/*
 * https://github.com/morethanwords/tweb
 * Copyright (C) 2019-2021 Eduard Kuzmenko
 * https://github.com/morethanwords/tweb/blob/master/LICENSE
 */

import cancelEvent from '../helpers/dom/cancelEvent';
import {attachClickEvent} from '../helpers/dom/clickEvent';
import loadFonts from '../helpers/dom/loadFonts';
import {Config, LangPackDifference, LangPackString} from '../layer';
import I18n, {LangPackKey} from '../lib/langPack';
import rootScope from '../lib/rootScope';
import Button from './button';
import {putPreloader} from './putPreloader';

let set = false;

function getLang(): Promise<[Config.config, LangPackString[], LangPackDifference.langPackDifference]> {
  if(cachedPromise) return cachedPromise;
  return cachedPromise = rootScope.managers.apiManager.getConfig().then((config) => {
    if(config.suggested_lang_code !== I18n.lastRequestedLangCode) {
      // I18n.loadLangPack(config.suggested_lang_code);

      return Promise.all([
        config,
        I18n.getStrings(config.suggested_lang_code, ['Login.ContinueOnLanguage']),
        I18n.getCacheLangPack()
      ]);
    } else {
      return [] as any;
    }
  });
}

let cachedPromise: ReturnType<typeof getLang>;

export default function getLanguageChangeButton(appendTo: HTMLElement) {
  if(set) return;
  getLang().then(([config, strings]) => {
    if(!config) {
      return;
    }

    const backup: LangPackString[] = [];
    strings.forEach((string) => {
      const backupString = I18n.strings.get(string.key as LangPackKey);
      if(!backupString) {
        return;
      }

      backup.push(backupString);
      I18n.strings.set(string.key as LangPackKey, string);
    });

    const key: LangPackKey = 'Login.ContinueOnLanguage';
    const btnChangeLanguage = Button('btn-primary btn-secondary btn-primary-transparent primary', {text: key});
    btnChangeLanguage.lastElementChild.classList.remove('i18n'); // prevent changing language
    loadFonts({text: [I18n.format(key, true)]}).then(() => {
      window.requestAnimationFrame(() => {
        appendTo.append(btnChangeLanguage);
      });
    });

    rootScope.addEventListener('language_change', () => {
      btnChangeLanguage.remove();
    }, {once: true});

    backup.forEach((string) => {
      I18n.strings.set(string.key as LangPackKey, string);
    });

    attachClickEvent(btnChangeLanguage, (e) => {
      cancelEvent(e);

      set = true;

      btnChangeLanguage.disabled = true;
      putPreloader(btnChangeLanguage);

      I18n.getLangPack(config.suggested_lang_code);
    });
  });
}