//Sierpinski.java
import java.awt.*;
import java.awt.event.*;
import javax.swing.*;

public class Sierpinski extends JApplet {
    
    Point[] points;
    Point p;
    int clicks;
    int vertices=3;
    boolean mouseClick;


    public void init() {

	addMouseListener(
	    //anonymous inner class overrides mouseClicked
	    new MouseAdapter() {
		public void mouseClicked( MouseEvent event) {
		    if (clicks < vertices) {
			mouseClick = true;
			points[clicks].x = event.getX();
			points[clicks].y = event.getY();
			repaint();
		    }
		    else if (clicks == vertices) {
			p.x = event.getX();
			p.y = event.getY();
			clicks = vertices+1;
			repaint();
		    }
		}
	    }
	 );

    }


    public void start(){
	points = new Point[vertices];
	for (int i=0; i<vertices; i++)
	    points[i] = new Point();
	clicks = 0;
	p = new Point();

	mouseClick = false;    //prevent paint from processing no click
	JOptionPane.showMessageDialog( this, "click " + vertices + " vertices of a triangle" );
    }


    public void paint ( Graphics g )
    {
       super.paint( g );
       int x1, y1;
       int r;

       if (mouseClick) {
	   if (clicks < vertices) {    //still getting the vertices
	       g.setColor( Color.RED );
	       for (int i=0; i<=clicks; i++)   //all the vertices so far
		   g.fillOval(points[i].x-3, points[i].y-3, 3, 3);
	       clicks++;
	       if (clicks == vertices) {     //just did the Nth one
		   mouseClick = false;    
		   JOptionPane.showMessageDialog( this, "click any starting point" );
	       }
	       
	   }
       }
       else if (clicks == vertices+1) {
	   g.setColor( Color.BLACK );
	   for (int i=1; i<100000; i++) {
	       g.drawLine( p.x, p.y, p.x, p.y);
	       r = (int)(Math.random() * vertices); 
	       p.x = (p.x + points[r].x) / 2;   //halfway between p and random vertex
	       p.y = (p.y + points[r].y) / 2;
	   }
       }
    }
}