import java.awt.*;
import java.awt.geom.*;

/**
 * An edge type representing a link in a network.
 *
 * This class adds a new edge approval method that is used to 
 * check network constraints before adding edges.
 *
 * @author Eric Lemar
 */
public class NetworkEdge extends LineEdge
{
   public NetworkEdge()
   {
        super();
   }

   /**
    * Try to add this edge between nodes aStart and aEnd
    *
    * To add a connection, both nodes must be of type NetworkNode, and the
    * <code>Node.isConnectOk(Edge,otherNode)</code> method must return
    * <code>true</code> for each side.
    *
    * @param aStart The starting node
    * @param anEnd   The ending node
    * @return <code>true</code> if the edge was added, <code>false</code>
    *         otherwise.
    */
   public boolean approvedConnect(Node aStart, Node anEnd) {
      if (aStart instanceof NetworkNode && anEnd instanceof NetworkNode) {
         NetworkNode n1,n2;
         n1 = (NetworkNode)aStart;
         n2 = (NetworkNode)anEnd;
         if (n1.isOkConnect(this,n2) && n2.isOkConnect(this,n1)) {
            connect(aStart,anEnd);
            n1.addedEdge(this,n2);
            n2.addedEdge(this,n1);
            return true;
         }
      }
      return false;
   }

   /**
    * Tell the edge that it is being removed.
    *
    * This gives the edge the chance to tell the nodes that the edge is being
    * removed.  It does so by calling signalRemove(this) on each end end.
    */
   public void signalRemove() {
     NetworkNode n1,n2;
     n1 = (NetworkNode)getStart();
     n2 = (NetworkNode)getEnd();
     n1.signalRemove(this);
     n2.signalRemove(this);
   }
}