/*
 * Copyright (c) 2014, 2015, Dynatrace and/or its affiliates. All rights reserved.
 * 
 * This file is part of the Lock Contention Tracing Subsystem for the HotSpot
 * Virtual Machine, which is developed at Christian Doppler Laboratory on
 * Monitoring and Evolution of Very-Large-Scale Software Systems. Please
 * contact us at <http://mevss.jku.at/> if you need additional information
 * or have any questions.
 *
 * This code is free software; you can redistribute it and/or modify it
 * under the terms of the GNU General Public License version 2 only, as
 * published by the Free Software Foundation.
 *
 * This code 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
 * version 2 for more details (a copy is included in the LICENSE file that
 * accompanied this code).
 *
 * You should have received a copy of the GNU General Public License version
 * 2 along with this work. If not, see <http://www.gnu.org/licenses/>.
 *
 */ 
package sun.evtracing.processing;

import java.util.Comparator;
import java.util.PriorityQueue;
import java.util.Queue;

import sun.evtracing.parser.SequenceOrderedEvent;

public class SequenceOrderedEventQueue {
	private static class SequenceOrderedEventComparator implements Comparator<SequenceOrderedEvent> {
		@Override
		public int compare(SequenceOrderedEvent e1, SequenceOrderedEvent e2) {
			return (int) (e1.sequenceNumber() - e2.sequenceNumber());
		}
	}

	private final TraceEventHandler delegateHandler;

	public SequenceOrderedEventQueue(TraceEventHandler delegate) {
		this.delegateHandler = delegate;
	}

	private long nextSeqNumber = 1;
	private final Queue<SequenceOrderedEvent> queue = new PriorityQueue<>(new SequenceOrderedEventComparator());

	public int size() {
		return queue.size();
	}

	public void addEvent(SequenceOrderedEvent event) {
		if (tryNotify(event)) {
			tryFlushQueue();
		} else {
			queue.add(event);
		}
	}

	private boolean tryNotify(SequenceOrderedEvent event) {
		if (nextSeqNumber == event.sequenceNumber()) {
			event.accept(delegateHandler);
			nextSeqNumber++;
			return true;
		}
		return false;
	}

	private void tryFlushQueue() {
		while (!queue.isEmpty() && tryNotify(queue.peek())) {
			queue.remove();
		}
	}

}