// Vela storage callbacks return raw strings, not { data } wrappers.
// https://iot.mi.com/vela/quickapp/en/features/data/storage.html
function createStore(storage) {
  let value = 0
  let saved = 0
  let loaded = false
  let reading = false
  let writing = false
  let listener = null
  function notify() { if (listener) listener(value) }
  function flush() {
    if (!loaded || writing || value <= saved) return
    writing = true
    const target = value
    let settled = false
    const fail = () => { if (!settled) { settled = true; writing = false } }
    try {
      storage.set({ key: 'snake.best', value: String(target), success() {
        if (settled) return
        settled = true
        writing = false
        saved = target
        flush()
      }, fail })
    } catch (e) { fail() }
  }
  function sync() {
    if (loaded) { flush(); return }
    if (reading) return
    reading = true
    let settled = false
    const fail = () => { if (!settled) { settled = true; reading = false } }
    try {
      storage.get({ key: 'snake.best', default: '0', success(raw) {
        if (settled) return
        settled = true
        reading = false
        const n = Number(raw)
        saved = Number.isInteger(n) && n >= 0 && n <= 253 ? n : 0
        value = Math.max(value, saved)
        loaded = true
        notify()
        flush()
      }, fail })
    } catch (e) { fail() }
  }
  return {
    subscribe(fn) { listener = fn; notify() },
    record(score) { value = Math.max(value, score); notify(); sync() },
    sync
  }
}
// One coordinator per native storage module, retained across page recreation.
let sharedAPI
let sharedStore
function getStore(storage) {
  if (storage !== sharedAPI) {
    sharedAPI = storage
    sharedStore = createStore(storage)
  }
  return sharedStore
}
module.exports = { getStore }