using BuildFlow.Platform.Application.Users.DTOs;
using BuildFlow.Platform.Application.Users.Queries;
using MediatR;

namespace BuildFlow.IM.Integration.Tests;

/// <summary>
/// 进程内用户摘要查询处理器。测试前可预置用户展示名和头像，由 MediatR 按用户 ID 批量返回。
/// </summary>
public sealed class InMemoryUserSummaryQueryHandler
    : IRequestHandler<GetUserSummariesQuery, IReadOnlyDictionary<Guid, UserSummaryDto>>
{
    private readonly Dictionary<Guid, UserSummaryDto> _users = new();

    /// <summary>
    /// 预置一个用户摘要。
    /// </summary>
    public void SetUser(Guid userId, string username, string? avatar = null) =>
        _users[userId] = new UserSummaryDto(userId, username, avatar);

    public Task<IReadOnlyDictionary<Guid, UserSummaryDto>> Handle(
        GetUserSummariesQuery request,
        CancellationToken ct)
    {
        IReadOnlyDictionary<Guid, UserSummaryDto> result = request.UserIds
            .Distinct()
            .Where(_users.ContainsKey)
            .ToDictionary(userId => userId, userId => _users[userId]);

        return Task.FromResult(result);
    }
}