Resolves #125 UI building refactored

lib/view_builder.class.dart

@@ -0,0 +1,102 @@
+part of 'main.dart';
+
+class ViewBuilder{
+
+  EntityCollection entityCollection;
+  List<View> _views;
+
+  ViewBuilder({
+    Key key,
+    this.entityCollection
+  }) {
+    _compose();
+  }
+
+  Widget buildWidget(BuildContext context) {
+    return ViewBuilderWidget(
+      entities: _views
+    );
+  }
+
+  void _compose() {
+    TheLogger.log("Debug", "Rebuilding all UI...");
+    _views = [];
+    if (!entityCollection.hasDefaultView) {
+      _views.add(_composeDefaultView());
+    }
+    _views.addAll(_composeViews());
+  }
+
+  View _composeDefaultView() {
+    Map<String, List<String>> userGroupsList = entityCollection.getDefaultViewTopLevelEntities();
+    List<Entity> entitiesForView = [];
+    //TODO WTF? Why two arrays?
+    userGroupsList["userGroups"].forEach((groupId){
+      entitiesForView.add(entityCollection.get(groupId));
+    });
+    userGroupsList["notGroupedEntities"].forEach((entityId){
+      entitiesForView.add(entityCollection.get(entityId));
+    });
+    return View(
+      entities: entitiesForView,
+      count: 0
+    );
+  }
+
+  List<View> _composeViews() {
+    List<View> result = [];
+    int counter = 0;
+    entityCollection.viewList.forEach((viewId) {
+      counter += 1;
+      //try {
+        Entity viewGroupEntity = entityCollection.get(viewId);
+        List<Entity> entitiesForView = [];
+        viewGroupEntity.childEntityIds.forEach((
+            entityId) { //Each entity or group in view
+          if (entityCollection.isExist(entityId)) {
+            Entity en = entityCollection.get(entityId);
+            if (en.isGroup) {
+              en.childEntities = entityCollection.getAll(en.childEntityIds);
+            }
+            entitiesForView.add(en);
+          } else {
+            TheLogger.log("Warning", "Unknown entity inside view: $entityId");
+          }
+        });
+        result.add(View(
+          count: counter,
+          entities: entitiesForView
+        ));
+      /*} catch (error) {
+        TheLogger.log("Error","Error parsing view: $viewId");
+      }*/
+    });
+    return result;
+  }
+}
+
+class ViewBuilderWidget extends StatelessWidget {
+
+  final List<View> entities;
+
+  const ViewBuilderWidget({
+    Key key,
+    this.entities
+  }) : super(key: key);
+
+  @override
+  Widget build(BuildContext context) {
+    return TabBarView(
+        children: _buildChildren(context)
+    );
+  }
+
+  List<Widget> _buildChildren(BuildContext context) {
+    List<Widget> result = [];
+    entities.forEach((View view){
+      result.add(view.buildWidget(context));
+    });
+    return result;
+  }
+
+}