package com.inspect.tcpserver.sip.utils;

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

public class DigestUtil {

    /**
     * 计算Digest响应值
     * @param username 用户名
     * @param password 密码
     * @param realm 域
     * @param nonce 随机数
     * @param method SIP请求方法，如REGISTER
     * @param uri 请求URI
     * @param nc 请求计数（可以传null或"00000001"初始值）
     * @param cnonce 客户端随机串（可传null）
     * @param qop 质量保护参数（可传null）
     * @return response摘要字符串
     */
    public static String computeResponse(String username, String password, String realm, String nonce,
                                         String method, String uri, String nc, String cnonce, String qop) {
        try {
            String ha1 = md5Hex(username + ":" + realm + ":" + password);
            String ha2 = md5Hex(method + ":" + uri);

            String response;
            if (qop != null && (qop.equals("auth") || qop.equals("auth-int"))) {
                response = md5Hex(ha1 + ":" + nonce + ":" + nc + ":" + cnonce + ":" + qop + ":" + ha2);
            } else {
                response = md5Hex(ha1 + ":" + nonce + ":" + ha2);
            }
            return response;
        } catch (Exception e) {
            throw new RuntimeException("Failed to compute digest response", e);
        }
    }

    /**
     * MD5加密，返回16进制字符串
     */
    private static String md5Hex(String data) throws NoSuchAlgorithmException {
        MessageDigest md = MessageDigest.getInstance("MD5");
        byte[] digest = md.digest(data.getBytes(StandardCharsets.UTF_8));
        return byteArrayToHexString(digest);
    }

    /**
     * 将字节数组转为16进制字符串
     */
    private static String byteArrayToHexString(byte[] bytes) {
        Formatter formatter = new Formatter();
        for (byte b : bytes) {
            formatter.format("%02x", b);
        }
        String res = formatter.toString();
        formatter.close();
        return res;
    }
}