/*
 * Copyright 1999,2004 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
 */

package org.apache.catalina.tribes.group.interceptors;

import org.apache.catalina.tribes.Channel;
import org.apache.catalina.tribes.ChannelException;
import org.apache.catalina.tribes.ChannelMessage;
import org.apache.catalina.tribes.Member;
import org.apache.catalina.tribes.group.ChannelInterceptorBase;
import org.apache.catalina.tribes.group.InterceptorPayload;
import org.apache.catalina.tribes.transport.bio.util.FastQueue;
import org.apache.catalina.tribes.transport.bio.util.LinkObject;
import org.apache.catalina.tribes.UniqueId;

/**
 *
 * The message dispatcher is a way to enable asynchronous communication
 * through a channel. The dispatcher will look for the <code>Channel.SEND_OPTIONS_ASYNCHRONOUS</code>
 * flag to be set, if it is, it will queue the message for delivery and immediately return to the sender.
 * 
 * 
 * 
 * @author Filip Hanik
 * @version 1.0
 */
public class MessageDispatchInterceptor extends ChannelInterceptorBase implements Runnable {
    protected static org.apache.commons.logging.Log log = org.apache.commons.logging.LogFactory.getLog(MessageDispatchInterceptor.class);

    protected long maxQueueSize = 1024*1024*64; //64MB
    protected FastQueue queue = new FastQueue();
    protected boolean run = false;
    protected Thread msgDispatchThread = null;
    protected long currentSize = 0;
    protected boolean useDeepClone = true;
    protected boolean alwaysSend = true;

    public MessageDispatchInterceptor() {
        setOptionFlag(Channel.SEND_OPTIONS_ASYNCHRONOUS);
    }

    public void sendMessage(Member[] destination, ChannelMessage msg, InterceptorPayload payload) throws ChannelException {
        boolean async = (msg.getOptions() & Channel.SEND_OPTIONS_ASYNCHRONOUS) == Channel.SEND_OPTIONS_ASYNCHRONOUS;
        if ( async && run ) {
            if ( (getCurrentSize()+msg.getMessage().getLength()) > maxQueueSize ) {
                if ( alwaysSend ) {
                    super.sendMessage(destination,msg,payload);
                    return;
                } else {
                    throw new ChannelException("Asynchronous queue is full, reached its limit of " + maxQueueSize +" bytes, current:" + getCurrentSize() + " bytes.");
                }//end if
            }//end if
            //add to queue
            if ( useDeepClone ) msg = (ChannelMessage)msg.deepclone();
            if (!addToQueue(msg, destination, payload) ) {
                throw new ChannelException("Unable to add the message to the async queue, queue bug?");
            }
            addAndGetCurrentSize(msg.getMessage().getLength());
        } else {
            super.sendMessage(destination, msg, payload);
        }
    }
    
    public boolean addToQueue(ChannelMessage msg, Member[] destination, InterceptorPayload payload) {
        return queue.add(msg,destination,payload);
    }
    
    public LinkObject removeFromQueue() {
        return queue.remove();
    }
    
    public void startQueue() {
        msgDispatchThread = new Thread(this);
        msgDispatchThread.setName("MessageDispatchInterceptor.MessageDispatchThread");
        msgDispatchThread.setDaemon(true);
        msgDispatchThread.setPriority(Thread.MAX_PRIORITY);
        queue.setEnabled(true);
        run = true;
        msgDispatchThread.start();
    }
    
    public void stopQueue() {
        run = false;
        msgDispatchThread.interrupt();
        queue.setEnabled(false);
        setAndGetCurrentSize(0);
    }
    
    
    public void setOptionFlag(int flag) {
        if ( flag != Channel.SEND_OPTIONS_ASYNCHRONOUS ) log.warn("Warning, you are overriding the asynchronous option flag, this will disable the Channel.SEND_OPTIONS_ASYNCHRONOUS that other apps might use.");
        super.setOptionFlag(flag);
    }

    public void setMaxQueueSize(long maxQueueSize) {
        this.maxQueueSize = maxQueueSize;
    }

    public void setUseDeepClone(boolean useDeepClone) {
        this.useDeepClone = useDeepClone;
    }

    public long getMaxQueueSize() {
        return maxQueueSize;
    }

    public boolean getUseDeepClone() {
        return useDeepClone;
    }
    
    public long getCurrentSize() {
        return currentSize;
    }
    
    public synchronized long addAndGetCurrentSize(long inc) {
        currentSize += inc;
        return currentSize;
    }
    
    public synchronized long setAndGetCurrentSize(long value) {
        currentSize = value;
        return value;
    }

    public void start(int svc) throws ChannelException {
        //start the thread
        if (!run ) {
            synchronized (this) {
                if ( !run && ((svc & Channel.SND_TX_SEQ)==Channel.SND_TX_SEQ) ) {//only start with the sender
                    startQueue();
                }//end if
            }//sync
        }//end if
        super.start(svc);
    }

    
    public void stop(int svc) throws ChannelException {
        //stop the thread
        if ( run ) {
            synchronized (this) {
                if ( run && ((svc & Channel.SND_TX_SEQ)==Channel.SND_TX_SEQ)) {
                    stopQueue();
                }//end if
            }//sync
        }//end if

        super.stop(svc);
    }
    
    public void run() {
        while ( run ) {
            LinkObject link = removeFromQueue();
            if ( link == null ) continue; //should not happen unless we exceed wait time
            while ( link != null && run ) {
                link = sendAsyncData(link);
            }//while
        }//while
    }//run

    protected LinkObject sendAsyncData(LinkObject link) {
        ChannelMessage msg = link.data();
        Member[] destination = link.getDestination();
        try {
            super.sendMessage(destination,msg,null);
            try {
                if ( link.getHandler() != null ) link.getHandler().handleCompletion(new UniqueId(msg.getUniqueId())); 
            } catch ( Exception ex ) {
                log.error("Unable to report back completed message.",ex);
            }
        } catch ( Exception x ) {
            ChannelException cx = null;
            if ( x instanceof ChannelException ) cx = (ChannelException)x;
            else cx = new ChannelException(x);
            if ( log.isDebugEnabled() ) log.debug("Error while processing async message.",x);
            try {
                if (link.getHandler() != null) link.getHandler().handleError(cx, new UniqueId(msg.getUniqueId()));
            } catch ( Exception ex ) {
                log.error("Unable to report back error message.",ex);
            }
        } finally {
            addAndGetCurrentSize(-msg.getMessage().getLength());
            link = link.next();
        }//try
        return link;
    }


}