// netprod.java
// Net Production
// adapted from a program in basic by H.T. Odum & E. Odum, 1994

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

public class netprod extends Applet
{
 Label prompt1, prompt2, prompt3;
 TextField input1, input2, input3;
 Button drawbutton;
 double q, k1, k2, t, t0, t1, d0, q0, q1, dq1, p, c, s, dq, s1, p1;
 int n;

 public void init()
 {
 	prompt1 = new Label("Start value for Q : ");
	input1 = new TextField("1", 5);
	add(prompt1); add(input1);

	prompt2 = new Label("K1 Rate of production : ");
	input2 = new TextField("1", 5);
	add(prompt2); add(input2);

	prompt3 = new Label("K2 Rate of consumption : ");
	input3 = new TextField("20", 5);
	add(prompt3); add(input3);

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

 public boolean action(Event e, Object o)
 {
 	q = 0.1f*(float)Integer.parseInt(input1.getText());
 	k1 = 0.01f*(float)Integer.parseInt(input2.getText());
	k2 = 0.01f*(float)Integer.parseInt(input3.getText());
 	repaint();
 	return true;
 }

 public void paint(Graphics g)
 {
 	g.drawRect(0,90,320,250);
	g.drawLine(0,150,320,150);
	g.drawLine(0,200,320,200);
	g.drawString("Source S", 30,140);
	g.drawString("Gross Production P", 30,180);
	g.drawString("Net Production P-C", 30,215);
	g.drawString("Storage Q", 30,320);
	t=0; t1=0.001f; n=1;
	d0=300; q0=300; dq1=0.001f;

 	while (t<320)
 	{
		switch(n) {
			case 1:	 s=200000; break;
			case 2:	 s=350000; break;
			case 3:	 s=450000; break;
			case 4:	 s=350000; break;
			default: n=1; s=200000; break;
			}
	n+=1;
	p=k1*s;
	c=k2*q;
	dq=p-c;
	q+=dq;
	if (t>0)
	{
		g.setColor(Color.red);
		g.drawLine((int)t1*10, (int)(150-s1/10000), (int)t*10, (int)(150-s/10000));
		g.setColor(Color.green);
		g.drawLine((int)t1*10, (int)(340-q1/q0), (int)t*10, (int)(340-q/q0));
		g.setColor(Color.blue);
		g.drawLine((int)t1*10, (int)(200-dq1/d0), (int)t*10, (int)(200-dq/d0));
		g.setColor(Color.blue);
		g.drawLine((int)t1*10, (int)(200-p1/d0), (int)t*10, (int)(200-p/d0));
	}
	q1=q; dq1=dq;
	s1=s; p1=p;
	t1=t; t+=1;
	}
 }
}
// Manuel Basler & e. Ortega, November 11th 2000