import store from '@/store'
import globalMessages from '@/locales/messages'

export const ZH_LOCALE = 'zh-Hans'
export const EN_LOCALE = 'en'
export const DEFAULT_LOCALE = ZH_LOCALE

function safeReadStorageLocale() {
  try {
    const lifeData = uni.getStorageSync('lifeData') || {}
    return lifeData.vuex_locale || ''
  } catch (error) {
    return ''
  }
}

export function normalizeLocale(locale) {
  const normalized = String(locale || '').trim().toLowerCase()
  if (!normalized) {
    return DEFAULT_LOCALE
  }
  if (normalized === 'en' || normalized === 'en-us' || normalized === 'en_us') {
    return EN_LOCALE
  }
  if (normalized === 'zh' || normalized === 'zh-cn' || normalized === 'zh_cn' || normalized === 'zh-hans') {
    return ZH_LOCALE
  }
  return normalized.startsWith('en') ? EN_LOCALE : ZH_LOCALE
}

export function getLocaleShort(locale) {
  return normalizeLocale(locale) === EN_LOCALE ? 'en' : 'zh'
}

export function getCurrentLocale() {
  const stateLocale = store && store.state ? store.state.vuex_locale : ''
  return normalizeLocale(stateLocale || safeReadStorageLocale())
}

export function getCurrentLanguage() {
  return getLocaleShort(getCurrentLocale())
}

export function getNextLocale(locale) {
  return normalizeLocale(locale) === EN_LOCALE ? ZH_LOCALE : EN_LOCALE
}

export function resolveLanguageHeader(locale) {
  return getLocaleShort(locale) === 'en' ? 'en-US' : 'zh-CN'
}

export function formatI18nText(template, params = {}) {
  return String(template || '').replace(/\{(\w+)\}/g, (match, key) => {
    return Object.prototype.hasOwnProperty.call(params, key) ? params[key] : match
  })
}

function getMessageText(messages = {}, locale, key) {
  const shortLocale = getLocaleShort(locale)
  const fallbackMessages = messages.zh || messages[ZH_LOCALE] || {}
  const scopedMessages = messages[shortLocale] || messages[normalizeLocale(locale)] || fallbackMessages
  if (scopedMessages[key] !== undefined) {
    return scopedMessages[key]
  }
  return fallbackMessages[key]
}

export function translateMessages(messages = {}, locale, key, params = {}) {
  const text = getMessageText(messages, locale, key)
  return formatI18nText(text !== undefined ? text : key, params)
}

export function getMessageScope(messages = {}, namespace = '') {
  if (!namespace) {
    return messages
  }
  return String(namespace)
    .split('.')
    .filter(Boolean)
    .reduce((current, segment) => {
      if (!current || typeof current !== 'object') {
        return undefined
      }
      return current[segment]
    }, messages)
}

export function getGlobalMessages(namespace = '') {
  if (!namespace) {
    return globalMessages
  }
  const zhScope = getMessageScope(globalMessages.zh || globalMessages[ZH_LOCALE] || {}, namespace)
  const enScope = getMessageScope(globalMessages.en || globalMessages[EN_LOCALE] || {}, namespace)
  
  if (!zhScope && !enScope) {
    return undefined
  }
  
  return {
    zh: zhScope || {},
    en: enScope || {}
  }
}

export function translateGlobalMessages(namespace, locale, key, params = {}) {
  const scopedMessages = getGlobalMessages(namespace)
  if (!scopedMessages || typeof scopedMessages !== 'object') {
    return key
  }
  return translateMessages(scopedMessages, locale, key, params)
}

export function getGlobalMessage(namespace, locale, key, params = {}) {
  const scopedMessages = getGlobalMessages(namespace)
  if (!scopedMessages || typeof scopedMessages !== 'object') {
    return ''
  }
  const text = getMessageText(scopedMessages, locale, key)
  return text === undefined ? '' : formatI18nText(text, params)
}

export function pickLocalizedText(options = {}) {
  const locale = getLocaleShort(options.locale)
  const zhText = options.zh !== undefined ? options.zh : ''
  const enText = options.en !== undefined ? options.en : zhText
  if (locale === 'en') {
    return enText || options.fallback || zhText || ''
  }
  return zhText || options.fallback || enText || ''
}

