/* this version works with Java 1.0 (MSJ++ 1.1)
 * Oct. 8, 1998
 */
import java.awt.*;
//import java.awt.event.*;
import java.applet.Applet;

public class CalculatorV10 extends Applet
{
    public void init()
    {
	backgroundColor = new Color(200, 255, 255);
        // FlowLayout(alignment, hgap, vgap) where gaps are measured in pixels
	this.setLayout(new FlowLayout(FlowLayout.CENTER, 4, 1));

	result = new Label(initialString, Label.RIGHT);
	result.setBackground(new Color(255,255,255));
	add(result);
	makeButtons();

	row1 = makePanel(new FlowLayout(FlowLayout.LEFT, 4, 2),
                                        backgroundColor);
        row1.add(c);     // clear
	row1.add(eq);    // =
	row1.add(div);   // /
	row1.add(times); // *

	row2 = makePanel(new FlowLayout(FlowLayout.LEFT, 4, 2),
                                        backgroundColor);

        row2.add(d7);
        row2.add(d8);
        row2.add(d9);
        row2.add(minus);

	row3 = makePanel(new FlowLayout(FlowLayout.LEFT, 4, 2),
                                        backgroundColor);

	row3.add(d4);
	row3.add(d5);
	row3.add(d6);
	row3.add(plus);

	add(row1);
	add(row2);
	add(row3);

        // BorderLayout(hgap, vgap) where gaps are measured in pixels
	p12 = makePanel(new BorderLayout(2,2),
                        backgroundColor);
	p12.add("West",d1);
	p12.add("East",d2);

	p120 = makePanel(new BorderLayout(2,2),
                        backgroundColor);
	p120.add("North",p12);
	p120.add("South",d0);

	p3p = makePanel(new BorderLayout(2,2),
                        backgroundColor);
	p3p.add("North", d3);
	p3p.add("South", dp);

        p3peq = makePanel(new BorderLayout(2,2),
                        backgroundColor);
	p3peq.add("West",p3p);
	p3peq.add("East",eq2);

	add(p120);
	add(p3peq);

	setBackground(backgroundColor);

	/***
	c.addActionListener(this);
	eq.addActionListener(this);
	eq2.addActionListener(this);
	div.addActionListener(this);
	times.addActionListener(this);
	minus.addActionListener(this);
	plus.addActionListener(this);
	d0.addActionListener(this);
	d1.addActionListener(this);
	d2.addActionListener(this);
	d3.addActionListener(this);
	d4.addActionListener(this);
	d5.addActionListener(this);
	d6.addActionListener(this);
	d7.addActionListener(this);
	d8.addActionListener(this);
	d9.addActionListener(this);
**/
	clearCalc();
    } // end of init()

    public void start()
    {
	appletWidth = 8 * 4 + row1.size().width;
	appletHeight = 8 * (2 + d1.size().height);
    } // end of start

    public void paint(Graphics g)
    {
	resize(appletWidth, appletHeight);
	validate();
    }  // end of paint

    public boolean handleEvent(Event e)
    {
	String s = (String)e.arg;

        if (s != null)
        {
	if (digits.indexOf(s) != -1)
	    handleDigit(s);
	else if (s.equals("."))
	    handleDecimal();
	else if (operators.indexOf(s) != -1)
	    handleOperator(s);
	else if (s.equals("C"))
	    handleClear();
        }
	return true;
    }  // end actionPerformed

    private void handleDigit(String s)
    {
	if (newOpd)
	{
	    result.setText(s);
	    newOpd = false;
	}
	else
	    result.setText(result.getText() + s);
	sawAnOpd = true;
    }  // end handleDigit

    private void handleClear()
    {
	clearCalc();
    }  // end handleClear

    private void clearCalc()
    {
	sawDecimal = false;
	newOpd = true;
	sawAnOpd = false;
	lastOptr = "";
	result.setText(initialString);
    }  // end clearCalc

    private void handleOperator(String s)
    {
	if (!sawAnOpd)
	    return;

	if (lastOptr.equals("+"))
	    opd1 += getDisplay();
	else if (lastOptr.equals("-"))
	    opd1 -= getDisplay();
	else if (lastOptr.equals("*"))
	    opd1 *= getDisplay();
	else if (lastOptr.equals("/"))
	    opd1 /= getDisplay();
	else
	    opd1 = getDisplay();

	result.setText(opd1 + "");
	
	lastOptr = s;
	sawDecimal = false;
	newOpd = true;
    } // end handleOperator

    private void handleDecimal()
    {
	if (!sawDecimal)
	{
	    if (newOpd)
	    {
		result.setText("0.");
		newOpd = false;
	    }
	    else
		result.setText(result.getText() + ".");
	    sawDecimal = true;
	}
    }  // end handleDecimal

    private double getDisplay()
    {
	return Double.valueOf(result.getText()).doubleValue();
    }  // end getDisplay

    private Button makeButton(String label, Color color, Font font)
    {
	Button b = new Button(label);
	b.setBackground(color);
	b.setFont(font);
	return b;
    }  // end makeButton

    private Panel makePanel(LayoutManager lm, Color c)
    {
	Panel p = new Panel();
	p.setLayout(lm);
	p.setBackground(c);
	return p;
    }  // end makePanel

    private void makeButtons()
    {
	Font f = new Font("Courier", Font.BOLD, 10);
	Color lightRed = new Color(255, 100, 100);
	Color lightBlue = new Color(100, 100, 255);
	Color yellow   = new Color(255, 255, 0);

	c = makeButton("C",lightRed,f);
	eq = makeButton("=",lightBlue,f);
	div = makeButton("/",lightBlue,f);
	times = makeButton("*",lightBlue,f);
	d7 = makeButton("7",yellow,f);
	d8 = makeButton("8",yellow,f);
	d9 = makeButton("9",yellow,f);
	minus = makeButton("-",lightBlue,f);
	d4 = makeButton("4",yellow,f);
	d5 = makeButton("5",yellow,f);
	d6 = makeButton("6",yellow,f);
	plus = makeButton("+",lightBlue,f);
	d1 = makeButton("1",yellow,f);
	d2 = makeButton("2",yellow,f);
	d3 = makeButton("3",yellow,f);
	d0 = makeButton("0",yellow,f);
	dp = makeButton(".",yellow,f);
	eq2 = makeButton("=",lightBlue,f);
    }  // end makeButtons

    static final String initialString  = "0.00000";
    static final String digits = "0123456789";
    static final String operators = "+-*/=";
    String lastOptr;
    boolean sawDecimal, newOpd, sawAnOpd;
    double opd1;

    Panel row1, row2, row3, p12, p120, p3p, p3peq;
    int appletWidth, appletHeight;

    Button c, eq, div, times,
           d7, d8, d9, minus,
           d4, d5, d6, plus,
           d1, d2, d3,
           d0,     dp, eq2;
    Color backgroundColor;
    Label result;
}  // end of Calculator