/*
 * noVNC: HTML5 VNC client
 * Copyright (C) 2012 Joel Martin
 * Licensed under MPL 2.0 (see LICENSE.txt)
 *
 * See README.md for usage and integration instructions.
 */

/*
 * Localization Utilities
 */

export class Localizer {
  constructor() {
    // Currently configured language
    this.language = 'en';

    // Current dictionary of translations
    this.dictionary = undefined;
  }

  // Configure suitable language based on user preferences
  setup(supportedLanguages) {
    this.language = 'en'; // Default: US English

    /*
         * Navigator.languages only available in Chrome (32+) and FireFox (32+)
         * Fall back to navigator.language for other browsers
         */
    let userLanguages;
    if (typeof window.navigator.languages == 'object') {
      userLanguages = window.navigator.languages;
    } else {
      userLanguages = [navigator.language || navigator.userLanguage];
    }

    for (let i = 0; i < userLanguages.length; i++) {
      const userLang = userLanguages[i]
        .toLowerCase()
        .replace('_', '-')
        .split('-');

      // Built-in default?
      if ((userLang[0] === 'en')
                && ((userLang[1] === undefined) || (userLang[1] === 'us'))) {
        return;
      }

      // First pass: perfect match
      for (let j = 0; j < supportedLanguages.length; j++) {
        const supLang = supportedLanguages[j]
          .toLowerCase()
          .replace('_', '-')
          .split('-');

        if (userLang[0] !== supLang[0]) continue;
        if (userLang[1] !== supLang[1]) continue;

        this.language = supportedLanguages[j];
        return;
      }

      // Second pass: fallback
      for (let j = 0; j < supportedLanguages.length; j++) {
        const supLang = supportedLanguages[j]
          .toLowerCase()
          .replace('_', '-')
          .split('-');

        if (userLang[0] !== supLang[0]) continue;
        if (supLang[1] !== undefined) continue;

        this.language = supportedLanguages[j];
        return;
      }
    }
  }

  // Retrieve localised text
  get(id) {
    if (typeof this.dictionary !== 'undefined' && this.dictionary[id]) {
      return this.dictionary[id];
    } else {
      return id;
    }
  }

  // Traverses the DOM and translates relevant fields
  // See https://html.spec.whatwg.org/multipage/dom.html#attr-translate
  translateDOM() {
    const self = this;

    function process(elem, enabled) {
      function isAnyOf(searchElement, items) {
        return items.indexOf(searchElement) !== -1;
      }

      function translateAttribute(elem, attr) {
        const str = self.get(elem.getAttribute(attr));
        elem.setAttribute(attr, str);
      }

      function translateTextNode(node) {
        const str = self.get(node.data.trim());
        node.data = str;
      }

      if (elem.hasAttribute('translate')) {
        if (isAnyOf(elem.getAttribute('translate'), ['', 'yes'])) {
          enabled = true;
        } else if (isAnyOf(elem.getAttribute('translate'), ['no'])) {
          enabled = false;
        }
      }

      if (enabled) {
        if (elem.hasAttribute('abbr')
                    && elem.tagName === 'TH') {
          translateAttribute(elem, 'abbr');
        }
        if (elem.hasAttribute('alt')
                    && isAnyOf(elem.tagName, ['AREA', 'IMG', 'INPUT'])) {
          translateAttribute(elem, 'alt');
        }
        if (elem.hasAttribute('download')
                    && isAnyOf(elem.tagName, ['A', 'AREA'])) {
          translateAttribute(elem, 'download');
        }
        if (elem.hasAttribute('label')
                    && isAnyOf(elem.tagName, ['MENUITEM', 'MENU', 'OPTGROUP',
                      'OPTION', 'TRACK'])) {
          translateAttribute(elem, 'label');
        }
        // FIXME: Should update "lang"
        if (elem.hasAttribute('placeholder')
                    && isAnyOf(elem.tagName, ['INPUT', 'TEXTAREA'])) {
          translateAttribute(elem, 'placeholder');
        }
        if (elem.hasAttribute('title')) {
          translateAttribute(elem, 'title');
        }
        if (elem.hasAttribute('value')
                    && elem.tagName === 'INPUT'
                    && isAnyOf(elem.getAttribute('type'), ['reset', 'button', 'submit'])) {
          translateAttribute(elem, 'value');
        }
      }

      for (let i = 0; i < elem.childNodes.length; i++) {
        const node = elem.childNodes[i];
        if (node.nodeType === node.ELEMENT_NODE) {
          process(node, enabled);
        } else if (node.nodeType === node.TEXT_NODE && enabled) {
          translateTextNode(node);
        }
      }
    }

    process(document.body, true);
  }
}

export const l10n = new Localizer();
export default l10n.get.bind(l10n);