export const SUPPORTED_LOCALES = ['en', 'zh'] as const
export type AppLocale = typeof SUPPORTED_LOCALES[number]

export const DEFAULT_LOCALE: AppLocale = 'en'

export const LOCALE_OPTIONS: Array<{
  value: AppLocale
  label: string
  shortLabel: string
}> = [
  {
    value: 'en',
    label: 'English',
    shortLabel: 'EN'
  },
  {
    value: 'zh',
    label: '中文',
    shortLabel: '中'
  }
]

export function resolveLocale(value: string | null | undefined, fallback: AppLocale = DEFAULT_LOCALE): AppLocale {
  const normalized = String(value || '').trim().toLowerCase()

  if (!normalized) {
    return fallback
  }

  if (normalized === 'zh' || normalized.startsWith('zh-') || normalized.startsWith('cn')) {
    return 'zh'
  }

  if (normalized === 'en' || normalized.startsWith('en-')) {
    return 'en'
  }

  return fallback
}

export function getOppositeLocale(locale: AppLocale): AppLocale {
  return locale === 'zh' ? 'en' : 'zh'
}