package com.nationalelectric.greenH5.identityAuth.util.devon;

/**
 * 16进制工具类。考虑使用{@link org.apache.commons.codec.binary.Hex}代替
 *
 * @author <a href="mailto:93785732@qq.com">ZhengDaHong@fzfx</a>
 * @since 2017/4/28 15:24
 */
public abstract class HexUtils {

	private final static String HEX_DIGITS_STRING = "0123456789ABCDEF";

	private final static char[] LOWERCASE_HEX_DIGITS = HEX_DIGITS_STRING.toLowerCase().toCharArray();

	private final static char[] UPPERCASE_HEX_DIGITS = HEX_DIGITS_STRING.toCharArray();


	public static String encodeWithLowerCase(byte[] data) {
		return encode(data, true);
	}

	public static String encodeWithUpperCase(byte[] data) {
		return encode(data, false);
	}

	/**
	 * 转换字节数组为16进制字串
	 *
	 * @param data 字节数组
	 * @return 16进制字串
	 */
	public static String encode(byte[] data, boolean useLowercase) {
		StringBuilder result = new StringBuilder();
		for (int i = 0; i < data.length; i++) {
			result.append(encode(data[i], useLowercase));
		}
		return result.toString();
	}

	/**
	 *
	 * @param hexString 必须以两位16进制为一个单位
	 * @return
	 */
	public static byte[] decode(String hexString) {
		if (hexString == null || hexString.equals("")) {
			return null;
		}
		hexString = hexString.toUpperCase();
		int length = hexString.length() / 2;
		char[] hexChars = hexString.toCharArray();
		byte[] d = new byte[length];
		for (int i = 0; i < length; i++) {
			int pos = i * 2;
			d[i] = (byte) (decode(hexChars[pos]) << 4 | decode(hexChars[pos + 1]));

		}
		return d;
	}


	//---------------------------------------------------------------------
	//
	//---------------------------------------------------------------------

	private static byte decode(char c) {
		return (byte) HEX_DIGITS_STRING.indexOf(c);
	}

	private static String encode(byte b, boolean useLowercase) {
		char[] hexDigitsToUse = useLowercase ? LOWERCASE_HEX_DIGITS : UPPERCASE_HEX_DIGITS;
		int i = b;
		if (i < 0)
			i = 256 + i;
		int d1 = i / 16;
		int d2 = i % 16;
		return String.valueOf(hexDigitsToUse[d1]) + hexDigitsToUse[d2];
	}
}