// stworld.java
// regional economy driven by world growth minimodel
// adapted from a program in basic by H.T. Odum & E. Odum, 1994

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

public class stworld extends Applet
{
  double i,j,s,q,w,f,u,k1,k2,k3,k4,k5,k6,k7,k8,l,l1,l2,l3,l4,l5,l6,s0,q0,f0,dt;
  double t0,u0,w0,t,ti,si,qi,fi,wi,ui,d1,d2,d3,d4,d5;
  int y;
  Label pr1,pr2,pr3;
  TextField in1,in2,in3;
  Button drawbutton;

  public void init()
  {
	pr1 = new Label("L2 Rate of use of world resources (1 to 10): ");
    in1 = new TextField("2",3);
	add(pr1);add(in1);

	pr2 = new Label("I Amount of world´s sunlight: ");
	in2 = new TextField("120",4);
	add(pr2);add(in2);

	pr3 = new Label("F New rich fuel source in the year: ");
	in3 = new TextField("4",3);
	add(pr3);add(in3);

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

  public boolean action (Event e, Object o)
  {
	l2 = 0.0000266*(double)Integer.parseInt(in1.getText());
    i = (double)Integer.parseInt(in2.getText());
	y = Integer.parseInt(in3.getText());
	repaint();
	return true;
  }

  public void paint (Graphics g)
  {
	j=2;s=60000;si=60000;q=1;qi=1;w=10;wi=10;f=0;fi=0;u=0.1;ui=0.1;
	k1=1e-09;k2=5e-07;k3=0.04;k4=2e-09;
	k5=1.8e-08;k6=0.000018;k7=0.0018;
	k8=1e-05;l=0.1;l1=0.00016;
	l3=0.17;l4=0.01;l5=0.006;l6=0.04666;
	s0=0.001;q0=0.3;f0=0.08;dt=1;t0=0.45;
	u0=3;w0=3;t=0;ti=0;

	g.drawRect(0,90,320,180);
	g.drawLine(0,170,320,170);

	while ((t*t0)<320)
	{
	 if (t==300) f=1000;
	 if (y==0)   f=f;
	 else
	 if (t==(y-1600)) f=1000;
	 d1=k1*s*f*q+k2*s*q-k3*q+k8*s;
	 d2=i-k5*f*s*q-k6*s*q-k7*s;
	 d3=-k4*s*f*q;
	 d4=j-l1*q*u*w-l3*w-l5*w;
	 d5=-l*u+l2*u*q*w+l4*w-l6*u;
	 q=q+d1*dt;
	 s=s+d2*dt;
	 f=f+d3*dt;
	 w=w+d4*dt;
	 if (w<0.1) w=0.1;
	 u=u+d5*dt;

	 g.setColor(Color.blue);
	 g.drawLine((int)(ti*t0),(int)(170-qi*q0),(int)(t*t0),(int)(170-q*q0));
	 g.setColor(Color.red);
	 g.drawLine((int)(ti*t0),(int)(170-si*s0),(int)(t*t0),(int)(170-s*s0));
	 g.setColor(Color.green);
	 g.drawLine((int)(ti*t0),(int)(170-fi*f0),(int)(t*t0),(int)(170-f*f0));
	 g.setColor(Color.orange);
	 g.drawLine((int)(ti*t0),(int)(270-wi*w0),(int)(t*t0),(int)(270-w*w0));
	 g.setColor(Color.magenta);
	 g.drawLine((int)(ti*t0),(int)(270-ui*u0),(int)(t*t0),(int)(270-u*u0));
	 ti=t;
	 t+=dt;
	 qi=q;si=s;fi=f;wi=w;ui=u;
  }
 }
}
// Stefan Kontur & E. Ortega, August 29th 2000