(function (global, factory) {
  typeof exports === 'object' && typeof module !== 'undefined' ? factory(exports) :
  typeof define === 'function' && define.amd ? define('GOVUKFrontend', ['exports'], factory) :
  (factory((global.GOVUKFrontend = {})));
}(this, (function (exports) { 'use strict';

  /**
   * Internal support for selecting messages to render, with placeholder
   * interpolation and locale-aware number formatting and pluralisation
   *
   * @class
   * @private
   * @param {Object<string, unknown>} translations - Key-value pairs of the translation strings to use.
   * @param {object} [config] - Configuration options for the function.
   * @param {string} [config.locale] - An overriding locale for the PluralRules functionality.
   */
  function I18n (translations, config) {
    // Make list of translations available throughout function
    this.translations = translations || {};

    // The locale to use for PluralRules and NumberFormat
    this.locale = (config && config.locale) || document.documentElement.lang || 'en';
  }

  /**
   * The most used function - takes the key for a given piece of UI text and
   * returns the appropriate string.
   *
   * @param {string} lookupKey - The lookup key of the string to use.
   * @param {Object<string, unknown>} [options] - Any options passed with the translation string, e.g: for string interpolation.
   * @returns {string} The appropriate translation string.
   * @throws {Error} Lookup key required
   * @throws {Error} Options required for `${}` placeholders
   */
  I18n.prototype.t = function (lookupKey, options) {
    if (!lookupKey) {
      // Print a console error if no lookup key has been provided
      throw new Error('i18n: lookup key missing')
    }

    // If the `count` option is set, determine which plural suffix is needed and
    // change the lookupKey to match. We check to see if it's numeric instead of
    // falsy, as this could legitimately be 0.
    if (options && typeof options.count === 'number') {
      // Get the plural suffix
      lookupKey = lookupKey + '.' + this.getPluralSuffix(lookupKey, options.count);
    }

    // Fetch the translation string for that lookup key
    var translationString = this.translations[lookupKey];

    if (typeof translationString === 'string') {
      // Check for ${} placeholders in the translation string
      if (translationString.match(/%{(.\S+)}/)) {
        if (!options) {
          throw new Error('i18n: cannot replace placeholders in string if no option data provided')
        }

        return this.replacePlaceholders(translationString, options)
      } else {
        return translationString
      }
    } else {
      // If the key wasn't found in our translations object,
      // return the lookup key itself as the fallback
      return lookupKey
    }
  };

  /**
   * Takes a translation string with placeholders, and replaces the placeholders
   * with the provided data
   *
   * @param {string} translationString - The translation string
   * @param {Object<string, unknown>} options - Any options passed with the translation string, e.g: for string interpolation.
   * @returns {string} The translation string to output, with ${} placeholders replaced
   */
  I18n.prototype.replacePlaceholders = function (translationString, options) {
    /** @type {Intl.NumberFormat | undefined} */
    var formatter;

    if (this.hasIntlNumberFormatSupport()) {
      formatter = new Intl.NumberFormat(this.locale);
    }

    return translationString.replace(
      /%{(.\S+)}/g,

      /**
       * Replace translation string placeholders
       *
       * @param {string} placeholderWithBraces - Placeholder with braces
       * @param {string} placeholderKey - Placeholder key
       * @returns {string} Placeholder value
       */
      function (placeholderWithBraces, placeholderKey) {
        if (Object.prototype.hasOwnProperty.call(options, placeholderKey)) {
          var placeholderValue = options[placeholderKey];

          // If a user has passed `false` as the value for the placeholder
          // treat it as though the value should not be displayed
          if (placeholderValue === false || (
            typeof placeholderValue !== 'number' &&
            typeof placeholderValue !== 'string')
          ) {
            return ''
          }

          // If the placeholder's value is a number, localise the number formatting
          if (typeof placeholderValue === 'number') {
            return formatter ? formatter.format(placeholderValue) : placeholderValue.toString()
          }

          return placeholderValue
        } else {
          throw new Error('i18n: no data found to replace ' + placeholderWithBraces + ' placeholder in string')
        }
      })
  };

  /**
   * Check to see if the browser supports Intl and Intl.PluralRules.
   *
   * It requires all conditions to be met in order to be supported:
   * - The browser supports the Intl class (true in IE11)
   * - The implementation of Intl supports PluralRules (NOT true in IE11)
   * - The browser/OS has plural rules for the current locale (browser dependent)
   *
   * @returns {boolean} Returns true if all conditions are met. Returns false otherwise.
   */
  I18n.prototype.hasIntlPluralRulesSupport = function () {
    return Boolean(window.Intl && ('PluralRules' in window.Intl && Intl.PluralRules.supportedLocalesOf(this.locale).length))
  };

  /**
   * Check to see if the browser supports Intl and Intl.NumberFormat.
   *
   * It requires all conditions to be met in order to be supported:
   * - The browser supports the Intl class (true in IE11)
   * - The implementation of Intl supports NumberFormat (also true in IE11)
   * - The browser/OS has number formatting rules for the current locale (browser dependent)
   *
   * @returns {boolean} Returns true if all conditions are met. Returns false otherwise.
   */
  I18n.prototype.hasIntlNumberFormatSupport = function () {
    return Boolean(window.Intl && ('NumberFormat' in window.Intl && Intl.NumberFormat.supportedLocalesOf(this.locale).length))
  };

