1 files changed, 395 insertions, 0 deletions
diff --git a/intl/locale/LangPackMatcher.sys.mjs b/intl/locale/LangPackMatcher.sys.mjs
new file mode 100644
index 0000000000..977398b082
--- /dev/null
+++ b/intl/locale/LangPackMatcher.sys.mjs
@@ -0,0 +1,395 @@
+/* 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/. */
+
+const lazy = {};
+
+ChromeUtils.defineESModuleGetters(lazy, {
+  AddonManager: "resource://gre/modules/AddonManager.sys.mjs",
+  AddonRepository: "resource://gre/modules/addons/AddonRepository.sys.mjs",
+});
+
+if (Services.appinfo.processType !== Services.appinfo.PROCESS_TYPE_DEFAULT) {
+  // This check ensures that the `mockable` API calls can be consisently mocked in tests.
+  // If this requirement needs to be eased, please ensure the test logic remains valid.
+  throw new Error("This code is assumed to run in the parent process.");
+}
+
+/**
+ * Attempts to find an appropriate langpack for a given language. The async function
+ * is infallible, but may not return a langpack.
+ *
+ * @returns {{
+ *   langPack: LangPack | null,
+ *   langPackDisplayName: string | null
+ * }}
+ */
+async function negotiateLangPackForLanguageMismatch() {
+  const localeInfo = getAppAndSystemLocaleInfo();
+  const nullResult = {
+    langPack: null,
+    langPackDisplayName: null,
+  };
+  if (!localeInfo.systemLocale) {
+    // The system locale info was not valid.
+    return nullResult;
+  }
+
+  /**
+   * Fetch the available langpacks from AMO.
+   *
+   * @type {Array<LangPack>}
+   */
+  const availableLangpacks = await mockable.getAvailableLangpacks();
+  if (!availableLangpacks) {
+    return nullResult;
+  }
+
+  /**
+   * Figure out a langpack to recommend.
+   * @type {LangPack | null}
+   */
+  const langPack =
+    // First look for a langpack that matches the baseName, which may include a script.
+    // e.g. system "fr-FR" matches langpack "fr-FR"
+    //      system "en-GB" matches langpack "en-GB".
+    //      system "zh-Hant-CN" matches langpack "zh-Hant-CN".
+    availableLangpacks.find(
+      ({ target_locale }) => target_locale === localeInfo.systemLocale.baseName
+    ) ||
+    // Next try matching language and region while excluding script
+    // e.g. system "zh-Hant-TW" matches langpack "zh-TW" but not "zh-CN".
+    availableLangpacks.find(
+      ({ target_locale }) =>
+        target_locale ===
+        `${localeInfo.systemLocale.language}-${localeInfo.systemLocale.region}`
+    ) ||
+    // Next look for langpacks that just match the language.
+    // e.g. system "fr-FR" matches langpack "fr".
+    //      system "en-AU" matches langpack "en".
+    availableLangpacks.find(
+      ({ target_locale }) => target_locale === localeInfo.systemLocale.language
+    ) ||
+    // Next look for a langpack that matches the language, but not the region.
+    // e.g. "es-CL" (Chilean Spanish) as a system language matching
+    //      "es-ES" (European Spanish)
+    availableLangpacks.find(({ target_locale }) =>
+      target_locale.startsWith(`${localeInfo.systemLocale.language}-`)
+    ) ||
+    null;
+
+  if (!langPack) {
+    return nullResult;
+  }
+
+  return {
+    langPack,
+    langPackDisplayName: Services.intl.getLocaleDisplayNames(
+      undefined,
+      [langPack.target_locale],
+      { preferNative: true }
+    )[0],
+  };
+}
+
+// If a langpack is being installed, allow blocking on that.
+let installingLangpack = new Map();
+
+/**
+ * @typedef {LangPack}
+ * @type {object}
+ * @property {string} target_locale
+ * @property {string} url
+ * @property {string} hash
+ */
+
+/**
+ * Ensure that a given lanpack is installed.
+ *
+ * @param {LangPack} langPack
+ * @returns {Promise<boolean>} Success or failure.
+ */
+function ensureLangPackInstalled(langPack) {
+  if (!langPack) {
+    throw new Error("Expected a LangPack to install.");
+  }
+  // Make sure any outstanding calls get resolved before attempting another call.
