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package io.craft.atom.nio;

import io.craft.atom.io.ChannelEvent;
import io.craft.atom.nio.spi.AbstractNioChannelEventDispatcher;
import io.craft.atom.util.thread.NamedThreadFactory;

import java.util.Queue;
import java.util.concurrent.BlockingQueue;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
import java.util.concurrent.LinkedBlockingQueue;

import lombok.ToString;

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

/**
 * An {@link NioOrderedThreadPoolChannelEventDispatcher} that maintains order of {@link NioByteChannelEvent} in the same channel.
 * It use a new thread pool for event dispatch, isolate io process thread and event process thread.
 * 
 * @author mindwind
 * @version 1.0, Feb 22, 2013
 */
@ToString(callSuper = true, of = { "channelQueue", "executor" })
public class NioOrderedThreadPoolChannelEventDispatcher extends AbstractNioChannelEventDispatcher {
	
	
	private static final Logger LOG = LoggerFactory.getLogger(NioOrderedThreadPoolChannelEventDispatcher.class);
	
	
	private final BlockingQueue channelQueue;
	private final ExecutorService               executor    ;

	
	// ~ ------------------------------------------------------------------------------------------------------------
	
	
	public NioOrderedThreadPoolChannelEventDispatcher() {
		this(Runtime.getRuntime().availableProcessors() * 8, Integer.MAX_VALUE);
	}
	
	public NioOrderedThreadPoolChannelEventDispatcher(int executorSize, int totalEventSize) {
		super(totalEventSize);
		
		if (executorSize <= 0) {
			executorSize = Runtime.getRuntime().availableProcessors() * 8;
		}
		
		this.channelQueue = new LinkedBlockingQueue();
		this.executor = Executors.newFixedThreadPool(executorSize, new NamedThreadFactory("craft-atom-nio-ordered-dispatcher"));
		for (int i = 0; i < executorSize; i++) {
			executor.execute(new Worker());
		}
	}
	
	// ~ ------------------------------------------------------------------------------------------------------------
	
	
	@Override
	public void dispatch(ChannelEvent event) {
		NioByteChannel channel = (NioByteChannel) event.getChannel();
		beforeDispatch(channel);
		dispatch0(event, channel);
	}
	
	private void dispatch0(ChannelEvent event, NioByteChannel channel) {
		channel.add(event);
		if (!channel.isEventProcessing()) {
			channelQueue.offer(channel);
		}
	}
	
	
	// ~ ------------------------------------------------------------------------------------------------------------
	
	
	@Override
	public void shutdown() { 
		executor.shutdownNow();
	}
	
	private class Worker implements Runnable {
		
		private static final int SPIN_COUNT = 256;
		
		private void fire(NioByteChannel channel) {
			int count = 0;
			Queue> q = channel.getEventQueue();
			for (ChannelEvent event = q.poll(); event != null; event = q.poll()) {
				try {
					event.fire();
				} finally {
					afterDispatch(channel);
				}
				count++;
				if (count > SPIN_COUNT) {
					// quit loop to avoid stick same worker thread by same session
					break;
				}
			}
		}

		@Override
		public void run() {
			try {
				for (NioByteChannel channel = channelQueue.take(); channel != null; channel = channelQueue.take()) {					
					// first check any worker is processing this channel? if any other worker thread is processing this event with same channel, just ignore it.
					synchronized (channel) {
						if (!channel.isEventProcessing()) {
							channel.setEventProcessing(true);
						} else {
							continue;
						}
					}
					
					// fire events with same channel
					fire(channel);
					
					// last reset processing flag and quit current thread processing
					channel.setEventProcessing(false);
					
					// if remaining events, so re-insert to channel queue
					if (channel.getEventQueue().size() > 0 && !channel.isEventProcessing()) {
						channelQueue.offer(channel);
					}
				}
			} catch (Throwable t) {
				LOG.warn("[CRAFT-ATOM-NIO] Fire event exception", t);
			}
		}
	}

}