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

const COLLECTION = 'plank_data'
const PAGE_SIZE = 100

/**
 * One-shot admin tool: deduplicate plank_data docs by _openid.
 *
 * Background: before the client-side fix in utils/cloud.js (always locate
 * by _openid before add()), every cold start of the mini program created
 * a brand-new cloud doc for the same user. The leaderboard cloud function
 * then summed duration across N docs for the same _openid, inflating the
 * board. This function walks the whole collection, groups by _openid, and
 * deletes every doc except the most-recently-updated one for each user.
 *
 * DEPLOYMENT NOTES — read before invoking:
 *   1. Upload + deploy this function from the WeChat DevTools or `wx-cli`.
 *   2. The default collection security rule only allows reading docs whose
 *      `doc._openid == auth.openid`, which prevents this function from
 *      seeing other users' docs. Temporarily flip the collection's read
 *      permission to "所有用户可读" in the CloudBase console, OR configure
 *      the function's role to a privileged account that bypasses the
 *      custom rule.
 *   3. Invoke the function once from the CloudBase console test panel.
 *   4. **Delete or disable this function immediately afterwards** so it
 *      can't be re-run by a user. It's destructive.
 */
exports.main = async () => {
  // 安全闸门:仅允许白名单内的管理员调用,否则直接拒绝,防止被任意用户
  // 触发批量删除(该函数以特权身份运行且会删文档)。白名单在云函数环境变量
  // ADMIN_OPENIDS 中以逗号分隔配置;未配置时默认拒绝(失败安全),避免误部署后被滥用。
  const ctx = cloud.getWXContext()
  const caller = (ctx && ctx.OPENID) || ''
  const allowlist = (process.env.ADMIN_OPENIDS || '')
    .split(',')
    .map(s => s.trim())
    .filter(Boolean)
  if (!caller || allowlist.length === 0 || !allowlist.includes(caller)) {
    return { err: 'forbidden', msg: '无权限执行该操作' }
  }

  // 1. Page through every doc in the collection.
  const docs = []
  let skip = 0
  while (true) {
    const res = await db.collection(COLLECTION).skip(skip).limit(PAGE_SIZE).get()
    if (!res.data || res.data.length === 0) break
    docs.push(...res.data)
    if (res.data.length < PAGE_SIZE) break
    skip += PAGE_SIZE
  }

  // 2. Sort by updatedAt descending so the freshest doc per openid is
  //    first; that one is the one we keep.
  const tsOf = (d) => {
    if (!d.updatedAt) return 0
    // CloudBase sometimes returns Date objects, sometimes ISO strings
    // depending on the SDK version — normalize both.
    if (d.updatedAt instanceof Date) return d.updatedAt.getTime()
    const t = new Date(d.updatedAt).getTime()
    return Number.isFinite(t) ? t : 0
  }
  docs.sort((a, b) => tsOf(b) - tsOf(a))

  // 3. Walk the sorted list, marking all but the first occurrence of
  //    each openid for deletion.
  const seen = new Set()
  const toDelete = []
  const keptByOpenid = {}
  for (const doc of docs) {
    const openid = doc._openid || 'unknown'
    if (seen.has(openid)) {
      toDelete.push({ id: doc._id, openid })
    } else {
      seen.add(openid)
      keptByOpenid[openid] = doc._id
    }
  }

  // 4. Delete. Remove one at a time so a single permission/permission
  //    failure doesn't abort the whole cleanup.
  let deleted = 0
  const errors = []
  for (const { id, openid } of toDelete) {
    try {
      await db.collection(COLLECTION).doc(id).remove()
      deleted++
    } catch (e) {
      errors.push({ id, openid, msg: (e && e.message) || String(e) })
    }
  }

  return {
    scanned: docs.length,
    uniqueOpenids: seen.size,
    duplicatesFound: toDelete.length,
    duplicatesDeleted: deleted,
    duplicatesFailed: errors.length,
    errors,
    sampleKept: Object.fromEntries(
      Object.entries(keptByOpenid).slice(0, 5)
    )
  }
}