/* 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";

/**
 * The downloaded Fluent file is located in this sub-directory of the local
 * profile directory.
 */
const RS_DOWNLOADED_FILE_SUBDIR = "settings/main/ms-language-packs";
const USE_REMOTE_L10N_PREF =
  "browser.newtabpage.activity-stream.asrouter.useRemoteL10n";

const { XPCOMUtils } = ChromeUtils.import(
  "resource://gre/modules/XPCOMUtils.jsm"
);

XPCOMUtils.defineLazyModuleGetters(this, {
  L10nRegistry: "resource://gre/modules/L10nRegistry.jsm",
  FileSource: "resource://gre/modules/L10nRegistry.jsm",
  OS: "resource://gre/modules/osfile.jsm",
  Services: "resource://gre/modules/Services.jsm",
});

class _RemoteL10n {
  constructor() {
    this._l10n = null;
  }

  /**
   * Creates a new DOMLocalization instance with the Fluent file from Remote Settings.
   *
   * Note: it will use the local Fluent file in any of following cases:
   *   * the remote Fluent file is not available
   *   * it was told to use the local Fluent file
   */
  _createDOML10n() {
    /* istanbul ignore next */
    async function* generateBundles(resourceIds) {
      const appLocale = Services.locale.appLocaleAsBCP47;
      const appLocales = Services.locale.appLocalesAsBCP47;
      const l10nFluentDir = OS.Path.join(
        OS.Constants.Path.localProfileDir,
        RS_DOWNLOADED_FILE_SUBDIR
      );
      const fs = new FileSource("cfr", [appLocale], `file://${l10nFluentDir}/`);
      // In the case that the Fluent file has not been downloaded from Remote Settings,
      // `fetchFile` will return `false` and fall back to the packaged Fluent file.
      const resource = await fs.fetchFile(appLocale, "asrouter.ftl");
      for await (let bundle of L10nRegistry.generateBundles(
        appLocales.slice(0, 1),
        resourceIds
      )) {
        // Override built-in messages with the resource loaded from remote settings for
        // the app locale, i.e. the first item of `appLocales`.
        if (resource) {
          bundle.addResource(resource, { allowOverrides: true });
        }
        yield bundle;
      }
      // Now generating bundles for the rest of locales of `appLocales`.
      yield* L10nRegistry.generateBundles(appLocales.slice(1), resourceIds);
    }

    return new DOMLocalization(
      [
        "browser/newtab/asrouter.ftl",
        "browser/branding/brandings.ftl",
        "browser/branding/sync-brand.ftl",
        "branding/brand.ftl",
      ],
      false,
      Services.prefs.getBoolPref(USE_REMOTE_L10N_PREF, true)
        ? { generateBundles }
        : {}
    );
  }

  get l10n() {
    if (!this._l10n) {
      this._l10n = this._createDOML10n();
    }
    return this._l10n;
  }

  reloadL10n() {
    this._l10n = null;
  }
}

this.RemoteL10n = new _RemoteL10n();

const EXPORTED_SYMBOLS = ["RemoteL10n", "_RemoteL10n"];