// EuclidGCD.java
// 

import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
import java.util.*;


public class EuclidGCD extends JApplet {

    JTextField numAField;
    JTextField numBField;
    JLabel gcdLabel;
    JTextArea listArea;


    public void init() {

	Container container = getContentPane();
	int panelRowsSize = 3;
	container.setLayout( new GridLayout( panelRowsSize, 1 ) );
	//container.setLayout( new FlowLayout( ) );

	JPanel [] panelRows = new JPanel[panelRowsSize];
	for (int i=0; i<panelRowsSize; i++) {
	    panelRows[i] = new JPanel();
	    panelRows[i].setLayout( new FlowLayout() );
	    container.add( panelRows[i] );
	}

	Font bigFont = new Font( "Monospaced", Font.BOLD, 16 );
        
	numAField = new JTextField( 12 );
	numAField.setFont( bigFont );
	panelRows[0].add( numAField );

	numBField = new JTextField( 12 );
	numBField.setFont( bigFont );
	panelRows[0].add( numBField );

	gcdLabel = new JLabel( "        " );
	gcdLabel.setFont( bigFont );
	panelRows[1].add( gcdLabel );

	listArea = new JTextArea( 10, 30 );
	Font smallFont = new Font( "Monospaced", Font.BOLD, 12 );
	listArea.setFont( smallFont );
	JScrollPane listScroll = new JScrollPane( listArea );
	panelRows[2].add( listScroll );


	numAField.addActionListener( 
        	new ActionListener () {
		    public void actionPerformed( ActionEvent event ) {
			gcd();
		    }
		}
		);

	numBField.addActionListener( 
        	new ActionListener () {
		    public void actionPerformed( ActionEvent event ) {
			gcd();
		    }
		}
		);


    }


    public void start() {
	numAField.requestFocusInWindow();
    }


    void gcd() {
	int numA=0;
	try {
	    numA = Integer.parseInt( numAField.getText() );
	}
	catch (NumberFormatException e) {
	    numAField.setText( "integer please" );
	}
	if ( numA <= 0 )
	    numAField.setText( "positive please" );
	else {
	    int numB=0;
	    try {
		numB = Integer.parseInt( numBField.getText() );
	    }
	    catch (NumberFormatException e) {
		numBField.setText( "integer please" );
	    }
	    if ( numB <= 0 )
		numBField.setText( "positive please" );
	    else {

		int a=numA, b=numB, r;
		listArea.setText( "" );

		//a = Math.abs(a);    //avoid negative gcd
		//b = Math.abs(b);
		
		if (b > a) {   //make sure a is largest
		    int temp=a;
		    a = b;
		    b = temp;
		}
		
		while (b != 0) {
		    r = a % b;
		    listArea.append( a + " " + b + " " + r + "\n" );
		    a = b;
		    b = r;
		}
		
		gcdLabel.setText( "" + a );
		
	    }
	}
    }
    
}