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/*
* Fabric3
* Copyright (c) 2009-2013 Metaform Systems
*
* Fabric3 is free software: you can redistribute it and/or modify
* it under the terms of the GNU General Public License as
* published by the Free Software Foundation, either version 3 of
* the License, or (at your option) any later version, with the
* following exception:
*
* Linking this software statically or dynamically with other
* modules is making a combined work based on this software.
* Thus, the terms and conditions of the GNU General Public
* License cover the whole combination.
*
* As a special exception, the copyright holders of this software
* give you permission to link this software with independent
* modules to produce an executable, regardless of the license
* terms of these independent modules, and to copy and distribute
* the resulting executable under terms of your choice, provided
* that you also meet, for each linked independent module, the
* terms and conditions of the license of that module. An
* independent module is a module which is not derived from or
* based on this software. If you modify this software, you may
* extend this exception to your version of the software, but
* you are not obligated to do so. If you do not wish to do so,
* delete this exception statement from your version.
*
* Fabric3 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 for more details.
*
* You should have received a copy of the
* GNU General Public License along with Fabric3.
* If not, see .
*/
package org.fabric3.util.graph;

import java.util.ArrayList;
import java.util.Collections;
import java.util.HashSet;
import java.util.List;
import java.util.Set;


/**
 * Default implementation of a depth first search.
 */
public class DepthFirstTraverserImpl implements DepthFirstTraverser {

    public List> traverse(DirectedGraph graph, Vertex start) {
        return traverse(graph, start, new TrueVisitor());
    }

    public List> traversePath(DirectedGraph graph, Vertex start, Vertex end) {
        TerminatingVisitor visitor = new TerminatingVisitor(end);
        List> path = traverse(graph, start, visitor);
        if (visitor.wasFound()) {
            return path;
        }
        return Collections.emptyList();
    }

    private List> traverse(DirectedGraph graph, Vertex start, Visitor visitor) {
        List> visited = new ArrayList>();
        List> stack = new ArrayList>();
        Set> seen = new HashSet>(visited);
        stack.add(start);
        seen.add(start);
        do {
            // mark as visited
            Vertex next = stack.remove(stack.size() - 1);
            visited.add(next);
            if (!visitor.visit(next)) {
                return visited;
            }

            // add all non-visited adjacent vertices to the stack
            Set> adjacentVertices = graph.getAdjacentVertices(next);
            for (Vertex v : adjacentVertices) {
                seen.add(v);
                stack.add(v);
            }

        } while (!stack.isEmpty());
        return visited;
    }


}