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.HashMap;
023import java.util.List;
024import java.util.function.Consumer;
025
026import org.eclipse.aether.ConfigurationProperties;
027import org.eclipse.aether.graph.DependencyFilter;
028import org.eclipse.aether.graph.DependencyNode;
029
030/**
031 * Processes dependency graph by traversing the graph in level order. This visitor visits each node exactly once
032 * regardless how many paths within the dependency graph lead to the node such that the resulting node sequence is
033 * free of duplicates.
034 * <p>
035 * <strong>Instances of this class cannot be embedded into {@link FilteringDependencyVisitor}</strong>, pass in the
036 * filter {@link DependencyFilter} into  constructor instead.
037 *
038 * @see NodeListGenerator
039 * @since 2.0.0
040 */
041public final class LevelOrderDependencyNodeConsumerVisitor extends AbstractDependencyNodeConsumerVisitor {
042
043    public static final String NAME = ConfigurationProperties.REPOSITORY_SYSTEM_DEPENDENCY_VISITOR_LEVELORDER;
044
045    private final HashMap<Integer, ArrayList<DependencyNode>> nodesPerLevel;
046
047    private final Stack<Boolean> visits;
048
049    /**
050     * Creates a new level order list generator.
051     */
052    public LevelOrderDependencyNodeConsumerVisitor(Consumer<DependencyNode> nodeConsumer) {
053        this(nodeConsumer, null);
054    }
055
056    /**
057     * Creates a new level order list generator with filter.
058     *
059     * @since 2.0.12
060     */
061    public LevelOrderDependencyNodeConsumerVisitor(Consumer<DependencyNode> nodeConsumer, DependencyFilter filter) {
062        super(nodeConsumer, filter);
063        nodesPerLevel = new HashMap<>(16);
064        visits = new Stack<>();
065    }
066
067    @Override
068    protected boolean doVisitEnter(DependencyNode node) {
069        boolean visited = !setVisited(node);
070        visits.push(visited);
071        if (!visited) {
072            List<DependencyNode> nodesOnLevel = nodesPerLevel.computeIfAbsent(visits.size(), k -> new ArrayList<>());
073            if (acceptNode(node)) {
074                nodesOnLevel.add(node);
075            }
076        }
077        return !visited;
078    }
079
080    @Override
081    protected boolean doVisitLeave(DependencyNode node) {
082        Boolean visited = visits.pop();
083        if (visited) {
084            return true;
085        }
086        if (visits.isEmpty()) {
087            for (int l = 1; nodesPerLevel.containsKey(l); l++) {
088                nodesPerLevel.get(l).forEach(this::consumeNode);
089            }
090        }
091        return true;
092    }
093}