1 files changed, 249 insertions, 0 deletions
diff --git a/browser/components/newtab/lib/RemoteL10n.sys.mjs b/browser/components/newtab/lib/RemoteL10n.sys.mjs
new file mode 100644
index 0000000000..fe25c56a79
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+++ b/browser/components/newtab/lib/RemoteL10n.sys.mjs
@@ -0,0 +1,249 @@
+/* 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/. */
+
+/**
+ * The downloaded Fluent file is located in this sub-directory of the local
+ * profile directory.
+ */
+const USE_REMOTE_L10N_PREF =
+  "browser.newtabpage.activity-stream.asrouter.useRemoteL10n";
+
+/**
+ * All supported locales for remote l10n
+ *
+ * This is used by ASRouter.jsm to check if the locale is supported before
+ * issuing the request for remote fluent files to RemoteSettings.
+ *
+ * Note:
+ *   * this is generated based on "browser/locales/all-locales" as l10n doesn't
+ *     provide an API to fetch that list
+ *
+ *   * this list doesn't include "en-US", though "en-US" is well supported and
+ *     `_RemoteL10n.isLocaleSupported()` will handle it properly
+ */
+const ALL_LOCALES = new Set([
+  "ach",
+  "af",
+  "an",
+  "ar",
+  "ast",
+  "az",
+  "be",
+  "bg",
+  "bn",
+  "bo",
+  "br",
+  "brx",
+  "bs",
+  "ca",
+  "ca-valencia",
+  "cak",
+  "ckb",
+  "cs",
+  "cy",
+  "da",
+  "de",
+  "dsb",
+  "el",
+  "en-CA",
+  "en-GB",
+  "eo",
+  "es-AR",
+  "es-CL",
+  "es-ES",
+  "es-MX",
+  "et",
+  "eu",
+  "fa",
+  "ff",
+  "fi",
+  "fr",
+  "fy-NL",
+  "ga-IE",
+  "gd",
+  "gl",
+  "gn",
+  "gu-IN",
+  "he",
+  "hi-IN",
+  "hr",
+  "hsb",
+  "hu",
+  "hy-AM",
+  "hye",
+  "ia",
+  "id",
+  "is",
+  "it",
+  "ja",
+  "ja-JP-mac",
+  "ka",
+  "kab",
+  "kk",
+  "km",
+  "kn",
+  "ko",
+  "lij",
+  "lo",
+  "lt",
+  "ltg",
+  "lv",
+  "meh",
+  "mk",
+  "mr",
+  "ms",
+  "my",
+  "nb-NO",
+  "ne-NP",
+  "nl",
+  "nn-NO",
+  "oc",
+  "pa-IN",
+  "pl",
+  "pt-BR",
+  "pt-PT",
+  "rm",
+  "ro",
+  "ru",
+  "scn",
+  "si",
+  "sk",
+  "sl",
+  "son",
+  "sq",
+  "sr",
+  "sv-SE",
+  "szl",
+  "ta",
+  "te",
+  "th",
+  "tl",
+  "tr",
+  "trs",
+  "uk",
+  "ur",
+  "uz",
+  "vi",
+  "wo",
+  "xh",
+  "zh-CN",
+  "zh-TW",
+]);
+
+export class _RemoteL10n {
+  constructor() {
+    this._l10n = null;
+  }
+
+  createElement(doc, elem, options = {}) {
+    let node;
+    if (options.content && options.content.string_id) {
+      node = doc.createElement("remote-text");
+    } else {
+      node = doc.createElementNS("http://www.w3.org/1999/xhtml", elem);
+    }
+    if (options.classList) {
+      node.classList.add(options.classList);
+    }
+    this.setString(node, options);
+
+    return node;
+  }
+
+  // If `string_id` is present it means we are relying on fluent for translations.
+  // Otherwise, we have a vanilla string.
+  setString(el, { content, attributes = {} }) {
+    if (content && content.string_id) {
+      for (let [fluentId, value] of Object.entries(attributes)) {
+        el.setAttribute(`fluent-variable-${fluentId}`, value);
+      }
+      el.setAttribute("fluent-remote-id", content.string_id);
+    } else {
+      el.textContent = content;
+    }
+  }
+
+  /**
+   * Creates a new DOMLocalization instance with the Fluent file from Remote Settings.
+   *
+   * Note: it will use the local Fluent file in any of following cases:
+   *   * the remote Fluent file is not available
+   *   * it was told to use the local Fluent file
+   */
+  _createDOML10n() {
+    /* istanbul ignore next */
+    let useRemoteL10n = Services.prefs.getBoolPref(USE_REMOTE_L10N_PREF, true);
+    if (useRemoteL10n && !L10nRegistry.getInstance().hasSource("cfr")) {
+      const appLocale = Services.locale.appLocaleAsBCP47;
+      const l10nFluentDir = PathUtils.join(
+        Services.dirsvc.get("ProfLD", Ci.nsIFile).path,
+        "settings",
+        "main",
+        "ms-language-packs"
+      );
+      let cfrIndexedFileSource = new L10nFileSource(
+        "cfr",
+        "app",
+        [appLocale],
+        `file://${l10nFluentDir}/`,
+        {
+          addResourceOptions: {
+            allowOverrides: true,
+          },
+        },
+        [`file://${l10nFluentDir}/browser/newtab/asrouter.ftl`]
+      );
+      L10nRegistry.getInstance().registerSources([cfrIndexedFileSource]);
+    } else if (!useRemoteL10n && L10nRegistry.getInstance().hasSource("cfr")) {
+      L10nRegistry.getInstance().removeSources(["cfr"]);
+    }
+
+    return new DOMLocalization(
+      [
+        "branding/brand.ftl",
+        "browser/defaultBrowserNotification.ftl",
+        "browser/newtab/asrouter.ftl",
+        "toolkit/branding/accounts.ftl",
+        "toolkit/branding/brandings.ftl",
+      ],
+      false
+    );
+  }
+
+  get l10n() {
+    if (!this._l10n) {
+      this._l10n = this._createDOML10n();
+    }
+    return this._l10n;
+  }
+
+  reloadL10n() {
+    this._l10n = null;
+  }
+
+  isLocaleSupported(locale) {
+    return locale === "en-US" || ALL_LOCALES.has(locale);
+  }
+
+  /**
+   * Format given `localizableText`.
+   *
+   * Format `localizableText` if it is an object using any `string_id` field,
+   * otherwise return `localizableText` unmodified.
+   *
+   * @param {object|string} `localizableText` to format.
+   * @return {string} formatted text.
+   */
+  async formatLocalizableText(localizableText) {
+    if (typeof localizableText !== "string") {
+      // It's more useful to get an error than passing through an object without
+      // a `string_id` field.
+      let value = await this.l10n.formatValue(localizableText.string_id);
+      return value;
+    }
+    return localizableText;
+  }
+}
+
+export const RemoteL10n = new _RemoteL10n();