/**

* $Id: mxSession.java,v 1.15 2012/01/13 11:07:37 david Exp $

* Copyright (c) 2007-2012, JGraph Ltd

*/

package com.mxgraph.sharing;

import org.w3c.dom.Node;

import com.mxgraph.sharing.mxSharedState.mxDiagramChangeListener;

import com.mxgraph.util.mxUtils;

/**

* Implements a session that may be attached to a shared diagram. The session

* contains a synchronized buffer which is used to hold the pending edits which

* are to be sent to a specific client. The update mechnism between the server

* and the client uses HTTP requests (polling). The request is kept on the server

* for an amount of time or wakes up / returns immediately if the buffer is no

* longer empty.

*/

public class mxSession implements mxDiagramChangeListener

{

/**

* Default timeout is 10000 ms.

*/

public static int DEFAULT_TIMEOUT = 10000;

/**

* Holds the session ID.

*/

protected String id;

/**

* Reference to the shared diagram.

*/

protected mxSharedState diagram;

/**

* Holds the send buffer for this session.

*/

protected StringBuffer buffer = new StringBuffer();

/**

* Holds the last active time millis.

*/

protected long lastTimeMillis = 0;

/**

* Constructs a new session with the given ID.

*

* @param id Specifies the session ID to be used.

* @param diagram Reference to the shared diagram.

*/

public mxSession(String id, mxSharedState diagram)

{

this.id = id;

this.diagram = diagram;

this.diagram.addDiagramChangeListener(this);

lastTimeMillis = System.currentTimeMillis();

}

/**

* Returns the session ID.

*/

public String getId()

{

return id;

}

/**

* Initializes the session buffer and returns a string that represents the

* state of the session.

*

* @return Returns the initial state of the session.

*/

public synchronized String init()

{

synchronized (this)

{

buffer = new StringBuffer();

notify();

}

return getInitialMessage();

}

/**

* Returns an XML string that represents the current state of the session

* and the shared diagram. A globally unique ID is used as the session's

* namespace, which is used on the client side to prefix IDs of newly

* created cells.

*/

public String getInitialMessage()

{

String ns = mxUtils.getMd5Hash(id);

StringBuffer result = new StringBuffer("<message namespace=\"" + ns

+ "\">");

result.append("<state>");

result.append(diagram.getState());

result.append("</state>");

result.append("<delta>");

result.append(diagram.getDelta());

result.append("</delta>");

result.append("</message>");

return result.toString();

}

/**

* Posts the change represented by the given XML string to the shared diagram.

*

* @param message XML that represents the change.

*/

public void receive(Node message)

{

//System.out.println(getId() + ": " + mxUtils.getPrettyXml(message));

Node child = message.getFirstChild();

while (child != null)

{

if (child.getNodeName().equals("delta"))

{

diagram.processDelta(this, child);

}

child = child.getNextSibling();

}

/*System.out.println(mxUtils.getPrettyXml(new mxCodec()

.encode(((mxSharedGraphModel) diagram).getModel())));*/

}

/**

* Returns the changes received by other sessions for the shared diagram.

* The method returns an empty XML node if no change was received within

* 10 seconds.

*

* @return Returns a string representing the changes to the shared diagram.

*/

public String poll() throws InterruptedException

{

return poll(DEFAULT_TIMEOUT);

}

/**

* Returns the changes received by other sessions for the shared diagram.

* The method returns an empty XML node if no change was received within

* the given timeout.

*

* @param timeout Time in milliseconds to wait for changes.

* @return Returns a string representing the changes to the shared diagram.

*/

public String poll(long timeout) throws InterruptedException

{

lastTimeMillis = System.currentTimeMillis();

StringBuffer result = new StringBuffer("<message>");

synchronized (this)

{

if (buffer.length() == 0)

{

wait(timeout);

}

if (buffer.length() > 0)

{

result.append("<delta>");

result.append(buffer.toString());

result.append("</delta>");

buffer = new StringBuffer();

}

notify();

}

result.append("</message>");

return result.toString();

}

/*

* (non-Javadoc)

* @see com.mxgraph.sharing.mxSharedDiagram.mxDiagramChangeListener#diagramChanged(java.lang.Object, org.w3c.dom.Node)

*/

public synchronized void diagramChanged(Object sender, String edits)

{

if (sender != this)

{

synchronized (this)

{

buffer.append(edits);

notify();

}

}

}

/**

* Returns the number of milliseconds this session has been inactive.

*/

public long inactiveTimeMillis()

{

return System.currentTimeMillis() - lastTimeMillis;

}

/**

* Destroys the session and removes its listener from the shared diagram.

*/

public void destroy()

{

diagram.removeDiagramChangeListener(this);

}

}