content: /*
   * Copyright (c) 1999, 2013, Oracle and/or its affiliates. All rights reserved.
   * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
   *
   * This code is free software; you can redistribute it and/or modify it
   * under the terms of the GNU General Public License version 2 only, as
   * published by the Free Software Foundation.  Oracle designates this
   * particular file as subject to the "Classpath" exception as provided
   * by Oracle in the LICENSE file that accompanied this code.
   *
   * This code 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 General Public License
   * version 2 for more details (a copy is included in the LICENSE file that
   * accompanied this code).
   *
   * You should have received a copy of the GNU General Public License version
   * 2 along with this work; if not, write to the Free Software Foundation,
   * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
   *
   * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
   * or visit www.oracle.com if you need additional information or have any
   * questions.
   */
  
  package openjdk.tools.javac.util;
  
  import java.util.ArrayList;
  import java.util.Collection;
  import java.util.Properties;
  
  /** <p><b>This is NOT part of any supported API.
   *  If you write code that depends on this, you do so at your own risk.
   *  This code and its internal interfaces are subject to change or
   *  deletion without notice.</b>
   */
  public class GraphUtils {
  
      /**
       * Basic interface for defining various dependency kinds.
       */
      public interface DependencyKind { }
  
      /**
       * Common superinterfaces to all graph nodes.
       */
      public interface Node<D, N extends Node<D, N>> {
          /**
           * visitor method.
           */
          <A> void accept(NodeVisitor<D, N, A> visitor, A arg);
      }
  
      /**
       * Visitor for graph nodes.
       */
      static abstract class NodeVisitor<D, N extends Node<D, N>, A> {
          /**
           * Visitor action for nodes.
           */
          public abstract void visitNode(N node, A arg);
          /**
           * Visitor action for a dependency between 'from' and 'to' with given kind.
           */
          public abstract void visitDependency(DependencyKind dk, N from, N to, A arg);
  
          /**
           * Visitor entry point.
           */
          public void visit(Collection<? extends N> nodes, A arg) {
              for (N n : new ArrayList<>(nodes)) {
                  n.accept(this, arg);
              }
          }
      }
  
      /**
       * Optional interface for nodes supporting dot-based representation.
       */
      public interface DottableNode<D, N extends DottableNode<D, N>> extends Node<D, N> {
          /**
           * Retrieves the set of dot attributes associated with the node.
           */
          Properties nodeAttributes();
          /**
           * Retrieves the set of dot attributes associated with a given dependency.
           */
          Properties dependencyAttributes(N to, DependencyKind dk);
      }
  
      /**
       * This class is a basic abstract class for representing a node.
       * A node is associated with a given data.
       */
      public static abstract class AbstractNode<D, N extends AbstractNode<D, N>> implements Node<D, N> {
          public final D data;
  
          public AbstractNode(D data) {
              this.data = data;
          }
  
          /**
           * Get an array of the dependency kinds supported by this node.
           */
          public abstract DependencyKind[] getSupportedDependencyKinds();
  
          /**
           * Get all dependencies of a given kind
           */
          public abstract Collection<? extends N> getDependenciesByKind(DependencyKind dk);
  
          @Override
          public String toString() {
              return data.toString();
          }
  
          @SuppressWarnings("unchecked")
          public <A> void accept(NodeVisitor<D, N, A> visitor, A arg) {
              visitor.visitNode((N)this, arg);
              for (DependencyKind dk : getSupportedDependencyKinds()) {
                  for (N dep : new ArrayList<>(getDependenciesByKind(dk))) {
                      visitor.visitDependency(dk, (N)this, dep, arg);
                  }
              }
          }
      }
  
      /**
       * This class specialized Node, by adding elements that are required in order
       * to perform Tarjan computation of strongly connected components.
       */
      public static abstract class TarjanNode<D, N extends TarjanNode<D, N>> extends AbstractNode<D, N>
              implements Comparable<N> {
          int index = -1;
          int lowlink;
          boolean active;
  
          public TarjanNode(D data) {
              super(data);
          }
  
          public abstract Iterable<? extends N> getAllDependencies();
  
          public int compareTo(N o) {
              return (index < o.index) ? -1 : (index == o.index) ? 0 : 1;
          }
      }
  