+  // This guards against any quick page refreshes attempting to install the langpack
+  // twice.
+  const inProgress = installingLangpack.get(langPack.hash);
+  if (inProgress) {
+    return inProgress;
+  }
+  const promise = _ensureLangPackInstalledImpl(langPack);
+  installingLangpack.set(langPack.hash, promise);
+  promise.finally(() => {
+    installingLangpack.delete(langPack.hash);
+  });
+  return promise;
+}
+
+/**
+ * @param {LangPack} langPack
+ * @returns {boolean} Success or failure.
+ */
+async function _ensureLangPackInstalledImpl(langPack) {
+  const availablelocales = await getAvailableLocales();
+  if (availablelocales.includes(langPack.target_locale)) {
+    // The langpack is already installed.
+    return true;
+  }
+
+  return mockable.installLangPack(langPack);
+}
+
+/**
+ * These are all functions with side effects or configuration options that should be
+ * mockable for tests.
+ */
+const mockable = {
+  /**
+   * @returns {LangPack[] | null}
+   */
+  async getAvailableLangpacks() {
+    try {
+      return lazy.AddonRepository.getAvailableLangpacks();
+    } catch (error) {
+      console.error(
+        `Failed to get the list of available language packs: ${error?.message}`
+      );
+      return null;
+    }
+  },
+
+  /**
+   * Use the AddonManager to install an addon from the URL.
+   * @param {LangPack} langPack
+   */
+  async installLangPack(langPack) {
+    let install;
+    try {
+      install = await lazy.AddonManager.getInstallForURL(langPack.url, {
+        hash: langPack.hash,
+        telemetryInfo: {
+          source: "about:welcome",
+        },
+      });
+    } catch (error) {
+      console.error(error);
+      return false;
+    }
+
+    try {
+      await install.install();
+    } catch (error) {
+      console.error(error);
+      return false;
+    }
+    return true;
+  },
+
+  /**
+   * Returns the available locales, including the fallback locale, which may not include
+   * all of the resources, in cases where the defaultLocale is not "en-US".
+   *
+   * @returns {string[]}
+   */
+  getAvailableLocalesIncludingFallback() {
+    return Services.locale.availableLocales;
+  },
+
+  /**
+   * @returns {string}
+   */
+  getDefaultLocale() {
+    return Services.locale.defaultLocale;
+  },
+
+  /**
+   * @returns {string}
+   */
+  getLastFallbackLocale() {
+    return Services.locale.lastFallbackLocale;
+  },
+
+  /**
+   * @returns {string}
+   */
+  getAppLocaleAsBCP47() {
+    return Services.locale.appLocaleAsBCP47;
+  },
+
+  /**
+   * @returns {string}
+   */
+  getSystemLocale() {
+    // Allow the system locale to be overridden for manual testing.
+    const systemLocaleOverride = Services.prefs.getCharPref(
+      "intl.multilingual.aboutWelcome.systemLocaleOverride",
+      null
+    );
+    if (systemLocaleOverride) {
+      try {
+        // If the locale can't be parsed, ignore the pref.
+        new Services.intl.Locale(systemLocaleOverride);
+        return systemLocaleOverride;
+      } catch (_error) {}
+    }
+
+    const osPrefs = Cc["@mozilla.org/intl/ospreferences;1"].getService(
+      Ci.mozIOSPreferences
+    );
+    return osPrefs.systemLocale;
+  },
+
+  /**
+   * @param {string[]} locales The BCP 47 locale identifiers.
+   */
+  setRequestedAppLocales(locales) {
+    Services.locale.requestedLocales = locales;
+  },
+};
+
+/**
+ * This function is really only setting `Services.locale.requestedLocales`, but it's
+ * using the `mockable` object to allow this behavior to be mocked in tests.
+ *
+ * @param {string[]} locales The BCP 47 locale identifiers.
+ */
+function setRequestedAppLocales(locales) {
+  mockable.setRequestedAppLocales(locales);
+}
+
+/**
+ * A serializable Intl.Locale.
+ *
+ * @typedef StructuredLocale
+ * @type {object}
+ * @property {string} baseName
+ * @property {string} language
+ * @property {string} region
+ */
+
+/**
+ * In telemetry data, some of the system locales show up as blank. Guard against this
+ * and any other malformed locale information provided by the system by wrapping the call
+ * into a catch/try.
