// Author: Jim Carlson (copyright) 1996
// Date: June 17, 1996
// Web: http://www.math.utah.edu
// E-mail: carlson@math.utah.edu
// All rights reserved, non-commercial use OK.



import java.applet.*;
import java.awt.*;
import java.util.Random;

public class GamblersRuin extends Applet implements Runnable {

	int thisHeight, thisWidth;
	
	Thread runner;
	boolean running;
	int delay;
	boolean ruin = true;
	
	Image offscreenImg;
	Graphics offscreenG;
	Color lineColor = Color.red;
	
	
	int trial, nSteps, stake;
	int x0, y0, x, y;
	int hMargin = 20;
	int vMargin = 20;
	double kx = 5;
	double ky = 5;
	
	public void init() {
	
		thisHeight = this.size().height; thisWidth = this.size().width;
		offscreenImg = createImage( this.size().width, this.size().height );
		offscreenG = offscreenImg.getGraphics();
		
		String s = getParameter("delay");
		if ( s != null )
			delay = Integer.parseInt( s );
		else
			delay = 100;
		
		s = getParameter("nSteps");	
		if ( s != null )
			nSteps = Integer.parseInt( s );
		else
			nSteps = 60;
			
		s = getParameter("stake");	
		if ( s != null )
			stake = Integer.parseInt( s );
		else
			stake = 0;
			
		s = getParameter("ruin");	
		if ( s != null )
			ruin = s.equals("true");
		else
			ruin = false;
			
		s = getParameter("ky");	
		if ( s != null )
			ky = Double.valueOf( s ).doubleValue();
			
		kx = (thisWidth - 2.0*hMargin)/nSteps;
							
		x = 0; y = stake;
		trial = 0;
				
		offscreenG.setColor( Color.lightGray );
		offscreenG.fillRect( 0, 0, thisWidth, thisHeight );
		offscreenG.setColor( Color.black );
			
	}
	
	public void start() {
		
		if ( runner == null ) {
			runner = new Thread(this);
			running = true;
			runner.start();
		}
	}
	
	public void stop() {
	
		if ( runner != null ) {
			runner.stop();
			runner = null;
		}
		
	}
	
	
	public void run() {
	
		Random R = new Random();
		
		offscreenG.drawLine( sx(0), sy(0), sx(nSteps), sy(0) );
		offscreenG.drawLine( sx(0), thisHeight - vMargin, sx(0), vMargin );
		offscreenG.drawLine( sx(-2/kx), sy(stake), sx(2/kx), sy(stake) );
		offscreenG.drawLine(  sx(-2/kx), sy(-stake), sx(2/kx), sy(-stake) );
		int stringX = hMargin + 40;
		int stringY = thisHeight - 30;
		
		while( true ) {
		
			trial++;					
			
			x0 = x;
			y0 = y;
			x++; 
	    	if (( R.nextDouble() - 0.5 ) > 0)
	    		y++;
	    	else
	    		y--;
	    				
			offscreenG.setColor( lineColor );
			offscreenG.drawLine( sx( x0 ), sy( y0 ), sx( x ), sy( y )  );
			
			//showStatus("trial = "+trial+", $$ = "+y);	
			offscreenG.setColor( Color.lightGray);
			offscreenG.fillRect(stringX-2, stringY-20, 140, 30 );
			offscreenG.setColor( Color.black);
			offscreenG.drawString("trial = "+trial+", $$ = "+y, stringX, stringY );
	   		repaint();
	   		
	   		if ( ruin == true && y == 0 ) {
	    		running = false;
	    		runner.suspend();
	    		x = 0;
	    		y = stake;
	    		trial = 0;
	    		changeColors();	    		
	    	}
	    	
			try { Thread.sleep( delay ); }
			catch ( InterruptedException e ) { }
		
		}
	}
	
	public void update( Graphics g ) {
		paint (g);
	}
	
	public void paint( Graphics g ) {
		
		g.drawImage( offscreenImg, 0, 0, this );
		
	}
	
	int changeColor( int c, int dc ) {
	
		c = c + dc;
		c = c%256;
		if ( c < 0 )
			c += 256;
		return c;
	}
	
	void changeColors() {
	
		int dColor = 60;
		int red = lineColor.getRed();
		red = changeColor( red, -dColor );
		int blue = lineColor.getBlue();
		blue = changeColor( blue, dColor );
		int green = lineColor.getGreen();
		lineColor = new Color( red , green, blue );
	}
	
	
	public boolean mouseDown( Event evt, int mx, int my ) {
	
		if (running) {	
			if ( mx < hMargin + 1 ) {
				x = 0; y = stake; trial = 0;
				changeColors();
			}
			else {
				running = false;
				runner.suspend();
			}
		}
		else {
			running = true;
			runner.resume();
		}
		return true;
		
	}
	
	int sx( double x ) {
	
		return (int) (kx*x + hMargin);
		
	}
	
	int sy( double y ) {
	
		
		return (int) (-ky*y + thisHeight/2);
		
	}
	
	
}