const DB_COLLECTION = 'plank_data'

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

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.
 */
const init = () => {
  try {
    wx.cloud.init({ env: 'cloudbase-d1g56kl2q8f4f7d8a', traceUser: true })
    _enabled = true
  } catch (e) {
    _enabled = false
  }
}

/**
 * Pull all user data from cloud. Returns null if no data or unavailable.
 * Collection is auto-created by first push, so .get() on empty collection
 * is safe — it just returns empty set.
 */
const pullAll = async () => {
  const db = getDb()
  if (!db) return null
  try {
    const res = await db.collection(DB_COLLECTION)
      .where({ _openid: '{openid}' })
      .get()
    if (res && res.data && res.data.length > 0) {
      return res.data[0]
    }
    return null
  } catch (e) {
    // Collection may not exist yet — that's fine, first push will create it
    return null
  }
}

/**
 * Schedule a push (debounced 2s).
 */
const pushAll = () => {
  if (!_enabled) return
  if (_pushTimer) clearTimeout(_pushTimer)
  _pushTimer = setTimeout(() => _doPush(), 2000)
}

const _doPush = async () => {
  const db = getDb()
  if (!db) return
  try {
    const storage = require('./storage')
    const themeMod = require('./theme')

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

    // Strategy: try add() first. On first use, this auto-creates the
    // collection. If the user already has a doc, it returns
    // 'duplicate' error; we fall back to update via query.
    try {
      await db.collection(DB_COLLECTION).add({ data })
    } catch (addErr) {
      // Likely already has a doc — find and update it
      const existing = await db.collection(DB_COLLECTION)
        .where({ _openid: '{openid}' })
        .get()
      if (existing && existing.data && existing.data.length > 0) {
        await db.collection(DB_COLLECTION)
          .doc(existing.data[0]._id)
          .update({ data })
      }
    }
  } catch (e) {
    // Silently ignore — data stays in local storage, will retry next write
  }
}

/**
 * Delete all cloud data for current user.
 */
const clearAll = async () => {
  const db = getDb()
  if (!db) return
  try {
    const existing = await db.collection(DB_COLLECTION)
      .where({ _openid: '{openid}' })
      .get()
    if (existing && existing.data && existing.data.length > 0) {
      await db.collection(DB_COLLECTION)
        .doc(existing.data[0]._id)
        .remove()
    }
  } catch (e) {
    // Collection or doc missing — nothing to clear
  }
}

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