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Graph Database API for Neo4j.
/*
* Copyright (c) "Neo4j"
* Neo4j Sweden AB [https://neo4j.com]
*
* This file is part of Neo4j.
*
* Neo4j is free software: you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation, either version 3 of the License, or
* (at your option) any later version.
*
* This program 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 for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program. If not, see .
*/
package org.neo4j.graphdb.impl.traversal;
import java.util.ArrayList;
import java.util.Collection;
import java.util.HashMap;
import java.util.HashSet;
import java.util.Map;
import java.util.Set;
import java.util.function.Predicate;
import org.neo4j.function.Predicates;
import org.neo4j.graphdb.Direction;
import org.neo4j.graphdb.Node;
import org.neo4j.graphdb.Path;
import org.neo4j.graphdb.traversal.BranchCollisionDetector;
import org.neo4j.graphdb.traversal.Evaluation;
import org.neo4j.graphdb.traversal.Evaluator;
import org.neo4j.graphdb.traversal.TraversalBranch;
public class StandardBranchCollisionDetector implements BranchCollisionDetector {
private final Map[]> paths = new HashMap<>(1000);
private final Evaluator evaluator;
private final Set returnedPaths = new HashSet<>();
private Predicate pathPredicate = Predicates.alwaysTrue();
public StandardBranchCollisionDetector(Evaluator evaluator, Predicate pathPredicate) {
this.evaluator = evaluator;
if (pathPredicate != null) {
this.pathPredicate = pathPredicate;
}
}
@Override
@SuppressWarnings("unchecked")
public Collection evaluate(TraversalBranch branch, Direction direction) {
// [0] for paths from start, [1] for paths from end
Collection[] pathsHere = paths.get(branch.endNode());
int index = direction.ordinal();
if (pathsHere == null) {
pathsHere = new Collection[] {new ArrayList<>(), new ArrayList<>()};
paths.put(branch.endNode(), pathsHere);
}
pathsHere[index].add(branch);
// If there are paths from the other side then include all the
// combined paths
Collection otherCollections = pathsHere[index == 0 ? 1 : 0];
if (!otherCollections.isEmpty()) {
Collection foundPaths = new ArrayList<>();
for (TraversalBranch otherBranch : otherCollections) {
TraversalBranch startPath = index == 0 ? branch : otherBranch;
TraversalBranch endPath = index == 0 ? otherBranch : branch;
BidirectionalTraversalBranchPath path = new BidirectionalTraversalBranchPath(startPath, endPath);
if (isAcceptablePath(path)) {
if (returnedPaths.add(path) && includePath(path, startPath, endPath)) {
foundPaths.add(path);
}
}
}
if (!foundPaths.isEmpty()) {
return foundPaths;
}
}
return null;
}
private boolean isAcceptablePath(BidirectionalTraversalBranchPath path) {
return pathPredicate.test(path);
}
protected boolean includePath(Path path, TraversalBranch startPath, TraversalBranch endPath) {
Evaluation eval = evaluator.evaluate(path);
if (!eval.continues()) {
startPath.evaluation(eval);
endPath.evaluation(eval);
}
return eval.includes();
}
}