const cloud = require('wx-server-sdk')
cloud.init({ env: cloud.DYNAMIC_CURRENT_ENV })
const db = cloud.database()
const _ = db.command
const PAGE_SIZE = 30

exports.main = async (event, context) => {
  const { OPENID } = cloud.getWXContext()
  const { peerId, page = 0 } = event || {}

  try {
    const meRes = await db.collection('users').where({ openid: OPENID }).get()
    if (meRes.data.length === 0) return { code: -1, message: '用户不存在' }
    const myId = meRes.data[0]._id

    let list = []
    if (peerId) {
      const skip = page * PAGE_SIZE
      const msgRes = await db.collection('messages')
        .where(_.or([
          { fromId: myId, toId: peerId },
          { fromId: peerId, toId: myId },
        ]))
        .orderBy('createdAt', 'desc')
        .skip(skip)
        .limit(PAGE_SIZE)
        .get()

      list = msgRes.data.reverse().map(m => ({ ...m, isMe: m.fromId === myId }))

      // 把对方发来的未读消息标记为已读
      const unreadIds = msgRes.data.filter(m => m.toId === myId && !m.isRead).map(m => m._id)
      if (unreadIds.length) {
        await db.collection('messages').where({ _id: _.in(unreadIds) }).update({ data: { isRead: true } })
      }
    }

    const unreadRes = await db.collection('messages')
      .where({ toId: myId, isRead: _.neq(true) })
      .count()

    return { code: 0, data: { list, unreadCount: unreadRes.total } }
  } catch (e) {
    return { code: -1, message: e.message }
  }
}