001/*
002 * Licensed to the Apache Software Foundation (ASF) under one
003 * or more contributor license agreements.  See the NOTICE file
004 * distributed with this work for additional information
005 * regarding copyright ownership.  The ASF licenses this file
006 * to you under the Apache License, Version 2.0 (the
007 * "License"); you may not use this file except in compliance
008 * with the License.  You may obtain a copy of the License at
009 *
010 *   http://www.apache.org/licenses/LICENSE-2.0
011 *
012 * Unless required by applicable law or agreed to in writing,
013 * software distributed under the License is distributed on an
014 * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
015 * KIND, either express or implied.  See the License for the
016 * specific language governing permissions and limitations
017 * under the License.
018 */
019package org.eclipse.aether.util.graph.visitor;
020
021import java.util.ArrayList;
022import java.util.Arrays;
023import java.util.List;
024
025import org.eclipse.aether.graph.DependencyFilter;
026import org.eclipse.aether.graph.DependencyNode;
027import org.eclipse.aether.graph.DependencyVisitor;
028
029/**
030 * A dependency visitor that records all paths leading to nodes matching a certain filter criteria.
031 */
032public final class PathRecordingDependencyVisitor implements DependencyVisitor {
033
034    private final DependencyFilter filter;
035
036    private final List<List<DependencyNode>> paths;
037
038    private final Stack<DependencyNode> parents;
039
040    private final boolean excludeChildrenOfMatches;
041
042    /**
043     * Creates a new visitor that uses the specified filter to identify terminal nodes of interesting paths. The visitor
044     * will not search for paths going beyond an already matched node.
045     *
046     * @param filter The filter used to select terminal nodes of paths to record, may be {@code null} to match any node.
047     */
048    public PathRecordingDependencyVisitor(DependencyFilter filter) {
049        this(filter, true);
050    }
051
052    /**
053     * Creates a new visitor that uses the specified filter to identify terminal nodes of interesting paths.
054     *
055     * @param filter The filter used to select terminal nodes of paths to record, may be {@code null} to match any node.
056     * @param excludeChildrenOfMatches Flag controlling whether children of matched nodes should be excluded from the
057     *            traversal, thereby ignoring any potential paths to other matching nodes beneath a matching ancestor
058     *            node. If {@code true}, all recorded paths will have only one matching node (namely the terminal node),
059     *            if {@code false} a recorded path can consist of multiple matching nodes.
060     */
061    public PathRecordingDependencyVisitor(DependencyFilter filter, boolean excludeChildrenOfMatches) {
062        this.filter = filter;
063        this.excludeChildrenOfMatches = excludeChildrenOfMatches;
064        paths = new ArrayList<>();
065        parents = new Stack<>();
066    }
067
068    /**
069     * Gets the filter being used to select terminal nodes.
070     *
071     * @return The filter being used or {@code null} if none.
072     */
073    public DependencyFilter getFilter() {
074        return filter;
075    }
076
077    /**
078     * Gets the paths leading to nodes matching the filter that have been recorded during the graph visit. A path is
079     * given as a sequence of nodes, starting with the root node of the graph and ending with a node that matched the
080     * filter.
081     *
082     * @return The recorded paths, never {@code null}.
083     */
084    public List<List<DependencyNode>> getPaths() {
085        return paths;
086    }
087
088    @Override
089    public boolean visitEnter(DependencyNode node) {
090        boolean accept = filter == null || filter.accept(node, parents);
091
092        boolean hasDuplicateNodeInParent = parents.contains(node);
093        parents.push(node);
094
095        if (accept) {
096            DependencyNode[] path = new DependencyNode[parents.size()];
097            for (int i = 0, n = parents.size(); i < n; i++) {
098                path[n - i - 1] = parents.get(i);
099            }
100            paths.add(Arrays.asList(path));
101
102            if (excludeChildrenOfMatches) {
103                return false;
104            }
105        }
106
107        return !hasDuplicateNodeInParent;
108    }
109
110    @Override
111    public boolean visitLeave(DependencyNode node) {
112        parents.pop();
113
114        return true;
115    }
116}