const cloud = require('wx-server-sdk')
cloud.init({ env: cloud.DYNAMIC_CURRENT_ENV })
const db = cloud.database()
const _ = db.command
const PAGE_SIZE = 20

exports.main = async (event, context) => {
  const { postId, page = 0 } = event
  if (!postId) return { code: -1, message: '缺少 postId' }

  try {
    const skip = page * PAGE_SIZE
    const [totalRes, commentsRes] = await Promise.all([
      db.collection('comments').where({ postId }).count(),
      db.collection('comments')
        .where({ postId })
        .orderBy('createdAt', 'asc')
        .skip(skip)
        .limit(PAGE_SIZE)
        .get(),
    ])

    const comments = commentsRes.data
    const authorIds = [...new Set(comments.map(c => c.authorId))]

    let authorMap = {}
    if (authorIds.length > 0) {
      const authorsRes = await db.collection('users')
        .where({ openid: _.in(authorIds) })
        .field({ nickName: true, avatarUrl: true, openid: true })
        .get()
      authorsRes.data.forEach(u => { authorMap[u.openid] = u })
    }

    return {
      code: 0,
      data: {
        list: comments.map(c => ({ ...c, author: authorMap[c.authorId] || null })),
        total: totalRes.total,
      },
    }
  } catch (e) {
    return { code: -1, message: e.message }
  }
}