1 files changed, 207 insertions, 0 deletions
diff --git a/toolkit/components/translations/actors/TranslationsEngineChild.sys.mjs b/toolkit/components/translations/actors/TranslationsEngineChild.sys.mjs
new file mode 100644
index 0000000000..a4ab8e2640
--- /dev/null
+++ b/toolkit/components/translations/actors/TranslationsEngineChild.sys.mjs
@@ -0,0 +1,207 @@
+/* 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",
+  });
+});
+
+/**
+ * The engine child is responsible for exposing privileged code to the un-privileged
+ * space the engine runs in.
+ */
+export class TranslationsEngineChild extends JSWindowActorChild {
+  /**
+   * The resolve function for the Promise returned by the
+   * "TranslationsEngine:ForceShutdown" message.
+   * @type {null | () => {}}
+   */
+  #resolveForceShutdown = null;
+
+  actorCreated() {
+    this.#exportFunctions();
+  }
+
+  handleEvent(event) {
+    switch (event.type) {
+      case "DOMContentLoaded":
+        this.sendAsyncMessage("TranslationsEngine:Ready");
+        break;
+    }
+  }
+
+  // eslint-disable-next-line consistent-return
+  async receiveMessage({ name, data }) {
+    switch (name) {
+      case "TranslationsEngine:StartTranslation": {
+        const { fromLanguage, toLanguage, innerWindowId, port } = data;
+        const transferables = [port];
+        const message = {
+          type: "StartTranslation",
+          fromLanguage,
+          toLanguage,
+          innerWindowId,
+          port,
+        };
+        this.contentWindow.postMessage(message, "*", transferables);
+        break;
+      }
+      case "TranslationsEngine:DiscardTranslations": {
+        const { innerWindowId } = data;
+        this.contentWindow.postMessage({
+          type: "DiscardTranslations",
+          innerWindowId,
+        });
+        break;
+      }
+      case "TranslationsEngine:ForceShutdown": {
+        this.contentWindow.postMessage({
+          type: "ForceShutdown",
+        });
+        return new Promise(resolve => {
+          this.#resolveForceShutdown = resolve;
+        });
+      }
+      default:
+        console.error("Unknown message received", name);
+    }
+  }
+
+  /**
+   * Export any of the child functions that start with "TE_" to the unprivileged content
+   * page. This restricts the security capabilities of the content page.
+   */
+  #exportFunctions() {
+    const fns = [
+      "TE_addProfilerMarker",
+      "TE_getLogLevel",
+      "TE_log",
+      "TE_logError",
+      "TE_requestEnginePayload",
+      "TE_reportEngineStatus",
+      "TE_resolveForceShutdown",
+      "TE_destroyEngineProcess",
+    ];
+    for (const defineAs of fns) {
+      Cu.exportFunction(this[defineAs].bind(this), this.contentWindow, {
+        defineAs,
+      });
+    }
+  }
+
+  /**
+   * 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 TranslationsEngine 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));
+      })
+    );
+  }
+
+  /**
+   * @param {Object} options
+   * @param {number?} options.startTime
+   * @param {string} options.message
+   */
+  TE_addProfilerMarker({ startTime, message, innerWindowId }) {
+    ChromeUtils.addProfilerMarker(
+      "TranslationsEngine",
+      { startTime, innerWindowId },
+      message
+    );
+  }
+
+  /**
+   * Pass the message from content that the engines were shut down.
+   */
+  TE_resolveForceShutdown() {
+    this.#resolveForceShutdown();
+  }
+
+  /**
+   * @returns {string}
+   */
+  TE_getLogLevel() {
+    return Services.prefs.getCharPref("browser.translations.logLevel");
+  }
+
+  /**
+   * Log messages if "browser.translations.logLevel" is set to "All".
+   *
+   * @param {...any} args
+   */
+  TE_log(...args) {
+    lazy.console.log(...args);
+  }
+
+  /**
+   * Report an error to the console.
+   *
+   * @param {...any} args
+   */
+  TE_logError(...args) {
+    lazy.console.error(...args);
+  }
+
+  /**
+   * @param {string} fromLanguage
+   * @param {string} toLanguage
+   */
+  TE_requestEnginePayload(fromLanguage, toLanguage) {
+    return this.#convertToContentPromise(
+      this.sendQuery("TranslationsEngine:RequestEnginePayload", {
+        fromLanguage,
+        toLanguage,
+      })
+    );
+  }
+
+  /**
+   * @param {number} innerWindowId
+   * @param {"ready" | "error"} status
+   */
+  TE_reportEngineStatus(innerWindowId, status) {
+    this.sendAsyncMessage("TranslationsEngine:ReportEngineStatus", {
+      innerWindowId,
+      status,
+    });
+  }
+
+  /**
+   * No engines are still alive, destroy the process.
+   */
+  TE_destroyEngineProcess() {
+    this.sendAsyncMessage("TranslationsEngine:DestroyEngineProcess");
+  }
+}