using IM.Application.Chat.Queries;
using IM.Infrastructure.Persistence;
using MediatR;

namespace IM.Application.Chat.Handlers;

/// <summary>
/// 用户会话 ID 查询处理器。供 SignalR 按会话分组订阅。
/// </summary>
public class GetUserConversationIdsQueryHandler(ImDbContext db)
    : IRequestHandler<GetUserConversationIdsQuery, List<Guid>>
{
    public async Task<List<Guid>> Handle(GetUserConversationIdsQuery request, CancellationToken ct)
    {
        return await db.ConversationParticipants
            .Where(p => p.UserId == request.UserId)
            .Select(p => p.ConversationId)
            .ToListAsync(ct);
    }
}