import java.awt.*;
import java.awt.event.*;
import java.applet.*;
import java.net.URL;

public class Expon extends Applet
{
  CurvePanel mainpanel;
  Button restartButton, mathReviewButton, applicationButton;
  Panel buttonpanel = new Panel();
  Panel allbuttons = new Panel();
  Scrollbar aslider, bslider, cslider;
  Panel sliderpanel = new Panel();
  int a = 4; int b = -1; int c = -4;

  AdjustmentListener sliderListener = new AdjustmentListener() {
    public void adjustmentValueChanged( AdjustmentEvent e ) {
      a=aslider.getValue();
      b=bslider.getValue();
      c=cslider.getValue();
      mainpanel.repaint();
    }
  };

  ActionListener restartListener = new ActionListener() {
    public void actionPerformed (ActionEvent e) {
      a=4; b=-1; c=-4;
      mainpanel.repaint();
    }
  };

  public void init()
  {
    setBackground(Color.white);
    int a = 4; int b = -1; int c = -4;
    mainpanel = new CurvePanel();
    setLayout(new BorderLayout());
    add("Center",mainpanel);
    mainpanel.init();
    add("South",sliderpanel);
    sliderpanel.setLayout(new GridLayout(1,3));

    aslider = new Scrollbar(Scrollbar.HORIZONTAL,4,1,-5,6);
    aslider.addAdjustmentListener(sliderListener);
    aslider.setBlockIncrement(1);
    sliderpanel.add(aslider);

    bslider = new Scrollbar(Scrollbar.HORIZONTAL,-1,1,-3,3);
    bslider.addAdjustmentListener(sliderListener);
    bslider.setBlockIncrement(1);
    sliderpanel.add(bslider);

    cslider = new Scrollbar(Scrollbar.HORIZONTAL,-4,1,-5,6);
    cslider.addAdjustmentListener(sliderListener);
    cslider.setBlockIncrement(1);
    sliderpanel.add(cslider);

    add("North",buttonpanel);
    buttonpanel.setLayout(new BorderLayout());
    buttonpanel.add("East",allbuttons);

    allbuttons.setLayout(new GridLayout(1,1));

    restartButton = new Button("restart");
    restartButton.addActionListener(restartListener);
    allbuttons.add(restartButton);

  }

  public class CurvePanel extends Panel {

    public void init(){   }

    public void paint(Graphics g){     

      g.setColor(Color.black);
	g.drawRect(0,0,599,399); //box it
      g.drawLine(0, getSize().height / 2, getSize().width, getSize().height/ 2);
      g.drawLine(50, 0, 50, getSize().height-20);

      for (int i = -8; i<10; i++) {

        int y=getSize().height/2-i*getSize().height/20;
        g.drawLine(45, y, 55, y);
        g.drawString(""+i,58,y);
      }

      for (int i=1; i<4; i++) {
        double x=150.0*i+50;
        g.drawLine((int)x,getSize().height/2-5,(int)x,getSize().height/2+5);
//	  if (i==1) {g.drawString("\u03c0",(int)x-3,getSize().height/2-7);
//	  } else { g.drawString(""+i+"\u03c0",(int)x-5,getSize().height/2-7); }
	  g.drawString(""+i+"",(int)x-5,getSize().height/2-7);
      }

      int sx = getSize().width/8-10;
      int sy = getSize().height - 8;
      g.drawString("a = " + a + "  ", sx, sy);
      g.drawString("b = " + b + "  ", sx + getSize().width/3, sy);
      g.drawString("c = " + c + "  ", sx + getSize().width/3*2, sy);
      g.drawString("t",getSize().width-20,getSize().height/2-2);
      g.drawString("v",40,10);
	g.setFont(new Font("Dialog",0,16));
      g.drawString("v = a*exp(b*t)+c",getSize().width/4-15,20);

      g.setColor(Color.red);
      for (int x = 0 ; x < getSize().width ; x=x+3)
        if (Math.abs(f(x))<1000) {g.drawLine(x, (int)f(x), x+3, (int)f(x+3)); 
         g.drawLine(x, (int)f(x)+1, x+3, (int)f(x+3)+1);
	   g.drawLine(x, (int)f(x)-1, x+3, (int)f(x+3)-1);
 	 }
    }

    double f(double x) {

//      return (-d-a*Math.sin(b*((x-50)/50-c)))*getSize().height/20 + getSize().height/2;
      return (-c-a*Math.exp(b*((x-50)/150)))*getSize().height/20 + getSize().height/2;
    }
  }