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.apache.maven.enforcer.rules.utils;
020
021import java.util.Deque;
022import java.util.HashMap;
023import java.util.Map;
024import java.util.concurrent.ConcurrentLinkedDeque;
025
026import org.eclipse.aether.graph.DependencyNode;
027import org.eclipse.aether.graph.DependencyVisitor;
028
029/**
030 * A {@link DependencyVisitor} building a map of parent nodes
031 */
032public class ParentsVisitor implements DependencyVisitor, ParentNodeProvider {
033
034    private final Map<DependencyNode, DependencyNode> parents = new HashMap<>();
035    private final Deque<DependencyNode> parentStack = new ConcurrentLinkedDeque<>();
036
037    @Override
038    public DependencyNode getParent(DependencyNode node) {
039        return parents.get(node);
040    }
041
042    @Override
043    public boolean visitEnter(DependencyNode node) {
044        parents.put(node, parentStack.isEmpty() ? null : parentStack.peek());
045        parentStack.push(node);
046        return true;
047    }
048
049    @Override
050    public boolean visitLeave(DependencyNode node) {
051        parentStack.pop();
052        return true;
053    }
054}