package service

import (
	"context"
	"fmt"
	"strings"

	roomeventsv1 "hyapp/api/proto/events/room/v1"
	roomv1 "hyapp/api/proto/room/v1"
	"hyapp/pkg/roomid"
	"hyapp/pkg/xerr"
	"hyapp/services/room-service/internal/room/cell"
	"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"
)

// CreateRoom 创建一个新的房间执行单元，并把首个快照和事件落盘。
func (s *Service) CreateRoom(ctx context.Context, req *roomv1.CreateRoomRequest) (*roomv1.CreateRoomResponse, error) {
	if req.GetMeta() == nil || req.GetMeta().GetRoomId() == "" {
		// 创建房间必须指定 room_id，后续 lease、meta、snapshot 都依赖它。
		return nil, xerr.New(xerr.InvalidArgument, "room_id is required")
	}
	if !roomid.ValidStringID(req.GetMeta().GetRoomId()) {
		// 新房间必须能同时映射到腾讯云 IM GroupID 和 RTC strRoomId，避免创建后无法进语音。
		return nil, xerr.New(xerr.InvalidArgument, "room_id format is invalid")
	}
	mode := strings.TrimSpace(req.GetMode())
	if mode == "" {
		// mode 是房间状态对客户端和后续策略分发的基础维度，不能创建空模式房。
		return nil, xerr.New(xerr.InvalidArgument, "mode is required")
	}
	actorUserID := req.GetMeta().GetActorUserId()
	if actorUserID == 0 {
		// CreateRoom 的 owner/host 默认来自已鉴权调用方，不允许匿名内部命令造房间。
		return nil, xerr.New(xerr.InvalidArgument, "actor_user_id is required")
	}

	// protobuf 请求先收敛为 command，后续幂等、持久化和恢复都只认识 command 模型。
	cmd := command.CreateRoom{
		Base:            baseFromMeta(req.GetMeta()),
		OwnerUserID:     actorUserID,
		HostUserID:      actorUserID,
		SeatCount:       req.GetSeatCount(),
		Mode:            mode,
		VisibleRegionID: normalizeVisibleRegionID(req.GetVisibleRegionId()),
	}

	if cmd.SeatCount <= 0 {
		// 没有麦位的房间不符合语音房 v1 的状态模型。
		return nil, xerr.New(xerr.InvalidArgument, "seat_count must be positive")
	}

	payload, seen, err := s.commandPayloadForIdempotency(ctx, cmd)
	if err != nil {
		return nil, err
	}
	if seen {
		// CreateRoom 幂等重试也要确保腾讯云 IM 群组存在，避免上次创建在外部桥接处失败。
		if err := s.syncPublisher.EnsureRoomGroup(ctx, cmd.RoomID(), cmd.OwnerUserID); err != nil {
			return nil, err
		}

		// 重复 CreateRoom 不再写入状态，直接返回当前快照保证命令幂等。
		snapshot, err := s.currentSnapshot(ctx, cmd.RoomID())
		if err != nil {
			return nil, err
		}

		return &roomv1.CreateRoomResponse{
			Result: commandResult(false, snapshot.GetVersion(), s.clock.Now()),
			Room:   snapshot,
		}, nil
	}

	// 创建房间前先获得 owner lease，避免两个节点同时创建同一个 room_id。
	lease, err := s.directory.EnsureOwner(ctx, cmd.RoomID(), s.nodeID, s.clock.Now(), s.leaseTTL)
	if err != nil {
		return nil, err
	}

	if lease.NodeID != s.nodeID {
		// 有其他有效 owner 时当前节点不能创建或接管该房间。
		return nil, xerr.New(xerr.Conflict, fmt.Sprintf("room is owned by %s", lease.NodeID))
	}

	if _, exists, err := s.repository.GetRoomMeta(ctx, cmd.RoomID()); err != nil {
		return nil, err
	} else if exists {
		// meta 已存在但 command 未命中，说明 room_id 已被其他创建命令占用。
		return nil, xerr.New(xerr.Conflict, "room already exists")
	}

	if err := s.syncPublisher.EnsureRoomGroup(ctx, cmd.RoomID(), cmd.OwnerUserID); err != nil {
		// 房间创建必须先保证外部群组可用。
		return nil, err
	}

	// 创建态直接初始化 RoomState，owner 作为首个在线用户进入房间。
	now := s.clock.Now()
	roomState := state.NewRoomState(cmd.RoomID(), cmd.OwnerUserID, cmd.HostUserID, cmd.SeatCount, cmd.Mode)
	roomState.Version = 1
	roomState.OnlineUsers[cmd.ActorUserID()] = &state.RoomUserState{
		UserID:       cmd.ActorUserID(),
		Role:         "owner",
		JoinedAtMS:   now.UnixMilli(),
		LastSeenAtMS: now.UnixMilli(),
	}

	// RoomCreated 进入 outbox，供 activity/audit 等房间外系统异步消费。
	createdEvent, err := outbox.Build(cmd.RoomID(), "RoomCreated", roomState.Version, now, &roomeventsv1.RoomCreated{
		OwnerUserId: cmd.OwnerUserID,
		HostUserId:  cmd.HostUserID,
		SeatCount:   cmd.SeatCount,
		Mode:        cmd.Mode,
	})
	if err != nil {
		return nil, err
	}

	// 首次创建按 meta -> command log -> outbox -> snapshot 的顺序落盘，保证恢复有基础元数据和首版本命令。
	if err := s.repository.SaveRoomMeta(ctx, RoomMeta{
		RoomID:          cmd.RoomID(),
		OwnerUserID:     cmd.OwnerUserID,
		HostUserID:      cmd.HostUserID,
		SeatCount:       cmd.SeatCount,
		Mode:            cmd.Mode,
		Status:          "active",
		VisibleRegionID: cmd.VisibleRegionID,
	}); err != nil {
		return nil, err
	}

	if err := s.repository.SaveCommand(ctx, CommandRecord{
		RoomID:      cmd.RoomID(),
		RoomVersion: roomState.Version,
		CommandID:   cmd.ID(),
		CommandType: cmd.Type(),
		Payload:     payload,
		Replayable:  true,
		CreatedAt:   now,
	}); err != nil {
		return nil, err
	}

	if err := s.repository.SaveOutbox(ctx, []outbox.Record{createdEvent}); err != nil {
		return nil, err
	}

	snapshot := roomState.ToProto()
	if err := s.persistSnapshot(ctx, snapshot); err != nil {
		return nil, err
	}
	s.projectRoomListBestEffort(ctx, snapshot)

	// 持久化成功后再安装内存 Cell，避免内存有房间但恢复来源不完整。
	s.installCell(cmd.RoomID(), cell.New(roomState.Clone(), rank.FromState(roomState.GiftRank, s.rankLimit)))

	return &roomv1.CreateRoomResponse{
		Result: commandResult(true, snapshot.GetVersion(), now),
		Room:   snapshot,
	}, nil
}