/*
 * Copyright (c) 2012, Synflow
 * All rights reserved.
 * 
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions are met:
 * 
 *   * Redistributions of source code must retain the above copyright notice,
 *     this list of conditions and the following disclaimer.
 *   * Redistributions in binary form must reproduce the above copyright notice,
 *     this list of conditions and the following disclaimer in the documentation
 *     and/or other materials provided with the distribution.
 *   * Neither the name of the IETR/INSA of Rennes nor the names of its
 *     contributors may be used to endorse or promote products derived from this
 *     software without specific prior written permission.
 * 
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
 * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
 * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
 * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
 * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
 * STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY
 * WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 */
package net.sf.orcc.graph.visit;

import java.util.List;
import java.util.ListIterator;

import net.sf.orcc.graph.Edge;
import net.sf.orcc.graph.GraphPackage;
import net.sf.orcc.graph.Vertex;

import org.eclipse.emf.ecore.EReference;

/**
 * This class defines Depth-First Search (DFS) for a graph.
 * 
 * @author Matthieu Wipliez
 * 
 */
public class DFS extends Ordering {

	private boolean containsCycle = false;

	/**
	 * current number. Starts at one.
	 */
	private int num = 1;

	private final EReference refEdges;

	private final EReference refVertex;

	/**
	 * Creates a new DFS. This constructor only delegates to
	 * <code>super(n)</code> and does not perform any visit.
	 * 
	 * @param n
	 *            the expected number of vertices
	 */
	protected DFS(EReference refEdges, EReference refVertex, int n) {
		super(n);
		this.refEdges = refEdges;
		this.refVertex = refVertex;
	}

	/**
	 * Initializes this DFS for a graph of <code>n</code> vertices. Does not
	 * perform any kind of visit.
	 * 
	 * @param n
	 *            the expected number of vertices
	 */
	public DFS(int n) {
		this(GraphPackage.Literals.VERTEX__OUTGOING,
				GraphPackage.Literals.EDGE__TARGET, n);
	}

	/**
	 * Builds the list of vertices that can be reached from the given vertex
	 * using depth-first search. Equivalent to <code>this(vertex, false)</code>
	 * 
	 * @param vertex
	 *            a vertex
	 * @see {@link #DFS(Vertex, boolean)}
	 */
	public DFS(Vertex vertex) {
		this(vertex, false);
	}

	/**
	 * Builds the list of vertices that can be reached from the given vertex
	 * using depth-first search.
	 * 
	 * @param vertex
	 *            a vertex
	 * @param order
	 *            if <code>true</code>, the vertices are visited in a post-order
	 *            manner, otherwise in a pre-order manner
	 * @throws NullPointerException
	 *             if the given vertex is not contained in a graph
	 */
	public DFS(Vertex vertex, boolean order) {
		this(vertex.getGraph().getVertices().size());

		if (order) {
			visitPost(vertex);
		} else {
			visitPre(vertex);
		}
	}

	/**
	 * Returns true if the visited graph contains at least one cycle.
	 * 
	 * @return true if the visited graph contains at least one cycle
	 */
	public boolean containsCycle() {
		return containsCycle;
	}

	/**
	 * Visits the given vertex. Adds it to the vertices list and sets its
	 * number.
	 * 
	 * @param v
	 *            a vertex
	 */
	protected void visit(Vertex v) {
		vertices.add(v);
		v.setNumber(num);
		num++;
	}

	/**
	 * Visits the given vertex and its successors in a post-order manner. The
	 * successors are visited in a reverse order (i.e. last successor is visited
	 * first) to give a more natural reverse post-ordering.
	 * 
	 * @param v
	 *            a vertex
	 */
	public final void visitPost(Vertex v) {
		visited.add(v);

		@SuppressWarnings("unchecked")
		List<Edge> edges = (List<Edge>) v.eGet(refEdges);
		ListIterator<Edge> it = edges.listIterator(edges.size());
		while (it.hasPrevious()) {
			Vertex w = (Vertex) it.previous().eGet(refVertex);
			if (!visited.contains(w)) {
				visitPost(w);
			} else {
				containsCycle = true;
			}
		}

		visit(v);
	}

	/**
	 * Visits the given vertex and its successors in a pre-order manner.
	 * 
	 * @param v
	 *            a vertex
	 */
	public final void visitPre(Vertex v) {
		visited.add(v);
		visit(v);

		@SuppressWarnings("unchecked")
		List<Edge> edges = (List<Edge>) v.eGet(refEdges);
		for (Edge edge : edges) {
			Vertex w = (Vertex) edge.eGet(refVertex);
			if (!visited.contains(w)) {
				visitPre(w);
			} else {
				containsCycle = true;
			}
		}
	}

}