? new ChatRoomConfigLoader.RoomConfig(false, false, 0, null)
            : new ChatRoomConfigLoader.RoomConfig(true, row.IsActive, row.SlowModeSeconds, row.Notice);

        if (!ChatRoomConfigLoader.IsRoomOpen(roomKey, config))
        {
            return Result.Failure<Response>(Error.NotFound("Chat.RoomNotOpen", "아직 열리지 않은 채팅방입니다."));
        }

        var count = Math.Clamp(request.Count <= 0 ? DefaultCount : request.Count, 1, ChatSettings.MaxMessages);
        var messages = await messageStore.GetRecentMessagesAsync(roomKey, count);

        return new Response
        {
            RoomKey = roomKey,
            Notice = config.Notice,
            SlowModeSeconds = config.SlowModeSeconds,
            Messages = messages
        };
    }
}