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/*******************************************************************************
* Copyright (c) 2004-2008 Gabor Bergmann and Daniel Varro
* This program and the accompanying materials are made available under the
* terms of the Eclipse Public License v. 2.0 which is available at
* http://www.eclipse.org/legal/epl-v20.html.
*
* SPDX-License-Identifier: EPL-2.0
*******************************************************************************/
package tools.refinery.viatra.runtime.rete.misc;
import java.util.Collection;
import java.util.LinkedHashSet;
import tools.refinery.viatra.runtime.matchers.tuple.Tuple;
import tools.refinery.viatra.runtime.matchers.util.Clearable;
import tools.refinery.viatra.runtime.matchers.util.Direction;
import tools.refinery.viatra.runtime.rete.network.ReteContainer;
import tools.refinery.viatra.runtime.rete.network.communication.Timestamp;
/**
* A monitoring object that connects to the rete network as a receiver to reflect changes since an arbitrary state
* acknowledged by the client. Match tuples are represented by a type MatchType.
*
* <p>
* <b>Usage</b>. If a new matching is found, it appears in the matchFoundEvents collection, and disappears when that
* particular matching cannot be found anymore. If the event of finding a match has been processed by the client, it can
* be removed manually. In this case, when a previously found matching is lost, the Tuple will appear in the
* matchLostEvents collection, and disappear upon finding the same matching again. "Matching lost" events can also be
* acknowledged by removing a Tuple from the collection. If the matching is found once again, it will return to
* matchFoundEvents.
*
* <p>
* <b>Technical notes</b>. Does NOT propagate updates!
*
* By overriding statelessConvert(), results can be stored to a MatchType. MatchType must provide equals() and
* hashCode() reflecting its contents. The default implementation (DefaultDeltaMonitor) uses Tuple as MatchType.
*
* By overriding statelessFilter(), some tuples can be filtered.
*
* @author Gabor Bergmann
*
*/
public abstract class DeltaMonitor<MatchType> extends SimpleReceiver implements Clearable {
/**
* matches that are newly found
*/
public Collection<MatchType> matchFoundEvents;
/**
* matches that are newly lost
*/
public Collection<MatchType> matchLostEvents;
/**
* @param reteContainer
*/
public DeltaMonitor(ReteContainer reteContainer) {
super(reteContainer);
matchFoundEvents = new LinkedHashSet<MatchType>();
matchLostEvents = new LinkedHashSet<MatchType>();
reteContainer.registerClearable(this);
}
// /**
// * Build a delta monitor into the head container of the network.
// *
// * @param network
// */
// public DeltaMonitor(Network network) {
// this(network.getHeadContainer());
// }
/**
* Override this method to provide a lightweight, stateless filter on the tuples
*
* @param tuple
* the occurrence that is to be filtered
* @return true if this tuple should be monitored, false if ignored
*/
public boolean statelessFilter(Tuple tuple) {
return true;
}
public abstract MatchType statelessConvert(Tuple tuple);
@Override
public void update(Direction direction, Tuple updateElement, Timestamp timestamp) {
if (statelessFilter(updateElement)) {
MatchType match = statelessConvert(updateElement);
if (direction == Direction.INSERT) {
if (!matchLostEvents.remove(match)) // either had before but
// lost
matchFoundEvents.add(match); // or brand-new
} else // revoke
{
if (!matchFoundEvents.remove(match)) // either never found
// in the first
// place
matchLostEvents.add(match); // or newly lost
}
}
}
@Override
public void clear() {
matchFoundEvents.clear();
matchLostEvents.clear();
}
}
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