// saltmrsh.java
// Program for a salt marsh illustrating external rhythms
// adapted from a program in basic by H.T. Odum & E. Odum, 1994

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

public class saltmrsh extends Applet
{
  float i0,m,n,e0,j0,q1,q2,q3,j,e,p1,p2,p3,k0,k1,k2,k3,k4,k5,k6,k7,k8,k9,i,r,d1,
	  d2,d3,t,ti,qi1,qi2,qi3,ii,ji,ei;
  int x,y,z;
  Label pr1,pr2,pr3,pr4;
  TextField in1,in2,in3,in4;
  Button drawbutton;

  public void init()
  {
	    pr1 = new Label("Q3 Initial storage of organic matter: ");
		in1 = new TextField("500",6);
		add(pr1);add(in1);

		pr2 = new Label("Multiply tidal range by (1 or 2): ");
		in2 = new TextField("1",3);
		add(pr2);add(in2);

		pr3 = new Label("Multiply inflow of sunlight by (1 or 2): ");
		in3 = new TextField("1",3);
		add(pr3);add(in3);

		pr4 = new Label("Multiply inflow of nutrients by (1 or 2): ");
		in4 = new TextField("1",3);
		add(pr4);add(in4);

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

	public boolean action (Event e, Object o)
	{
	  	q3 = (float)Integer.parseInt(in1.getText());
		x = Integer.parseInt(in2.getText());
		y = Integer.parseInt(in3.getText());
		z = Integer.parseInt(in4.getText());
		repaint();
		return true;
	}

	public void paint (Graphics g)
	{
	    g.drawRect(55,120,320,180);
		g.drawLine(55,150,380,150);
		g.drawLine(55,170,380,170);
		g.drawLine(55,190,380,190);
		g.drawLine(55,210,380,210);
		g.drawString("Sun", 5, 145);
		g.drawString("Tide", 5, 165);
		g.drawString("River", 5, 185);
		g.drawString("Nutrients", 5, 205);
		g.drawString("Peat", 5, 250);
		g.drawString("Grass", 5, 295);
		i0=200;m=7;n=6.5f;e0=0.2f;j0=0.002f;q1=0.2f;q2=10;
		j=0.02f;e=1;p1=0.05f;p2=30;p3=30;k0=20;k1=0.02f;k2=0.0004f;
		k3=4e-07f;k4=0.05f;k5=2e-05f;k6=4e-05f;k7=0.0036f;k8=6.000001e-04f;
		k9=3.2e-09f;t=0;ti=0;
		while ((t/n)<320) {
	  	i=(float)(2000+(1+Math.sin(t/58))*2000)*(float)y;
		j=(float)(0.02f*(1+Math.cos(t/58)))*(float)z;
		e=(float)(2+Math.sin(t/27))*(float)x;
		r=i/(1+k0*q1);
		d1=j-k5*q1*r+k3*q2+k9*q3-k4*q1*e;
		d2=k1*q1*r-k7*q2-k2*q2;
		d3=k7*q2-k8*q3-k6*q3*e;
		q1=q1+m*d1;
		qi1=q1;
		if (q1<0.01){
		q1=0.01f;
		}
		q2=q2+m*d2;
		qi2=q2;
		q3=q3+m*d3;
		qi3=q3;
		g.setColor(Color.blue);
		g.drawLine((int)(55+ti/n),(int)(210-qi1/p1),(int)(55+t/n),(int)(210-q1/p1));
		g.setColor(Color.red);
		g.drawLine((int)(55+ti/n),(int)(190-ji/j0),(int)(55+t/n),(int)(190-j/j0));
		g.setColor(Color.green);
		g.drawLine((int)(55+ti/n),(int)(300-qi2/p2),(int)(55+t/n),(int)(300-q2/p2));
		g.setColor(Color.pink);
		g.drawLine((int)(55+ti/n),(int)(150-ii/i0),(int)(55+t/n),(int)(150-i/i0));
		g.setColor(Color.orange);
		g.drawLine((int)(55+ti/n),(int)(300-qi3/p3),(int)(55+t/n),(int)(300-q3/p3));
		g.setColor(Color.black);
		g.drawLine((int)(55+ti/n),(int)(170-ei/e0),(int)(55+t/n),(int)(170-e/e0));
		ti=t;qi1=q1;ji=j;qi2=q2;ii=i;qi3=q3;ei=e;
		t+=m;
		}
	}
}
// Stefan Kontur & E. Ortega, August 29th 2000