1 /*
2 * Licensed to the Apache Software Foundation (ASF) under one
3 * or more contributor license agreements. See the NOTICE file
4 * distributed with this work for additional information
5 * regarding copyright ownership. The ASF licenses this file
6 * to you under the Apache License, Version 2.0 (the
7 * "License"); you may not use this file except in compliance
8 * with the License. You may obtain a copy of the License at
9 *
10 * http://www.apache.org/licenses/LICENSE-2.0
11 *
12 * Unless required by applicable law or agreed to in writing,
13 * software distributed under the License is distributed on an
14 * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
15 * KIND, either express or implied. See the License for the
16 * specific language governing permissions and limitations
17 * under the License.
18 */
19 package org.eclipse.aether.util.graph.visitor;
20
21 import java.util.ArrayList;
22 import java.util.HashMap;
23 import java.util.List;
24 import java.util.function.Consumer;
25
26 import org.eclipse.aether.ConfigurationProperties;
27 import org.eclipse.aether.graph.DependencyFilter;
28 import org.eclipse.aether.graph.DependencyNode;
29
30 /**
31 * Processes dependency graph by traversing the graph in level order. This visitor visits each node exactly once
32 * regardless how many paths within the dependency graph lead to the node such that the resulting node sequence is
33 * free of duplicates.
34 * <p>
35 * <strong>Instances of this class cannot be embedded into {@link FilteringDependencyVisitor}</strong>, pass in the
36 * filter {@link DependencyFilter} into constructor instead.
37 *
38 * @see NodeListGenerator
39 * @since 2.0.0
40 */
41 public final class LevelOrderDependencyNodeConsumerVisitor extends AbstractDependencyNodeConsumerVisitor {
42
43 public static final String NAME = ConfigurationProperties.REPOSITORY_SYSTEM_DEPENDENCY_VISITOR_LEVELORDER;
44
45 private final HashMap<Integer, ArrayList<DependencyNode>> nodesPerLevel;
46
47 private final Stack<Boolean> visits;
48
49 /**
50 * Creates a new level order list generator.
51 */
52 public LevelOrderDependencyNodeConsumerVisitor(Consumer<DependencyNode> nodeConsumer) {
53 this(nodeConsumer, null);
54 }
55
56 /**
57 * Creates a new level order list generator with filter.
58 *
59 * @since 2.0.12
60 */
61 public LevelOrderDependencyNodeConsumerVisitor(Consumer<DependencyNode> nodeConsumer, DependencyFilter filter) {
62 super(nodeConsumer, filter);
63 nodesPerLevel = new HashMap<>(16);
64 visits = new Stack<>();
65 }
66
67 @Override
68 protected boolean doVisitEnter(DependencyNode node) {
69 boolean visited = !setVisited(node);
70 visits.push(visited);
71 if (!visited) {
72 List<DependencyNode> nodesOnLevel = nodesPerLevel.computeIfAbsent(visits.size(), k -> new ArrayList<>());
73 if (acceptNode(node)) {
74 nodesOnLevel.add(node);
75 }
76 }
77 return !visited;
78 }
79
80 @Override
81 protected boolean doVisitLeave(DependencyNode node) {
82 Boolean visited = visits.pop();
83 if (visited) {
84 return true;
85 }
86 if (visits.isEmpty()) {
87 for (int l = 1; nodesPerLevel.containsKey(l); l++) {
88 nodesPerLevel.get(l).forEach(this::consumeNode);
89 }
90 }
91 return true;
92 }
93 }