using BuildFlow.Shared.Domain.Exceptions;
using IM.Application.Chat.Commands;
using IM.Infrastructure.Persistence;
using MediatR;

namespace IM.Application.Chat.Handlers;

/// <summary>
/// 解散群组处理器。仅群主可操作，级联软删群与会话。
/// </summary>
public class DeleteGroupCommandHandler(ImDbContext db) : IRequestHandler<DeleteGroupCommand, Unit>
{
    public async Task<Unit> Handle(DeleteGroupCommand request, CancellationToken ct)
    {
        var group = await db.Groups.FindAsync([request.GroupId], ct)
            ?? throw new NotFoundException("群组不存在");

        // 解散群组是高危操作，仅限群主本人；管理员亦无此权限
        if (group.OwnerId != request.OperatorId)
            throw new BusinessException("只有群主才能解散群组");

        // GroupEntity 配置了软删除（ISoftDelete），Remove 会被 AuditInterceptor 改写为 IsDeleted=true，
        // 关联的 ConversationEntity/GroupMemberEntity 因级联策略同步处理
        db.Groups.Remove(group);
        await db.SaveChangesAsync(ct);
        return Unit.Value;
    }
}