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.function.Consumer;
022
023import org.eclipse.aether.ConfigurationProperties;
024import org.eclipse.aether.graph.DependencyFilter;
025import org.eclipse.aether.graph.DependencyNode;
026
027/**
028 * Processes dependency graph by traversing the graph in preorder. This visitor visits each node exactly once
029 * regardless how many paths within the dependency graph lead to the node such that the resulting node sequence is
030 * free of duplicates.
031 * <p>
032 * <strong>Instances of this class cannot be embedded into {@link FilteringDependencyVisitor}</strong>, pass in the
033 * filter {@link DependencyFilter} into  constructor instead.
034 *
035 * @see NodeListGenerator
036 * @since 2.0.0
037 */
038public final class PreorderDependencyNodeConsumerVisitor extends AbstractDependencyNodeConsumerVisitor {
039
040    public static final String NAME = ConfigurationProperties.REPOSITORY_SYSTEM_DEPENDENCY_VISITOR_PREORDER;
041
042    /**
043     * Creates a new preorder list generator.
044     */
045    public PreorderDependencyNodeConsumerVisitor(Consumer<DependencyNode> nodeConsumer) {
046        this(nodeConsumer, null);
047    }
048
049    /**
050     * Creates a new preorder list generator.
051     *
052     * @since 2.0.12
053     */
054    public PreorderDependencyNodeConsumerVisitor(Consumer<DependencyNode> nodeConsumer, DependencyFilter filter) {
055        super(nodeConsumer, filter);
056    }
057
058    @Override
059    protected boolean doVisitEnter(DependencyNode node) {
060        if (!setVisited(node)) {
061            return false;
062        }
063        if (acceptNode(node)) {
064            consumeNode(node);
065        }
066        return true;
067    }
068
069    @Override
070    protected boolean doVisitLeave(DependencyNode node) {
071        return true;
072    }
073}