import java.awt.*;
import java.applet.*;

/**
    Program:  Euclidean Algorithm
    Purpose:  computes gcd of two smallish integers by Euclidean Algorithm
    @author:  Paul Garrett, garrett@math.umn.edu
	 copyright Paul Garrett, GNU Public License, 2000
    @version: 18 July 2000
*/

final public class Euclid extends Applet {

  int height, width;
  Color background_color, foreground_color;

  TextField firstTF, secondTF; // to enter the two numbers
  TextArea TA; // to display the computation
  Button computeB; // to do computation, also

  long theX, theY;
  long origX, origY; // the two numbers whose GCD is being computed
  boolean queryOK; // boolean which tells whether data is ok
  // to try to execute algorithm upon

  String ErrorMessage;

  /*********************/

  public void init() {

    try {
		  background_color = 
				new Color(Integer.parseInt(getParameter("background_color"), 16));
		  foreground_color = 
				new Color(Integer.parseInt(getParameter("foreground_color"), 16));
		  height = Integer.parseInt(getParameter("height"));
		  width = Integer.parseInt(getParameter("width"));
    }
    catch (Exception e) {
		  background_color = new Color(0xbaaaaa);
		  foreground_color = new Color(0x503030);
		  height = 320;
		  width = 550;
    }
    setBackground(background_color);
    setForeground(foreground_color);
	 
    setFont(new Font("TimesRoman", Font.PLAIN, 12));
	 
    ErrorMessage = new String("Inputs are too large for the implementation");
    origX = theX = 7654321;
    origY = theY = 56789;
    add(new Label("First "));
    firstTF = new TextField(""+theX, 18);
    add(firstTF);
    add(new Label("  Second "));
    secondTF = new TextField(""+theY, 18);
    add(secondTF);

    computeB = new Button("compute");
    add(computeB);

    TA = new TextArea(35,60);
	 TA.resize(500,500);
	 add(TA);

    queryOK = true; // not OK yet to try to compute
    recursiveComputation();
  }

  final synchronized void recursiveComputation() {
    TA.setText("");
    long q,r;
    r = theX % Math.abs(theY); // ((x % Math.abs(y)) + Math.abs(y)) % Math.abs(y);
    q = theX/Math.abs(theY); // ((x-r)/y;
    TA.appendText(" "+theX+" - ("+q+") * ("+theY+") = "+r);
    theX = theY;
    theY = r;

    while (r != 0) {
      r = theX % Math.abs(theY);
		// ((x % Math.abs(theY)) + Math.abs(y)) % Math.abs(y);
		q = theX/Math.abs(theY); // ((x-r)/y;
      TA.appendText("\n "+theX+" - ("+q+") * ("+theY+") = "+r);
      theX = theY;
      theY = r;
    }
    TA.appendText("\n\n So gcd of ");
	 TA.appendText(origX+" and "+origY);
    TA.appendText(" is "+theX);
  }

  public final synchronized boolean action(Event e, Object arg) {
    if (e.target instanceof TextField || e.target == computeB) {
      String first = Clean.clean(firstTF.getText());
      String second = Clean.clean(secondTF.getText());
      if (first.length() <= 18 && second.length() <= 18) {
			 origX = theX = Long.parseLong(first);
			 origY = theY = Long.parseLong(second);
			 queryOK = true;
      }
      else {
			 queryOK = false;
      }
      if (queryOK) {
			 recursiveComputation();
      }
      else {
			 TA.setText(ErrorMessage); 
      }
      return true;
    }
    else {
		  return false; // old AWT event model...
    }
  } 
	 
} // the end of class EuclideanAlgorithm