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 * @see NodeListGenerator
36 */
37 public final class LevelOrderDependencyNodeConsumerVisitor extends AbstractDependencyNodeConsumerVisitor {
38
39 public static final String NAME = ConfigurationProperties.REPOSITORY_SYSTEM_DEPENDENCY_VISITOR_LEVELORDER;
40
41 private final HashMap<Integer, ArrayList<DependencyNode>> nodesPerLevel;
42
43 private final Stack<Boolean> visits;
44
45 /**
46 * Creates a new level order list generator.
47 */
48 public LevelOrderDependencyNodeConsumerVisitor(Consumer<DependencyNode> nodeConsumer) {
49 super(nodeConsumer);
50 nodesPerLevel = new HashMap<>(16);
51 visits = new Stack<>();
52 }
53
54 @Override
55 public boolean visitEnter(DependencyNode node) {
56 boolean visited = !setVisited(node);
57 visits.push(visited);
58 if (!visited) {
59 nodesPerLevel.computeIfAbsent(visits.size(), k -> new ArrayList<>()).add(node);
60 }
61 return !visited;
62 }
63
64 @Override
65 public boolean visitLeave(DependencyNode node) {
66 Boolean visited = visits.pop();
67 if (visited) {
68 return true;
69 }
70 if (visits.isEmpty()) {
71 for (int l = 1; nodesPerLevel.containsKey(l); l++) {
72 nodesPerLevel.get(l).forEach(nodeConsumer);
73 }
74 }
75 return true;
76 }
77 }