/**
 * MetonaEditor i18n — internationalization
 * @module i18n
 * @version 0.2.0
 */

import { LOCALES } from './constants';
import type { EditorOptions } from './constants';

let currentLocale = 'zh-CN';
let localeListeners = new Set<(locale: string) => void>();
let fallbackLocale = 'zh-CN';

type PluralRule = (n: number) => string;

const pluralRules: Record<string, PluralRule> = {
  zh: () => 'other',
  en: (n) => n === 1 ? 'one' : 'other',
  ru: (n) => {
    const m = n % 10, h = n % 100;
    if (m === 1 && h !== 11) return 'one';
    if (m >= 2 && m <= 4 && !(h >= 12 && h <= 14)) return 'few';
    if (m === 0 || (m >= 5 && m <= 9) || (h >= 11 && h <= 14)) return 'many';
    return 'other';
  },
};

const getPluralForm = (locale: string, count: number): string => {
  const lang = locale.split('-')[0].toLowerCase();
  const rule = pluralRules[lang] || pluralRules.en;
  return rule(Math.abs(count));
};

export const getCurrentLocale = (): string => currentLocale;

export const setCurrentLocale = (locale: string): void => {
  let target = locale;
  if (!LOCALES[target]) {
    console.warn(`Locale "${target}" not found, falling back to "${fallbackLocale}"`);
    target = fallbackLocale;
  }
  currentLocale = target;
  notifyLocaleListeners(target);
  saveLocale(target);
};

export const t = (key: string, params: Record<string, any> = {}, locale?: string): string => {
  const loc = locale || currentLocale;
  let translation: any = getTranslation(loc, key);
  if (translation && typeof translation === 'object' && params.count !== undefined) {
    const form = getPluralForm(loc, params.count);
    translation = translation[form] || translation.other || key;
  }
  if (typeof translation === 'string') return interpolate(translation, params);
  if (loc !== fallbackLocale) {
    let fb: any = getTranslation(fallbackLocale, key);
    if (fb && typeof fb === 'object' && params.count !== undefined) {
      const form = getPluralForm(fallbackLocale, params.count);
      fb = fb[form] || fb.other;
    }
    if (typeof fb === 'string') return interpolate(fb, params);
  }
  console.warn(`Translation missing for key "${key}" in locale "${loc}"`);
  return key;
};

const getTranslation = (locale: string, key: string): any => {
  const localeData: any = LOCALES[locale];
  if (!localeData) return undefined;
  const keys = key.split('.');
  let result: any = localeData;
  for (const k of keys) {
    if (result && typeof result === 'object' && k in result) {
      result = result[k];
    } else return undefined;
  }
  return result;
};

const interpolate = (str: string, params: Record<string, any>): string => {
  return str.replace(/\{(\w+)\}/g, (_match, key) => params[key] !== undefined ? String(params[key]) : _match);
};

export const hasTranslation = (key: string): boolean => {
  return getTranslation(currentLocale, key) !== undefined || getTranslation(fallbackLocale, key) !== undefined;
};

export const getTranslations = (locale: string): Record<string, any> => LOCALES[locale] || {};

export const addTranslations = (locale: string, translations: Record<string, any>): void => {
  if (!LOCALES[locale]) LOCALES[locale] = {};
  deepMergeI18n(LOCALES[locale], translations);
};

export const loadRemote = async (url: string, locale: string): Promise<boolean> => {
  try {
    const res = await fetch(url);
    if (!res.ok) throw new Error(`HTTP ${res.status}`);
    const data = await res.json();
    addTranslations(locale, data);
    return true;
  } catch (e) {
    console.error(`MeEditor: failed to load locale "${locale}" from ${url}`, e);
    return false;
  }
};

const deepMergeI18n = (target: Record<string, any>, source: Record<string, any>): Record<string, any> => {
  for (const key in source) {
    if (source[key] instanceof Object && key in target && target[key] instanceof Object && !Array.isArray(source[key])) {
      deepMergeI18n(target[key], source[key]);
    } else {
      target[key] = source[key];
    }
  }
  return target;
};

