/*
 ******************************************************************************
 * Source Code         : NineDivisorAxiomApplet.java                          *
 * Description         : Determine which digit the user circled by using a    *
 *                       known axiom.                                         *
 * Version             : 1.0.0                                                *
 * Programmer          : Christopher V. Bellini                               *
 *                                                                            *
 * ----------------                                                           *
 * | REVISION LOG |                                                           *
 *----------------------------------------------------------------------------*
 * Programmers Notes:                                                         *
 *     - cvb (07/29/2005): V1.0.0 completed                                   *
 *                                                                            *
 * ///////////////////////////////////////////////////////////////////////////*
 *  This library is free software; you can redistribute it and/or modify it   *
 *  under the terms of the GNU Lesser General Public License as published by  *
 *  the Free Software Foundation; either version 2.1 of the License,          *
 *  or (at your option) any later version.  This library is distributed in the*
 *  hope that it will be useful, but WITHOUT ANY WARRANTY; without even the   *
 *  implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  *
 *  See the GNU Lesser General Public License for more details.               *
 *                                                                            *
 *  You should have received a copy of the GNU Lesser General Public          *
 *  License along with this library; if not, visit:                           *
 *  http://www.gnu.org/licenses/lgpl.txt or write to the Free Software        *
 *  Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA*
 * ///////////////////////////////////////////////////////////////////////////*
 *----------------------------------------------------------------------------*
 */

import java.applet.*;
import java.awt.*;
import java.lang.*;
import java.awt.event.*;
import java.util.*;


public class NineDivisorAxiomApplet extends Applet implements ActionListener
{
    private Button cmdEnterButton;
    private TextField txtNumber;
    private String strResult;
    private String strNumberEntered;
    private boolean bError;


    // Purpose: Initialize the applet.
    //       I: (none)
    //       O: (none)
    public void init()
    {
        // Use a FlowLayout to hold a text field for the user to enter their
        // number into and a button to begin the "guessing".
        setLayout(new FlowLayout());
        txtNumber = new TextField("", 4);
        cmdEnterButton = new Button("Enter");
        add(txtNumber);
        add(cmdEnterButton);

        // Attach action listener to the "Enter" button.
        cmdEnterButton.addActionListener(this);
     }


    // Purpose: Process onPaint events in the applet's window.
    //       I: Graphics object
    //       O: (none)
    public void paint(Graphics g)
    {
        // If the user didn't enter a 2 or 3 digit number
        // or they tried to enter non-digits, then set
        // set the font colour to red to show that we
        // mean business.
        //
        // Write the result to the screen.
        if (bError == true)
            g.setColor(Color.red);

        g.drawString(strResult, 20, 80);
    }


    // Prupose: Listen for when events are fired.
    //       I: ActionEvent object
    //       O: (none)
    public void actionPerformed(ActionEvent evt)
    {
    	String strMissingNumber;
    	int iMissingNumber;


        // If the user clicked the "Enter" button, retrieve the number and
        // check to see if a valid number was entered (contains only 2 or
        // 3 digits).  Store an error message in the result string if the
        // number wasn't valid.  If the number was valid, determine which
        // digit the user circled.
        if (evt.getSource() == cmdEnterButton)
        {
            strNumberEntered = txtNumber.getText();

            if ((strNumberEntered.length() < 2) ||
                (strNumberEntered.length() > 3))
            {
                bError = true;
                strResult = "Error: Enter a 2 or 3 digit number.";
            }
            else if (!IsNumeric(strNumberEntered))
            {
                bError = true;
        	strResult = "Error: Numbers only, please.";
            }
            else
            {
                bError = false;
        	iMissingNumber = DetermineDigit(Integer.parseInt(strNumberEntered),
                                                strNumberEntered.length());
                strResult = "Chris predicts your number is " +
                            Integer.toString(iMissingNumber) + ".";
            }

            repaint();
        }
    }


    // Purpose: Find which digit the user circled by using the
    //          axiom that states that the sum of the digits of a
    //          3 or 4 digit number is always evenly divisble by 9.
    //       I: number entered
    //       I: number of digits in the number entered
    //       O: the circled digit
    public int DetermineDigit(int iEntered, int iLen)
    {
    	int iSum = 0;


        // Sum up the digits of the number.
    	while (iEntered > 0)
    	{
    	    iSum += (iEntered % 10);
    	    iEntered /= 10;
    	}

        // Find which digit, when added to the existing sum of
        // digits of the entered number, results in a new number
        // evenly divisible by 9.
    	for (int j = 1; j <= 9; j++ )
    	{
    	    if (((iSum + j) % 9) == 0)
    	    {
    		return j;
    	    }
    	}

    	return -1;
    }


    // Purpose: Determine if the entered string value contains
    //          only numeric values.
    //       I: string
    //       O: true=numeric, false=contains non-numeric characters
    public boolean IsNumeric(String var)
    {
        int iNum = 0;
    	boolean bNumeric = false;
      	StringBuffer sbTemp = new StringBuffer();
      	byte[] b = var.getBytes();


     	for (int i = 0; i < b.length; i++)
     	{
    	    // check if each byte is 0-9
     	    if((int)b[i] < 58 && (int)b[i] >= 48)
            {
    	        // add it to the StringBufer as a char
     	 	sbTemp.append((char)b[i]);
     	 	bNumeric = true;
            }
     	    else
     	    {
     	 	bNumeric = false;

                // non-numeric character found, don't continue with this string
     	 	break;
     	    }
      	}

        return bNumeric;
      }
}