package service

import (
	"context"
	"time"

	roomeventsv1 "hyapp/api/proto/events/room/v1"
	roomv1 "hyapp/api/proto/room/v1"
	"hyapp/pkg/tencentim"
	"hyapp/pkg/xerr"
	"hyapp/services/room-service/internal/room/command"
	"hyapp/services/room-service/internal/room/outbox"
	"hyapp/services/room-service/internal/room/rank"
	"hyapp/services/room-service/internal/room/state"
)

// MicUp 把目标用户放到指定麦位。
func (s *Service) MicUp(ctx context.Context, req *roomv1.MicUpRequest) (*roomv1.MicUpResponse, error) {
	// MicUp 以 actor 作为上麦目标，管理员代操作走 MicDown/ChangeMicSeat 等显式 target 命令。
	cmd := command.MicUp{
		Base:   baseFromMeta(req.GetMeta()),
		SeatNo: req.GetSeatNo(),
	}

	result, err := s.mutateRoom(ctx, cmd, true, func(now time.Time, current *state.RoomState, _ *rank.LocalRank) (mutationResult, []outbox.Record, error) {
		if _, exists := current.OnlineUsers[cmd.ActorUserID()]; !exists {
			// 不在 room-service presence 的用户不能上麦。
			return mutationResult{}, nil, xerr.New(xerr.NotFound, "user not in room")
		}

		if _, exists := current.SeatByUser(cmd.ActorUserID()); exists {
			// 一个用户同一时间只能占一个麦位。
			return mutationResult{}, nil, xerr.New(xerr.Conflict, "user already on seat")
		}

		index := current.SeatIndex(cmd.SeatNo)
		if index < 0 {
			// 麦位编号必须来自房间初始化的 MicSeats。
			return mutationResult{}, nil, xerr.New(xerr.InvalidArgument, "seat does not exist")
		}

		if current.MicSeats[index].Locked {
			// 锁定麦位不能被普通上麦命令占用。
			return mutationResult{}, nil, xerr.New(xerr.PermissionDenied, "seat is locked")
		}

		if current.MicSeats[index].UserID != 0 {
			// 非空麦位不能被覆盖，避免两个用户同时占同一麦位。
			return mutationResult{}, nil, xerr.New(xerr.Conflict, "seat is occupied")
		}

		// 麦位占用和房间版本必须在同一个 Room Cell 任务里更新。
		current.MicSeats[index].UserID = cmd.ActorUserID()
		current.Version++

		// RoomMicChanged 是房间外消费者和腾讯云 IM 共同使用的麦位事件源。
		micEvent, err := outbox.Build(current.RoomID, "RoomMicChanged", current.Version, now, &roomeventsv1.RoomMicChanged{
			ActorUserId:  cmd.ActorUserID(),
			TargetUserId: cmd.ActorUserID(),
			FromSeat:     0,
			ToSeat:       cmd.SeatNo,
			Action:       "up",
		})
		if err != nil {
			return mutationResult{}, nil, err
		}

		return mutationResult{
			snapshot: current.ToProto(),
			seatNo:   cmd.SeatNo,
			syncEvent: &tencentim.RoomEvent{
				EventID:      micEvent.EventID,
				RoomID:       current.RoomID,
				EventType:    "room_mic_up",
				ActorUserID:  cmd.ActorUserID(),
				TargetUserID: cmd.ActorUserID(),
				SeatNo:       cmd.SeatNo,
				RoomVersion:  current.Version,
			},
		}, []outbox.Record{micEvent}, nil
	})
	if err != nil {
		return nil, err
	}

	return &roomv1.MicUpResponse{
		Result: commandResult(result.applied, result.snapshot.GetVersion(), s.clock.Now()),
		SeatNo: result.seatNo,
		Room:   result.snapshot,
	}, nil
}

// MicDown 把目标用户从当前麦位移下。
func (s *Service) MicDown(ctx context.Context, req *roomv1.MicDownRequest) (*roomv1.MicDownResponse, error) {
	// MicDown 支持操作者和目标用户不同，权限策略后续可在命令入口扩展。
	cmd := command.MicDown{
		Base:         baseFromMeta(req.GetMeta()),
		TargetUserID: req.GetTargetUserId(),
	}

	result, err := s.mutateRoom(ctx, cmd, true, func(now time.Time, current *state.RoomState, _ *rank.LocalRank) (mutationResult, []outbox.Record, error) {
		seat, exists := current.SeatByUser(cmd.TargetUserID)
		if !exists {
			// 目标用户不在麦上时不能生成下麦事件。
			return mutationResult{}, nil, xerr.New(xerr.NotFound, "target not on seat")
		}

