public class Lab04 {
    private static final String eKey = "foobarbaz";
    private static final String dKey = "aoq.geasl";
    public static void main(String[] args) {
        /* Converts the encryption key into a matrix */
        int[][] eMatrix = keyToMatrix(eKey);
        /* Converts the decryption key into a matrix */
        int[][] dMatrix = keyToMatrix(dKey);
        /* Our plaintext to be encrypted */
        String text = "hello, test.";
        String cipher = transform(eMatrix, text);
        /* The below should be "nuvfxprhkjn " */
        System.out.println("\"" + cipher + "\"");
        /* The below should be "hello, test." */
        System.out.println("\"" + transform(dMatrix, cipher) + "\"");
    }

    /**
     * Converts a character into its integer equivalent for the Hill cipher.
     * <p>
     * This means a = 1; b = 2; c = 3; ... ; z = 25; SPACE=26, .=27, COMMA=28.
     *
     * @param c The character which is being converted.
     */
    public static int charToNumber(char c) {
        switch (c) {
            case ' ':  return 26;
            case '.':  return 27;
            case ',':  return 28;
            default:   return c - 'a';
        }
    }

    /**
     * Performs a matrix by vector multiplication modulo 29.
     *
     * @param matrix The matrix being multiplied
     * @param vector The vector to multiply by
     */
    public static int[] multiply(int[][] matrix, int[] vector) {
        /* TODO 2:  Write this method. */
    }

    /**
     * Converts text to an array.  The text must consist only of lowercase
     * letters.  The conversion is a=0, b=1, c=2, etc.
     *
     * @param text The text; must consist only of lowercase letters.
     */
    public static int[] stringToArray(String text) {
        /* TODO 3:  Write this method. */
    }

    /**
     * Converts an array given from stringToArray back to a String.
     *
     * @param array The array to convert.
     */
    public static String arrayToString(int[] array) {
        /* The accumulating variable for the end result. */
        String r = "";

        /* TODO 4:  Write the loop to convert the array back to a String.  You
         *          should store the result in r.
         */

        return r;
    }

    /**
     * Encrypts some text with the Hill cipher.  The text must consist of only
     * lowercase letters and must be a multiple of the length of the key matrix.
     * The encryption encrypts the text in blocks and returns the concatenation
     * of the results.
     *
     * @param key  The key matrix.  Must be be of dimensions N by N.
     * @param text The text to encrypt.  Must be of length k*N, k is an integer.
     */
    public static String transform(int[][] key, String text) {
        // The number of blocks of text that you'll have to encrypt.
        int blocks = text.length() / key.length;
        // The size of each block
        int size = key.length;
        // The variable that accumulates the result from each block
        String result = "";

        /* TODO 5:  Write the code to encrypt each block. */

        return result;
    }

    /**
     * Transforms a text key to a matrix key.  The text key must consist only of
     * lowercase letters.  The conversion is a=0, b=1, c=2, etc.
     *
     * @param key The text key; must consist only of lowercase letters.
     */
    public static int[][] keyToMatrix(String key) {
        // The length of one side of the matrix.
        int length = (int)Math.sqrt(key.length());

        /* TODO 6:  Write the loop(s) to convert the key into a 2D matrix. */
    }
}