// fire.java
// Fire - a rapid pulse of nutrients return and selection process
// adapted from a program in basic by H.T. Odum & E. Odum, 1994

import java.applet.*;
import java.awt.*;

public class fire extends Applet
{

 Label prompt1, prompt2;
 TextField input1, input2;
 Button drawbutton;
 CheckboxGroup fire;
 Checkbox on, off;
 double i, q, qi, tn, g1, g2, k, k1, k2, f, q0, n0, n, ni, r, dq, t, ti;
 int a;

 public void init()
 {
 	prompt1 = new Label("TN Total nutrients: ");
	input1 = new TextField("100", 5);
	add(prompt1); add(input1);

	prompt2 = new Label("Fire burns down to G2: ");
	input2 = new TextField("2000", 5);
	add(prompt2); add(input2);

	drawbutton = new Button("Draw");
	add(drawbutton);

	fire = new CheckboxGroup();
	on = new Checkbox("Fire on", fire, true);
	off = new Checkbox("Fire off", fire, false);
	add(on); add(off);
 }

 public boolean action(Event e, Object o)
 {
	if(e.target instanceof Checkbox) {
		if(on.getState() == true) a=0;
		else a=1;
	}
	tn = (float)Integer.parseInt(input1.getText());
 	g2 = (float)Integer.parseInt(input2.getText());
 	repaint();
 	return true;
 }

 public void paint(Graphics g)
 {
 	g.drawRect(0,90,320,240);
	g.drawLine(0,210,320,210);
	t=0; ti=0;
	i=10; q=1000; g1=5000;
	k=0.9; k1=8; k2=0.01f; f=0.01f; q0=0.01f; n0=0.9f;
	n=tn-f*q;

 	while (t<320)
    {
		r=i/(1+k*n);
		if (q > g1 && a==0) {
		  g.setColor(Color.red);
		  g.drawLine((int)t, (int)(330-g1/100), (int)t, (int)(330-g2/100));
		  g.setColor(Color.blue);
		  g.drawLine((int)t, (int)(210-(tn-f*g1)*n0), (int)t, (int)(210-(tn-f*g2)*n0));
		  q=g2;
		  }
		dq=k1*n*r-k2*q;
		qi=q+dq;
		ni=tn-f*qi;
		g.setColor(Color.green);
		g.drawLine((int)t, (int)(330-q/100), (int)ti, (int)(330-qi/100));
		g.setColor(Color.blue);
		g.drawLine((int)t, (int)(210-n*n0), (int)ti, (int)(210-ni*n0));
		ti=t; t+=1;
		q=qi; n=ni;
	}
  }
}
// Manuel Basler & e. Ortega, November 14th 2000