export const getSupportedLocales = (): string[] => Object.keys(LOCALES);
export const isLocaleSupported = (locale: string): boolean => locale in LOCALES;

export const getLocaleName = (locale: string): string => {
  const names: Record<string, string> = {
    'zh-CN': '简体中文', 'zh-TW': '繁體中文', 'en-US': 'English (US)', 'en-GB': 'English (UK)',
    ja: '日本語', ko: '한국어', fr: 'Français', de: 'Deutsch', es: 'Español', pt: 'Português',
    ru: 'Русский', ar: 'العربية', hi: 'हिन्दी', th: 'ไทย',
    vi: 'Tiếng Việt', id: 'Bahasa Indonesia', tr: 'Türkçe',
    it: 'Italiano', nl: 'Nederlands', pl: 'Polski',
  };
  return names[locale] || locale;
};

export const getLocaleDirection = (locale: string): 'ltr' | 'rtl' => {
  const rtlLocales = ['ar', 'he', 'fa', 'ur', 'yi', 'ps', 'sd', 'ug', 'dv', 'ku', 'syr'];
  const short = locale.split('-')[0].toLowerCase();
  return rtlLocales.includes(short) ? 'rtl' : 'ltr';
};

export const formatNumber = (number: number, options: Intl.NumberFormatOptions = {}): string => {
  try { return new Intl.NumberFormat(currentLocale, options).format(number); }
  catch (_) { return String(number); }
};

export const formatCurrency = (amount: number, currency: string = 'USD', options: Intl.NumberFormatOptions = {}): string => {
  try { return new Intl.NumberFormat(currentLocale, { style: 'currency', currency, ...options }).format(amount); }
  catch (_) { return String(amount); }
};

export const formatDate = (date: Date | string, options: Intl.DateTimeFormatOptions = {}): string => {
  try {
    const d = date instanceof Date ? date : new Date(date);
    return new Intl.DateTimeFormat(currentLocale, options).format(d);
  } catch (_) { return String(date); }
};

export const addLocaleListener = (fn: (locale: string) => void): () => void => {
  localeListeners.add(fn);
  return () => { localeListeners.delete(fn); };
};

export const removeLocaleListener = (fn: (locale: string) => void): void => { localeListeners.delete(fn); };
export const clearLocaleListeners = (): void => { localeListeners.clear(); };

const notifyLocaleListeners = (locale: string): void => {
  localeListeners.forEach((fn) => {
    try { fn(locale); } catch (e) { console.error('Locale listener error:', e); }
  });
};

export const saveLocale = (locale: string): void => {
  if (typeof localStorage !== 'undefined') {
    try { localStorage.setItem('metona-editor-locale', locale); } catch (_) {}
  }
};

export const loadLocale = (): string => {
  if (typeof localStorage !== 'undefined') {
    try { return localStorage.getItem('metona-editor-locale') || getDefaultLocale(); } catch (_) {}
  }
  return getDefaultLocale();
};

export const getDefaultLocale = (): string => {
  if (typeof navigator !== 'undefined') {
    const browserLocale: string = (navigator as any).language || (navigator as any).userLanguage;
    if (browserLocale && isLocaleSupported(browserLocale)) return browserLocale;
    const short = browserLocale?.split('-')[0];
    if (short && isLocaleSupported(short)) return short;
  }
  return fallbackLocale;
};

export const getFallbackLocale = (): string => fallbackLocale;
export const setFallbackLocale = (locale: string): void => { fallbackLocale = locale; };

export const initI18n = (): void => {
  const saved = loadLocale();
  setCurrentLocale(saved);
};

export const switchLocale = (locale: string): void => { setCurrentLocale(locale); };

export interface InstanceI18n {
  set: (locale: string) => string;
  get: () => string;
  getDirection: () => 'ltr' | 'rtl';
  t: (key: string, params?: Record<string, any>) => string;
  formatNumber: (n: number, opts?: Intl.NumberFormatOptions) => string;
  formatDate: (d: Date | string, opts?: Intl.DateTimeFormatOptions) => string;
}

