Nested groups order logic (#3206)

* Fix sorting of nestedgroups when groups added after initial groups setting

* Fix nesteded groups logic when adding and removing

* Remove empty lines

* Fix comments from PR

* Remove spaces from empty line

* Fix PR review comments

lib/timeline/component/ItemSet.js

@@ -146,6 +146,28 @@ function ItemSet(body, options) {
   this.groupListeners = {
     'add': function (event, params, senderId) {  // eslint-disable-line no-unused-vars
       me._onAddGroups(params.items);
+      
+      if (me.groupsData && me.groupsData.length > 0) {
+          var groupsData = me.groupsData.getDataSet();
+          groupsData.get().forEach(function (groupData) {
+          if (groupData.nestedGroups) {
+            if (groupData.showNested != false) {
+              groupData.showNested = true;
+            }
+            var updatedGroups = [];
+            groupData.nestedGroups.forEach(function(nestedGroupId) {
+              var updatedNestedGroup = groupsData.get(nestedGroupId);
+              if (!updatedNestedGroup) { return; }
+              updatedNestedGroup.nestedInGroup = groupData.id;
+              if (groupData.showNested == false) {
+                updatedNestedGroup.visible = false;
+              }
+              updatedGroups = updatedGroups.concat(updatedNestedGroup);
+            });
+            groupsData.update(updatedGroups, senderId);
+          }
+        });
+      }
     },
     'update': function (event, params, senderId) {  // eslint-disable-line no-unused-vars
       me._onUpdateGroups(params.items);
@@ -1662,21 +1684,20 @@ ItemSet.prototype._onGroupClick = function (event) {
 
   if (!group || !group.nestedGroups) return;
 
-  var groupsData = this.groupsData;
-  if (this.groupsData instanceof DataView) {
-    groupsData = this.groupsData.getDataSet()
-  }
+  var groupsData = this.groupsData.getDataSet();
 
-  group.showNested = !group.showNested;
+  var nestingGroup = groupsData.get(group.groupId)
+  if (nestingGroup.showNested == undefined) { nestingGroup.showNested = true; }
+  nestingGroup.showNested = !nestingGroup.showNested;
 
   var nestedGroups = groupsData.get(group.nestedGroups).map(function(nestedGroup) {
-    if (nestedGroup.visible == undefined) { nestedGroup.visible = true; }
-    nestedGroup.visible = !!group.showNested;
+    nestedGroup.visible = nestingGroup.showNested;
     return nestedGroup;
   });
-  groupsData.update(nestedGroups);
 
-  if (group.showNested) {
+  groupsData.update(nestedGroups.concat(nestingGroup));
+
+  if (nestingGroup.showNested) {
     util.removeClassName(group.dom.label, 'collapsed');
     util.addClassName(group.dom.label, 'expanded');
   } else {