1 files changed, 72 insertions, 0 deletions
diff --git a/devtools/client/framework/local-tab-commands-factory.js b/devtools/client/framework/local-tab-commands-factory.js
new file mode 100644
index 0000000000..e7e32aa343
--- /dev/null
+++ b/devtools/client/framework/local-tab-commands-factory.js
@@ -0,0 +1,72 @@
+/* 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/. */
+
+"use strict";
+
+loader.lazyRequireGetter(
+  this,
+  "CommandsFactory",
+  "resource://devtools/shared/commands/commands-factory.js",
+  true
+);
+
+// Map of existing Commands objects, keyed by XULTab.
+const commandsMap = new WeakMap();
+
+/**
+ * Functions for creating unique Commands for Local Tabs.
+ */
+exports.LocalTabCommandsFactory = {
+  /**
+   * Create a unique commands object for the given tab.
+   *
+   * If a commands was already created by this factory for the provided tab,
+   * it will be returned and no new commands created.
+   *
+   * Otherwise, this will automatically:
+   * - spawn a DevToolsServer in the parent process,
+   * - create a DevToolsClient
+   * - connect the DevToolsClient to the DevToolsServer
+   * - call RootActor's `getTab` request to retrieve the WindowGlobalTargetActor's form
+   *
+   * @param {XULTab} tab
+   *        The tab to use in creating a new commands.
+   *
+   * @return {Commands object} The commands object for the provided tab.
+   */
+  async createCommandsForTab(tab) {
+    let commands = commandsMap.get(tab);
+    if (commands) {
+      // Keep in mind that commands can be either a promise
+      // or a commands object.
+      return commands;
+    }
+
+    const promise = CommandsFactory.forTab(tab);
+    // Immediately set the commands's promise in cache to prevent race
+    commandsMap.set(tab, promise);
+    commands = await promise;
+    // Then replace the promise with the commands object
+    commandsMap.set(tab, commands);
+
+    commands.descriptorFront.once("descriptor-destroyed", () => {
+      commandsMap.delete(tab);
+    });
+    return commands;
+  },
+
+  /**
+   * Retrieve an existing commands created by this factory for the provided
+   * tab. Returns null if no commands was created yet.
+   *
+   * @param {XULTab} tab
+   *        The tab for which the commands should be retrieved
+   */
+  async getCommandsForTab(tab) {
+    // commandsMap.get(tab) can either return an initialized commands, a promise
+    // which will resolve a commands, or null if no commands was ever created
+    // for this tab.
+    return commandsMap.get(tab);
+  },
+};