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/*
* SPDX-FileCopyrightText: 2023 The Refinery Authors <https://refinery.tools/>
*
* SPDX-License-Identifier: EPL-2.0
*/
package tools.refinery.interpreter.rete.itc.alg.representative;
import tools.refinery.interpreter.rete.itc.graphimpl.Graph;
import tools.refinery.interpreter.rete.itc.alg.misc.GraphHelper;
import tools.refinery.interpreter.rete.itc.alg.misc.bfs.BFS;
import tools.refinery.interpreter.rete.itc.alg.misc.scc.SCC;
import java.util.Collection;
import java.util.Set;
public class StronglyConnectedComponentAlgorithm<T> extends RepresentativeElectionAlgorithm<T> {
public StronglyConnectedComponentAlgorithm(Graph<T> graph) {
super(graph);
}
@Override
protected void initializeComponents() {
var computedSCCs = SCC.computeSCC(graph).getSccs();
for (var computedSCC : computedSCCs) {
initializeSet(computedSCC);
}
}
@Override
public void edgeInserted(T source, T target) {
var sourceRoot = getRepresentative(source);
var targetRoot = getRepresentative(target);
if (sourceRoot.equals(targetRoot)) {
// New edge does not change strongly connected components.
return;
}
if (BFS.isReachable(target, source, graph)) {
var sources = BFS.reachableSources(graph, target);
var targets = BFS.reachableTargets(graph, source);
sources.retainAll(targets);
merge(sources);
}
}
@Override
public void edgeDeleted(T source, T target) {
var sourceRoot = getRepresentative(source);
var targetRoot = getRepresentative(target);
if (!sourceRoot.equals(targetRoot)) {
// New edge does not change strongly connected components.
return;
}
var component = GraphHelper.getSubGraph(getComponent(sourceRoot), graph);
if (!BFS.isReachable(source, target, component)) {
var newSCCs = SCC.computeSCC(component).getSccs();
split(sourceRoot, newSCCs);
}
}
private void split(T preservedRepresentative, Collection<? extends Set<T>> sets) {
for (var set : sets) {
if (set.contains(preservedRepresentative)) {
components.put(preservedRepresentative, set);
} else {
assignNewRepresentative(preservedRepresentative, set);
}
}
}
}
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