1 files changed, 312 insertions, 0 deletions
diff --git a/toolkit/components/translations/actors/AboutTranslationsChild.sys.mjs b/toolkit/components/translations/actors/AboutTranslationsChild.sys.mjs
new file mode 100644
index 0000000000..112ac3c444
--- /dev/null
+++ b/toolkit/components/translations/actors/AboutTranslationsChild.sys.mjs
@@ -0,0 +1,312 @@
+/* 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/. */
+
+import { XPCOMUtils } from "resource://gre/modules/XPCOMUtils.sys.mjs";
+
+const lazy = {};
+
+XPCOMUtils.defineLazyGetter(lazy, "console", () => {
+  return console.createInstance({
+    maxLogLevelPref: "browser.translations.logLevel",
+    prefix: "Translations",
+  });
+});
+
+/**
+ * @typedef {import("./TranslationsChild.sys.mjs").LanguageIdEngine} LanguageIdEngine
+ * @typedef {import("./TranslationsChild.sys.mjs").TranslationsEngine} TranslationsEngine
+ * @typedef {import("./TranslationsChild.sys.mjs").SupportedLanguages} SupportedLanguages
+ */
+
+/**
+ * The AboutTranslationsChild is responsible for coordinating what privileged APIs
+ * are exposed to the un-privileged scope of the about:translations page.
+ */
+export class AboutTranslationsChild extends JSWindowActorChild {
+  /** @type {LanguageIdEngine | null} */
+  languageIdEngine = null;
+
+  /** @type {TranslationsEngine | null} */
+  translationsEngine = null;
+
+  /**
+   * The translations engine uses text translations by default in about:translations,
+   * but it can be changed to translate HTML by setting this pref to true. This is
+   * useful for manually testing HTML translation behavior, but is not useful to surface
+   * as a user-facing feature.
+   *
+   * @type {bool}
+   */
+  #isHtmlTranslation = Services.prefs.getBoolPref(
+    "browser.translations.useHTML"
+  );
+
+  handleEvent(event) {
+    if (event.type === "DOMDocElementInserted") {
+      this.#exportFunctions();
+    }
+
+    if (
+      event.type === "DOMContentLoaded" &&
+      Services.prefs.getBoolPref("browser.translations.enable")
+    ) {
+      this.#sendEventToContent({ type: "enable" });
+    }
+  }
+
+  /**
+   * @param {object} detail
+   */
+  #sendEventToContent(detail) {
+    this.contentWindow.dispatchEvent(
+      new this.contentWindow.CustomEvent("AboutTranslationsChromeToContent", {
+        detail: Cu.cloneInto(detail, this.contentWindow),
+      })
+    );
+  }
+
+  /**
+   * @returns {TranslationsChild}
+   */
+  #getTranslationsChild() {
+    const child = this.contentWindow.windowGlobalChild.getActor("Translations");
+    if (!child) {
+      throw new Error("Unable to find the TranslationsChild");
+    }
+    return child;
+  }
+
+  /**
+   * A privileged promise can't be used in the content page, so convert a privileged
+   * promise into a content one.
+   *
+   * @param {Promise<any>} promise
+   * @returns {Promise<any>}
+   */
+  #convertToContentPromise(promise) {
+    return new this.contentWindow.Promise((resolve, reject) =>
+      promise.then(resolve, error => {
+        let contentWindow;
+        try {
+          contentWindow = this.contentWindow;
+        } catch (error) {
+          // The content window is no longer available.
+          reject();
+          return;
+        }
+        // Create an error in the content window, if the content window is still around.
+        let message = "An error occured in the AboutTranslations actor.";
+        if (typeof error === "string") {
+          message = error;
+        }
+        if (typeof error?.message === "string") {
+          message = error.message;
+        }
+        if (typeof error?.stack === "string") {
+          message += `\n\nOriginal stack:\n\n${error.stack}\n`;
+        }
+
+        reject(new contentWindow.Error(message));
+      })
+    );
+  }
+
+  /**
+   * Export any of the child functions that start with "AT_" to the unprivileged content
+   * page. This restricts the security capabilities of the the content page.
+   */
+  #exportFunctions() {
+    const window = this.contentWindow;
+
+    const fns = [
+      "AT_log",
+      "AT_logError",
+      "AT_getAppLocale",
+      "AT_getSupportedLanguages",
+      "AT_isTranslationEngineSupported",
+      "AT_createLanguageIdEngine",
+      "AT_createTranslationsEngine",
+      "AT_identifyLanguage",
+      "AT_translate",
+      "AT_destroyTranslationsEngine",
+      "AT_getScriptDirection",
+    ];
+    for (const name of fns) {
+      Cu.exportFunction(this[name].bind(this), window, { defineAs: name });
+    }
+  }
+
+  /**
+   * Log messages if "browser.translations.logLevel" is set to "All".
+   *
+   * @param {...any} args
+   */
+  AT_log(...args) {
+    lazy.console.log(...args);
+  }
+
+  /**
+   * Report an error to the console.