  /**
   * Get the appropriate suffix for the plural form.
   *
   * Uses Intl.PluralRules (or our own fallback implementation) to get the
   * 'preferred' form to use for the given count.
   *
   * Checks that a translation has been provided for that plural form – if it
   * hasn't, it'll fall back to the 'other' plural form (unless that doesn't exist
   * either, in which case an error will be thrown)
   *
   * @param {string} lookupKey - The lookup key of the string to use.
   * @param {number} count - Number used to determine which pluralisation to use.
   * @returns {PluralRule} The suffix associated with the correct pluralisation for this locale.
   * @throws {Error} Plural form `.other` required when preferred plural form is missing
   */
  I18n.prototype.getPluralSuffix = function (lookupKey, count) {
    // Validate that the number is actually a number.
    //
    // Number(count) will turn anything that can't be converted to a Number type
    // into 'NaN'. isFinite filters out NaN, as it isn't a finite number.
    count = Number(count);
    if (!isFinite(count)) { return 'other' }

    var preferredForm;

    // Check to verify that all the requirements for Intl.PluralRules are met.
    // If so, we can use that instead of our custom implementation. Otherwise,
    // use the hardcoded fallback.
    if (this.hasIntlPluralRulesSupport()) {
      preferredForm = new Intl.PluralRules(this.locale).select(count);
    } else {
      preferredForm = this.selectPluralFormUsingFallbackRules(count);
    }

    // Use the correct plural form if provided
    if (lookupKey + '.' + preferredForm in this.translations) {
      return preferredForm
    // Fall back to `other` if the plural form is missing, but log a warning
    // to the console
    } else if (lookupKey + '.other' in this.translations) {
      if (console && 'warn' in console) {
        console.warn('i18n: Missing plural form ".' + preferredForm + '" for "' +
          this.locale + '" locale. Falling back to ".other".');
      }

      return 'other'
    // If the required `other` plural form is missing, all we can do is error
    } else {
      throw new Error(
        'i18n: Plural form ".other" is required for "' + this.locale + '" locale'
      )
    }
  };

  /**
   * Get the plural form using our fallback implementation
   *
   * This is split out into a separate function to make it easier to test the
   * fallback behaviour in an environment where Intl.PluralRules exists.
   *
   * @param {number} count - Number used to determine which pluralisation to use.
   * @returns {PluralRule} The pluralisation form for count in this locale.
   */
  I18n.prototype.selectPluralFormUsingFallbackRules = function (count) {
    // Currently our custom code can only handle positive integers, so let's
    // make sure our number is one of those.
    count = Math.abs(Math.floor(count));

    var ruleset = this.getPluralRulesForLocale();

    if (ruleset) {
      return I18n.pluralRules[ruleset](count)
    }

    return 'other'
  };

  /**
   * Work out which pluralisation rules to use for the current locale
   *
   * The locale may include a regional indicator (such as en-GB), but we don't
   * usually care about this part, as pluralisation rules are usually the same
   * regardless of region. There are exceptions, however, (e.g. Portuguese) so
   * this searches by both the full and shortened locale codes, just to be sure.
   *
   * @returns {string | undefined} The name of the pluralisation rule to use (a key for one
   *   of the functions in this.pluralRules)
   */
  I18n.prototype.getPluralRulesForLocale = function () {
    var locale = this.locale;
    var localeShort = locale.split('-')[0];

    // Look through the plural rules map to find which `pluralRule` is
    // appropriate for our current `locale`.
    for (var pluralRule in I18n.pluralRulesMap) {
      if (Object.prototype.hasOwnProperty.call(I18n.pluralRulesMap, pluralRule)) {
        var languages = I18n.pluralRulesMap[pluralRule];
        for (var i = 0; i < languages.length; i++) {
          if (languages[i] === locale || languages[i] === localeShort) {
            return pluralRule
          }
        }
      }
    }
  };

