/**
    * 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.ksb.messaging.threadpool;
  
  import org.kuali.rice.ksb.messaging.MessageServiceInvoker;
  import org.kuali.rice.ksb.messaging.PersistedMessageBO;
  
  import java.util.Comparator;
  import java.util.concurrent.PriorityBlockingQueue;
  
  /**
   * A comparator to put into the {@link PriorityBlockingQueue} used in the {@link KSBThreadPoolImpl}.
   * 
   *  Determines execution order by priority and create date.
   * 
   * @author Kuali Rice Team (rice.collab@kuali.org)
   *
   */
  public class PriorityBlockingQueuePersistedMessageComparator implements Comparator {
  
      
      public int compare(Object arg0, Object arg1) {
  	if (! (arg0 instanceof MessageServiceInvoker) || ! (arg1 instanceof MessageServiceInvoker) ) {
  	    return 0;
  	}
  	PersistedMessageBO message0 = ((MessageServiceInvoker)arg0).getMessage();
  	PersistedMessageBO message1 = ((MessageServiceInvoker)arg1).getMessage();
  	
  	if (message0.getQueuePriority() < message1.getQueuePriority()) {
  	    return -1;
  	} else if (message0.getQueuePriority() > message1.getQueuePriority()) {
  	    return 1;
  	}
  	
  	if (message0.getQueueDate().before(message1.getQueueDate())) {
  	    return -1;
  	} else if (message0.getQueueDate().after(message1.getQueueDate())) {
  	    return 1;
  	}
  	
  	return 0;
      }
  
  }