//------------
// Introduction to Programming Using Java: An Object-Oriented Approach
//	Arnow/Weiss
//------------

//------------
// Chapter 6 / GUI Supplement 2  / Page 239-243
//	The completed, event-handling, Calculator applet.
//------------ 

//------------
// Notes
//	- This applet may be run by opening the file 'Calculator.html'
//		in a browser or appletviewer.
//	!!!! Differences from the code in the text !!!!
//	- To avoid a 'deprecated API' warning, the following changes
//		have been made:
//			The invocation of the 'resize' method has been replaced with
//				an invocation of the 'setSize' method.
//			The invocation of the 'size' method has been replaced with
//				and invocation of the 'getSize' method.
//------------

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

public class Calculator extends Applet implements ActionListener {
	public void init() {
		backgroundColor = new Color(200,255,255);
		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);
		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);

		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();
	}

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

	public void paint(Graphics g) {
		setSize(appletWidth,appletHeight);
		validate();
	}

    public void actionPerformed(ActionEvent e) {
        String s = (String)e.getActionCommand();

        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();
    }

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

    private void handleClear() {
        clearCalc();
    }

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

    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;
    }

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

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

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

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

	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);
	}

    static final String initialString = "0.00000";
    static final String digits = "0123456789";
    static final String operators = "+-*/=";
    String lastOptr;
    String Filler = "       ";
    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;
}