/*
 *  Licensed to the Apache Software Foundation (ASF) under one
 *  or more contributor license agreements.  See the NOTICE file
 *  distributed with this work for additional information
 *  regarding copyright ownership.  The ASF licenses this file
 *  to you under the Apache License, Version 2.0 (the
 *  "License"); you may not use this file except in compliance
 *  with the License.  You may obtain a copy of the License at
 *
 *        http://www.apache.org/licenses/LICENSE-2.0
 *
 *  Unless required by applicable law or agreed to in writing,
 *  software distributed under the License is distributed on an
 *  "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
 *  KIND, either express or implied.  See the License for the
 *  specific language governing permissions and limitations
 *  under the License.
 */
package org.apache.isis.viewer.wicket.ui.components.widgets.select2;

import java.util.ArrayList;
import java.util.Collection;

import org.apache.wicket.model.IModel;
import org.wicketstuff.select2.Select2MultiChoice;

import org.apache.isis.core.commons.internal.base._Casts;
import org.apache.isis.core.metamodel.spec.ObjectSpecId;
import org.apache.isis.core.webapp.context.memento.ObjectMemento;
import org.apache.isis.viewer.wicket.model.models.ScalarModel;
import org.apache.isis.viewer.wicket.ui.components.widgets.select2.providers.EmptyChoiceProvider;

public class Select2MultiChoiceExt
extends Select2MultiChoice<ObjectMemento>
implements ChoiceExt {

    private static final long serialVersionUID = 1L;

    public static Select2MultiChoiceExt create(
            final String id,
            final IModel<ArrayList<ObjectMemento>> modelObject,
            final ScalarModel scalarModel) {
        
        return new Select2MultiChoiceExt(id, _Casts.uncheckedCast(modelObject), scalarModel);
    }

    private final ObjectSpecId specId;

    Select2MultiChoiceExt(
            final String id,
            final IModel<Collection<ObjectMemento>> model,
            final ScalarModel scalarModel) {
        
        super(id, model, EmptyChoiceProvider.INSTANCE);
        specId = scalarModel.getTypeOfSpecification().getSpecId();

        getSettings().setCloseOnSelect(true);

        setOutputMarkupPlaceholderTag(true);
    }

    @Override
    public ObjectSpecId getSpecId() {
        return specId;
    }
    
    
    @Override
    public void updateModel() {
        super.updateModel();
    }
    
    @Override
    public Collection<ObjectMemento> getModelObject() {
        return new ArrayList<>(super.getModelObject());
    }
    
}

@@ -945,16 +945,46 @@
 lection;
+%0Aimport java.util.Collections;
 %0A%0Aimport
@@ -1411,16 +1411,36 @@
 vider;%0A%0A
+import lombok.val;%0A%0A
 public c
@@ -2565,30 +2565,153 @@
 ) %7B%0A        
-return
+val modelObj = super.getModelObject();%0A        return modelObj==null%0A                ? Collections.emptyList() %0A                :
  new ArrayLi
@@ -2715,38 +2715,24 @@
 yList%3C%3E(
-super.getM
+m
 odelObj
-ect()
 );%0A    %7D

fix potential NPE with workaround