// mas964 ps4
// 2 second animation connecting two mouseclicks
// draws nested circles going into the first click, out of the second
// two circles are drawn each time to give overlapping frames
// the circle's speed gets quadratically slower the smaller it is.

import java.applet.*;
import java.awt.*;
import java.lang.Math;
import java.lang.String;
import TwoPointAnimator;

public class TwoPointLong extends TwoPointAnimator {
  public void drawFrame(int ms) {
    int halfway = animationLength / 2;		  // time half is done
    int circleThickness = 3;
    int maxSize = Math.max(imageBufferSize.width, imageBufferSize.height);

    Graphics g = imageBuffer.getGraphics();
    this.clearImageBuffer();
    g.setColor(this.getForeground());

    if (ms < halfway) {
      // draw a circle going in to the first click
      int size = maxSize * (halfway - ms) * (halfway - ms) / (halfway*halfway);
      thickCenteredCircle(g, x1, y1, size, circleThickness);

      // draw the next frame as well (gives nested circles)
      ms += frameDelay;
      size = maxSize * (halfway - ms) * (halfway - ms) / (halfway*halfway);
      thickCenteredCircle(g, x1, y1, size, circleThickness);
    } else {
      // draw circles going out of the second click
      // (have to draw the bigger circle first)
      ms += frameDelay;
      int size = maxSize * (ms - halfway) * (ms - halfway) / (halfway*halfway);
      thickCenteredCircle(g, x2, y2, size, circleThickness);

      ms -= frameDelay;
      size = maxSize * (ms - halfway) * (ms - halfway) / (halfway*halfway);
      thickCenteredCircle(g, x2, y2, size, circleThickness);
    }
    
    repaint(); 
  }
  
  public void thickCenteredCircle(Graphics g, int x, int y, int radius, int thickness) {
    Color c = g.getColor();
    g.fillOval(x - radius, y - radius, radius * 2 + 1, radius * 2 + 1);
    g.setColor(this.getBackground());
    g.fillOval(x - (radius - thickness), y - (radius - thickness),
	       (radius - thickness) * 2 + 1, (radius - thickness) * 2 + 1);
    g.setColor(c);
  }

  public void stop() {
    this.clearImageBuffer();
    repaint();
    super.stop();
  }
  
  public void init() {
    this.setBackground(Color.white);
    this.setForeground(Color.black);
    super.init();
    if (frameDelay == 0 || animationLength == 0) {
      frameDelay = 50;
      animationLength = 2000;
    }
  }
}