ANTOOZA-BACKEND/Application/Features/Api/Note/GetDetail/Handler.cs

using Application.Abstractions.Data;
using Application.Abstractions.Messaging;
using Application.Abstractions.Notification;
using Domain.Entities.Notifications.ValueObject;
using Microsoft.EntityFrameworkCore;
using SharedKernel.Results;

namespace Application.Features.Api.Note.GetDetail;

internal sealed class Handler(
    IAppDbContext db,
    INotificationService notification
) : IQueryHandler<Query, Result<Response>>
{
    public async Task<Result<Response>> Handle(Query r, CancellationToken ct)
    {
        // 받은쪽지(receiver 본인) 또는 보낸쪽지(sender 본인) 둘 다 조회 허용
        var note = await db.Note
            .Where(n => n.ID == r.NoteID && (
                (n.ReceiverMemberID == r.CurrentMemberID && !n.IsDeletedByReceiver) ||
                (n.SenderMemberID == r.CurrentMemberID && !n.IsDeletedBySender)
            ))
            .FirstOrDefaultAsync(ct);

        if (note is null)
        {
            return Result.Failure<Response>(Error.NotFound("Note.NotFound", "쪽지를 찾을 수 없습니다."));
        }

        var isReceiverView = note.ReceiverMemberID == r.CurrentMemberID;
        var wasUnread = !note.IsRead;

        // receiver 본인이 처음 조회한 경우만 읽음 처리
        if (isReceiverView && wasUnread)
        {
            note.MarkRead();
            await db.SaveChangesAsync(ct);
        }

        // 발신자 정보 + 채널 (시스템 쪽지면 sender=0 → null)
        var sender = note.SenderMemberID > 0
            ? await db.Member.AsNoTracking()
                .Where(m => m.ID == note.SenderMemberID)
                .Select(m => new {
                    m.Name, m.Thumb, m.SID,
                    ChannelName = m.Channel != null ? m.Channel.Name : null,
                    ChannelHandle = m.Channel != null ? m.Channel.Handle : null
                })
                .FirstOrDefaultAsync(ct)
            : null;

        // 수신자 정보 + 채널
        var receiver = await db.Member.AsNoTracking()
            .Where(m => m.ID == note.ReceiverMemberID)
            .Select(m => new {
                m.Name, m.Thumb, m.SID,
                ChannelName = m.Channel != null ? m.Channel.Name : null,
                ChannelHandle = m.Channel != null ? m.Channel.Handle : null
            })
            .FirstOrDefaultAsync(ct);

        // 처음 읽었고 일반 쪽지면 발신자에게 NoteRead 알림 (receiver 본인 조회 시에만)
        if (isReceiverView && wasUnread && !note.IsSystem && note.SenderMemberID > 0)
        {
            // 채널명 > 회원 별명, 보조 @handle / #sid
            var primary = receiver?.ChannelName ?? receiver?.Name ?? "알 수 없는 회원";
            var secondary = !string.IsNullOrEmpty(receiver?.ChannelHandle)
                ? $"@{receiver.ChannelHandle}"
                : (!string.IsNullOrEmpty(receiver?.SID) ? $"#{receiver.SID}" : null);
            var receiverDisplay = secondary is null ? primary : $"{primary} ({secondary})";

            await notification.SendAsync(
                note.SenderMemberID,
                NotificationType.NoteRead,
                "쪽지를 읽었습니다",
                $"{receiverDisplay}님이 \"{note.Title}\" 쪽지를 읽었습니다.",
                actionUrl: null,
                relatedType: "Note",
                relatedID: note.ID,
                ct: ct
            );
        }

        return Result.Success(new Response(
            note.ID,
            note.IsSystem ? null : note.SenderMemberID,
            note.IsSystem ? "시스템" : sender?.Name,
            note.IsSystem ? null : sender?.Thumb,
            note.IsSystem ? null : sender?.SID,
            note.IsSystem ? null : sender?.ChannelName,
            note.IsSystem ? null : sender?.ChannelHandle,
            note.ReceiverMemberID,
            receiver?.Name,
            receiver?.Thumb,
            receiver?.SID,
            receiver?.ChannelName,
            receiver?.ChannelHandle,
            note.Title,
            note.Content,
            note.IsSystem,
            note.IsRead,
            note.CreatedAt
        ));
    }
}