/*
 *  ============================================================
 *  Edge.java: An edge is defined by its two endpoints...
 *  ============================================================
 */

public class Edge {
   protected Node node1, node2;
   protected String sName;

   // Constructor methods ....

   public Edge() {}

   public Edge( Node node1, Node node2 ) {
      this.node1 = node1;
      this.node2 = node2;
   }

   public Edge( String sName, Node node1, Node node2 ) {
      this.node1 = node1;
      this.node2 = node2;
      this.sName   = sName;
   }

   // Compute edge length ...

   public double length () {
       return node1.sub(node2).length();
   }

   // Compute min distance from edge (line segment) to a point ...

   public double distanceToPoint( Node pt1 ) {

      // Get vector direction along line segment ...

      Vector direction = node2.sub(node1);

      // Compute intercept point ....

      double rhs = pt1.sub(node1).dotProduct ( direction );
      double lhs =   direction.dotProduct ( direction );
      double t = rhs/lhs;

      // If intercept lies in "end zones" compute Euclidean distance
      // to end points of edge line segments....

      if ( 0.0 < t && t < 1.0 )
           return pt1.sub( node1.add( direction.scale(t)) ).length();
      else 
           return Math.min ( pt1.sub( node1 ).length(),
                             pt1.sub( node2 ).length() );
   }

   // Convert node to a string ...

   public String toString() {
      return "Edge(\"" + sName + "\") connects nodes (" + node1.sName +
             ", " + node2.sName + ")";
   }

   // Exercise methods in the Edge class .....

   public static void main( String args[] ) {

      System.out.println( "Exercise methods in Edge class" );
      System.out.println( "==============================" );

      // Create "Edge 1" .....

      Edge eA  = new Edge();
      eA.node1 = new Node ("Point 1", 0.0,0.0);
      eA.node2 = new Node ("Point 2", 5.0,0.0);
      eA.sName  = "Edge 1";

      // Create "Edge 2" and "Edge 3" ....

      Node node3 = new Node ("Point 3", 5.0,5.0);
      Edge eB    = new Edge ("Edge 2", eA.node2, node3 );
      Edge eC    = new Edge ("Edge 3", node3, eA.node1 );

      // Create details of edges ....

      System.out.println( eA.toString() );
      System.out.println( eB.toString() );
      System.out.println( eC.toString() );

      // Compute and print lengths of each edge ....

      System.out.println( "Length (" + eA.sName + ") = " + eA.length() );
      System.out.println( "Length (" + eB.sName + ") = " + eB.length() );
      System.out.println( "Length (" + eC.sName + ") = " + eC.length() );

      // Compute distance of a point from a length segment....

      Node pt1 = new Node ( "pt1", 0.0,  0.0 );
      System.out.println( pt1.toString() + ": Distance to line = " +
                          eA.distanceToPoint( pt1 ) );
      Node pt2 = new Node ( "pt2", 1.0,  0.0 );
      System.out.println( pt2.toString() + ": Distance to line = " +
                          eA.distanceToPoint( pt2 ) );
      Node pt3 = new Node ( "pt3", 5.0,  1.0 );
      System.out.println( pt3.toString() + ": Distance to line = " +
                          eA.distanceToPoint( pt3 ) );
      Node pt4 = new Node ( "pt4", 6.0, -1.0 );
      System.out.println( pt4.toString() + ": Distance to line = " +
                          eA.distanceToPoint( pt4 ) );
   }
}