/*
 *  JFLAP - Formal Languages and Automata Package
 * 
 * 
 *  Susan H. Rodger
 *  Computer Science Department
 *  Duke University
 *  August 27, 2009

 *  Copyright (c) 2002-2009
 *  All rights reserved.

 *  JFLAP is open source software. Please see the LICENSE for terms.
 *
 */




package automata.graph;

import automata.Automaton;

/**
 * Constructs a graph of an automaton, but does not, for each edge, classify
 * the object to which an edge points as adjacent to the object from which
 * the edge points.  It only classifies a "from" object as adjacent to a "to"
 * object.  The default <code>degree()</code> method for this graph
 * will return the number of all edges leading from a vertex, including those
 * pointing to itself.
 * 
 * @author Chris Morgan
 */
public class AutomatonDirectedGraph extends AutomatonGraph {	
	
		/**
	 * Constructs a directed graph using an automaton.
	 * 
	 * @param automaton
	 *            the automaton to build the graph from
	 */
	public AutomatonDirectedGraph(Automaton automaton) {
		super(automaton);
	}
	
	/** Adds an edge between two vertices.  Overwrites <code>Graph.addEdge()</code>.
	 * 
	 * @param from the object from which this edge is pointing.
	 * @param to the object to which this edge is pointing.
	 */
	public void addEdge(Object from, Object to) {
		adjacent(from).add(to);			
	}
	
	/**Removes an edge between two vertices.  Overwrites <code>Graph.removeEdge()</code>.
	 * 
	 * @param from the object from which this edge is pointing.
	 * @param to the object to which this edge is pointing.
	 */
	public void removeEdge(Object from, Object to) {
		adjacent(from).remove(to);		
	}
	
	/**
	 * Returns the number of vertices that point from this object.  
	 * 
	 * @param from the object to get the degree for.
	 * @param excludeSameVertexEdges boolean that if <i>true</i> will exclude edges
	 * leading from and to the same vertex from consideration.
	 */
	public int fromDegree(Object from, boolean excludeSameVertexEdges) {
		if (!excludeSameVertexEdges)
			return degree(from);		
		int count = 0;
		Object[] vertices = verticesToNeighbors.keySet().toArray();
		for (int i=0; i<vertices.length; i++)			
			if (hasEdge(from, vertices[i]) && !vertices[i].equals(from))
				count++;
		return count;
	}
	
	/**
	 * Returns the number of vertices that point to this object.  
	 * 
	 * @param to the object to get the degree for.
	 * @param excludeSameVertexEdges boolean that if <i>true</i> will exclude edges
	 * leading from and to the same vertex from consideration.
	 */
	public int toDegree(Object to, boolean excludeSameVertexEdges) {				
		int count = 0;
		Object[] vertices = verticesToNeighbors.keySet().toArray();
		for (int i=0; i<vertices.length; i++)			
			if (hasEdge(vertices[i], to) && (!vertices[i].equals(to) || !excludeSameVertexEdges))
				count++;
		return count;
	}
}