1 files changed, 264 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..c501c1b0cd
--- /dev/null
+++ b/toolkit/components/translations/actors/AboutTranslationsChild.sys.mjs
@@ -0,0 +1,264 @@
+/* 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.defineLazyGetter(lazy, "console", () => {
+  return console.createInstance({
+    maxLogLevelPref: "browser.translations.logLevel",
+    prefix: "Translations",
+  });
+});
+
+ChromeUtils.defineESModuleGetters(lazy, {
+  LanguageDetector:
+    "resource://gre/modules/translation/LanguageDetector.sys.mjs",
+});
+
+/**
+ * @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 {
+  /**
+   * 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" });
+    }
+  }
+
+  receiveMessage({ name, data }) {
+    switch (name) {
+      case "AboutTranslations:SendTranslationsPort":
+        const { fromLanguage, toLanguage, port } = data;
+        const transferables = [port];
+        this.contentWindow.postMessage(
+          {
+            type: "GetTranslationsPort",
+            fromLanguage,
+            toLanguage,
+            port,
+          },
+          "*",
+          transferables
+        );
+        break;
+      default:
+        throw new Error("Unknown AboutTranslations message: " + name);
+    }
+  }
+
+  /**
+   * @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_isHtmlTranslation",
+      "AT_createTranslationsPort",
+      "AT_identifyLanguage",
+      "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.sendQuery("AboutTranslations:GetSupportedLanguages").then(data =>
+        Cu.cloneInto(data, this.contentWindow)
+      )
+    );
+  }
+
+  /**
+   * Does this device support the translation engine?
+   * @returns {Promise<boolean>}
+   */
+  AT_isTranslationEngineSupported() {
+    return this.#convertToContentPromise(
+      this.sendQuery("AboutTranslations:IsTranslationsEngineSupported")
+    );
+  }
+
+  /**
+   * Expose the #isHtmlTranslation property.
+   *
+   * @returns {bool}
+   */
+  AT_isHtmlTranslation() {
+    return this.#isHtmlTranslation;
+  }
+
+  /**
+   * Requests a port to the TranslationsEngine process. An engine will be created on
+   * the fly for translation requests through this port. This port is unique to its
+   * language pair. In order to translate a different language pair, a new port must be
+   * created for that pair. The lifecycle of the engine is managed by the
+   * TranslationsEngine.
+   *
+   * @param {string} fromLanguage
+   * @param {string} toLanguage
+   * @returns {void}
+   */
+  AT_createTranslationsPort(fromLanguage, toLanguage) {
+    this.sendAsyncMessage("AboutTranslations:GetTranslationsPort", {
+      fromLanguage,
+      toLanguage,
+    });
+  }
+
+  /**
+   * Attempts to identify the human language in which the message is written.
+   *
+   * @param {string} message
+   * @returns {Promise<{ langTag: string, confidence: number }>}
+   */
+  AT_identifyLanguage(message) {
+    return this.#convertToContentPromise(
+      lazy.LanguageDetector.detectLanguage(message).then(data =>
+        Cu.cloneInto(
+          // This language detector reports confidence as a boolean instead of
+          // a percentage, so we need to map the confidence to 0.0 or 1.0.
+          { langTag: data.language, confidence: data.confident ? 1.0 : 0.0 },
+          this.contentWindow
+        )
+      )
+    );
+  }
+
+  /**
+   * 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);
+  }
+}