const cloud = require('wx-server-sdk')
cloud.init({ env: cloud.DYNAMIC_CURRENT_ENV })
const db = cloud.database()
const SCAN_LIMIT = 200
const TOP_N = 10

exports.main = async (event, context) => {
  try {
    const res = await db.collection('posts')
      .orderBy('createdAt', 'desc')
      .limit(SCAN_LIMIT)
      .field({ hashtags: true })
      .get()

    const counts = {}
    res.data.forEach(p => {
      ;(p.hashtags || []).forEach(tag => {
        if (!tag) return
        counts[tag] = (counts[tag] || 0) + 1
      })
    })

    const topics = Object.keys(counts)
      .map(tag => ({ tag, count: counts[tag] }))
      .sort((a, b) => b.count - a.count)
      .slice(0, TOP_N)

    return { code: 0, data: topics }
  } catch (e) {
    return { code: -1, message: e.message }
  }
}