// 云函数入口文件
const cloud = require('wx-server-sdk')

cloud.init()
const db = cloud.database()
const _ = db.command
const $ = db.command.aggregate

// 云函数入口函数
exports.main = async (event, context) => {
  const {
    OPENID
  } = cloud.getWXContext()

  try {
    await db.collection('message')
      .doc(event.msg_id)
      .get()
  } catch (err) {
    return {
      errMsg: '信息不存在',
      status: 'ERR'
    }
  }

  const read_check = await db.collection('read')
    .aggregate()
    .match(_.expr($.and([
      $.eq(['$user_id', OPENID]),
      $.eq(['$msg_id', event.msg_id]),
      $.lt([$.subtract([new Date(), '$read_time']), 1000 * 60 * 30])
    ])))
    .end()
  if (read_check.list.length !== 0) {
    return {
      errMsg: '30分钟内只算一次阅读量',
      status: 'ERR'
    }
  }

  const read = await db.collection('read')
    .add({
      data: {
        user_id: OPENID,
        msg_id: event.msg_id || '',
        read_time: new Date()
      }
    })

  return {
    _id: read._id,
    status: 'OK'
  }
}