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

cloud.init()
const db = cloud.database()

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

  try {
    const message = await db.collection('message')
      .aggregate()
      .match({
        _id: event.msg_id
      })
      .lookup({
        from: 'publisher',
        localField: 'pub_id',
        foreignField: '_id',
        as: 'publisher'
      })
      .end()
    if (message.list.length !== 1) {
      throw 'error'
    }

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

    return message
  } catch (err) {
    return {
      errMsg: 'no such message'
    }
  }
}