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/*
 * Sonar, open source software quality management tool.
 * Copyright (C) 2009 SonarSource SA
 * mailto:contact AT sonarsource DOT com
 *
 * Sonar is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Lesser General Public
 * License as published by the Free Software Foundation; either
 * version 3 of the License, or (at your option) any later version.
 *
 * Sonar is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public
 * License along with Sonar; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02
 */
package org.sonar.api.utils.dag;

import org.sonar.api.utils.SonarException;

import java.util.*;

/**
 * http://en.wikipedia.org/wiki/Directed_acyclic_graph
 *
 * @since 1.10
 */
public class DirectAcyclicGraph {

  private Map registeredObjects = new HashMap();
  private List nodes = new ArrayList();

  public DirectAcyclicGraph(final Object... objects) {
    if (objects != null) {
      for (Object object : objects) {
        add(object);
      }
    }
  }

  public Node add(final Object object, final Object... dependencies) {
    Node node = registeredObjects.get(object);
    if (node == null) {
      node = new Node(object);
      nodes.add(node);
      registeredObjects.put(object, node);
    }

    if (dependencies != null) {
      for (Object dependency : dependencies) {
        Node depNode = add(dependency);
        node.addDependency(depNode);
      }
    }
    return node;
  }

  public List sort() {
    sortNodes();

    List result = new ArrayList();
    for (Node node : nodes) {
      result.add(node.getObject());
    }
    return result;
  }

  private List sortNodes() {
    verify();
    Collections.sort(nodes);
    return nodes;
  }

  private void verify() {
    for (Node node : nodes) {
      node.reset();
    }

    for (Node node : nodes) {
      for (Node dep : node.getDependencies()) {
        if (!nodes.contains(dep)) {
          throw new SonarException("A dependent node (" + dep + ") of "
              + " (" + node + ") was not included in the nodes list.");
        }
      }

      node.resolveOrder();
    }
  }
}