const cloud = require('wx-server-sdk')
cloud.init({ env: cloud.DYNAMIC_CURRENT_ENV })
const db = cloud.database()
const _ = db.command

exports.main = async (event, context) => {
  const { OPENID } = cloud.getWXContext()
  const {
    latitude,
    longitude,
    maxDistance = 5000,  // 默认 5km，单位：米
    page = 0,
    pageSize = 20,
  } = event

  if (!latitude || !longitude) return { code: -1, message: '缺少位置' }

  try {
    // ✅ geoNear 聚合管道：依赖 users.lastLocation 字段上的 2dsphere 地理位置索引
    const { list } = await db.collection('users')
      .aggregate()
      .geoNear({
        near: db.Geo.Point(longitude, latitude),  // 注意：CloudBase GeoPoint 是 (lng, lat) 顺序
        spherical: true,
        distanceField: 'dist',   // 在每条记录上附加实际距离（米）
        maxDistance,
        query: {
          openid: _.neq(OPENID),       // 排除自己
          'pets.0': _.exists(true),    // 至少有一只宠物
        },
      })
      .skip(page * pageSize)
      .limit(pageSize)
      .project({
        openid: false,
      })
      .end()

    // 在线状态：5 分钟内活跃
    const fiveMin = 5 * 60 * 1000
    const now = Date.now()

    const result = list.map(u => ({
      userId: u._id,
      user: u,
      pet: u.pets?.[0] || null,
      distance: Math.round(u.dist),
      distanceText: formatDist(u.dist),
      isOnline: u.lastSeen && (now - new Date(u.lastSeen).getTime()) < fiveMin,
      location: {
        latitude: u.lastLocation?.coordinates?.[1],
        longitude: u.lastLocation?.coordinates?.[0],
      },
    }))

    return { code: 0, data: result }
  } catch (e) {
    return { code: -1, message: e.message }
  }
}

function formatDist(meters) {
  if (!meters && meters !== 0) return '未知'
  if (meters < 1000) return Math.round(meters) + 'm'
  return (meters / 1000).toFixed(1) + 'km'
}