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

public class SpringView {
   private static final double xPoints[]={0,0.10, 0.125, 0.175, 0.225, 0.275, 0.325, 
                                          0.375, 0.425, 0.475, 0.525,0.575,0.625,
                                          0.675,0.725,0.775,0.825,0.875, 0.90,1.0};
   private static final double yPoints[]={0,0,-0.1,0.1,-0.1,0.1,-0.1,0.1,-0.1,0.1,
                                          -0.1,0.1,-0.1,0.1,-0.1,0.1,-0.1,0.1,0,0};
   private static final Path2D.Double polyline = 
                      new Path2D.Double(Path2D.WIND_EVEN_ODD,xPoints.length);
   private Path2D.Double shape;
   private Stroke stroke;

   private Spring spring;   

   static {  // static initialization block. It creates a spring of length = 1.
      polyline.moveTo (xPoints[0], yPoints[0]);
      for (int index = 1; index < xPoints.length;index++)
         polyline.lineTo(xPoints[index], yPoints[index]);
   }
   public SpringView(Spring spring) {
      this.spring = spring;
      AffineTransform at = AffineTransform.getTranslateInstance(0,0);
      double  x = spring.getBendPosition() - spring.getAendPosition();
      at.rotate(x, 0);
      at.scale(Math.abs(x), spring.getRestLength());
      shape = (Path2D.Double) at.createTransformedShape(polyline);
      stroke = new BasicStroke(0.02f);
   }
   public void updateView (Graphics2D g){
      double ax=spring.getAendPosition();
      double xa_b = spring.getBendPosition() - spring.getAendPosition();
      AffineTransform at = AffineTransform.getTranslateInstance(ax, 0);
      at.rotate(xa_b, 0);
      at.scale(Math.abs(xa_b),  spring.getRestLength());
      shape = (Path2D.Double) at.createTransformedShape(polyline);
      if (Math.abs(xa_b) < spring.getRestLength())
         g.setColor(Color.BLACK);
      else
         g.setColor(Color.RED);
      g.setStroke(stroke);
      g.draw(shape);
   }
   public boolean contains(double x, double y){
      return shape.getBounds2D().contains(x,y);
   }
   public void setSelected() {
      /*    */
   }
   public void setReleased() {
      /* .... */
   }

}