Move Add-on SDK source to toolkit/jetpack

toolkit/jetpack/sdk/model/core.js

@@ -0,0 +1,23 @@
+/* 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";
+
+module.metadata = {
+  "stability": "unstable"
+};
+
+const { dispatcher } = require("../util/dispatcher");
+
+
+// Define `modelFor` accessor function that can be implemented
+// for different types of views. Since view's we'll be dealing
+// with types that don't really play well with `instanceof`
+// operator we're gonig to use `dispatcher` that is slight
+// extension over polymorphic dispatch provided by method.
+// This allows models to extend implementations of this by
+// providing predicates:
+//
+// modelFor.when($ => $ && $.nodeName === "tab", findTabById($.id))
+const modelFor = dispatcher("modelFor");
+exports.modelFor = modelFor;