		// SeatByUser 返回的是值拷贝，真正修改需要再定位切片下标。
		index := current.SeatIndex(seat.SeatNo)
		current.MicSeats[index].UserID = 0
		current.Version++

		micEvent, err := outbox.Build(current.RoomID, "RoomMicChanged", current.Version, now, &roomeventsv1.RoomMicChanged{
			ActorUserId:  cmd.ActorUserID(),
			TargetUserId: cmd.TargetUserID,
			FromSeat:     seat.SeatNo,
			ToSeat:       0,
			Action:       "down",
		})
		if err != nil {
			return mutationResult{}, nil, err
		}

		return mutationResult{
			snapshot: current.ToProto(),
			seatNo:   seat.SeatNo,
			syncEvent: &tencentim.RoomEvent{
				EventID:      micEvent.EventID,
				RoomID:       current.RoomID,
				EventType:    "room_mic_down",
				ActorUserID:  cmd.ActorUserID(),
				TargetUserID: cmd.TargetUserID,
				SeatNo:       seat.SeatNo,
				RoomVersion:  current.Version,
			},
		}, []outbox.Record{micEvent}, nil
	})
	if err != nil {
		return nil, err
	}

	return &roomv1.MicDownResponse{
		Result: commandResult(result.applied, result.snapshot.GetVersion(), s.clock.Now()),
		SeatNo: result.seatNo,
		Room:   result.snapshot,
	}, nil
}

// ChangeMicSeat 调整指定用户所在麦位。
func (s *Service) ChangeMicSeat(ctx context.Context, req *roomv1.ChangeMicSeatRequest) (*roomv1.ChangeMicSeatResponse, error) {
	// ChangeMicSeat 是原子换位：从原麦位清空和写入新麦位必须同版本完成。
	cmd := command.ChangeMicSeat{
		Base:         baseFromMeta(req.GetMeta()),
		TargetUserID: req.GetTargetUserId(),
		SeatNo:       req.GetSeatNo(),
	}

	result, err := s.mutateRoom(ctx, cmd, true, func(now time.Time, current *state.RoomState, _ *rank.LocalRank) (mutationResult, []outbox.Record, error) {
		fromSeat, exists := current.SeatByUser(cmd.TargetUserID)
		if !exists {
			// 未上麦用户没有可换出的源麦位。
			return mutationResult{}, nil, xerr.New(xerr.NotFound, "target not on seat")
		}

		toIndex := current.SeatIndex(cmd.SeatNo)
		if toIndex < 0 {
			// 目标麦位必须存在。
			return mutationResult{}, nil, xerr.New(xerr.InvalidArgument, "seat does not exist")
		}

		if current.MicSeats[toIndex].Locked {
			// 锁定麦位不能换入。
			return mutationResult{}, nil, xerr.New(xerr.PermissionDenied, "seat is locked")
		}

		if current.MicSeats[toIndex].UserID != 0 {
			// 目标麦位被占用时拒绝换位，避免覆盖另一个用户。
			return mutationResult{}, nil, xerr.New(xerr.Conflict, "seat is occupied")
		}

		// 清空源麦位和占用目标麦位在同一 Cell 任务内完成，客户端不会看到中间态。
		fromIndex := current.SeatIndex(fromSeat.SeatNo)
		current.MicSeats[fromIndex].UserID = 0
		current.MicSeats[toIndex].UserID = cmd.TargetUserID
		current.Version++

		micEvent, err := outbox.Build(current.RoomID, "RoomMicChanged", current.Version, now, &roomeventsv1.RoomMicChanged{
			ActorUserId:  cmd.ActorUserID(),
			TargetUserId: cmd.TargetUserID,
			FromSeat:     fromSeat.SeatNo,
			ToSeat:       cmd.SeatNo,
			Action:       "change",
		})
		if err != nil {
			return mutationResult{}, nil, err
		}

		return mutationResult{
			snapshot: current.ToProto(),
			syncEvent: &tencentim.RoomEvent{
				EventID:      micEvent.EventID,
				RoomID:       current.RoomID,
				EventType:    "room_mic_change",
				ActorUserID:  cmd.ActorUserID(),
				TargetUserID: cmd.TargetUserID,
				SeatNo:       cmd.SeatNo,
				RoomVersion:  current.Version,
			},
		}, []outbox.Record{micEvent}, nil
	})
	if err != nil {
		return nil, err
	}

	return &roomv1.ChangeMicSeatResponse{
		Result: commandResult(result.applied, result.snapshot.GetVersion(), s.clock.Now()),
		Room:   result.snapshot,
	}, nil
}