/*
* The JTS Topology Suite is a collection of Java classes that
* implement the fundamental operations required to validate a given
* geo-spatial data set to a known topological specification.
*
* Copyright (C) 2001 Vivid Solutions
*
* 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 2.1 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; without 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
*
* For more information, contact:
*
* Vivid Solutions
* Suite #1A
* 2328 Government Street
* Victoria BC V8T 5G5
* Canada
*
* (250)385-6040
* www.vividsolutions.com
*/
package com.revolsys.geometry.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(final DirectedEdge de0, final DirectedEdge de1) {
setDirectedEdges(de0, 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(final int i) {
return this.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(final Node fromNode) {
if (this.dirEdge[0].getFromNode() == fromNode) {
return this.dirEdge[0];
}
if (this.dirEdge[1].getFromNode() == fromNode) {
return this.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(final Node node) {
if (this.dirEdge[0].getFromNode() == node) {
return this.dirEdge[0].getToNode();
}
if (this.dirEdge[1].getFromNode() == node) {
return this.dirEdge[1].getToNode();
}
// node not found
// possibly should throw an exception here?
return null;
}
/**
* Tests whether this edge has been removed from its containing graph
*
* @return <code>true</code> if this edge is removed
*/
@Override
public boolean isRemoved() {
return this.dirEdge == null;
}
/**
* Removes this edge from its containing graph.
*/
void remove() {
this.dirEdge = null;
}
/**
* 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(final DirectedEdge de0, final DirectedEdge de1) {
this.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);
}
}