const DB_COLLECTION = 'plank_data'

let _db = null
let _pushTimer = null
let _enabled = false

const getDb = () => {
  if (!_enabled) return null
  if (!_db) {
    try { _db = wx.cloud.database() } catch (e) { _enabled = false }
  }
  return _db
}

/**
 * Call once from app.js onLaunch to initialize cloud.
 * Gracefully degrades if cloud environment isn't configured yet.
 */
const init = () => {
  try {
    wx.cloud.init({ traceUser: true })
    _enabled = true
  } catch (e) {
    _enabled = false
  }
}

/**
 * Pull all user data from cloud. Returns null if cloud is unavailable or no data exists.
 */
const pullAll = async () => {
  const db = getDb()
  if (!db) return null
  try {
    const coll = db.collection(DB_COLLECTION)
    const res = await coll.where({ _openid: '{openid}' }).get()
    if (res && res.data && res.data.length > 0) {
      return res.data[0]
    }
    return null
  } catch (e) {
    console.error('Cloud pull failed:', e)
    return null
  }
}

/**
 * Schedule a cloud push (debounced at 2s).
 * Call this after any local data mutation.
 */
const pushAll = () => {
  if (!_enabled) return
  if (_pushTimer) clearTimeout(_pushTimer)
  _pushTimer = setTimeout(() => _doPush(), 2000)
}

const _doPush = async () => {
  const db = getDb()
  if (!db) return
  try {
    // Lazily require to avoid circular dependency at module-load time
    const storage = require('./storage')
    const themeMod = require('./theme')

    const data = {
      records: storage.getRecords(),
      settings: storage.getSettings(),
      streak: storage.getStreak(),
      themeId: themeMod.getCurrentTheme().id,
      updatedAt: new Date()
    }

    const coll = db.collection(DB_COLLECTION)
    const existing = await coll.where({ _openid: '{openid}' }).get()
    if (existing && existing.data && existing.data.length > 0) {
      await coll.doc(existing.data[0]._id).update({ data })
    } else {
      await coll.add({ data })
    }
  } catch (e) {
    console.error('Cloud push failed:', e)
  }
}

/**
 * Delete all cloud data for current user.
 */
const clearAll = async () => {
  const db = getDb()
  if (!db) return
  try {
    const coll = db.collection(DB_COLLECTION)
    const existing = await coll.where({ _openid: '{openid}' }).get()
    if (existing && existing.data && existing.data.length > 0) {
      await coll.doc(existing.data[0]._id).remove()
    }
  } catch (e) {
    console.error('Cloud clear failed:', e)
  }
}

module.exports = { init, pullAll, pushAll, clearAll, get enabled() { return _enabled } }