// pulse.java
// pulse and recycle
// adapted from a program in basic by H.T. Odum & E. Odum, 1994

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

public class pulse extends Applet
{

 Label prompt1, prompt2, prompt3;
 TextField input1, input2, input3;
 Button drawbutton;
 double tm, k2, k4, e, q, qi, c, ci, k1, k3;
 double f1, f2, q0, c0, dt, m, dq, dc, t, ti;
 int t0;

 public void init()
 {
 	prompt1 = new Label("TM Total Nutrients: ");
	input1 = new TextField("200", 5);
	add(prompt1); add(input1);

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

	prompt2 = new Label("K2 coefficient : ");
	input2 = new TextField("1", 3);
	add(prompt2); add(input2);

	prompt3 = new Label("K4 coefficient : ");
	input3 = new TextField("20", 3);
	add(prompt3); add(input3);
 }

 public boolean action(Event e, Object o)
 {
 	tm = (float)Integer.parseInt(input1.getText());
 	k2 = 0.01f*(float)Integer.parseInt(input2.getText());
	k4 = 0.01f*(float)Integer.parseInt(input3.getText());
 	repaint();
 	return true;
 }

 public void paint(Graphics g)
 {
 	g.drawRect(0,60,320,180);
	t=0; ti=0;
	e=1; q=2; c=2; k1=0.02f; k3=0.0003f;
	f1=0.05f; f2=0.1; q0=1; c0=1; t0=2; dt=0.5;

 	while ((t*t0)<320)
 		{
		m=tm-f1*q-f2*c;
		dq=k1*e*m-k2*q-k3*c*c*q;
		dc=k2*q+k3*q*c*c-k4*c;
		qi=q+dq*dt;
		ci=c+dc*dt;
		ti=t+dt;
		g.setColor(Color.blue);
		g.drawLine((int)t*t0, (int)(240-q*q0), (int)ti*t0, (int)(240-qi*q0));
		g.setColor(Color.pink);
		g.drawLine((int)t*t0, (int)(240-c*c0), (int)ti*t0, (int)(240-ci*c0));
		t=ti; q=qi; c=ci;
		}
 }
}
// Manuel Basler & e. Ortega, November 10th 2000