+ *
+ * @param {string} locale
+ * @returns {StructuredLocale | null}
+ */
+function getStructuredLocaleOrNull(localeString) {
+  try {
+    const locale = new Services.intl.Locale(localeString);
+    return {
+      baseName: locale.baseName,
+      language: locale.language,
+      region: locale.region,
+    };
+  } catch (_err) {
+    return null;
+  }
+}
+
+/**
+ * Determine the system and app locales, and how much the locales match.
+ *
+ * @returns {{
+ *  systemLocale: StructuredLocale,
+ *  appLocale: StructuredLocale,
+ *  matchType: "unknown" | "language-mismatch" | "region-mismatch" | "match",
+ * }}
+ */
+function getAppAndSystemLocaleInfo() {
+  // Convert locale strings into structured locale objects.
+  const systemLocaleRaw = mockable.getSystemLocale();
+  const appLocaleRaw = mockable.getAppLocaleAsBCP47();
+
+  const systemLocale = getStructuredLocaleOrNull(systemLocaleRaw);
+  const appLocale = getStructuredLocaleOrNull(appLocaleRaw);
+
+  let matchType = "unknown";
+  if (systemLocale && appLocale) {
+    if (systemLocale.language !== appLocale.language) {
+      matchType = "language-mismatch";
+    } else if (systemLocale.region !== appLocale.region) {
+      matchType = "region-mismatch";
+    } else {
+      matchType = "match";
+    }
+  }
+
+  // Live reloading with bidi switching may not be supported.
+  let canLiveReload = null;
+  if (systemLocale && appLocale) {
+    const systemDirection = Services.intl.getScriptDirection(
+      systemLocale.language
+    );
+    const appDirection = Services.intl.getScriptDirection(appLocale.language);
+    const supportsBidiSwitching = Services.prefs.getBoolPref(
+      "intl.multilingual.liveReloadBidirectional",
+      false
+    );
+    canLiveReload = systemDirection === appDirection || supportsBidiSwitching;
+  }
+  return {
+    // Return the Intl.Locale in a serializable form.
+    systemLocaleRaw,
+    systemLocale,
+    appLocaleRaw,
+    appLocale,
+    matchType,
+    canLiveReload,
+
+    // These can be used as Fluent message args.
+    displayNames: {
+      systemLanguage: systemLocale
+        ? Services.intl.getLocaleDisplayNames(
+            undefined,
+            [systemLocale.baseName],
+            { preferNative: true }
+          )[0]
+        : null,
+      appLanguage: appLocale
+        ? Services.intl.getLocaleDisplayNames(undefined, [appLocale.baseName], {
+            preferNative: true,
+          })[0]
+        : null,
+    },
+  };
+}
+
+/**
+ * Filter the lastFallbackLocale from availableLocales if it doesn't have all
+ * of the needed strings.
+ *
+ * When the lastFallbackLocale isn't the defaultLocale, then by default only
+ * fluent strings are included. To fully use that locale you need the langpack
+ * to be installed, so if it isn't installed remove it from availableLocales.
+ */
+async function getAvailableLocales() {
+  const availableLocales = mockable.getAvailableLocalesIncludingFallback();
+  const defaultLocale = mockable.getDefaultLocale();
+  const lastFallbackLocale = mockable.getLastFallbackLocale();
+  // If defaultLocale isn't lastFallbackLocale, then we still need the langpack
+  // for lastFallbackLocale for it to be useful.
+  if (defaultLocale != lastFallbackLocale) {
+    let lastFallbackId = `langpack-${lastFallbackLocale}@firefox.mozilla.org`;
+    let lastFallbackInstalled = await lazy.AddonManager.getAddonByID(
+      lastFallbackId
+    );
+    if (!lastFallbackInstalled) {
+      return availableLocales.filter(locale => locale != lastFallbackLocale);
+    }
+  }
+  return availableLocales;
+}
+
+export var LangPackMatcher = {
+  negotiateLangPackForLanguageMismatch,
+  ensureLangPackInstalled,
+  getAppAndSystemLocaleInfo,
+  setRequestedAppLocales,
+  getAvailableLocales,
+  mockable,
+};