package net.educoder.util;

import org.springframework.util.DigestUtils;

import java.io.UnsupportedEncodingException;
import java.util.Arrays;
import java.util.Map;

/**
 * @Author: youys
 * @Date: 2022/4/20
 * @Description:
 */
public class SignatureUtil {

    /**
     * 按字典排序签名.
     *
     * @param secretKey
     * @param params
     * @return
     * @throws UnsupportedEncodingException
     */
    public static String genSignature(String secretKey, Map<String, Object> params) {
        if (secretKey == null || params == null || params.size() == 0) {
            return "";
        }
        // 1. 参数名按照ASCII码表升序排序
        String[] keys = params.keySet().toArray(new String[0]);
        Arrays.sort(keys);
        // 2. 按照排序拼接参数名与参数值
        StringBuffer paramBuffer = new StringBuffer();
        for (String key : keys) {
            paramBuffer.append("&" + key).append(params.get(key) == null ? "" : "=" + params.get(key));
        }
        // 3. 将secretKey拼接到最后
        paramBuffer = paramBuffer.append("&sk=" + secretKey);
        String pa = paramBuffer.substring(1);
        // 4. MD5是128位长度的摘要算法，用16进制表示，一个十六进制的字符能表示4个位，所以签名后的字符串长度固定为32个十六进制字符。
        try {
            return DigestUtils.md5DigestAsHex(pa.getBytes("UTF-8")).toUpperCase();
        } catch (UnsupportedEncodingException e) {
            return "";
        }
    }

}