export const createInstanceI18n = (editor: any): InstanceI18n => {
  let instanceLocale = editor.config?.locale || currentLocale || 'zh-CN';

  const instanceT = (key: string, params: Record<string, any> = {}): string => t(key, params, instanceLocale);

  const set = (locale: string): string => {
    if (!locale || instanceLocale === locale) return instanceLocale;
    instanceLocale = locale;
    if (editor.el) {
      editor.el.setAttribute('lang', locale);
      editor.el.setAttribute('dir', getLocaleDirection(locale));
    }
    if (editor.textarea) {
      editor.textarea.placeholder = instanceT('placeholder') || '';
      editor.textarea.setAttribute('aria-label', instanceT('edit') || '');
      editor.textarea.setAttribute('dir', getLocaleDirection(locale));
    }
    if (typeof editor._emit === 'function') {
      editor._emit('localeChange', { locale, direction: getLocaleDirection(locale) });
    }
    if (editor.toolbarEl) {
      editor.toolbarEl.querySelectorAll('.me-btn').forEach((btn: HTMLElement) => {
        const action = btn.dataset.action || btn.dataset.mode;
        if (action) {
          const label = instanceT(action);
          if (label && label !== action) {
            btn.title = label;
            btn.setAttribute('aria-label', label);
          }
        }
      });
    }
    // 语言切换即时刷新已渲染的 UI（状态栏统计标签、大纲标题），无需等待下一次输入
    if (typeof editor._updateWordCount === 'function') { try { editor._updateWordCount(); } catch (_) {} }
    if (editor.el && typeof editor.el.querySelector === 'function') {
      const outlineTitle = editor.el.querySelector('.me-outline-title');
      if (outlineTitle) outlineTitle.textContent = instanceT('outline') || 'Outline';
    }
    return instanceLocale;
  };

  return {
    set, get: () => instanceLocale, getDirection: () => getLocaleDirection(instanceLocale), t: instanceT,
    formatNumber: (n, opts) => { try { return new Intl.NumberFormat(instanceLocale, opts).format(n); } catch (_) { return String(n); } },
    formatDate: (d, opts) => { try { return new Intl.DateTimeFormat(instanceLocale, opts).format(d instanceof Date ? d : new Date(d)); } catch (_) { return String(d); } },
  };
};

export const createI18nManager = () => ({
  t, getCurrentLocale, setCurrentLocale, switchLocale,
  getFallbackLocale: () => fallbackLocale, setFallbackLocale: (locale: string) => { fallbackLocale = locale; },
  hasTranslation, getTranslations, addTranslations, loadRemote,
  getSupportedLocales, isLocaleSupported, getLocaleName, getLocaleDirection,
  formatNumber, formatCurrency, formatDate, addLocaleListener, removeLocaleListener, clearLocaleListeners,
  initI18n, saveLocale, loadLocale, getDefaultLocale, createInstanceI18n,
});

export const presetLocales = {
  'zh-CN': { name: '简体中文', nativeName: '简体中文', direction: 'ltr', translations: LOCALES['zh-CN'] },
  'en-US': { name: 'English (US)', nativeName: 'English (US)', direction: 'ltr', translations: LOCALES['en-US'] },
  ja: { name: '日本語', nativeName: '日本語', direction: 'ltr', translations: (LOCALES as any)['ja'] },
  ko: { name: '한국어', nativeName: '한국어', direction: 'ltr', translations: (LOCALES as any)['ko'] },
  fr: { name: 'Français', nativeName: 'Français', direction: 'ltr', translations: (LOCALES as any)['fr'] },
  de: { name: 'Deutsch', nativeName: 'Deutsch', direction: 'ltr', translations: (LOCALES as any)['de'] },
};

export const i18nUtils = createI18nManager();
export default i18nUtils;