/* -*- Mode: IDL; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
/* 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/. */

#include "nsISupports.idl"

[scriptable, uuid(65944815-e9ae-48bd-a2bf-f1108720950c)]
interface mozIOSPreferences : nsISupports
{
  const long dateTimeFormatStyleNone     = 0;
  const long dateTimeFormatStyleShort    = 1;
  const long dateTimeFormatStyleMedium   = 2;
  const long dateTimeFormatStyleLong     = 3;
  const long dateTimeFormatStyleFull     = 4;

  /**
   * Returns a list of locales used by the host environment for UI
   * localization.
   *
   * The result is a sorted list and we expect that the OS attempts to
   * use the top locale from the list for which it has data.
   *
   * Each element of the list is a valid locale ID that can be passed to ICU
   * and ECMA402 Intl APIs,
   * At the same time each element is a valid BCP47 language tag that can be
   * used for language negotiation.
   *
   * Example: ["en-US", "de", "pl", "sr-Cyrl", "zh-Hans-HK"]
   */
  readonly attribute Array<ACString> systemLocales;

  /**
   * Returns a list of locales used by host environment for regional
   * preferences internationalization.
   *
   * The result is a sorted list and we expect that the OS attempts to
   * use the top locale from the list for which it has data.
   *
   * Each element of the list is a valid locale ID that can be passed to ICU
   * and ECMA402 Intl APIs,
   *
   * Example: ["en-US", "de", "pl", "sr-Cyrl", "zh-Hans-HK"]
   */
  readonly attribute Array<ACString> regionalPrefsLocales;

  /**
   * Returns the best locale that the host environment is localized to.
   *
   * The result is a valid locale ID and it should be
   * used for all APIs that do not handle language negotiation.
   *
   * In any scenario involving language negotiation, systemLocales should
   * be preferred over the single value.
   *
   * Example: "zh-Hans-HK"
   */
  readonly attribute ACString systemLocale;

  /**
   * Returns the best possible date/time pattern for the host environment
   * taking into account date/time regional settings user defined in the OS
   * preferences.
   *
   * Notice, that depending on the OS it may take into account those settings
   * for all locales, or only if the locale matches the OS locale.
   *
   * It takes two integer arguments that must be valid `dateTimeFormatStyle*`
   * values (see constants defined above), and a string representing a
   * BCP47 locale.
   *
   * It returns a string with a LDML date/time pattern.
   *
   * If no pattern can be retrieved from the host environment, it will
   * lookup the best available pattern from ICU.
   *
   * Notice, this is a pretty unique method in this API in that it does
   * more than look up into host environment.
   * The reason for that is that constructing the right date/time pattern
   * requires a lot of OS-specific logic and it ends up being easier to just
   * handle all scenarios, including with cases where we fail to retrieve
   * anything from the OS, here.
   */
  AUTF8String getDateTimePattern(in long timeFormatStyle,
                                 in long dateFormatStyle,
                                 [optional] in ACString locale);
};