import javax.swing.*;
import java.awt.event.*;
import java.awt.Font;
import java.awt.Color;
import java.awt.BorderLayout;
import java.awt.GridLayout;
import java.awt.FlowLayout;


public class Calculator
    extends javax.swing.JPanel
    implements ActionListener
{
    private CalculatorController controller = null;
    private JLabel display = null;
    
    static final String EMPTYSTR = " ";
    
    static final String L_CE = "CE";
    static final String C_CE = "-1";
    static final int    I_CE = -1;
    
    static final String L_C = "C";
    static final String C_C = "-2";
    static final int    I_C = -2;
    
    static final String L_SIGN = "+/-";
    static final String C_SIGN = "-3";
    static final int    I_SIGN = -3;
    
    static final String L_POINT = ".";
    static final String C_POINT = "-4";
    static final int    I_POINT = -4;
    
    static final String L_PUSH = "PUSH";
    static final String C_PUSH = "-5";
    static final int    I_PUSH = -5;
    
    static final String L_POP = "POP";
    static final String C_POP = "-6";
    static final int    I_POP = -6;
    
    static final String L_DIV = "/";
    static final String C_DIV = "-7";
    static final int    I_DIV = -7;
    
    static final String L_MUL = "*";
    static final String C_MUL = "-8";
    static final int    I_MUL = -8;
    
    static final String L_SUB = "-";
    static final String C_SUB = "-9";
    static final int    I_SUB = -9;
    
    static final String L_ADD = "+";
    static final String C_ADD = "-10";
    static final int    I_ADD = -10;
    
    static final Font defaultKeyFont = new Font( "SansSerif", Font.BOLD, 18 );
    static final Font defaultDisplayFont = new Font( "MonoSpaced", Font.BOLD, 18 );
    
    public static boolean isDigit( int eT )
    {
        return( eT >= 0 && eT <= 9 );
    }
    
    public static boolean isOp( int eT )
    {
        return( eT <= I_PUSH && eT >= I_ADD );
    }
    
    class Keypad
        extends JPanel
    {
        Keypad()
        {
            setLayout( new GridLayout( 0, 5, 2, 2 ));
            setBackground( Color.blue );
            setBorder( BorderFactory.createLineBorder( Color.blue, 2 ) );
            setFont( defaultKeyFont ); 
        
            add( new KeyButton( L_PUSH, C_PUSH, Color.green, Calculator.this ));
            add( new KeyButton( "7", Color.black, Calculator.this ));
            add( new KeyButton( "8", Color.black, Calculator.this ));
            add( new KeyButton( "9", Color.black, Calculator.this ));
            add( new KeyButton( L_DIV, C_DIV, Color.red, Calculator.this ));
        
            add( new KeyButton( L_POP, C_POP, Color.green, Calculator.this ));
            add( new KeyButton( "4", Color.black, Calculator.this ));
            add( new KeyButton( "5", Color.black, Calculator.this ));
            add( new KeyButton( "6", Color.black, Calculator.this ));
            add( new KeyButton( L_MUL, C_MUL, Color.red, Calculator.this ));
        
            add( new KeyButton( L_CE, C_CE, Color.green, Calculator.this ));
            add( new KeyButton( "1", Color.black, Calculator.this ));
            add( new KeyButton( "2", Color.black, Calculator.this ));
            add( new KeyButton( "3", Color.black, Calculator.this ));
            add( new KeyButton( L_SUB, C_SUB, Color.red, Calculator.this ));
        
            add( new KeyButton( L_C, C_C, Color.green, Calculator.this ));
            add( new KeyButton( "0", Color.black, Calculator.this ));
            add( new KeyButton( L_SIGN, C_SIGN, Color.black, Calculator.this ));
            add( new KeyButton( L_POINT, C_POINT, Color.black, Calculator.this ));
            add( new KeyButton( L_ADD, C_ADD, Color.red, Calculator.this ));
        }
    }
    
    class KeyButton
        extends JButton
    {   
        KeyButton( String l, ActionListener a )
        {
            super( l );
            setBackground( Color.lightGray );
            addActionListener( a );
        }
    
        KeyButton( String l, Color f, ActionListener a )
        {
            this( l, a );
            setForeground( f );
        }
    
        KeyButton( String l, String c, Color f, ActionListener a )
        {
            this( l, a );
            setForeground( f );
            setActionCommand( c );
        }
    }

    public Calculator()
    {
        setBackground( Color.blue );
        setLayout( new BorderLayout(4, 4) );
        setBorder( BorderFactory.createLineBorder( Color.blue, 2 ) );
        
        JPanel displayPanel = new JPanel();
        displayPanel.setBorder( BorderFactory.createLineBorder( Color.black, 2 ) );
        displayPanel.setBackground( Color.white );
        displayPanel.setLayout( new FlowLayout( FlowLayout.RIGHT ));
        display = new JLabel( EMPTYSTR );
        display.setFont( defaultDisplayFont );
        display.setForeground( Color.black );
        display.setHorizontalAlignment( SwingConstants.RIGHT );
        displayPanel.add( display );

        add( displayPanel, BorderLayout.NORTH );
        add( new Keypad(), BorderLayout.CENTER );
    }
    
    public void setController( CalculatorController cc )
    { controller = cc; }
    
    public CalculatorController getController()
    { return controller; }
    
    public void setDisplay( String s )
    {
        display.setText( s );
    }
    
    public void clearDisplay()
    {
        display.setText( EMPTYSTR );
    }
    
    public void actionPerformed( ActionEvent e )
    {
        if ( controller != null )
            controller.actionPerformed( e );
    }
}