/**
@author  Scott Marshall
@author  University of Glasgow, MSc IT Project 2001
@author  Building an OnLine Course in Computing Fundamentals
*/


package ukacgla_BinaryConverter;

import javax.swing.*; 
import javax.swing.text.*; 

import java.awt.Toolkit;
import java.text.ParseException;
import java.util.Locale;

/** Code based on example Integer checking program Sun Microsystems Site. 
Validates user entered text as a specific format of String. Other entries are not allowed.
Error message displayed if user inputs any value except 0 or 1.*/
public class WholeNumberField extends JTextField {
  
    private Toolkit toolkit;

    public WholeNumberField(String value, int columns) {
        super(columns);
		toolkit = Toolkit.getDefaultToolkit(); 
        setValue(value);
    }

  
  	/**
	This is the key method. getValue() is called everytime the table is updated. 
	This method checks it is either a string 0 or 1. 
	If anything else is entered a new InvalidEntryException is thrown.	
	*/  
    protected String getValue() throws InvalidEntryException {
		String retVal = "";
		if (this.getText().equals("0"))
			retVal = "0";

		else if (this.getText().equals("1"))
			retVal = "1";

		else 
			throw new InvalidEntryException("Input must be 0 or 1");

		return retVal;	

    }

  	/**
	This sets the value. All entries have been validated by this stage, and value must
	be either 0 or 1	
	*/  
    private void setValue(String value) {
		if (value.equals("0"))
			setText(value);	
        else if (value.equals("1"))
			setText(value);			
		else 
			System.out.println(value);
		
    }

    protected Document createDefaultModel() {
        return new WholeNumberDocument();
    }



    private class WholeNumberDocument extends PlainDocument {
        public void insertString(int offs, 
                                 String str,
                                 AttributeSet a) 
                throws BadLocationException {
            char[] source = str.toCharArray();
            char[] result = new char[source.length];
            int j = 0;

            for (int i = 0; i < result.length; i++) {
                if (Character.isDigit(source[i]))
                    result[j++] = source[i];
                else {
                    toolkit.beep();
                }
            }
            super.insertString(offs, new String(result, 0, j), a);
        }
    }
}