/**
    * Copyright 2010-2014 The Kuali Foundation
    *
    * Licensed under the Educational Community 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.opensource.org/licenses/ecl2.php
    *
   * 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.kuali.common.util.xml.jaxb.adapter;
  
  import java.util.Collection;
  import java.util.Collections;
  
  import javax.xml.bind.annotation.adapters.XmlAdapter;
  
  import org.kuali.common.util.xml.jaxb.wrapper.CollectionWrapper;
  
  public class ImmutableCollectionAdapter<T> extends XmlAdapter<CollectionWrapper<T>, Collection<T>> {
  
  	private final Collection<T> EMPTY_COLLECTION = Collections.emptyList();
  	private final CollectionWrapper<T> EMPTY_WRAPPER = new CollectionWrapper<T>(EMPTY_COLLECTION);
  
  	@Override
  	public CollectionWrapper<T> marshal(Collection<T> c) {
  		if (isEmpty(c)) {
  			return EMPTY_WRAPPER;
  		} else {
  			return new CollectionWrapper<T>(c);
  		}
  	}
  
  	@Override
  	public Collection<T> unmarshal(CollectionWrapper<T> wrapper) {
  		if (isEmpty(wrapper.getCollection())) {
  			return EMPTY_COLLECTION;
  		} else {
  			return Collections.unmodifiableCollection(wrapper.getCollection());
  		}
  	}
  
  	protected static boolean isEmpty(Collection<?> c) {
  		return c == null || c.size() == 0;
  	}
  
  }