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/*
 * Event.java February 2007
 *
 * Copyright (C) 2007, Niall Gallagher 
 *
 * This library is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Lesser General Public
 * License as published by the Free Software Foundation.
 *
 * This library is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the 
 * GNU Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General 
 * Public License along with this library; if not, write to the 
 * Free Software Foundation, Inc., 59 Temple Place, Suite 330, 
 * Boston, MA  02111-1307  USA
 */

package org.simpleframework.util.select;

import java.nio.channels.SelectableChannel;

/**
 * The SelectEvent object is used to represent an event 
 * that the distributor is to process. This contains the operation 
 * and the required I/O events as an integer bit mask as well as the
 * selectable channel used to register for selection. In order to
 * ensure that the event does not remain within the distributor for
 * too long the event has an expiry time.
 * 
 * @author Niall Gallagher
 */
class SelectEvent implements Event {

   /**
    * The task to execute when the required operations is ready.
    */
   private final Operation task;

   /**
    * This is the bit mask of required operations to be executed.
    */
   private final int require;
   
   /**
    * This is the time in the future that the event will expire in.
    */
   private final long expiry;

   /**
    * Constructor for the Event object. The events are
    * used to encapsulate the task to execute and the operations
    * to listen to when some action is to be performed.
    * 
    * @param task this is the task to be executed when it is ready
    * @param require this is the required operations to listen to
    */
   public SelectEvent(Operation task, int require, long expiry) {
      this.expiry = System.currentTimeMillis() + expiry;
      this.require = require;
      this.task = task;
   }  
   
   /**
    * This is used to execute the operation for the event. This will
    * be executed when the interested I/O event is ready for the
    * associated SelectableChannel object. If the event
    * expires before the interested I/O operation is ready this will
    * not be executed, instead the operation is canceled. 
    */
   public void run() {
      task.run();
   }

   /**
    * This is used to get the expiry for the operation. The expiry
    * represents some static time in the future when the event will
    * expire if it does not become ready. This is used to cancel the
    * operation so that it does not remain in the distributor.
    *
    * @return the remaining time this operation will wait for
    */        
   public long getExpiry() {
      return expiry;
   }

   /**
    * This is the SelectableChannel which is used to 
    * determine if the operation should be executed. If the channel   
    * is ready for a given I/O event it can be run. For instance if
    * the operation is used to perform some form of read operation
    * it can be executed when ready to read data from the channel.
    *
    * @return this returns the channel used to govern execution
    */    
   public SelectableChannel getChannel() {
      return task.getChannel();
   }
   
   /**
    * This is used to acquire the Operation that is to
    * be executed when the required operations are ready. It is the
    * responsibility of the distributor to invoke the operation.
    * 
    * @return the operation to be executed when it is ready
    */
   public Operation getOperation() {
      return task;
   }

   /**
    * This returns the I/O operations that the event is interested
    * in as an integer bit mask. When any of these operations are
    * ready the distributor will execute the provided operation. 
    * 
    * @return the integer bit mask of interested I/O operations
    */
   public int getInterest() {
      return require;
   }
}