001    /*
002     * Sonar, open source software quality management tool.
003     * Copyright (C) 2009 SonarSource SA
004     * mailto:contact AT sonarsource DOT com
005     *
006     * Sonar is free software; you can redistribute it and/or
007     * modify it under the terms of the GNU Lesser General Public
008     * License as published by the Free Software Foundation; either
009     * version 3 of the License, or (at your option) any later version.
010     *
011     * Sonar is distributed in the hope that it will be useful,
012     * but WITHOUT ANY WARRANTY; without even the implied warranty of
013     * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
014     * Lesser General Public License for more details.
015     *
016     * You should have received a copy of the GNU Lesser General Public
017     * License along with Sonar; if not, write to the Free Software
018     * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02
019     */
020    package org.sonar.api.utils.dag;
021    
022    import org.sonar.api.utils.SonarException;
023    
024    import java.util.*;
025    
026    /**
027     * <a href="http://en.wikipedia.org/wiki/Directed_acyclic_graph">http://en.wikipedia.org/wiki/Directed_acyclic_graph</a>
028     *
029     * @since 1.10
030     */
031    public class DirectAcyclicGraph {
032    
033      private Map<Object, Node> registeredObjects = new HashMap<Object, Node>();
034      private List<Node> nodes = new ArrayList<Node>();
035    
036      public DirectAcyclicGraph(final Object... objects) {
037        if (objects != null) {
038          for (Object object : objects) {
039            add(object);
040          }
041        }
042      }
043    
044      public Node add(final Object object, final Object... dependencies) {
045        Node node = registeredObjects.get(object);
046        if (node == null) {
047          node = new Node(object);
048          nodes.add(node);
049          registeredObjects.put(object, node);
050        }
051    
052        if (dependencies != null) {
053          for (Object dependency : dependencies) {
054            Node depNode = add(dependency);
055            node.addDependency(depNode);
056          }
057        }
058        return node;
059      }
060    
061      public List sort() {
062        sortNodes();
063    
064        List result = new ArrayList();
065        for (Node node : nodes) {
066          result.add(node.getObject());
067        }
068        return result;
069      }
070    
071      private List<Node> sortNodes() {
072        verify();
073        Collections.sort(nodes);
074        return nodes;
075      }
076    
077      private void verify() {
078        for (Node node : nodes) {
079          node.reset();
080        }
081    
082        for (Node node : nodes) {
083          for (Node dep : node.getDependencies()) {
084            if (!nodes.contains(dep)) {
085              throw new SonarException("A dependent node (" + dep + ") of "
086                  + " (" + node + ") was not included in the nodes list.");
087            }
088          }
089    
090          node.resolveOrder();
091        }
092      }
093    }