import java.util.StringTokenizer;
import java.util.Hashtable;

import java.awt.BorderLayout;
import java.awt.Button;
import java.awt.Color;
import java.awt.Dimension;
import java.awt.Event;
import java.awt.GridLayout;
import java.awt.Label;
import java.awt.Panel;
import java.awt.Frame;
import java.awt.Toolkit;

import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.awt.event.KeyAdapter;
import java.awt.event.KeyEvent;
import java.awt.event.WindowEvent;
import java.awt.event.WindowAdapter;

import java.applet.Applet;


// Converts the Calculator application to run either as an application
// or as an applet by creating a "shared" panel -- a panel that will
// be shared by the application's Frame and by the Applet.  The panel
// will be the first component placed on each.  All other components are
// placed on the shared panel.

public class CalculatorE extends Applet {
    
    private boolean isApplet = false;
    private boolean lastKeyWasFunction = true;
    private double displayHold = 0;
    
    private Frame f;
    private Hashtable theKeys = new Hashtable();
    private Label display;
    private Panel pMain;
    private String lastFunction = "";
    private Toolkit tk = null;
    
    private KeyListener keyListener = new KeyListener();
    
    
    public static void main(String[] args) {
        
        CalculatorE calc = new CalculatorE();
        calc.isApplet = false;
        calc.tk = Toolkit.getDefaultToolkit();
        
        calc.f = new Frame("Calculator");
        // add Window closer
        calc.f.addWindowListener(new WindowAdapter() {
            public void windowClosing(WindowEvent e) {
                System.exit(0);
            }
            // close anon inner class
        });
        
        // add Key Listener to frame
        calc.f.addKeyListener(calc.keyListener);
        
        // create panel which will be shared by Frame and Applet
        calc.pMain = new Panel();
        calc.pMain.setLayout(new BorderLayout());
        calc.pMain.setBackground(Color.lightGray);
        calc.pMain.addKeyListener(calc.keyListener);
        
        // add shared panel to Frame
        calc.f.add(calc.pMain, BorderLayout.CENTER);
        
        calc.makeGUI();
    }
    
    
    public void init() {
        isApplet = true;
        
        setLayout(new BorderLayout());
        setBackground(Color.lightGray);
        this.addKeyListener(keyListener);
        
        // create the shared panel
        pMain = new Panel();
        pMain.setLayout(new BorderLayout());
        pMain.setBackground(Color.lightGray);
        pMain.addKeyListener(keyListener);
        
        // add the shared panel to the applet
        add(pMain, BorderLayout.CENTER);
        
        makeGUI();
    }
    
    
    private void makeGUI() {
        
        // add display
        display = new Label("0", Label.RIGHT);
        pMain.add(display, BorderLayout.NORTH);
        
        Panel numPanel = new Panel();
        numPanel.setBackground(pMain.getBackground());
        numPanel.addKeyListener(keyListener);
        numPanel.setLayout(new GridLayout(4, 3));
        
        Panel funcPanel = new Panel();
        funcPanel.setBackground(numPanel.getBackground());
        funcPanel.addKeyListener(keyListener);
        funcPanel.setLayout(new GridLayout(4, 2));
        
        
        // create number buttons
        if (true) {
            ButtonListener bl = new ButtonListener(0);
            
            for (int i = 0; i < 12; i++) {
                Button b = new Button("" + i);
                b.setForeground(Color.blue);
                b.addActionListener(bl);
                b.addKeyListener(keyListener);
                
                // handle blank and '.' buttons
                if (i == 10) {
                    b.setLabel("+/-");
                }
                if (i == 11) {
                    b.setLabel(".");
                }
                theKeys.put(b.getLabel(), b);
            }
        }
        
        // create function keys
        if (true) {
            ButtonListener bl = new ButtonListener(1);
            
            StringTokenizer st = new StringTokenizer("/ C * CE + none - =", " ");
            while (st.hasMoreTokens()) {
                Button b = new Button(st.nextToken());
                b.setForeground(Color.red);
                b.addActionListener(bl);
                b.addKeyListener(keyListener);
                
                // disable unneded 'b' key
                if (b.getLabel().equals("none")) {
                    b.setVisible(false);
                }
                // add the key to theKeys array
                theKeys.put(b.getLabel(), b);
                // add the key to the function panel
                funcPanel.add(b);
            }
        }

