| /* |
| * Licensed to the Apache Software Foundation (ASF) under one |
| * or more contributor license agreements. See the NOTICE file |
| * distributed with this work for additional information |
| * regarding copyright ownership. The ASF licenses this file |
| * to you under the Apache License, Version 2.0 (the |
| * "License"); you may not use this file except in compliance |
| * with the License. You may obtain a copy of the License at |
| * |
| * http://www.apache.org/licenses/LICENSE-2.0 |
| * |
| * Unless required by applicable law or agreed to in writing, |
| * software distributed under the License is distributed on an |
| * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY |
| * KIND, either express or implied. See the License for the |
| * specific language governing permissions and limitations |
| * under the License. |
| */ |
| package org.apache.maven.model.building; |
| |
| import java.util.ArrayList; |
| import java.util.Collection; |
| import java.util.Collections; |
| import java.util.HashMap; |
| import java.util.LinkedHashMap; |
| import java.util.LinkedList; |
| import java.util.List; |
| import java.util.Map; |
| |
| class Graph { |
| private enum DfsState { |
| VISITING, |
| VISITED |
| } |
| |
| final Map<String, Vertex> vertices = new LinkedHashMap<>(); |
| |
| public Vertex getVertex(String id) { |
| return vertices.get(id); |
| } |
| |
| public Collection<Vertex> getVertices() { |
| return vertices.values(); |
| } |
| |
| Vertex addVertex(String label) { |
| return vertices.computeIfAbsent(label, Vertex::new); |
| } |
| |
| void addEdge(Vertex from, Vertex to) throws CycleDetectedException { |
| from.children.add(to); |
| to.parents.add(from); |
| List<String> cycle = findCycle(to); |
| if (cycle != null) { |
| // remove edge which introduced cycle |
| removeEdge(from, to); |
| throw new CycleDetectedException( |
| "Edge between '" + from.label + "' and '" + to.label + "' introduces to cycle in the graph", cycle); |
| } |
| } |
| |
| void removeEdge(Vertex from, Vertex to) { |
| from.children.remove(to); |
| to.parents.remove(from); |
| } |
| |
| List<String> visitAll() { |
| return visitAll(vertices.values(), new HashMap<>(), new ArrayList<>()); |
| } |
| |
| List<String> findCycle(Vertex vertex) { |
| return visitCycle(Collections.singleton(vertex), new HashMap<>(), new LinkedList<>()); |
| } |
| |
| private static List<String> visitAll( |
| Collection<Vertex> children, Map<Vertex, DfsState> stateMap, List<String> list) { |
| for (Vertex v : children) { |
| DfsState state = stateMap.putIfAbsent(v, DfsState.VISITING); |
| if (state == null) { |
| visitAll(v.children, stateMap, list); |
| stateMap.put(v, DfsState.VISITED); |
| list.add(v.label); |
| } |
| } |
| return list; |
| } |
| |
| private static List<String> visitCycle( |
| Collection<Vertex> children, Map<Vertex, DfsState> stateMap, LinkedList<String> cycle) { |
| for (Vertex v : children) { |
| DfsState state = stateMap.putIfAbsent(v, DfsState.VISITING); |
| if (state == null) { |
| cycle.addLast(v.label); |
| List<String> ret = visitCycle(v.children, stateMap, cycle); |
| if (ret != null) { |
| return ret; |
| } |
| cycle.removeLast(); |
| stateMap.put(v, DfsState.VISITED); |
| } else if (state == DfsState.VISITING) { |
| // we are already visiting this vertex, this mean we have a cycle |
| int pos = cycle.lastIndexOf(v.label); |
| List<String> ret = cycle.subList(pos, cycle.size()); |
| ret.add(v.label); |
| return ret; |
| } |
| } |
| return null; |
| } |
| |
| static class Vertex { |
| final String label; |
| final List<Vertex> children = new ArrayList<>(); |
| final List<Vertex> parents = new ArrayList<>(); |
| |
| Vertex(String label) { |
| this.label = label; |
| } |
| |
| String getLabel() { |
| return label; |
| } |
| |
| List<Vertex> getChildren() { |
| return children; |
| } |
| |
| List<Vertex> getParents() { |
| return parents; |
| } |
| } |
| |
| public static class CycleDetectedException extends Exception { |
| private final List<String> cycle; |
| |
| CycleDetectedException(String message, List<String> cycle) { |
| super(message); |
| this.cycle = cycle; |
| } |
| |
| public List<String> getCycle() { |
| return cycle; |
| } |
| |
| @Override |
| public String getMessage() { |
| return super.getMessage() + " " + String.join(" --> ", cycle); |
| } |
| } |
| } |