package io.fio.sdk.utils;

public class Hex {

    /**
     * Used to build output as Hex
     */
    private static final char[] DIGITS_LOWER = { '0', '1', '2', '3', '4', '5', '6', '7', '8', '9', 'a', 'b', 'c', 'd', 'e', 'f' };

    /**
     * Used to build output as Hex
     */
    private static final char[] DIGITS_UPPER = { '0', '1', '2', '3', '4', '5', '6', '7', '8', '9', 'A', 'B', 'C', 'D', 'E', 'F' };

    public static char[] encodeHex(final byte[] data) {
        return encodeHex(data, true);
    }

    public static char[] encodeHex(final byte[] data, final boolean toLowerCase) {
        return encodeHex(data, toLowerCase ? DIGITS_LOWER : DIGITS_UPPER);
    }

    protected static char[] encodeHex(final byte[] data, final char[] toDigits) {
        final int l = data.length;
        final char[] out = new char[l << 1];
        // two characters form the hex value.
        for (int i = 0, j = 0; i < l; i++) {
            out[j++] = toDigits[(0xF0 & data[i]) >>> 4];
            out[j++] = toDigits[0x0F & data[i]];
        }
        return out;
    }

    public static byte[] toBytes(final char[] data) throws RuntimeException {

        final int len = data.length;

        if ((len & 0x01) != 0) {
            throw new RuntimeException("Odd number of characters.");
        }

        final byte[] out = new byte[len >> 1];

        // two characters form the hex value.
        for (int i = 0, j = 0; j < len; i++) {
            int f = toDigit(data[j], j) << 4;
            j++;
            f = f | toDigit(data[j], j);
            j++;
            out[i] = (byte) (f & 0xFF);
        }

        return out;
    }

    public static byte[] toBytes(String hex) {
        return toBytes(hex.toCharArray());
    }

    protected static int toDigit(final char ch, final int index) throws RuntimeException {
        final int digit = Character.digit(ch, 16);
        if (digit == -1) {
            throw new RuntimeException("Illegal hexadecimal character " + ch + " at index " + index);
        }
        return digit;
    }

    public static String toHex(final byte[] data) {
        return new String(encodeHex(data));
    }
}