/**
    * Copyright 2005-2011 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.krad.comparator;
  
  import org.kuali.rice.core.web.format.DateFormatter;
  
  import java.io.Serializable;
  import java.util.Comparator;
  import java.util.Date;
  
  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;
      }
  }