      /**
       * Tarjan's algorithm to determine strongly connected components of a
       * directed graph in linear time. Works on TarjanNode.
       */
      public static <D, N extends TarjanNode<D, N>> List<? extends List<? extends N>> tarjan(Iterable<? extends N> nodes) {
          Tarjan<D, N> tarjan = new Tarjan<>();
          return tarjan.findSCC(nodes);
      }
      //where
      private static class Tarjan<D, N extends TarjanNode<D, N>> {
  
          /** Unique node identifier. */
          int index = 0;
  
          /** List of SCCs found fso far. */
          ListBuffer<List<N>> sccs = new ListBuffer<>();
  
          /** Stack of all reacheable nodes from given root. */
          ListBuffer<N> stack = new ListBuffer<>();
  
          private List<? extends List<? extends N>> findSCC(Iterable<? extends N> nodes) {
              for (N node : nodes) {
                  if (node.index == -1) {
                      findSCC(node);
                  }
              }
              return sccs.toList();
          }
  
          private void findSCC(N v) {
              visitNode(v);
              for (N n: v.getAllDependencies()) {
                  if (n.index == -1) {
                      //it's the first time we see this node
                      findSCC(n);
                      v.lowlink = Math.min(v.lowlink, n.lowlink);
                  } else if (stack.contains(n)) {
                      //this node is already reachable from current root
                      v.lowlink = Math.min(v.lowlink, n.index);
                  }
              }
              if (v.lowlink == v.index) {
                  //v is the root of a SCC
                  addSCC(v);
              }
          }
  
          private void visitNode(N n) {
              n.index = index;
              n.lowlink = index;
              index++;
              stack.prepend(n);
              n.active = true;
          }
  
          private void addSCC(N v) {
              N n;
              ListBuffer<N> cycle = new ListBuffer<>();
              do {
                  n = stack.remove();
                  n.active = false;
                  cycle.add(n);
              } while (n != v);
              sccs.add(cycle.toList());
          }
      }
  
      /**
       * Debugging: dot representation of a set of connected nodes. The resulting
       * dot representation will use {@code Node.toString} to display node labels
       * and {@code Node.printDependency} to display edge labels. The resulting
       * representation is also customizable with a graph name and a header.
       */
      public static <D, N extends DottableNode<D, N>> String toDot(Collection<? extends N> nodes, String name, String header) {
          StringBuilder buf = new StringBuilder();
          buf.append(String.format("digraph %s {\n", name));
          buf.append(String.format("label = %s;\n", DotVisitor.wrap(header)));
          DotVisitor<D, N> dotVisitor = new DotVisitor<>();
          dotVisitor.visit(nodes, buf);
          buf.append("}\n");
          return buf.toString();
      }
  
      /**
       * This visitor is used to dump the contents of a set of nodes of type {@link DottableNode}
       * onto a string builder.
       */
      public static class DotVisitor<D, N extends DottableNode<D, N>> extends NodeVisitor<D, N, StringBuilder> {
  
          @Override
          public void visitDependency(DependencyKind dk, N from, N to, StringBuilder buf) {
              buf.append(String.format("%s -> %s", from.hashCode(), to.hashCode()));
              buf.append(formatProperties(from.dependencyAttributes(to, dk)));
              buf.append('\n');
          }
  
          @Override
          public void visitNode(N node, StringBuilder buf) {
              buf.append(String.format("%s ", node.hashCode()));
              buf.append(formatProperties(node.nodeAttributes()));
              buf.append('\n');
          }
  
          protected String formatProperties(Properties p) {
              return p.toString().replaceAll(",", " ")
                  .replaceAll("\\{", "[")
                  .replaceAll("\\}", "]");
          }
  
          protected static String wrap(String s) {
              String res = "\"" + s + "\"";
              return res.replaceAll("\n", "");
          }
      }
  }
  