import java.awt.*;
//import java.awt.Component.*;
import java.awt.event.*;
import java.applet.Applet;

public class area extends Applet {
  CurvePanel mainpanel;
  Button resetButton;
  Panel buttonPanel = new Panel();
  Choice sampleChooser = new Choice();
  String sample="Left Endpoints";
  Choice numberBoxesChooser = new Choice();
  String numberBoxes="2"; int numBox=2;
  String shapes="rectangles";
  double area;
  int sampleShift=0;

  ActionListener resetListener = new ActionListener() {
    public void actionPerformed (ActionEvent e) {
	sample = sampleChooser.getSelectedItem();
	numberBoxes = numberBoxesChooser.getSelectedItem();
      mainpanel.repaint();
    }
  };

  double f(long x) {if (x<246) return 465491587/2519424.-455/544195584.*x*x*x+17563/30233088.*x*x-675311/5038848.*x; else return  387477211/5038848.+6097/1088391168.*x*x*x-264173/60466176.*x*x+11413129/10077696.*x;}
//return 220-91*(1-(x-174)*(x-174)/82944.0);}  //288^2=82944

  public void init(){
    setBackground(Color.white);
    mainpanel = new CurvePanel();
    setLayout(new BorderLayout());
    add("Center",mainpanel);
    add("South",buttonPanel);
    buttonPanel.setLayout(new GridLayout(1,3));

    resetButton = new Button("reset & redraw");
    resetButton.addActionListener(resetListener);

    sampleChooser.addItem("Left Endpoints"); sampleChooser.addItem("Midpoints");
    sampleChooser.addItem("Right Endpoints"); sampleChooser.addItem("Arbitrary Points");
    sampleChooser.addItem("Trapezoids");
    numberBoxesChooser.addItem("2"); numberBoxesChooser.addItem("4");
    numberBoxesChooser.addItem("6"); numberBoxesChooser.addItem("12");
    numberBoxesChooser.addItem("18"); numberBoxesChooser.addItem("36");
    buttonPanel.add(sampleChooser);
    buttonPanel.add(numberBoxesChooser);
    buttonPanel.add(resetButton); 
  }

  public class CurvePanel extends Panel {
    public void paint(Graphics g){
      g.setColor(Color.black);
	g.drawRect(0,0,499,299); //box it
      g.drawLine(0, 220, 485, 220);  //x-axis
      g.drawLine(30, 134, 30, 240); //y-axis
      for (int i = 0; i<=20; i+=10) {   //y-ticks
        int y=220-i*4;
        g.drawLine(25, y, 35, y);
        g.drawString(""+i,14,y);
      }
      for (int i=10; i<=110; i+=10) {     //x-ticks
        int x=i*4+30;
        g.drawLine(x,215,x,225);
	  g.drawString(""+i,x-7,235); 
      }
      g.drawString("x",485,210);
      g.drawString("y",35,134);
  
     g.setColor(Color.yellow);
  	for (int i = 10; i<=20; i+=10) {  //y-grid
        int y=220-i*4;
        g.drawLine(35, y, 470, y);
	}
      for (int i=10; i<=110; i+=10) {     //x-grid
        int x=i*4+30;
        g.drawLine(x,215,x,140);
      }

	if (numberBoxes=="2") numBox=2;
	else {
	  if (numberBoxes=="4") numBox=4;
	  else {
	    if (numberBoxes=="6") numBox=6;
	    else {
	      if (numberBoxes=="12") numBox=12;
		else {
		  if (numberBoxes=="18") numBox=18; else numBox=36;
		}
	    }
	  }
	}

      g.setColor(Color.blue);
      for (int x = 30 ; x < 462 ; x+=4) {   //curve
        g.drawLine(x, (int)f(x), x+4, (int)f(x+4)); 
        g.drawLine(x, (int)f(x)+1, x+4, (int)f(x+4)+1);
	  g.drawLine(x, (int)f(x)-1, x+4, (int)f(x+4)-1);
 	 }
	g.drawLine(30,220,30,(int)f(30));g.drawLine(29,220,29,(int)f(29));g.drawLine(31,220,31,(int)f(31));
	g.drawLine(30,220,462,220);g.drawLine(30,219,461,219);g.drawLine(30,221,462,221);

 	g.setColor(Color.red);
	int boxWidth=432/numBox; area=0;
	if (sample=="Left Endpoints") sampleShift=0;
	else {
	  if (sample=="Right Endpoints") sampleShift=boxWidth; else sampleShift=boxWidth/2; //midpoint 
	}

	if (sample != "Trapezoids"){
	  shapes="rectangles";
	  for (int box=0; box<numBox; box++){
	    int x=30+box*boxWidth;
	    if (sample=="Arbitrary Points") sampleShift=(int)((boxWidth+1)*Math.random());
	    int y=(int) f(x+sampleShift);
	    g.drawRect(x,y,boxWidth,220-y);
	    area=area+boxWidth*(220-f(x+sampleShift))/16.0;
	  }
	}
	else{
	  shapes="trapezoids";
	  for (int box=0; box<numBox; box++){
	    int x=30+box*boxWidth;
	    int y=(int) f(x); int y2=(int) f(x+boxWidth);
	    g.drawLine(x,y,x,220);g.drawLine(x,220,x+boxWidth,220);
	    g.drawLine(x+boxWidth,220,x+boxWidth,y2);g.drawLine(x+boxWidth,y2,x,y);
	    area=area+boxWidth*((220-f(x))+(220-f(x+boxWidth)))/2./16.0;
	  }
	}

	g.setColor(Color.black);
	g.drawString("Sample Point Choice:",5,270);
	g.drawString("Number of Subintervals:",170,270);


	g.setFont(new Font("Helvetica",0,16));
	g.drawString("Blue curve encloses port half of top view of USNA YP Craft",10,20);
	g.drawString("The exact area enclosed in blue, to 6 figures, is 1066.41 sq. ft.",10,40);
	g.drawString("Area enclosed by red "+shapes+" is "+Math.round(area*100)/100.0+" sq.ft.",10,60);
    }
  }