MD Bookmarks: Implement basis for new data-binding system

chrome/browser/resources/md_bookmarks/bookmarks_store.js

Index: chrome/browser/resources/md_bookmarks/bookmarks_store.js
diff --git a/chrome/browser/resources/md_bookmarks/bookmarks_store.js b/chrome/browser/resources/md_bookmarks/bookmarks_store.js
new file mode 100644
index 0000000000000000000000000000000000000000..27b1cec9484e23b9926f47ef42871d52477b1cef
--- /dev/null
+++ b/chrome/browser/resources/md_bookmarks/bookmarks_store.js
@@ -0,0 +1,81 @@
+// Copyright 2016 The Chromium Authors. All rights reserved.

[michaelpg, 2017/03/02 09:30:35]

2017 :-)

[tsergeant, 2017/03/02 23:20:35]

Oops, done.

+// Use of this source code is governed by a BSD-style license that can be

[michaelpg, 2017/03/02 09:30:35]

:-\ store.js would be a more consistent name (unlike settings, where tons of
files start with "settings_")

maybe `rename s/store/old_store store.*`?

[tsergeant, 2017/03/02 23:20:34]

I did previously have the new store live in store.js, and the old one moved to
polymer_store.js. I changed it to this version to reduce the amount of git churn
-- renaming the file like this caused an extra +500/-500 on the diff.

Chris: which version do you prefer?

[calamity, 2017/03/03 02:29:03]

I don't think it's worth the churn in other parts of the codebase to have a nice
name for such a brief period.. Eventually we'll just be moving this into
store.js anyway, right?

[tsergeant, 2017/03/03 05:08:00]

Yup, store.js is the eventual name. bookmarks_store.js is just a temporary name
for while we have both version in the codebase.

I've discussed this with Chris in person, and we'll keep this temporary name for
simplicity's sake.

[michaelpg, 2017/03/03 22:04:57]

Also SGTM!

+// 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} */

[michaelpg, 2017/03/02 09:30:35]

throughout: !BookmarksPageState for non-null?

[tsergeant, 2017/03/02 23:20:34]

This isn't strictly necessary, since BookmarksPageState is already defined as
non-nullable, but I've gone ahead and changed it for consistency/safety.

+    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,
+  };
+});