// Lightweight i18n for WeChat Mini Program (no official i18n API).
//
// Usage in a page:
//   var i18n = require('../../i18n/index')
//   onShow: function () { i18n.bind(this) }   // injects `i18n` + `locale` into page data
//   WXML:  {{i18n.common.loading}}   /   {{i18n.profile.title}}
//   JS strings: i18n.t('common.loading')
//
// Locale is persisted in storage; switching locale notifies listeners and the
// convention is that every page re-runs i18n.bind(this) in onShow, so tab pages
// pick up the new language the next time they are shown.

var locales = require('./locales/index')

var STORAGE_KEY = 'app_locale'
var DEFAULT_LOCALE = 'zh'
var SUPPORTED = ['zh', 'en']
var LOCALE_NAMES = { zh: '中文', en: 'English' }

var _listeners = []
var _current = null

function getSystemLocale() {
  try {
    var sys = wx.getSystemInfoSync()
    var lang = (sys.language || '').toLowerCase()
    return lang.indexOf('en') === 0 ? 'en' : 'zh'
  } catch (e) {
    return DEFAULT_LOCALE
  }
}

function getLocale() {
  if (_current) return _current
  var saved = ''
  try { saved = wx.getStorageSync(STORAGE_KEY) } catch (e) {}
  _current = SUPPORTED.indexOf(saved) !== -1 ? saved : getSystemLocale()
  return _current
}

function setLocale(locale) {
  if (SUPPORTED.indexOf(locale) === -1 || locale === _current) return
  _current = locale
  try { wx.setStorageSync(STORAGE_KEY, locale) } catch (e) {}
  applyTabBar()
  for (var i = 0; i < _listeners.length; i++) {
    try { _listeners[i](locale) } catch (e) {}
  }
}

function onChange(fn) { if (typeof fn === 'function') _listeners.push(fn) }
function offChange(fn) {
  _listeners = _listeners.filter(function (f) { return f !== fn })
}

function getDict() {
  var loc = getLocale()
  return locales[loc] || locales[DEFAULT_LOCALE]
}

function _lookup(dict, key) {
  if (!dict) return undefined
  var parts = key.split('.')
  var cur = dict
  for (var i = 0; i < parts.length; i++) {
    if (cur == null) return undefined
    cur = cur[parts[i]]
  }
  return cur
}

// t('profile.title', {name: 'x'}) — falls back to zh, then to the raw key.
function t(key, params) {
  var loc = getLocale()
  var val = _lookup(locales[loc], key)
  if (val === undefined) val = _lookup(locales[DEFAULT_LOCALE], key)
  if (typeof val !== 'string') return val === undefined ? key : val
  if (params) {
    val = val.replace(/\{(\w+)\}/g, function (m, k) {
      return params[k] !== undefined ? params[k] : m
    })
  }
  return val
}

// Inject the full dictionary + current locale into a page/component's data.
function bind(page) {
  if (page && typeof page.setData === 'function') {
    page.setData({ i18n: getDict(), locale: getLocale() })
  }
}

// Refresh the bottom tabBar labels to the current locale.
function applyTabBar() {
  var d = getDict()
  var tab = (d && d.common && d.common.tab) || {}
  var items = [
    { index: 0, text: tab.home },
    { index: 1, text: tab.records },
    { index: 2, text: tab.mine }
  ]
  items.forEach(function (it) {
    if (!it.text) return
    wx.setTabBarItem({ index: it.index, text: it.text, fail: function () {} })
  })
}

module.exports = {
  SUPPORTED: SUPPORTED,
  LOCALE_NAMES: LOCALE_NAMES,
  getLocale: getLocale,
  setLocale: setLocale,
  getSystemLocale: getSystemLocale,
  onChange: onChange,
  offChange: offChange,
  getDict: getDict,
  bind: bind,
  applyTabBar: applyTabBar,
  t: t
}