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Cristal-ise is a description-driven software platform originally developed to track the construction of the CMS ECAL detector of the LHC at CERN. This is its core library, known as the kernel, which manages business objects called Items. Items are entirely configured from data, called descriptions, held in other Items. Every change of a state in an Item is a consequence of an execution of an activity in that Item's lifecycle, meaning that Cristal-ise applications are completely traceable, even in their design. It also supports extensive versioning of Item description data, giving the system a high level of flexibility.

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/**
 * This file is part of the CRISTAL-iSE kernel.
 * Copyright (c) 2001-2015 The CRISTAL Consortium. All rights reserved.
 *
 * This library 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.
 *
 * This library is distributed in the hope that it will be useful, but WITHOUT
 * ANY WARRANTY; with out 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 this library; if not, write to the Free Software Foundation,
 * Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA.
 *
 * http://www.fsf.org/licensing/licenses/lgpl.html
 */
package org.cristalise.kernel.graph.traversal;


import java.util.LinkedHashSet;
import java.util.Set;
import java.util.Vector;
import org.cristalise.kernel.graph.model.GraphModel;
import org.cristalise.kernel.graph.model.Vertex;



public class GraphTraversal
{
    public static final int kUp   = 1;
    public static final int kDown = 2;


    private GraphTraversal()
    {
    }


    public static Vertex[] getTraversal(GraphModel graphModel, Vertex startVertex, int direction, boolean ignoreBackLinks)
    {
        Vector path = new Vector(10, 10);

        graphModel.clearTags(startVertex);
        visitVertex(startVertex, graphModel, path, direction, startVertex, ignoreBackLinks);

        return path.toArray(new Vertex[path.size()]);
    }


    private static void visitVertex(Vertex vertex, GraphModel graphModel, Vector path, int direction, Object tag, boolean ignoreBackLinks)
    {
        Vertex[] children = null;
        int i = 0;

        if(direction == kDown)
        {
            children = graphModel.getOutVertices(vertex);
        }
        else
        {
            children = graphModel.getInVertices(vertex);
        }

        vertex.setTag(tag);
        path.add(vertex);

        for(i=0; i path = new LinkedHashSet<>();

        graphModel.clearTags(startVertex);
        visitVertex(startVertex, endVertex, graphModel, path, direction, startVertex, ignoreBackLinks);

        return path.toArray(new Vertex[path.size()]);
    }

    private static void visitVertex(Vertex startVertex, Vertex endVertex, GraphModel graphModel, Set path, int direction, Object tag, boolean ignoreBackLinks) {
        Vertex[] siblings = null;

        if(direction == kDown) siblings = graphModel.getOutVertices(startVertex);
        else                   siblings = graphModel.getInVertices(startVertex);

        startVertex.setTag(tag);
        path.add(startVertex);

        for(int i = 0; i < siblings.length; i++) {
            //visit until it is tagged or we found the endVertex
            if(! siblings[i].hasTag(tag) && ! siblings[i].equals(endVertex)) {
                boolean skipBackLink = false;

                if ( ignoreBackLinks &&
                    ((startVertex.isJoin() && direction == kUp) ||
                     (startVertex.isLoop() && direction == kDown)))
                {
                    Vertex[] following = getTraversal(graphModel, siblings[i], endVertex, direction, false);
                    for (Vertex element : following) {
                        if (element == startVertex) {
                            skipBackLink = true;
                            break;
                        }
                    }
                }

                if (!skipBackLink) visitVertex(siblings[i], endVertex, graphModel, path, direction, tag, ignoreBackLinks);
            }

            //add endVertex to the result
            if (siblings[i].equals(endVertex)) path.add(endVertex);
        }
    }
}