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/* XLogo4Schools - A Logo Interpreter specialized for use in schools, based on XLogo by Loic Le Coq
* Copyright (C) 2013 Marko Zivkovic
*
* Contact Information: marko88zivkovic at gmail dot com
*
* This program is free software; you can redistribute it and/or modify it
* under the terms of the GNU General Public License as published by the Free
* Software Foundation; either version 2 of the License, or (at your option)
* any later version. This program 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 General
* Public License for more details. You should have received a copy of the
* GNU General Public License along with this program; if not, write to the Free
* Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston,
* MA 02110-1301, USA.
*
*
* This Java source code belongs to XLogo4Schools, written by Marko Zivkovic
* during his Bachelor thesis at the computer science department of ETH Zurich,
* in the year 2013 and/or during future work.
*
* It is a reengineered version of XLogo written by Loic Le Coq, published
* under the GPL License at http://xlogo.tuxfamily.org/
*
* Contents of this file were entirely written by Marko Zivkovic
*/
package xlogo.messages.async;
import java.util.concurrent.ConcurrentLinkedQueue;
import xlogo.Application;
/**
* <p> This class was implemented with the purpose to decouple various parts of XLogo4Schools from the Application-class. <br>
* Before, almost every part had to have a reference to {@link Application}. Without the reference to the current frame, no errors or other messages could be displayed.
* <p>
* This class also allows to dispatch messages before a Medium (such as JFrame for dialogs or HistoryPanel for history messages) is set up. Therefore it maintains an internal queue of messages.
* As soon as the medium is set up and ready, the queue will be emptied by displaying all the messages, one after the other.
* <p>
* This class is thread-safe.
*/
public abstract class AbstractAsyncMessenger<M extends AsyncMessage<T>, T> implements AsyncMessenger
{
AsyncMediumAdapter<M, T> mediumAdapter;
private ConcurrentLinkedQueue<M> messageQueue;
private boolean isWorking;
public AbstractAsyncMessenger()
{
messageQueue = new ConcurrentLinkedQueue<M>();
}
/**
* @return whether medium is set (not null) and ready
*/
protected synchronized boolean isMediumReady()
{
return mediumAdapter != null && mediumAdapter.isReady();
}
/**
* @return Whether the worker thread is currently not working off the message
*/
protected synchronized boolean isReady()
{
return isMediumReady() && !isWorking;
}
private synchronized void setIsWorking(boolean isWorking)
{
this.isWorking = isWorking;
}
public synchronized void setMedium(AsyncMediumAdapter<M, T> medium)
{
this.mediumAdapter = medium;
if (medium == null)
return;
if (isReady())
workOffQueue();
else
medium.addMediumReadyListener(this);
}
/**
* This should be called by
*/
public void onMediumReady()
{
workOffQueue();
}
protected void installReadyEventListener(AsyncMediumAdapter<M, T> medium)
{
medium.addMediumReadyListener(this);
}
protected synchronized AsyncMediumAdapter<M, T> getMedium()
{
return mediumAdapter;
}
protected void deliverMessage(M message)
{
messageQueue.add(message);
if (isReady())
workOffQueue();
}
protected synchronized void workOffQueue()
{
setIsWorking(true);
new Thread(new Runnable(){
@Override
public void run()
{
while(!messageQueue.isEmpty() && isMediumReady())
{
M msg = messageQueue.peek();
prepareMessage(msg);
msg.displayMessage();
messageQueue.remove();
}
setIsWorking(false);
}
}).run();
}
/**
* @param message
*/
protected void prepareMessage(M message){
message.setMedium(mediumAdapter.getMedium());
}
}
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