package com.ctg.ai.platform.demo.util;


import org.apache.commons.lang3.RandomStringUtils;

import java.nio.charset.StandardCharsets;
import java.security.MessageDigest;
import java.security.NoSuchAlgorithmException;
import java.util.*;


public class OpenApiUtil {

    private static final String KEY_SEPARATOR = "&";
    /** ak 由管理员提供 */
    private static final String HTTP_HEADER_YL_APPCODE = "YL-3rd-Appcode";
    /** 时间戳 单位毫秒 */
    private static final String HTTP_HEADER_YL_TIMESTAMP = "YL-Timestamp";
    /** 8位随机数 */
    private static final String HTTP_HEADER_YL_RANDOM = "YL-Random";
    /** 签名 */
    private static final String HTTP_HEADER_YL_SIGNATURE = "YL-Signature";


    /**
     * 组装验签头部
     * @param appKey
     * @param appSecret
     * @param paramMap
     * @return
     */
    public static Map<String, String> buildHeaders(String appKey, String appSecret, Map<String, String[]> paramMap) {
        if (appKey == null || appSecret == null) {
            return null;
        }
        // 组装前置条件
        Long timestamp = System.currentTimeMillis();
        String random = RandomStringUtils.randomAlphanumeric(8);
        // 计算签名
        String signature = buildSignature(appKey, appSecret, random, timestamp, paramMap);
        // 组装HTTP头部
        return buildHeaders(appKey, random, timestamp, signature);
    }

    /**
     * 签名
     * @param appKey
     * @param appSecret
     * @param random
     * @param timestamp
     * @param paramMap
     * @return
     */
    private static String buildSignature(String appKey, String appSecret, String random, Long timestamp, Map<String, String[]> paramMap) {
        if (appKey == null || appSecret == null || random == null || timestamp == null) {
            return null;
        }
        // 组成签名前原串
        StringBuilder sb = new StringBuilder();
        if (paramMap != null && paramMap.size() > 0) {
            List<String> keys = new ArrayList<>(paramMap.keySet());
            // 参数排序 (ASCII 升序)
            Collections.sort(keys);
            for (String key : keys) {
                String val = paramMap.get(key)[0];
                sb.append(key).append("=").append(val).append(KEY_SEPARATOR);
            }
        }
        sb.append(appSecret).append(KEY_SEPARATOR)
                .append(timestamp).append(KEY_SEPARATOR)
                .append(random).append(KEY_SEPARATOR)
                .append(appKey);
        //System.out.println("text=\n"+sb);
        return sha256(sb.toString().getBytes(StandardCharsets.UTF_8));
    }

    /**
     * 组装验签头部
     * @param appKey
     * @param random
     * @param timestamp
     * @param signature
     * @return
     */
    private static Map<String, String> buildHeaders(String appKey, String random, Long timestamp, String signature) {
        Map<String, String> headers = new HashMap<>(4);
        if (appKey != null) {
            headers.put(HTTP_HEADER_YL_APPCODE, appKey);
        }
        if (random != null) {
            headers.put(HTTP_HEADER_YL_RANDOM, random);
        }
        if (timestamp != null) {
            headers.put(HTTP_HEADER_YL_TIMESTAMP, ""+timestamp);
        }
        if (signature != null) {
            headers.put(HTTP_HEADER_YL_SIGNATURE, signature);
        }
        return headers;
    }

    // 哈希部分逻辑
    private static final char[] LOWER_HEX_DIGITS =
            new char[]{'0', '1', '2', '3', '4', '5', '6', '7', '8', '9', 'a', 'b', 'c', 'd', 'e', 'f'};
    private static final String MD5_ALGORITHM_NAME = "MD5";
    private static final String SHA256_ALGORITHM_NAME = "SHA-256";

    public static String md5(byte[] data) {
        return encodeAsHexString(MD5_ALGORITHM_NAME, data);
    }

    public static String sha256(byte[] data) {
        return encodeAsHexString(SHA256_ALGORITHM_NAME, data);
    }

    /**
     * 使用 {@code algorithmName} 加密算法编码 {@code data}
     * @param algorithmName 算法名
     * @param data 被编码的字节数组
     * @return {@code data} 编码后的小写 16 进制形式字符串
     * @throw IllegalStateException 当找不到 {@code algorithmName} 对应算法
     */
    private static String encodeAsHexString(String algorithmName, byte[] data) {
        try {
            byte[] hash = MessageDigest.getInstance(algorithmName).digest(data);
            return new String(encodeHex(hash));
        } catch (NoSuchAlgorithmException e) {
            throw new IllegalStateException("MessageDigest 找不到算法：" + algorithmName, e);
        }
    }

    private static char[] encodeHex(byte[] data) {
        int l = data.length;
        char[] arr = new char[l << 1];
        int i = 0;
        for(int j = 0; i < l; ++i) {
            arr[j++] = LOWER_HEX_DIGITS[(240 & data[i]) >>> 4];
            arr[j++] = LOWER_HEX_DIGITS[15 & data[i]];
        }
        return arr;
    }

    public static void main(String[] args) {
        String ak = "ak";
        String sk = "sk";
        Map<String, String[]> paramMap = new HashMap<>(2);
        paramMap.put("param2", new String[]{"456","789"});
        paramMap.put("param1", new String[]{"123"});

        Map<String, String> header = buildHeaders(ak, sk, paramMap);
        System.out.println("header="+header);
    }
}