package service

import (
	"context"

	roomv1 "hyapp.local/api/proto/room/v1"
	"hyapp/pkg/appcode"
	"hyapp/pkg/roomid"
	"hyapp/pkg/xerr"
)

const (
	defaultRoomOnlineUsersPageSize = 50
	maxRoomOnlineUsersPageSize     = 100
)

// ListRoomOnlineUsers 分页读取房间在线用户列表。
// 该接口用于右上角在线人数弹窗，不能让客户端用完整 RoomSnapshot 做分页。
func (s *Service) ListRoomOnlineUsers(ctx context.Context, req *roomv1.ListRoomOnlineUsersRequest) (*roomv1.ListRoomOnlineUsersResponse, error) {
	ctx = appcode.WithContext(ctx, req.GetMeta().GetAppCode())
	roomID := req.GetRoomId()
	viewerUserID := req.GetViewerUserId()
	if !roomid.ValidStringID(roomID) {
		return nil, xerr.New(xerr.InvalidArgument, "room_id is invalid")
	}
	if viewerUserID <= 0 {
		return nil, xerr.New(xerr.InvalidArgument, "viewer_user_id is required")
	}

	presence, exists, err := s.repository.GetCurrentRoomPresence(ctx, viewerUserID)
	if err != nil {
		return nil, err
	}
	if !exists || presence.RoomID != roomID || presence.Status != roomPresenceStatusActive {
		return nil, xerr.New(xerr.PermissionDenied, "viewer is not in room")
	}

	page := int(req.GetPage())
	if page <= 0 {
		page = 1
	}
	pageSize := int(req.GetPageSize())
	if pageSize <= 0 {
		pageSize = defaultRoomOnlineUsersPageSize
	}
	if pageSize > maxRoomOnlineUsersPageSize {
		pageSize = maxRoomOnlineUsersPageSize
	}

	result, err := s.repository.ListRoomOnlineUsers(ctx, RoomOnlineUserQuery{
		AppCode:  appcode.FromContext(ctx),
		RoomID:   roomID,
		Page:     page,
		PageSize: pageSize,
	})
	if err != nil {
		return nil, err
	}

	users := make([]*roomv1.RoomUser, 0, len(result.Users))
	for _, user := range result.Users {
		users = append(users, &roomv1.RoomUser{
			UserId:       user.UserID,
			Role:         user.Role,
			LastSeenAtMs: user.LastSeenAtMS,
		})
	}

	return &roomv1.ListRoomOnlineUsersResponse{
		Users:        users,
		Total:        result.Total,
		Page:         int32(result.Page),
		PageSize:     int32(result.PageSize),
		ServerTimeMs: s.clock.Now().UnixMilli(),
	}, nil
}