using System.Security.Cryptography;
using System.Text;

namespace IotManager.Common
{
    public class Base64
    {
        public static void MainTest()
        {
            // 要加密的原始字符串
            string originalText = "Hello, World!";

            // 加密成Base64字符串
            string base64EncodedText = EncodeBase64(originalText);
            Console.WriteLine("Base64 编码结果: " + base64EncodedText);

            // 解密Base64字符串
            string decodedText = DecodeBase64(base64EncodedText);
            Console.WriteLine("Base64 解码结果: " + decodedText);
        }

        // 使用Base64编码字符串
        public static string EncodeBase64(string text)
        {
            byte[] bytesToEncode = Encoding.UTF8.GetBytes(text);
            string encodedText = Convert.ToBase64String(bytesToEncode);
            return encodedText;
        }

        // 使用Base64解码字符串
        public static string DecodeBase64(string encodedText)
        {
            byte[] decodedBytes = Convert.FromBase64String(encodedText);
            string decodedText = Encoding.UTF8.GetString(decodedBytes);
            return decodedText;
        }



        // 使用3DES-MAC签名消息
        public static string Sign3DESMAC(string key, string message)
        {
            byte[] keyBytes = Encoding.UTF8.GetBytes(key);
            byte[] messageBytes = Encoding.UTF8.GetBytes(message);

            using (TripleDESCryptoServiceProvider des = new TripleDESCryptoServiceProvider())
            {
                des.Key = keyBytes;
                des.Mode = CipherMode.ECB; // 3DES-MAC通常使用ECB模式
                des.Padding = PaddingMode.PKCS7; // PKCS7填充

                using (HMACMD5 hmac = new HMACMD5(des.Key))
                {
                    byte[] hashBytes = hmac.ComputeHash(messageBytes);
                    return BitConverter.ToString(hashBytes).Replace("-", "").ToLower();
                }
            }
        }

        // 验证3DES-MAC签名
        public static bool Verify3DESMAC(string key, string message, string macToVerify)
        {
            string calculatedMAC = Sign3DESMAC(key, message);
            return string.Equals(calculatedMAC, macToVerify, StringComparison.OrdinalIgnoreCase);
        }



        /// <summary>
        /// 取前16个字节
        /// </summary>
        /// <param name="message"></param>
        /// <param name="key"></param>
        /// <returns></returns>
        public static byte[] ComputeHMACSHA256Short(string message, string key)
        {
            using (HMACSHA256 hmac = new HMACSHA256(Encoding.UTF8.GetBytes(key)))
            {
                byte[] messageBytes = Encoding.UTF8.GetBytes(message);
                byte[] fullHash = hmac.ComputeHash(messageBytes);

                // 对完整哈希再做一次SHA256并取前16字节
                using (SHA256 sha = SHA256.Create())
                {
                    byte[] rehashed = sha.ComputeHash(fullHash);
                    byte[] result = new byte[16];
                    Array.Copy(rehashed, result, 16);
                    return result;
                }
            }
        }

        public static byte[] ComputeHMACSHA256(string message, string key)
        {
            using (HMACSHA256 hmac = new HMACSHA256(Encoding.UTF8.GetBytes(key)))
            {
                byte[] messageBytes = Encoding.UTF8.GetBytes(message);
                return hmac.ComputeHash(messageBytes);
            }
        }


        public static bool VerifyHMACSHA256(byte[] message, byte[] key, byte[] expectedMac)
        {
            using (HMACSHA256 hmac = new HMACSHA256(key))
            {
                byte[] computedMac = hmac.ComputeHash(message);
                return CryptographicOperations.FixedTimeEquals(computedMac, expectedMac); // 防止时间攻击
            }
        }


        static void Test()
        {
            string key = "ThisIsASecretKey"; // 密钥长度必须是24字节（192位）
            string message = "Hello, World!";

            // 使用3DES-MAC签名消息
            string mac = Sign3DESMAC(key, message);
            Console.WriteLine("3DES-MAC 签名: " + mac);

            // 验证3DES-MAC签名
            bool isVerified = Verify3DESMAC(key, message, mac);
            if (isVerified)
            {
                Console.WriteLine("消息验证成功！");
            }
            else
            {
                Console.WriteLine("消息验证失败！");
            }
        }
    }
}