  /**
   * Map of plural rules to languages where those rules apply.
   *
   * Note: These groups are named for the most dominant or recognisable language
   * that uses each system. The groupings do not imply that the languages are
   * related to one another. Many languages have evolved the same systems
   * independently of one another.
   *
   * Code to support more languages can be found in the i18n spike:
   * {@link https://github.com/alphagov/govuk-frontend/blob/spike-i18n-support/src/govuk/i18n.mjs}
   *
   * Languages currently supported:
   *
   * Arabic: Arabic (ar)
   * Chinese: Burmese (my), Chinese (zh), Indonesian (id), Japanese (ja),
   *   Javanese (jv), Korean (ko), Malay (ms), Thai (th), Vietnamese (vi)
   * French: Armenian (hy), Bangla (bn), French (fr), Gujarati (gu), Hindi (hi),
   *   Persian Farsi (fa), Punjabi (pa), Zulu (zu)
   * German: Afrikaans (af), Albanian (sq), Azerbaijani (az), Basque (eu),
   *   Bulgarian (bg), Catalan (ca), Danish (da), Dutch (nl), English (en),
   *   Estonian (et), Finnish (fi), Georgian (ka), German (de), Greek (el),
   *   Hungarian (hu), Luxembourgish (lb), Norwegian (no), Somali (so),
   *   Swahili (sw), Swedish (sv), Tamil (ta), Telugu (te), Turkish (tr),
   *   Urdu (ur)
   * Irish: Irish Gaelic (ga)
   * Russian: Russian (ru), Ukrainian (uk)
   * Scottish: Scottish Gaelic (gd)
   * Spanish: European Portuguese (pt-PT), Italian (it), Spanish (es)
   * Welsh: Welsh (cy)
   *
   * @type {Object<string, string[]>}
   */
  I18n.pluralRulesMap = {
    arabic: ['ar'],
    chinese: ['my', 'zh', 'id', 'ja', 'jv', 'ko', 'ms', 'th', 'vi'],
    french: ['hy', 'bn', 'fr', 'gu', 'hi', 'fa', 'pa', 'zu'],
    german: [
      'af', 'sq', 'az', 'eu', 'bg', 'ca', 'da', 'nl', 'en', 'et', 'fi', 'ka',
      'de', 'el', 'hu', 'lb', 'no', 'so', 'sw', 'sv', 'ta', 'te', 'tr', 'ur'
    ],
    irish: ['ga'],
    russian: ['ru', 'uk'],
    scottish: ['gd'],
    spanish: ['pt-PT', 'it', 'es'],
    welsh: ['cy']
  };

  /**
   * Different pluralisation rule sets
   *
   * Returns the appropriate suffix for the plural form associated with `n`.
   * Possible suffixes: 'zero', 'one', 'two', 'few', 'many', 'other' (the actual
   * meaning of each differs per locale). 'other' should always exist, even in
   * languages without plurals, such as Chinese.
   * {@link https://cldr.unicode.org/index/cldr-spec/plural-rules}
   *
   * The count must be a positive integer. Negative numbers and decimals aren't accounted for
   *
   * @type {Object<string, function(number): PluralRule>}
   */
  I18n.pluralRules = {
    /* eslint-disable jsdoc/require-jsdoc */
    arabic: function (n) {
      if (n === 0) { return 'zero' }
      if (n === 1) { return 'one' }
      if (n === 2) { return 'two' }
      if (n % 100 >= 3 && n % 100 <= 10) { return 'few' }
      if (n % 100 >= 11 && n % 100 <= 99) { return 'many' }
      return 'other'
    },
    chinese: function () {
      return 'other'
    },
    french: function (n) {
      return n === 0 || n === 1 ? 'one' : 'other'
    },
    german: function (n) {
      return n === 1 ? 'one' : 'other'
    },
    irish: function (n) {
      if (n === 1) { return 'one' }
      if (n === 2) { return 'two' }
      if (n >= 3 && n <= 6) { return 'few' }
      if (n >= 7 && n <= 10) { return 'many' }
      return 'other'
    },
    russian: function (n) {
      var lastTwo = n % 100;
      var last = lastTwo % 10;
      if (last === 1 && lastTwo !== 11) { return 'one' }
      if (last >= 2 && last <= 4 && !(lastTwo >= 12 && lastTwo <= 14)) { return 'few' }
      if (last === 0 || (last >= 5 && last <= 9) || (lastTwo >= 11 && lastTwo <= 14)) { return 'many' }
      // Note: The 'other' suffix is only used by decimal numbers in Russian.
      // We don't anticipate it being used, but it's here for consistency.
      return 'other'
    },
    scottish: function (n) {
      if (n === 1 || n === 11) { return 'one' }
      if (n === 2 || n === 12) { return 'two' }
      if ((n >= 3 && n <= 10) || (n >= 13 && n <= 19)) { return 'few' }
      return 'other'
    },
    spanish: function (n) {
      if (n === 1) { return 'one' }
      if (n % 1000000 === 0 && n !== 0) { return 'many' }
      return 'other'
    },
    welsh: function (n) {
      if (n === 0) { return 'zero' }
      if (n === 1) { return 'one' }
      if (n === 2) { return 'two' }
      if (n === 3) { return 'few' }
      if (n === 6) { return 'many' }
      return 'other'
    }
    /* eslint-enable jsdoc/require-jsdoc */
  };

  /**
   * Plural rule category mnemonic tags
   *
   * @typedef {'zero' | 'one' | 'two' | 'few' | 'many' | 'other'} PluralRule
   */

  /**
   * Translated message by plural rule they correspond to.
   *
   * Allows to group pluralised messages under a single key when passing
   * translations to a component's constructor
   *
   * @typedef {object} TranslationPluralForms
   * @property {string} [other] - General plural form
   * @property {string} [zero] - Plural form used with 0
   * @property {string} [one] - Plural form used with 1
   * @property {string} [two] - Plural form used with 2
   * @property {string} [few] - Plural form used for a few
   * @property {string} [many] - Plural form used for many
   */

  exports.I18n = I18n;

})));
//# sourceMappingURL=i18n.js.map