/**********************************************************************
 * Matt Kretchmar
 * April 1, 2006
 * Cryptogram.java
 * This program prompts the user to enter a famous quote or phrase.
 * It then uses a permuted alphabet to substitute letters in the
 * phrase to create a scrambled version of the quote.  Basically, 
 * this program creates a cryptogram puzzle.
 ***********************************************************************/
import java.util.Scanner;
import java.util.Random;

class Cryptogram
{
    public static void main ( String args[] )
    {
        // prompt the user for a famous quote or phrase
        String quote = getQuote();
        // create an array with 'A'...'Z' letters
        char key[] = getAlphabet();
        // print the quote
        print(quote);
        // print the alphabet
        print(key);
        // randomly re-order the alphabet
        permute(key);
        // print the shuffled alphabet
        print(key);
        // scramble the quote by using the shuffled alphabet (key)
        String puzzle = scramble(key,quote);
        // print the scrambled quote
        print(puzzle);
    }
  
    /**
     * A method to read the user's quote, convert all letters
     * to uppercase and return the quote.
     */
    public static String getQuote ( )
    {
        System.out.println("Enter a famous quote or phrase: ");
        Scanner keyboard = new Scanner(System.in);
        return (keyboard.nextLine()).toUpperCase();
    }
    
    /**
     * A method to create and return an array of 26 characters
     * containing the upper case alphabet.
     */
    public static char[] getAlphabet()
    {
        char a[] = new char[26];
        for ( int i = 0; i < 26; i++ )
            a[i] = (char)('A' + i);
        return a;
    }

    /**
     * A method to print an array of characters.
     */
    public static void print ( char a[] )
    {
        System.out.println(a);
    }
    
    /**
     * A method to print a string.
     */
    public static void print ( String s )
    {
        System.out.println(s);
    }
    
    /**
     * This method permutes the charaters in the array
     * in a new random order.  Each character has equal
     * probability of ending up in each location.
     */
    public static void permute ( char a[] )
    {
        Random generator = new Random();
        for ( int i = 0; i < a.length-1; i++ )
        {
            int position = generator.nextInt(a.length-i)+i;
            char temp = a[i];
            a[i] = a[position];
            a[position] = temp;
        }
    }
    
    /**
     * This method creates a new "scrambled" version of the
     * phrase input string.  It uses the permuted alphabet in
     * the key array to make the letter substitutions. 
     */
    public static String scramble ( char key[], String phrase )
    {
        String puzzle = "";
        for ( int i = 0; i < phrase.length(); i++ )
        {
            char c = phrase.charAt(i);
            if ( c >= 'A' && c <= 'Z' )
            {
                int position = phrase.charAt(i) - 'A';
                puzzle = puzzle + key[position];
            }
            else
            {
                puzzle = puzzle + c;
            }
        }
        return puzzle;
    }
}