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