/**
 * @license
 * Copyright 2016 Google Inc.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */


goog.provide('shaka.ui.LanguageUtils');

goog.require('mozilla.LanguageMapping');
goog.require('shaka.util.Dom');


shaka.ui.LanguageUtils = class {
  /**
   * @param {!Array.<shaka.extern.Track>} tracks
   * @param {!HTMLElement} langMenu
   * @param {!Array.<string>} languages
   * @param {function(string)} onLanguageSelected
   * @param {boolean} updateChosen
   * @param {!HTMLElement} currentSelectionElement
   * @param {shaka.ui.Localization} localization
   */
  // TODO: Do the benefits of having this common code in a method still
  // outweigh the complexity of the parameter list?
  static updateLanguages(tracks, langMenu, languages, onLanguageSelected,
      updateChosen, currentSelectionElement, localization) {
    // Using array.filter(f)[0] as an alternative to array.find(f) which is
    // not supported in IE11.
    const activeTracks = tracks.filter((track) => {
      return track.active == true;
    });
    const selectedTrack = activeTracks[0];

    // Remove old languages
    // 1. Save the back to menu button
    const backButton = shaka.ui.Utils.getFirstDescendantWithClassName(
        langMenu, 'shaka-back-to-overflow-button');

    // 2. Remove everything
    shaka.util.Dom.removeAllChildren(langMenu);

    // 3. Add the backTo Menu button back
    langMenu.appendChild(backButton);

    // 4. Add new buttons
    for (const language of languages) {
      const button = shaka.util.Dom.createHTMLElement('button');
      button.addEventListener('click', () => {
        onLanguageSelected(language);
      });

      const span = shaka.util.Dom.createHTMLElement('span');
      span.textContent =
        shaka.ui.LanguageUtils.getLanguageName(language, localization);
      button.appendChild(span);

      if (updateChosen && (language == selectedTrack.language)) {
        button.appendChild(shaka.ui.Utils.checkmarkIcon());
        span.classList.add('shaka-chosen-item');
        button.setAttribute('aria-selected', 'true');
        currentSelectionElement.textContent = span.textContent;
      }
      langMenu.appendChild(button);
    }
  }


  /**
   * Returns the language's name for itself in its own script (autoglottonym),
   * if we have it.
   *
   * If the locale, including region, can be mapped to a name, we return a very
   * specific name including the region.  For example, "de-AT" would map to
   * "Deutsch (Österreich)" or Austrian German.
   *
   * If only the language part of the locale is in our map, we append the locale
   * itself for specificity.  For example, "ar-EG" (Egyptian Arabic) would map
   * to "ﺎﻠﻋﺮﺒﻳﺓ (ar-EG)".  In this way, multiple versions of Arabic whose
   * regions are not in our map would not all look the same in the language
   * list, but could be distinguished by their locale.
   *
   * Finally, if language part of the locale is not in our map, we label it
   * "unknown", as translated to the UI locale, and we append the locale itself
   * for specificity.  For example, "sjn" would map to "Unknown (sjn)".  In this
   * way, multiple unrecognized languages would not all look the same in the
   * language list, but could be distinguished by their locale.
   *
   * @param {string} locale
   * @param {shaka.ui.Localization} localization
   * @return {string} The language's name for itself in its own script, or as
   *   close as we can get with the information we have.
   */
  static getLanguageName(locale, localization) {
    if (!locale && !localization) {
      return '';
    }

    // Shorthand for resolving a localization ID.
    const resolve = (id) => localization.resolve(id);

    // Handle some special cases first.  These are reserved language tags that
    // are used to indicate something that isn't one specific language.
    switch (locale) {
      case 'mul':
        return resolve(shaka.ui.Locales.Ids.MULTIPLE_LANGUAGES);
      case 'und':
        return resolve(shaka.ui.Locales.Ids.UNDETERMINED_LANGUAGE);
      case 'zxx':
        return resolve(shaka.ui.Locales.Ids.NOT_APPLICABLE);
    }

    // Extract the base language from the locale as a fallback step.
    const language = shaka.util.LanguageUtils.getBase(locale);

    // First try to resolve the full language name.
    // If that fails, try the base.
    // Finally, report "unknown".
    // When there is a loss of specificity (either to a base language or to
    // "unknown"), we should append the original language code.
    // Otherwise, there may be multiple identical-looking items in the list.
    if (locale in mozilla.LanguageMapping) {
      return mozilla.LanguageMapping[locale].nativeName;
    } else if (language in mozilla.LanguageMapping) {
      return mozilla.LanguageMapping[language].nativeName +
          ' (' + locale + ')';
    } else {
      return resolve(shaka.ui.Locales.Ids.UNRECOGNIZED_LANGUAGE) +
          ' (' + locale + ')';
    }
  }
};