MD Bookmarks: Implement basis for new data-binding system

chrome/browser/resources/md_bookmarks/bookmarks_store.js

+// Copyright 2017 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+/**
+ * @fileoverview A singleton datastore for the Bookmarks page. Page state is
+ * publicly readable, but can only be modified by dispatching an Action to
+ * the store.
+ */
+
+cr.define('bookmarks', function() {
+  /** @constructor */
+  function Store() {
+    /** @type {!BookmarksPageState} */
+    this.data_ = {};
+    /** @type {boolean} */
+    this.initialized_ = false;
+    /** @type {!Array<!StoreObserver>} */
+    this.observers_ = [];
+  }
+
+  Store.prototype = {
+    /**
+     * @param {!BookmarksPageState} initialState
+     */
+    init: function(initialState) {
+      this.data_ = initialState;
+      this.initialized_ = true;
+      this.notifyObservers_(this.data_);
+    },
+
+    /** @type {!BookmarksPageState} */
+    get data() {
+      return this.data_;
+    },
+
+    /** @return {boolean} */
+    isInitialized: function() {
+      return this.initialized_;
+    },
+
+    /** @param {!StoreObserver} observer */
+    addObserver: function(observer) {
+      this.observers_.push(observer);
+    },
+
+    /** @param {!StoreObserver} observer */
+    removeObserver: function(observer) {
+      var index = this.observers_.indexOf(observer);
+      this.observers_.splice(index, 1);
+    },
+
+    /**
+     * Transition to a new UI state based on the supplied |action|, and notify
+     * observers of the change.
+     * @param {Action} action
+     */
+    handleAction: function(action) {
+      if (!this.initialized_)
+        return;
+
+      this.data_ = bookmarks.reduceAction(this.data_, action);
+      this.notifyObservers_(this.data_);
+    },
+
+    /**
+     * @param {!BookmarksPageState} state
+     * @private
+     */
+    notifyObservers_: function(state) {
+      this.observers_.forEach(function(o) {
+        o.onStateChanged(state);
+      });
+    },
+  };
+
+  cr.addSingletonGetter(Store);
+
+  return {
+    Store: Store,
+  };
+});