/*
 *   @(#) $Id: IoFuture.java 190262 2005-06-12 12:29:37Z trustin $
 *
 *   Copyright 2004 The Apache Software Foundation
 *
 *   Licensed under the Apache 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.apache.org/licenses/LICENSE-2.0
 *
 *   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.apache.mina.common;


/**
 * Represents the result of an asynchronous I/O operation.
 * 
 * @author The Apache Directory Project
 * @version $Rev: 190262 $, $Date: 2005-06-12 13:29:37 +0100 (Sun, 12 Jun 2005) $
 */
public class IoFuture
{
    private Object result;
    private boolean ready;
    private Callback callback;
    
    /**
     * Something interested in being notified when the result
     * of an <code>IoFuture</code> becomes available
     */
    public interface Callback 
    {
    
      /**
       * Invoked when the result of an <code>IoFuture</code> 
       * becomes available
       * 
       * @param result  The result
       */
      public void resultReady(Object result);
            
    }
    
    /**
     * Creates a new instance.
     */
    protected IoFuture()
    {
    }

    /**
     * Wait for the asynchronous operation to end.
     */
    public synchronized void join()
    {
        while( !ready )
        {
            try
            {
                wait();
            }
            catch( InterruptedException e )
            {
            }
        }
    }

    /**
     * Wait for the asynchronous operation to end with the specified timeout.
     * 
     * @return <tt>true</tt> if the operation is finished.
     */
    public synchronized boolean join( long timeoutInMillis )
    {
        long startTime = ( timeoutInMillis <= 0 ) ? 0 : System
                .currentTimeMillis();
        long waitTime = timeoutInMillis;
        if( ready )
        {
            return ready;
        }
        else if( waitTime <= 0 )
        {
            return ready;
        }

        for( ;; )
        {
            try
            {
                wait( waitTime );
            }
            catch( InterruptedException e )
            {
            }

            if( ready )
                return true;
            else
            {
                waitTime = timeoutInMillis - ( System.currentTimeMillis() - startTime );
                if( waitTime <= 0 )
                {
                    return ready;
                }
            }
        }
    }

    /**
     * Returns if the asynchronous operation is finished.
     */
    public synchronized boolean isReady()
    {
        return ready;
    }

    /**
     * Sets a <code>Callback</code> to be notified when a result
     * becomes available.
     * If this <code>IoFuture</code>s result has already become obtained,
     * the specified callback is notified immediately
     * 
     * @param callback  The callback
     */
    public synchronized void setCallback(Callback callback) 
    {
      this.callback = callback;
      if (ready) {
        callback.resultReady(result);
      }
    }
    
    /**
     * Sets the result of the asynchronous operation, and mark it as finished.
     * If this future is associated with a <code>Callback</code>, the callback
     * is notified of the new value
     */
    protected synchronized void setValue( Object newValue )
    {
        result = newValue;
        ready = true;
        if (callback != null) {
          callback.resultReady(result);
        }
        notifyAll();
    }

    /**
     * Returns the result of the asynchronous operation.
     */
    protected synchronized Object getValue()
    {
        return result;
    }
    
}