/*******************************************************************************
 * Copyright (c) 2007, 2010 Association for Decentralized Information Management
 * in Industry THTH ry.
 * All rights reserved. This program and the accompanying materials
 * are made available under the terms of the Eclipse Public License v1.0
 * which accompanies this distribution, and is available at
 * http://www.eclipse.org/legal/epl-v10.html
 *
 * Contributors:
 *     VTT Technical Research Centre of Finland - initial API and implementation
 *******************************************************************************/
package org.simantics.db.common.procedure.single.wrapper;

import java.util.concurrent.atomic.AtomicBoolean;
import java.util.concurrent.atomic.AtomicInteger;

import org.simantics.db.AsyncReadGraph;
import org.simantics.db.common.utils.Logger;
import org.simantics.db.exception.NoSingleResultException;
import org.simantics.db.procedure.AsyncProcedure;

final public class NullSingleOrExceptionProcedure<Result> {

	private Result result = null;
	final AsyncProcedure<Result> procedure;
	final AtomicBoolean done = new AtomicBoolean(false);
	final AtomicBoolean found = new AtomicBoolean(false);
	final AtomicInteger ready = new AtomicInteger(1);

	public NullSingleOrExceptionProcedure(AsyncProcedure<Result> procedure) {

		this.procedure = procedure;

	}

	public void inc() {

		ready.incrementAndGet();

	}

	public void dec(AsyncReadGraph graph) {

		if(ready.decrementAndGet() == 0) {
			// Shall fire exactly once!
			if(done.compareAndSet(false, true)) {
				try {
					procedure.execute(graph, result);
				} catch (Throwable t) {
		    		Logger.defaultLogError(t);
				}
			}
		}

	}

	public void offer(AsyncReadGraph graph, Result result) {

		if(found.compareAndSet(false, true)) {
			this.result = result;
		} else {
			// Shall fire exactly once!
			if(done.compareAndSet(false, true)) {
				try {
					procedure.exception(graph, new NoSingleResultException(procedure.toString(), -1));
				} catch (Throwable t) {
		    		Logger.defaultLogError(t);
				}
			}
		}

	}

	public void exception(AsyncReadGraph graph, Throwable t) {
		// Shall fire exactly once!
		if(done.compareAndSet(false, true)) {
			try {
				procedure.exception(graph, t);
			} catch (Throwable t2) {
	    		Logger.defaultLogError(t2);
			}
		}
	}

}