package com.gzlh.utils;

import cn.hutool.core.util.StrUtil;

import javax.xml.bind.DatatypeConverter;

public class CRC16Util {
    private static final int PRESET_VALUE = 0xFFFF;
    private static final int POLYNOMIAL = 0x8408;

    /**
     * 计算CRC16校验值
     * @param bytes 需要计算的字节数组
     * @return CRC16校验值
     */
    /**
     * 计算CRC16校验值
     * @param bytes 需要计算的字节数组
     * @return CRC16校验值
     */
    /**
     * 计算CRC16校验值
     *
     * @param bytes 需要计算的字节数组
     * @return CRC16校验值
     */
    public static int calculateCRC16(byte[] bytes) {
        int crcValue = PRESET_VALUE;

        for (byte b : bytes) {
            // 将byte转换为无符号整数
            int unsignedByte = b & 0xFF;
            crcValue = crcValue ^ unsignedByte;

            for (int j = 0; j < 8; j++) {
                if ((crcValue & 0x0001) != 0) {
                    crcValue = (crcValue >> 1) ^ POLYNOMIAL;
                } else {
                    crcValue = crcValue >> 1;
                }
            }
        }

        return swapCRC16Bytes(crcValue);
    }

    /**
     * 将CRC16的高低位进行交换
     *
     * @param crc 原始CRC16值
     * @return 交换后的CRC16值
     */
    public static int swapCRC16Bytes(int crc) {
        // 获取高字节和低字节
        int highByte = (crc >> 8) & 0xFF;  // 右移8位得到高字节
        int lowByte = crc & 0xFF;          // 与0xFF相与得到低字节

        // 交换高低字节
        return (lowByte << 8) | highByte;
    }

    /**
     * 获取CRC16校验值的十六进制字符串
     *
     * @param bytes 需要计算的字节数组
     * @return CRC16校验值的十六进制字符串
     */
    public static String getCRC16Hex(byte[] bytes) {
        int crc = calculateCRC16(bytes);
        return String.format("%04X", crc);
    }

    public static String getCRC16Hex(String hexStr) {
        int crc = calculateCRC16(DatatypeConverter.parseHexBinary(hexStr));
        return String.format("%04X", crc);
    }


    // 测试方法
    public static void main(String[] args) {
        System.out.println("E20000001A0C02721820ECB8".length());
        // 测试数据
        String command = "2D000101030CE200001B170902202610C3A60CFEDC000000000000008102BA0CE200001D8817007817602D1F793F";
        int len = command.length();
        String crcStr = StrUtil.sub(command, len - 4, len);
        String packetStr = StrUtil.sub(command, 0, len - 4);
        String dataPack=StrUtil.subSuf(packetStr,10);
        int cardNum=Integer.parseInt(StrUtil.sub(packetStr,8,10));
        int startIndex=2;
        for (int i = 0; i < cardNum; i++) {
            String cardHex = StrUtil.sub(dataPack, startIndex, startIndex+24);
            startIndex += 26;
            System.out.println(cardHex);
        }
    }
}