fscan/fscan-lab/frontend/src/contexts/I18nContext.tsx

import { createContext, useContext, useState, ReactNode } from 'react'
import { translations, Language, TranslationKey } from '@/lib/i18n'

interface I18nContextType {
  language: Language
  setLanguage: (lang: Language) => void
  t: (key: TranslationKey) => string
}

const I18nContext = createContext<I18nContextType | undefined>(undefined)

export function I18nProvider({ children }: { children: ReactNode }) {
  const [language, setLanguage] = useState<Language>(() => {
    const saved = localStorage.getItem('language')
    return (saved === 'zh' || saved === 'en') ? saved : 'zh'
  })

  const handleSetLanguage = (lang: Language) => {
    setLanguage(lang)
    localStorage.setItem('language', lang)
  }

  const t = (key: TranslationKey): string => {
    return translations[language][key] || key
  }

  return (
    <I18nContext.Provider value={{ language, setLanguage: handleSetLanguage, t }}>
      {children}
    </I18nContext.Provider>
  )
}

export function useI18n() {
  const context = useContext(I18nContext)
  if (!context) {
    throw new Error('useI18n must be used within I18nProvider')
  }
  return context
}