package org.apache.commons.graph.search;

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 * reserved.
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 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
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 *    notice, this list of conditions and the following disclaimer.
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 *       "This product includes software developed by the
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 *    if and wherever such third-party acknowledgments normally appear.
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 * <http://www.apache.org/>.
 */

/**
 * This class does a Depth First Search. It visits all of the children nodes
 * before moving to the siblling nodes.
 */

import java.util.Set;
import java.util.Map;
import java.util.HashSet;
import java.util.HashMap;
import java.util.Iterator;

import org.apache.commons.graph.*;

/**
 * Description of the Class
 */
public class DFS
{
    private Map colors = new HashMap();// VERTEX X COLOR
    /**
     * Description of the Field
     */
    public final static String WHITE = "white";
    /**
     * Description of the Field
     */
    public final static String BLACK = "black";
    /**
     * Description of the Field
     */
    public final static String GRAY = "gray";

    /**
     * Constructor for the DFS object
     */
    public DFS() { }

    /**
     * Gets the color attribute of the DFS object
     */
    public String getColor(Vertex v)
    {
        return (String) colors.get(v);
    }


    /**
     * Description of the Method
     */
    private void visitEdge(DirectedGraph graph,
                           Edge e,
                           Visitor visitor)
    {
        visitor.discoverEdge(e);

        Vertex v = graph.getTarget(e);

        if (colors.get(v) == WHITE)
        {
            visitVertex(graph, v, visitor);
        }

        visitor.finishEdge(e);
    }

    /**
     * Description of the Method
     */
    private void visitVertex(DirectedGraph graph,
                             Vertex v,
                             Visitor visitor)
    {
        colors.remove(v);
        colors.put(v, GRAY);

        visitor.discoverVertex(v);

        Iterator edges = graph.getOutbound(v).iterator();
        while (edges.hasNext())
        {
            Edge e = (Edge) edges.next();
            visitEdge(graph, e, visitor);
        }

        visitor.finishVertex(v);

        colors.remove(v);
        colors.put(v, BLACK);
    }

    /**
     * visit - Visits the graph
     */
    public void visit(DirectedGraph graph,
                      Vertex root,
                      Visitor visitor)
    {
        Iterator vertices = graph.getVertices().iterator();
        while (vertices.hasNext())
        {
            colors.put(vertices.next(), WHITE);
        }

        visitor.discoverGraph(graph);

        visitVertex(graph, root, visitor);

        visitor.finishGraph(graph);
    }

}