/*

  * Copyright 2007-2009 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.rice.kns.web.comparator;

 import java.io.Serializable;

 import java.util.Comparator;

 import org.kuali.rice.core.util.KeyLabelPair;

 public class KeyLabelComparator implements Serializable, Comparator {

     private static final KeyLabelComparator theInstance = new KeyLabelComparator();

     public KeyLabelComparator() {

     }

     public static KeyLabelComparator getInstance() {

         return theInstance;

     }

     public int compare(Object o1, Object o2) {

         // null guard. non-null value is greater. equal if both are null

         if (null == o1 || null == o2) {

             return (null == o1 && null == o2) ? 0 : ((null == o1) ? -1 : 1);

         }

         KeyLabelPair keyLabelPair1 = (KeyLabelPair) o1;

         KeyLabelPair keyLabelPair2 = (KeyLabelPair) o2;

         if (null==keyLabelPair1 || null==keyLabelPair2) {

             return (null==keyLabelPair1 && null==keyLabelPair2) ? 0 : ((null==keyLabelPair1) ? -1 : 1);

         }

         if((keyLabelPair1.getKey() instanceof String) && (keyLabelPair2.getKey() instanceof String))

                 return String.CASE_INSENSITIVE_ORDER.compare((String)keyLabelPair1.getKey(), (String)keyLabelPair2.getKey());

         return 0;

     }

 }