package com.gs.xky.config;

import com.alibaba.fastjson.JSONObject;
import com.alibaba.fastjson.TypeReference;

import java.security.MessageDigest;
import java.util.*;


public class SignUtils {
    /*
     * 自定义比较器（比较字符串）
     */
    private static Comparator<String> keyComparator = new Comparator<String>() {
        @Override
        public int compare(String o1, String o2) {
            return o1.compareTo(o2);
        }
    };

    /*
     * 构造签名
     * @param paramJson   ApiCommonParam对象转Json后的字符串
     * @param appSecret
     * @return
     */
    public static String buildCurrentSign(String paramJson, String appSecret) {
        Map<String, String> commonMap = new HashMap<String, String>();
        Map<String, Object> jsonObject = JSONObject.parseObject(paramJson, new TypeReference<Map<String, Object>>() {
        });
        String value = "";
        List<String> keyList = new ArrayList<String>();
        for (Map.Entry<String, Object> entry : jsonObject.entrySet()) {
            value = entry.getValue().toString().trim();
            commonMap.put(entry.getKey(), value);
            if ("sign".equalsIgnoreCase(entry.getKey())) {
                continue;
            }
            keyList.add(entry.getKey());
        }
        // key排序
        Collections.sort(keyList, keyComparator);

        //拼接数据
        StringBuilder sb = new StringBuilder();
        for (String k : keyList) {
            sb.append(commonMap.get(k)).append(":");
        }
        sb.append(appSecret);

        // 计算MD5
        String signStr = null;
        try {
            signStr = getMD5(sb.toString());
        } catch (Exception e) {
            e.printStackTrace();
            return null;
        }
        return signStr.toLowerCase();
    }

    /*
     * 得到MD5值
     * @param str
     * @return
     * @throws Exception
     */
    private static String getMD5(String str) throws Exception {
        if (str == null || str.length() == 0) {
            return null;
        }
        StringBuffer ret = new StringBuffer();
        try {
            MessageDigest digest = MessageDigest.getInstance("MD5");
            digest.update(str.getBytes("UTF-8"));
            byte[] hash = digest.digest();
            // 转为ASCII码,byte为8位,计算机为32位,采用补码形式,所以要补全.
            for (byte b : hash) {
                if ((0xFF & b) < 0x10) {
                    ret.append("0" + Integer.toHexString((b & 0xFF)));
                } else {
                    ret.append(Integer.toHexString(b & 0xFF));
                }
            }
        } catch (Exception e) {
            e.printStackTrace();
            throw e;
        }
        return ret.toString().toUpperCase();
    }

}