package Utilities;
//======================================================================
//  PROJECT:            _programming.java_
//  FILE:               Keypad.java
//  PURPOSE:            Chapter 7 demo program, NumField class
//  VERSION:            1.0
//  TARGET:             Java v1.1
//  UPDATE HISTORY:     1.0    11/2/98     
//======================================================================

//------------------------------ IMPORTS -------------------------------

import java.awt.*;

//========================== NumField CLASS ============================

/**
 * A NumField stores and displays the text representation of
 * a floating-point number. We've designed this class so that
 * at any time, its display is either empty or contains a
 * legal representation of a floating-point number.
 */
public class NumField extends TextField
{
    boolean hasDecimalPoint = false;
	
    /**
     * Default constructor--build a NumField eight columns wide,
     * initially empty.
     */
    public NumField()
    {
        super(8);                   // Call the superclass constructor.
        super.setText("");
        setEditable(false);    		// Don't let the user in.
        hasDecimalPoint = false;
        setBackground(Color.white);
    }
	
   /**
     * Returns the value represented by this field's text,
     * or zero, if the text is empty or just contains a minus sign.
     */
    public double getValue()
    {
        if ((getText().equals("")) || (getText().equals("-")))
        {
            return 0.0;
        }
        else
        {
            Double d = new Double(getText());
            return d.doubleValue();
        }
    }
    
    /**
     * Set the text to represent the double value of the argument.
     */
    public void setValue(double d)
    {
        super.setText(String.valueOf(d));
    }
	
    /**
     * Set the text to be the empty String.
     */
    public void clear()
    {
        super.setText("");
        hasDecimalPoint = false;
    }
    
    /**
     * Append the character c to the end of the text.
     * We check that this method will result
     * in a legal number representation, and do nothing
     * if the char to be appended would result in an
     * invalid number representation.
     */
    public void append(char c)
    {
        if (isLegal(c))
        {
            if (c == '.')
            {
                hasDecimalPoint = true;
            }
										
            if ((getText()).equals("0"))
            {
                super.setText("");
            }
			
            super.setText(getText() + c);
        }
    }
    
    /**
     * Append the first character of s to the end of the text.
     * This uses the other version of append() to ensure
     * the representation is valid.
     */
    public void append(String s)
    {
        char c = s.charAt(0);
        append(c);
    }
    
    /**
     * Override of the TextComponent method.  We don't want to
     * allow the user to change the text arbitrarily.
     */
    public void setText(String s)
    { }
	
    //-------------- Utility -------------
    
    /**
     * Returns true if and only of c could legally be appended to
     * the end of the text.  In other words, return true if
     * (1) c is a digit, or (2) if c would be the only decimal point
     * in the text representation, or (3) if c is '-' and the current
     * text is 0 or empty.
     */
    private boolean isLegal(char c)
    {
        if (Character.isDigit(c))
        {
            return true;
        }
        else if (c == '.')
        {
            return !hasDecimalPoint;
        }
        else if ((c == '-') && 
                 ((getText().equals("")) || (getText().equals("0"))))
        {
            return true;
        }
        else
        {
            return false;
        }
    }
}