import Vue from 'vue'
import VueI18n from 'vue-i18n'
import messages from '../langs/index'
import { LOCALES_NAMES } from '@/constants'

Vue.use(VueI18n)

let lang = 'en'

if (process.browser) {
  const locale = localStorage.getItem('lang') || navigator.language.substr(0, 2).toLowerCase()
  lang = !messages[locale] ? 'en' : locale
}

const dateTimeFormats = {
  en: {
    long: {
      year: 'numeric',
      month: 'long',
      day: 'numeric',
      weekday: 'long',
      hour: 'numeric',
      minute: 'numeric',
      hour12: true
    }
  },
  es: {
    long: {
      year: 'numeric',
      month: 'long',
      day: 'numeric',
      hour: 'numeric',
      minute: 'numeric'
    }
  },
  fr: {
    long: {
      year: 'numeric',
      month: 'long',
      day: 'numeric',
      hour: 'numeric',
      minute: 'numeric'
    }
  },
  ru: {
    long: {
      year: 'numeric',
      month: 'long',
      day: 'numeric',
      hour: 'numeric',
      minute: 'numeric'
    }
  },
  tr: {
    long: {
      year: 'numeric',
      month: 'long',
      day: 'numeric',
      hour: 'numeric',
      minute: 'numeric'
    }
  },
  uk: {
    long: {
      year: 'numeric',
      month: 'long',
      day: 'numeric',
      hour: 'numeric',
      minute: 'numeric'
    }
  },
  zh: {
    long: {
      year: 'numeric',
      month: 'long',
      day: 'numeric',
      weekday: 'long',
      hour: 'numeric',
      minute: 'numeric',
      hour12: true
    }
  }
}

const numberFormats = {
  en: {
    compact: {
      notation: 'compact'
    }
  },
  es: {
    compact: {
      notation: 'compact'
    }
  },
  fr: {
    compact: {
      notation: 'compact'
    }
  },
  ru: {
    compact: {
      notation: 'compact'
    }
  },
  tr: {
    compact: {
      notation: 'compact'
    }
  },
  uk: {
    compact: {
      notation: 'compact'
    }
  },
  zh: {
    compact: {
      notation: 'compact'
    }
  }
}

function slavicPluralization(choice, choicesLength) {
  /**
   * @param choice {number} a choice index given by the input to $tc: `$tc('path.to.rule', choiceIndex)`
   * @param choicesLength {number} an overall amount of available choices
   * @returns a final choice index to select plural word by
   */

  if (choice === 0) {
    return 0
  }

  const teen = choice > 10 && choice < 20
  const endsWithOne = choice % 10 === 1

  if (choicesLength < 4) {
    return !teen && endsWithOne ? 1 : 2
  }
  if (!teen && endsWithOne) {
    return 1
  }
  if (!teen && choice % 10 >= 2 && choice % 10 <= 4) {
    return 2
  }

  return choicesLength < 4 ? 2 : 3
}

const pluralizationRules = {
  ru: slavicPluralization,
  uk: slavicPluralization
}

// Create VueI18n instance with options
export default ({ app, route, store }) => {
  app.i18n = new VueI18n({
    locale: lang,
    fallbackLocale: 'en',
    messages,
    silentFallbackWarn: true,
    dateTimeFormats,
    numberFormats,
    pluralizationRules
  })

  if (lang === 'zh') {
    lang += '-cn'
  }

  app.$moment.locale(lang)
  app.$numbro.setLanguage(LOCALES_NAMES[lang])
}