// === 派生扁平字典（中文 → 英文）===
// 从 globalMessages 的 zh/en 双套结构反向派生 {'中文':'英文'} map，
// 供 translateText / $tr 使用。模块加载后懒加载、进程内缓存。
let __flatDictionary = null
let __dictConflicts = null

// 手动裁决的冲突项：键为中文，值为优先采用的英文。
// 当同一中文在 messages.js 不同位置有不同英文译法时，在此指定通用译法；
// 强上下文相关、无法单一裁决的条目，组件内保留 $tm 作为逃生口。
const DICT_OVERRIDES = {}

function buildFlatDictionary() {
  if (__flatDictionary) return __flatDictionary

  const dict = Object.create(null)
  const conflicts = []
  const seen = Object.create(null)

  // 1. 优先注入手动裁决项
  Object.keys(DICT_OVERRIDES).forEach((zh) => {
    dict[zh] = DICT_OVERRIDES[zh]
    seen[zh] = { en: DICT_OVERRIDES[zh], path: '<override>' }
  })

  const zhRoot = globalMessages.zh || globalMessages[ZH_LOCALE] || {}
  const enRoot = globalMessages.en || globalMessages[EN_LOCALE] || {}

  // 2. 平行 DFS：以 zh 叶子（中文）为 key，同路径 en 叶子为 value
  function walk(zhNode, enNode, path) {
    if (zhNode && typeof zhNode === 'object' && !Array.isArray(zhNode)) {
      const keys = Object.keys(zhNode)
      for (let i = 0; i < keys.length; i += 1) {
        const k = keys[i]
        walk(zhNode[k], enNode ? enNode[k] : undefined, path ? path + '.' + k : k)
      }
      return
    }
    const zhText = zhNode == null ? '' : String(zhNode)
    if (!zhText) return
    const enText = enNode == null ? zhText : String(enNode)

    if (seen[zhText]) {
      if (seen[zhText].en !== enText) {
        conflicts.push({
          zh: zhText,
          enFirst: seen[zhText].en,
          enCurrent: enText,
          pathFirst: seen[zhText].path,
          pathCurrent: path
        })
      }
      // 首次写入优先：已存在则不覆盖
      return
    }
    dict[zhText] = enText
    seen[zhText] = { en: enText, path }
  }
  walk(zhRoot, enRoot, '')

  __flatDictionary = dict
  __dictConflicts = conflicts

  if (process.env.NODE_ENV !== 'production' && conflicts.length) {
    console.warn('[i18n] flat dictionary built with ' + conflicts.length + ' conflicts; call getDictionaryConflicts() for details')
  }

  return dict
}

// 中文即 key 的翻译函数：中文环境原样返回，英文环境查扁平字典，查不到回退中文。
// 支持与 $tm/$translate 一致的 {param} 占位符替换。
export function translateText(text, locale, params = {}) {
  if (text === null || text === undefined) return ''
  const zhText = String(text)
  if (!zhText) return ''

  if (normalizeLocale(locale) !== EN_LOCALE) {
    return formatI18nText(zhText, params)
  }

  const dict = buildFlatDictionary()
  const enText = dict[zhText]
  if (enText === undefined) {
    if (process.env.NODE_ENV !== 'production') {
      console.warn('[i18n] missing dictionary entry for: ' + zhText)
    }
    return formatI18nText(zhText, params)
  }
  return formatI18nText(enText, params)
}

export function getFlatDictionary() {
  return buildFlatDictionary()
}

export function getDictionaryConflicts() {
  if (!__dictConflicts) buildFlatDictionary()
  return __dictConflicts || []
}