import i18n from 'i18next';
import { initReactI18next } from 'react-i18next';
import { mergeTranslations } from '@/locales';
import * as z from 'zod';
import { setLocaleInClient } from '@/modules/auth/hooks/use-auth-hook';

export type SupportedLanguages = 'en' | 'ja';
const supportedLanguages: SupportedLanguages[] = ['en', 'ja'];
const defaultLanguage: SupportedLanguages = 'en';
const localStorageKey = 'app-language';

const setLanguageHooks = (language: SupportedLanguages) => {
  setLocaleInClient(language);
  z.config((z.locales[language] ?? z.locales[defaultLanguage] ?? z.locales['en'])());
};

const getStoredLanguage = (): SupportedLanguages => {
  try {
    const stored = localStorage.getItem(localStorageKey);
    if (!stored) {
      localStorage.setItem(localStorageKey, defaultLanguage);
      return defaultLanguage;
    }
    return stored as SupportedLanguages;
  } catch {
    return defaultLanguage;
  }
};

if (!i18n.isInitialized) {
  const lng = getStoredLanguage();
  const enResources = mergeTranslations('en');
  const jaResources = mergeTranslations('ja');
  i18n.use(initReactI18next).init({
    resources: {
      en: {
        translation: enResources,
        ...enResources,
      },
      ja: {
        translation: jaResources,
        ...jaResources,
      },
    },
    defaultNS: 'translation',
    ns: ['translation', 'auth', 'app', 'landing', 'common', 'theme'],
    supportedLngs: supportedLanguages,
    lng,
    fallbackLng: defaultLanguage,
    interpolation: {
      escapeValue: false,
    },
  });
  setLanguageHooks(lng);
}

export const getLanguage = () => {
  return i18n.language;
};

export const changeLanguage = (language: SupportedLanguages) => {
  try {
    localStorage.setItem(localStorageKey, language);
  } catch {
    // Fallback if localStorage is not available
  }
  i18n.changeLanguage(language);
  setLanguageHooks(language);
};

export default i18n;