/* This Source Code Form is subject to the terms of the Mozilla Public
 * License, v. 2.0. If a copy of the MPL was not distributed with this
 * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
"use strict";

const { Cc, Ci } = require("chrome");
const { getPreferedLocales, findClosestLocale } = require("api-utils/l10n/locale");
const { getRulesForLocale } = require("api-utils/l10n/plural-rules");

// Get URI for the addon root folder:
const { rootURI } = require("@packaging");

let globalHash = {};
let pluralMappingFunction = getRulesForLocale("en");

exports.get = function get(k) {

  // For now, we only accept a "string" as first argument
  // TODO: handle plural forms in gettext pattern
  if (typeof k !== "string")
    throw new Error("First argument of localization method should be a string");

  // Get translation from big hashmap or default to hard coded string:
  let localized = globalHash[k] || k;

  // # Simplest usecase:
  //   // String hard coded in source code:
  //   _("Hello world")
  //   // Identifier of a key stored in properties file
  //   _("helloString")
  if (arguments.length <= 1)
    return localized;

  let args = arguments;

  if (typeof localized == "object" && "other" in localized) {
    // # Plural form:
    //   // Strings hard coded in source code:
    //   _(["One download", "%d downloads"], 10);
    //   // Identifier of a key stored in properties file
    //   _("downloadNumber", 0);
    let n = arguments[1];

    // First handle simple universal forms that may not be mandatory
    // for each language, (i.e. not different than 'other' form,
    // but still usefull for better phrasing)
    // For example 0 in english is the same form than 'other'
    // but we accept 'zero' form if specified in localization file
    if (n === 0 && "zero" in localized)
      localized = localized["zero"];
    else if (n === 1 && "one" in localized)
      localized = localized["one"];
    else if (n === 2 && "two" in localized)
      localized = localized["two"];
    else {
      let pluralForm = pluralMappingFunction(n);
      if (pluralForm in localized)
        localized = localized[pluralForm];
      else // Fallback in case of error: missing plural form
        localized = localized["other"];
    }

    // Simulate a string with one placeholder:
    args = [null, n];
  }

  // # String with placeholders:
  //   // Strings hard coded in source code:
  //   _("Hello %s", username)
  //   // Identifier of a key stored in properties file
  //   _("helloString", username)
  // * We supports `%1s`, `%2s`, ... pattern in order to change arguments order
  // in translation.
  // * In case of plural form, we has `%d` instead of `%s`.
  let offset = 1;
  localized = localized.replace(/%(\d*)(s|d)/g, function (v, n) {
      let rv = args[n != "" ? n : offset];
      offset++;
      return rv;
    });

  return localized;
}

function readURI(uri) {
  let request = Cc["@mozilla.org/xmlextras/xmlhttprequest;1"].
                createInstance(Ci.nsIXMLHttpRequest);
  request.open('GET', uri, false);
  request.overrideMimeType('text/plain');
  request.send();
  return request.responseText;
}

function readJsonUri(uri) {
  try {
    return JSON.parse(readURI(uri));
  }
  catch(e) {
    console.error("Error while reading locale file:\n" + uri + "\n" + e);
  }
  return {};
}

// Returns the array stored in `locales.json` manifest that list available
// locales files
function getAvailableLocales() {
  let uri = rootURI + "locales.json";
  let manifest = readJsonUri(uri);

  return "locales" in manifest && Array.isArray(manifest.locales) ?
         manifest.locales : [];
}

// Returns URI of the best locales file to use from the XPI
function getBestLocaleFile() {

  // Read localization manifest file that contains list of available languages
  let availableLocales = getAvailableLocales();

  // Retrieve list of prefered locales to use
  let preferedLocales = getPreferedLocales();

  // Compute the most preferable locale to use by using these two lists
  let bestMatchingLocale = findClosestLocale(availableLocales, preferedLocales);

  // It may be null if the addon doesn't have any locale file
  if (!bestMatchingLocale)
    return null;

  // Retrieve the related plural mapping function
  let shortLocaleCode = bestMatchingLocale.split("-")[0].toLowerCase();
  pluralMappingFunction = getRulesForLocale(shortLocaleCode);

  return rootURI + "locale/" + bestMatchingLocale + ".json";
}

function init() {
  // First, search for a locale file:
  let localeURI = getBestLocaleFile();
  if (!localeURI)
    return;

  // Locale files only contains one big JSON object that is used as
  // an hashtable of: "key to translate" => "translated key"
  // TODO: We are likely to change this in order to be able to overload
  //       a specific key translation. For a specific package, module or line?
  globalHash = readJsonUri(localeURI);
}
init();