/*
* Copyright (c) 2016 Vivid Solutions.
*
* All rights reserved. This program and the accompanying materials
* are made available under the terms of the Eclipse Public License v1.0
* and Eclipse Distribution License v. 1.0 which accompanies this distribution.
* The Eclipse Public License is available at http://www.eclipse.org/legal/epl-v10.html
* and the Eclipse Distribution License is available at
*
* http://www.eclipse.org/org/documents/edl-v10.php.
*/
package org.locationtech.jts.planargraph;
/**
* Represents an undirected edge of a {@link PlanarGraph}. An undirected edge
* in fact simply acts as a central point of reference for two opposite
* {@link DirectedEdge}s.
* <p>
* Usually a client using a <code>PlanarGraph</code> will subclass <code>Edge</code>
* to add its own application-specific data and methods.
*
* @version 1.7
*/
public class Edge
extends GraphComponent
{
/**
* The two DirectedEdges associated with this Edge.
* Index 0 is forward, 1 is reverse.
*/
protected DirectedEdge[] dirEdge;
/**
* Constructs an Edge whose DirectedEdges are not yet set. Be sure to call
* {@link #setDirectedEdges(DirectedEdge, DirectedEdge)}
*/
public Edge()
{
}
/**
* Constructs an Edge initialized with the given DirectedEdges, and for each
* DirectedEdge: sets the Edge, sets the symmetric DirectedEdge, and adds
* this Edge to its from-Node.
*/
public Edge(DirectedEdge de0, DirectedEdge de1)
{
setDirectedEdges(de0, de1);
}
/**
* Initializes this Edge's two DirectedEdges, and for each DirectedEdge: sets the
* Edge, sets the symmetric DirectedEdge, and adds this Edge to its from-Node.
*/
public void setDirectedEdges(DirectedEdge de0, DirectedEdge de1)
{
dirEdge = new DirectedEdge[] { de0, de1 };
de0.setEdge(this);
de1.setEdge(this);
de0.setSym(de1);
de1.setSym(de0);
de0.getFromNode().addOutEdge(de0);
de1.getFromNode().addOutEdge(de1);
}
/**
* Returns one of the DirectedEdges associated with this Edge.
* @param i 0 or 1. 0 returns the forward directed edge, 1 returns the reverse
*/
public DirectedEdge getDirEdge(int i)
{
return dirEdge[i];
}
/**
* Returns the {@link DirectedEdge} that starts from the given node, or null if the
* node is not one of the two nodes associated with this Edge.
*/
public DirectedEdge getDirEdge(Node fromNode)
{
if (dirEdge[0].getFromNode() == fromNode) return dirEdge[0];
if (dirEdge[1].getFromNode() == fromNode) return dirEdge[1];
// node not found
// possibly should throw an exception here?
return null;
}
/**
* If <code>node</code> is one of the two nodes associated with this Edge,
* returns the other node; otherwise returns null.
*/
public Node getOppositeNode(Node node)
{
if (dirEdge[0].getFromNode() == node) return dirEdge[0].getToNode();
if (dirEdge[1].getFromNode() == node) return dirEdge[1].getToNode();
// node not found
// possibly should throw an exception here?
return null;
}
/**
* Removes this edge from its containing graph.
*/
void remove() {
this.dirEdge = null;
}
/**
* Tests whether this edge has been removed from its containing graph
*
* @return <code>true</code> if this edge is removed
*/
public boolean isRemoved()
{
return dirEdge == null;
}
}