/**
 * Copyright (c) Nicolas Gallagher.
 *
 * This source code is licensed under the MIT license found in the
 * LICENSE file in the root directory of this source tree.
 *
 * @flow
 */

const rtlScripts = new Set([
  'Arab',
  'Syrc',
  'Samr',
  'Mand',
  'Thaa',
  'Mend',
  'Nkoo',
  'Adlm',
  'Rohg',
  'Hebr',
])

const rtlLangs = new Set([
  'ae', // Avestan
  'ar', // Arabic
  'arc', // Aramaic
  'bcc', // Southern Balochi
  'bqi', // Bakthiari
  'ckb', // Sorani
  'dv', // Dhivehi
  'fa',
  'far', // Persian
  'glk', // Gilaki
  'he',
  'iw', // Hebrew
  'khw', // Khowar
  'ks', // Kashmiri
  'ku', // Kurdish
  'mzn', // Mazanderani
  'nqo', // N'Ko
  'pnb', // Western Punjabi
  'ps', // Pashto
  'sd', // Sindhi
  'ug', // Uyghur
  'ur', // Urdu
  'yi', // Yiddish
])

const cache = new Map()

/**
 * Determine the writing direction of a locale
 */
export function isLocaleRTL(locale: string): boolean {
  const cachedRTL = cache.get(locale)
  if (cachedRTL) {
    return cachedRTL
  }

  let isRTL = false
  // @ts-ignore
  if (Intl.Locale) {
    // @ts-ignore
    const script = new Intl.Locale(locale).maximize().script
    isRTL = rtlScripts.has(script as any)
  } else {
    // Fallback to inferring from language
    const lang = locale.split('-')[0]
    isRTL = rtlLangs.has(lang)
  }

  cache.set(locale, isRTL)
  return isRTL
}