+   *
+   * @param {...any} args
+   */
+  AT_logError(...args) {
+    lazy.console.error(...args);
+  }
+
+  /**
+   * Returns the app's locale.
+   *
+   * @returns {Intl.Locale}
+   */
+  AT_getAppLocale() {
+    return Services.locale.appLocaleAsBCP47;
+  }
+
+  /**
+   * Wire this function to the TranslationsChild.
+   *
+   * @returns {Promise<SupportedLanguages>}
+   */
+  AT_getSupportedLanguages() {
+    return this.#convertToContentPromise(
+      this.#getTranslationsChild()
+        .getSupportedLanguages()
+        .then(data => Cu.cloneInto(data, this.contentWindow))
+    );
+  }
+
+  /**
+   * Does this device support the translation engine?
+   * @returns {Promise<boolean>}
+   */
+  AT_isTranslationEngineSupported() {
+    return this.#convertToContentPromise(
+      this.#getTranslationsChild().isTranslationsEngineSupported
+    );
+  }
+
+  /**
+   * Creates the LanguageIdEngine which attempts to identify in which
+   * human language a string is written.
+   *
+   * Unlike TranslationsEngine, which handles only a single language pair
+   * and must be rebuilt to handle a new language pair, the LanguageIdEngine
+   * is a one-to-many engine that can recognize all of its supported languages.
+   *
+   * Subsequent calls to this function after the engine is initialized will do nothing
+   * instead of rebuilding the engine.
+   *
+   * @returns {Promise<void>}
+   */
+  AT_createLanguageIdEngine() {
+    if (this.languageIdEngine) {
+      return this.#convertToContentPromise(Promise.resolve());
+    }
+    return this.#convertToContentPromise(
+      this.#getTranslationsChild()
+        .createLanguageIdEngine()
+        .then(engine => {
+          this.languageIdEngine = engine;
+        })
+    );
+  }
+
+  /**
+   * Creates the TranslationsEngine which is responsible for translating
+   * from one language to the other.
+   *
+   * The instantiated TranslationsEngine is unique to its language pair.
+   * In order to translate a different language pair, a new engine must be
+   * created for that pair.
+   *
+   * Subsequent calls to this function will destroy the existing engine and
+   * rebuild a new engine for the new language pair.
+   *
+   * @param {string} fromLanguage
+   * @param {string} toLanguage
+   * @returns {Promise<void>}
+   */
+  AT_createTranslationsEngine(fromLanguage, toLanguage) {
+    if (this.translationsEngine) {
+      this.translationsEngine.terminate();
+      this.translationsEngine = null;
+    }
+    return this.#convertToContentPromise(
+      this.#getTranslationsChild()
+        .createTranslationsEngine(fromLanguage, toLanguage)
+        .then(engine => {
+          this.translationsEngine = engine;
+        })
+    );
+  }
+
+  /**
+   * Attempts to identify the human language in which the message is written.
+   * @see LanguageIdEngine#identifyLanguage for more detailed documentation.
+   *
+   * @param {string} message
+   * @returns {Promise<{ langTag: string, confidence: number }>}
+   */
+  AT_identifyLanguage(message) {
+    if (!this.languageIdEngine) {
+      const { Promise, Error } = this.contentWindow;
+      return Promise.reject(
+        new Error("The language identification was not created.")
+      );
+    }
+
+    return this.#convertToContentPromise(
+      this.languageIdEngine
+        .identifyLanguage(message)
+        .then(data => Cu.cloneInto(data, this.contentWindow))
+    );
+  }
+
+  /**
+   * @param {string[]} messageBatch
+   * @param {number} innerWindowId
+   * @returns {Promise<string[]>}
+   */
+  AT_translate(messageBatch, innerWindowId) {
+    if (!this.translationsEngine) {
+      throw new this.contentWindow.Error(
+        "The translations engine was not created."
+      );
+    }
+    const promise = this.#isHtmlTranslation
+      ? this.translationsEngine.translateHTML(messageBatch, innerWindowId)
+      : this.translationsEngine.translateText(messageBatch, innerWindowId);
+
+    return this.#convertToContentPromise(
+      promise.then(translations =>
+        Cu.cloneInto(translations, this.contentWindow)
+      )
+    );
+  }
+
+  /**
+   * This is not strictly necessary, but could free up resources quicker.
+   */
+  AT_destroyTranslationsEngine() {
+    if (this.translationsEngine) {
+      this.translationsEngine.terminate();
+      this.translationsEngine = null;
+    }
+  }
+
+  /**
+   * TODO - Remove this when Intl.Locale.prototype.textInfo is available to
+   * content scripts.
+   *
+   * https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Intl/Locale/textInfo
+   * https://bugzilla.mozilla.org/show_bug.cgi?id=1693576
+   *
+   * @param {string} locale
+   * @returns {string}
+   */
+  AT_getScriptDirection(locale) {
+    return Services.intl.getScriptDirection(locale);
+  }
+}