/*

  * Copyright 2007-2008 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 java.util.Date;

 import org.kuali.rice.core.web.format.DateFormatter;

 public class TemporalValueComparator implements Comparator, Serializable {

     private static final TemporalValueComparator theInstance = new TemporalValueComparator();

     public TemporalValueComparator() {

     }

     public static TemporalValueComparator 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;

         }

         String s1 = (String) o1;

         String s2 = (String) o2;

         DateFormatter f1 = new DateFormatter();

         Date d1 = (Date) f1.convertFromPresentationFormat(s1);

         Date d2 = (Date) f1.convertFromPresentationFormat(s2);

         if (null == d1 || null == d2) {

             return null == d1 && null == d2 ? 0 : null == d1 ? -1 : 1;

         }

         return d1.equals(d2) ? 0 : d1.before(d2) ? -1 : 1;

     }

 }