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.function.Consumer;
24
25 import org.eclipse.aether.ConfigurationProperties;
26 import org.eclipse.aether.graph.DependencyNode;
27
28 /**
29 * Processes dependency graph by traversing the graph in level order. This visitor visits each node exactly once
30 * regardless how many paths within the dependency graph lead to the node such that the resulting node sequence is
31 * free of duplicates.
32 *
33 * @since 2.0.0
34 */
35 public final class LevelOrderDependencyNodeConsumerVisitor extends AbstractDependencyNodeConsumerVisitor {
36
37 public static final String NAME = ConfigurationProperties.REPOSITORY_SYSTEM_DEPENDENCY_VISITOR_LEVELORDER;
38
39 private final HashMap<Integer, ArrayList<DependencyNode>> nodesPerLevel;
40
41 private final Stack<Boolean> visits;
42
43 /**
44 * Creates a new level order list generator.
45 */
46 public LevelOrderDependencyNodeConsumerVisitor(Consumer<DependencyNode> nodeConsumer) {
47 super(nodeConsumer);
48 nodesPerLevel = new HashMap<>(16);
49 visits = new Stack<>();
50 }
51
52 @Override
53 public boolean visitEnter(DependencyNode node) {
54 boolean visited = !setVisited(node);
55 visits.push(visited);
56 if (!visited) {
57 nodesPerLevel.computeIfAbsent(visits.size(), k -> new ArrayList<>()).add(node);
58 }
59 return !visited;
60 }
61
62 @Override
63 public boolean visitLeave(DependencyNode node) {
64 Boolean visited = visits.pop();
65 if (visited) {
66 return true;
67 }
68 if (visits.isEmpty()) {
69 for (int l = 1; nodesPerLevel.containsKey(l); l++) {
70 nodesPerLevel.get(l).forEach(nodeConsumer);
71 }
72 }
73 return true;
74 }
75 }