MD Bookmarks: Implement item selection in new data flow system

chrome/browser/resources/md_bookmarks/reducers.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 Module of functions which produce a new page state in response
  * to an action. Reducers (in the same sense as Array.prototype.reduce) must be
  * pure functions: they must not modify existing state objects, or make any API
  * calls.
  */
 
 cr.define('bookmarks', function() {
+  var SelectionState = {};
+
+  /**
+   * @param {SelectionState} selectionState
+   * @param {Action} action
+   * @return {SelectionState}
+   */
+  SelectionState.selectItems = function(selectionState, action) {
+    var newState = {};

[calamity, 2017/03/14 03:01:45]

nit: newItems

[tsergeant, 2017/03/14 05:42:02]

Done.

+    if (action.add)
+      Object.assign(newState, selectionState.items);
+
+    action.items.forEach(function(id) {
+      newState[id] = true;
+    });
+
+    return /** @type {SelectionState} */ (Object.assign({}, selectionState, {
+      items: newState,
+      anchor: action.anchor,
+    }));
+  };
+
+  /**
+   * @param {SelectionState} selectionState
+   * @return {SelectionState}
+   */
+  SelectionState.deselectAll = function(selectionState) {
+    return {
+      count: 0,

[calamity, 2017/03/14 03:01:45]

Is count used anywhere? Or is it just like, a #define for 0 =P

[tsergeant, 2017/03/14 05:42:02]

I kept meaning to either implement it or remove it for now, but forgot.

Removed for now, but we'll need it eventually.

+      items: {},
+      anchor: null,
+    };
+  };
+
+  /**
+   * @param {SelectionState} selection
+   * @param {Action} action
+   * @return {SelectionState}
+   */
+  SelectionState.updateSelection = function(selection, action) {
+    switch (action.name) {
+      case 'select-folder':
+      case 'finish-search':

[calamity, 2017/03/14 03:01:45]

Also clear-search.

+Test

[tsergeant, 2017/03/14 05:42:02]

Done.

+        return SelectionState.deselectAll(selection);
+      case 'select-items':
+        return SelectionState.selectItems(selection, action);

[calamity, 2017/03/14 03:01:45]

What happens to removed anchor indexes? They'll explode on the next shift
select, right?

[tsergeant, 2017/03/14 05:42:02]

Yup, again, that's something that's was fixed in the follow-up.

For now, I've made the action not assert in this case: It will just select the
single item if the anchor item is missing, and I've added a test.

+    }
+    return selection;
+  };
+
   var SearchState = {};
 
   /**
    * @param {SearchState} search
    * @param {Action} action
    * @return {SearchState}
    */
   SearchState.startSearch = function(search, action) {
     return {
       term: action.term,
@@ skipping 187 matching lines @@
 
     return Object.assign({}, state, modification);
   };
 
   /**
    * @param {ClosedFolderState} state
    * @param {Action} action
    * @param {NodeList} nodes
    * @return {ClosedFolderState}
    */
   ClosedFolderState.updateClosedFolders = function(state, action, nodes) {

[calamity, 2017/03/14 03:01:45]

Change state to closedFolders to be consistent with the other functions.

[tsergeant, 2017/03/14 05:42:02]

Done.

     switch (action.name) {
       case 'change-folder-open':
         return ClosedFolderState.changeFolderOpen(state, action);
       case 'select-folder':
         return ClosedFolderState.openAncestorsOf(state, action, nodes);
       default:
         return state;
     };
   };
 
   /**
    * Root reducer for the Bookmarks page. This is called by the store in
    * response to an action, and the return value is used to update the UI.
    * @param {!BookmarksPageState} state
    * @param {Action} action
    * @return {!BookmarksPageState}
    */
   function reduceAction(state, action) {
     return {
       nodes: NodeState.updateNodes(state.nodes, action),
       selectedFolder: SelectedFolderState.updateSelectedFolder(
           state.selectedFolder, action, state.nodes),
       closedFolders: ClosedFolderState.updateClosedFolders(
           state.closedFolders, action, state.nodes),
       search: SearchState.updateSearch(state.search, action),
+      selection: SelectionState.updateSelection(state.selection, action),
     };
   }
 
   return {
     reduceAction: reduceAction,
     ClosedFolderState: ClosedFolderState,
     NodeState: NodeState,
     SearchState: SearchState,
     SelectedFolderState: SelectedFolderState,
+    SelectionState: SelectionState,
   };
 });