        // place number buttons on numPanel
        for (int i = 1; i <= 9; i++) {
            numPanel.add((Button)theKeys.get("" + i));
        }
        numPanel.add((Button)theKeys.get("+/-"));
        numPanel.add((Button)theKeys.get("0"));
        numPanel.add((Button)theKeys.get("."));
        
        pMain.add(numPanel, BorderLayout.CENTER);
        pMain.add(funcPanel, BorderLayout.EAST);
        
        
        if (!isApplet) {
            f.pack();
            Dimension screensize = tk.getScreenSize();
            // set size
            f.setSize(screensize.width / 5, screensize.height / 4);
            // center form
            f.setLocation((screensize.width - f.getWidth()) / 2, 
                              (screensize.height - f.getHeight()) / 2);
            f.setResizable(false);
        }
        
        
        pMain.setVisible(true);
        setVisible(true);
        
        if (isApplet == false) {
            f.setVisible(true);
        }
    }
    
    private double getDisplayValue() {
        double d = 0.0;
        String s = display.getText();
        try {
            // Double.parseDouble doesn't work in 1.1v applets
            d = Double.valueOf(s).doubleValue();
        } catch (NumberFormatException e) {
            d = 0.0;
        }
        return d;
    }
    
    
    private void handleFuncKey(Button b) {
        String lbl = b.getLabel();
        
        if ("=CCE".indexOf(lbl) > -1) {
            if (lbl.equals("C")) {
                displayHold = 0d;
                lastFunction = "";
                display.setText("0");
            }
            if (lbl.equals("CE")) {
                display.setText("0");
                lastKeyWasFunction = true;
                return;
            }
            if (lbl.equals("=")) {}
        }
        
        
        if (lastFunction.equals("+")) {
            display.setText("" + (displayHold + getDisplayValue()));
        }
        if (lastFunction.equals("-")) {
            display.setText("" + (displayHold - getDisplayValue()));
        }
        if (lastFunction.equals("*")) {
            display.setText("" + (displayHold * getDisplayValue()));
        }
        if (lastFunction.equals("/")) {
            String r;
            try {
                r = "" + (displayHold / getDisplayValue());
            } catch (ArithmeticException ae) {
                r = "divison error";
                displayHold = 0d;
            }
            display.setText(r);
        }
        
        lastKeyWasFunction = true;
        lastFunction = lbl;
        displayHold = getDisplayValue();
    }
    
    
    private void handleNumKey(Button b) {
        String lbl = b.getLabel();
        
        if (lastKeyWasFunction) {
            display.setText("");
        }
        
        if (lbl.equals(".") || lbl.equals("+/-")) {
            if (lbl.equals(".")) {
                if (display.getText().indexOf(".") == -1) {
                    display.setText(display.getText() + ".");
                }
            } else {
                display.setText("" + getDisplayValue() * -1);
            }
        } else {
            display.setText(display.getText() + lbl);
        }
        
        lastKeyWasFunction = false;
    }
    
    
        
    private class ButtonListener implements ActionListener {
        // buttonType == 0 : number key listener
        // buttonType == 1 : function key listener
        private int listenerType = 0;
        
        ButtonListener(int listenerType) {
            this.listenerType = listenerType;
        }
        
        
        public void actionPerformed(ActionEvent e) {
            Button b = (Button)e.getSource();
            
            if (listenerType == 0) {
                handleNumKey(b);
            } else {
                handleFuncKey(b);
            }
        }
    }
    
    
    private class KeyListener extends KeyAdapter {
        // better to use Keystroke class, but it's not supported in v1.1
        private String lastKey = "";
        
        public void keyPressed(KeyEvent e) {
            Button b = null;
            String targ = "NUMPAD";
            
            String key = e.getKeyText(e.getKeyCode());
            key = key.toUpperCase();

            if (key.indexOf(targ) > -1) {
                key = key.substring(key.indexOf(targ) + 1 + targ.length());
            }
            
            // handle SHIFTed keys
            if (lastKey.equals("SHIFT")) {
                if (key.equals("8")) {
                    key = "*";
                }
                if (key.equals("=")) {
                    key = "+";
                }
            }
            
            if (key.equals("ENTER")) {
                key = "=";
            }
            if (key.equals("MINUS")) {
                key = "-";
            }
            
            
            b = (Button)theKeys.get(key);
            
            if (b != null) {
                if ("0123456789.".indexOf(key) > -1) {
                    handleNumKey(b);
                } else {
                    handleFuncKey(b);
                }
            }
            
            lastKey = key;
        }
    }
}