package org.kuali.common.util;
   
   public final class Ascii {
   
   	private Ascii() {
   	}
   
   	private static final int LETTER_OFFSET = 13;
   	private static final int NUMBER_OFFSET = 5;
  	private static final char NUMBER_MIDPOINT = '4';
  	private static final char LCASE_MIDPOINT = 'm';
  	private static final char UCASE_MIDPOINT = 'M';
  
  	/**
  	 * Return true if the character is in the range A-Z or a-z
  	 */
  	public static boolean isLetter(char c) {
  		return isLowerCase(c) || isUpperCase(c);
  	}
  
  	/**
  	 * Return true if the character is in the range 0-9
  	 */
  	public static boolean isDigit(char c) {
  		return c >= '0' && c <= '9';
  	}
  
  	/**
  	 * Return true if the character is in the range a-z
  	 */
  	public static boolean isLowerCase(char c) {
  		return c >= 'a' && c <= 'z';
  	}
  
  	/**
  	 * Return true if the character is in the range A-Z
  	 */
  	public static boolean isUpperCase(char c) {
  		return c >= 'A' && c <= 'Z';
  	}
  
  	/**
  	 * <p>
  	 * If the character is a letter or digit, apply the flip algorithm to it, otherwise leave it alone.
  	 * </p>
  	 * 
  	 * The flip algorithm makes the character in the top row become the character in the bottom row, and vice versa.
  	 * 
  	 * <pre>
  	 *  01234 abcdefghijklm ABCDEFGHIJKLM
  	 *  56789 nopqrstuvwxyz NOPQRSTUVWXYZ
  	 * </pre>
  	 */
  	public static char flip(char c) {
  		if (isLowerCase(c)) {
  			if (c > LCASE_MIDPOINT) {
  				return (char) ((int) c - LETTER_OFFSET);
  			} else {
  				return (char) ((int) c + LETTER_OFFSET);
  			}
  		} else if (isUpperCase(c)) {
  			if (c > UCASE_MIDPOINT) {
  				return (char) ((int) c - LETTER_OFFSET);
  			} else {
  				return (char) ((int) c + LETTER_OFFSET);
  			}
  		} else if (isDigit(c)) {
  			if (c > NUMBER_MIDPOINT) {
  				return (char) ((int) c - NUMBER_OFFSET);
  			} else {
  				return (char) ((int) c + NUMBER_OFFSET);
  			}
  		} else {
  			return c;
  		}
  	}
  
  }