org.eclipse.viatra2.gtasm.patternmatcher.incremental.rete/src/org/eclipse/viatra2/gtasm/patternmatcher/incremental/rete/index/ExistenceNode.java

/*******************************************************************************
 * Copyright (c) 2004-2008 Gabor Bergmann and Daniel Varro
 * 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:
 *    Gabor Bergmann - initial API and implementation
 *******************************************************************************/

package org.eclipse.viatra2.gtasm.patternmatcher.incremental.rete.index;

import java.util.Collection;

import org.eclipse.viatra2.gtasm.patternmatcher.incremental.rete.network.Direction;
import org.eclipse.viatra2.gtasm.patternmatcher.incremental.rete.network.ReteContainer;
import org.eclipse.viatra2.gtasm.patternmatcher.incremental.rete.tuple.Tuple;


/**
 * Propagates all substitutions arriving at the PRIMARY slot if and only if (a
 * matching substitution on the SECONDARY is present) xor (NEGATIVE).
 * 
 * The negative parameter specifies whether this node checks for existence or
 * non-existence.
 * 
 * @author Gabor Bergmann
 */
public class ExistenceNode extends DualInputNode {

	protected boolean negative;

	/**
	 * @param reteContainer
	 * @param primarySlot
	 * @param secondarySlot
	 * @param negative
	 *            if false, act as axistence checker, otherwise a
	 *            nonexistence-checker
	 */
	public ExistenceNode(ReteContainer reteContainer, IterableIndexer primarySlot,
			Indexer secondarySlot, boolean negative) {
		super(reteContainer, primarySlot, secondarySlot, null);
		this.negative = negative;
	}

	/*
	 * (non-Javadoc)
	 * 
	 * @see org.eclipse.viatra2.gtasm.patternmatcher.incremental.rete.index.DualInputNode#calibrate(org.eclipse.viatra2.gtasm.patternmatcher.incremental.rete.tuple.Tuple,
	 * org.eclipse.viatra2.gtasm.patternmatcher.incremental.rete.tuple.Tuple)
	 */
	@Override
	public Tuple calibrate(Tuple primary, Tuple secondary) {
		return primary;
	}

	/*
	 * (non-Javadoc)
	 * 
	 * @see org.eclipse.viatra2.gtasm.patternmatcher.incremental.rete.index.DualInputNode#notifyUpdate(org.eclipse.viatra2.gtasm.patternmatcher.incremental.rete.index.DualInputNode.Side,
	 * org.eclipse.viatra2.gtasm.patternmatcher.incremental.rete.network.Direction, org.eclipse.viatra2.gtasm.patternmatcher.incremental.rete.tuple.Tuple, org.eclipse.viatra2.gtasm.patternmatcher.incremental.rete.tuple.Tuple, boolean)
	 */
	@Override
	public void notifyUpdate(Side side, Direction direction,
			Tuple updateElement, Tuple signature, boolean change) {
		switch (side) {
		case PRIMARY:
			if ((retrieveOpposites(side, signature) != null) ^ negative)
				propagateUpdate(direction, updateElement);
			break;
		case SECONDARY:
			if (change) {
				Collection<Tuple> opposites = retrieveOpposites(side, signature);
				if (opposites != null)
					for (Tuple opposite : opposites) {
						propagateUpdate((negative ? direction.opposite()
								: direction), opposite);
					}
			}
			break;
		}
	}

	/*
	 * (non-Javadoc)
	 * 
	 * @see org.eclipse.viatra2.gtasm.patternmatcher.incremental.rete.network.Supplier#pullInto(org.eclipse.viatra2.gtasm.patternmatcher.incremental.rete.network.Receiver)
	 */
	public void pullInto(Collection<Tuple> collector) {
		reteContainer.flushUpdates();

		for (Tuple signature : primarySlot.getSignatures()) {
			Collection<Tuple> primaries = primarySlot.get(signature); // not null due to the contract of IterableIndex.getSignatures()
			Collection<Tuple> opposites = secondarySlot.get(signature);
			if ((opposites != null) ^ negative)
				collector.addAll(primaries);
		}
	}

}