// 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()

  if (event.pub_id) {
    const messages = await db.collection('message')
      .aggregate()
      .match({
        pub_id: event.pub_id
      })
      .sort({
        publish_time: -1
      })
      .skip(event.page_token)
      .limit(event.page_size)
      .end()

    return {
      list: messages.list,
      next_page_token: event.page_token + messages.list.length,
      status: 'OK'
    }
  } else if (event.keyword) {
    const regexp = db.RegExp({
      regexp: event.keyword,
      options: 'i'
    })
    const messages = await db.collection('message')
      .aggregate()
      .match(_.or([{
        name: regexp
      }, {
        brief: regexp
      }, {
        detail: regexp
      }]))
      .sort({
        publish_time: -1
      })
      .skip(event.page_token)
      .limit(event.page_size)
      .lookup({
        from: 'publisher',
        localField: 'pub_id',
        foreignField: '_id',
        as: 'publisher'
      })
      .unwind('$publisher')
      .end()

    if (event.page_token === 0) {
      await db.collection('search')
        .add({
          data: {
            user_id: OPENID,
            keyword: event.keyword || '',
            search_time: new Date()
          }
        })
    }

    return {
      list: messages.list,
      next_page_token: event.page_token + messages.list.length,
      status: 'OK'
    }
  } else if (event.hot) {
    const reads = await db.collection('read')
      .aggregate()
      .match(_.expr($.lt([$.subtract([new Date(), '$read_time']), 1000 * 60 * 60 * 24])))
      .group({
        _id: '$msg_id',
        total: $.sum(1)
      })
      .sort({
        total: -1
      })
      .limit(10)
      .lookup({
        from: 'message',
        localField: '_id',
        foreignField: '_id',
        as: 'message'
      })
      .unwind('$message')
      .lookup({
        from: 'publisher',
        localField: 'message.pub_id',
        foreignField: '_id',
        as: 'message.publisher'
      })
      .unwind('$message.publisher')
      .end()

    return {
      list: reads.list,
      status: 'OK'
    }
  } else if (event.favorite) {
    const messages = await db.collection('message')
      .aggregate()
      .lookup({
        from: 'favorite',
        let: {
          msg_id: '$_id'
        },
        pipeline: $.pipeline()
          .match(_.expr($.and([
            $.eq(['$user_id', OPENID]),
            $.eq(['$msg_id', '$$msg_id'])
          ])))
          .project({
            _id: 0,
            favorite_time: 1
          }).done(),
        as: 'favorite'
      })
      .unwind('$favorite')
      .skip(event.page_token)
      .limit(event.page_size)
      .lookup({
        from: 'publisher',
        localField: 'pub_id',
        foreignField: '_id',
        as: 'publisher'
      })
      .unwind('$publisher')
      .end()

    return {
      list: messages.list,
      next_page_token: event.page_token + messages.list.length,
      status: 'OK'
    }
  } else if (event.filter) {
    let messages = db.collection('message')
      .aggregate()
    if (event.filter[1] !== '') {
      messages = messages.match({
        type: event.filter[1]
      })
    }
    if (event.filter[3] !== '') {
      messages = messages.match({
        tag: db.RegExp({
          regexp: event.filter[3],
          options: 'i'
        })
      })
    }
    messages = messages.lookup({
        from: 'publisher',
        localField: 'pub_id',
        foreignField: '_id',
        as: 'publisher'
      })
      .unwind('$publisher')
    if (event.filter[2] !== '') {
      if (event.filter[2] === '我关注的') {
        messages = messages.lookup({
            from: 'follow',
            let: {
              pub_id: '$pub_id'
            },
            pipeline: $.pipeline()
              .match(_.expr($.and([
                $.eq(['$user_id', OPENID]),
                $.eq(['$pub_id', '$$pub_id'])
              ])))
              .project({
                _id: 0,
                follow_time: 1
              }).done(),
            as: 'follow'
          })
          .unwind('$follow')
      } else {
        messages = messages.match({
          'publisher.type': event.filter[2]
        })
      }
    }
    messages = await messages.sort({
        publish_time: -1
      })
      .skip(event.page_token)
      .limit(event.page_size)
      .end()

    return {
      list: messages.list,
      next_page_token: event.page_token + messages.list.length,
      status: 'OK'
    }
  } else {
    const messages = await db.collection('message')
      .aggregate()
      .sort({
        publish_time: -1
      })
      .skip(event.page_token)
      .limit(event.page_size)
      .lookup({
        from: 'publisher',
        localField: 'pub_id',
        foreignField: '_id',
        as: 'publisher'
      })
      .unwind('$publisher')
      .end()

    return {
      list: messages.list,
      next_page_token: event.page_token + messages.list.length,
      status: 'OK'
    }
  }
}