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

namespace Common
{
    public class AesHelper
    {
        public static string QrcodeLoginKey = "zyyxhlywkdatakey";

        /// <summary>
        /// AES 加密
        /// </summary>
        /// <param name="data"></param>
        /// <param name="key"></param>
        /// <returns>Encrypted 16 hex string</returns>
        public static string AesEncrypt(string data, string key = "")
        {
            if (string.IsNullOrWhiteSpace(key))
            {
                key = QrcodeLoginKey.PadRight(16, '0');
            }
            // 256-AES key      
            byte[] keyArray = Encoding.ASCII.GetBytes(key);
            byte[] toEncryptArray = Encoding.ASCII.GetBytes(data);
            RijndaelManaged rDel = new RijndaelManaged
            {
                Key = keyArray,
                Mode = CipherMode.ECB,
                Padding = PaddingMode.PKCS7
            };

            ICryptoTransform cTransform = rDel.CreateEncryptor();
            byte[] resultArray = cTransform.TransformFinalBlock(toEncryptArray, 0,
                    toEncryptArray.Length);

            return BytesToHexString(resultArray);
        }

        /// <summary>
        /// AES 解密
        /// </summary>
        /// <param name="hexString">Encrypted 16 hex string</param>
        /// <param name="key"></param>
        /// <returns>Decrypted string</returns>
        public static string AesDecrypt(string hexString, string key = "")
        {
            if (string.IsNullOrWhiteSpace(key))
            {
                key = QrcodeLoginKey.PadRight(16, '0');
            }
            // 256-AES key      
            byte[] keyArray = Encoding.ASCII.GetBytes(key);
            byte[] toEncryptArray = HexStringToBytes(hexString);

            RijndaelManaged rDel = new RijndaelManaged
            {
                Key = keyArray,
                Mode = CipherMode.ECB,
                Padding = PaddingMode.PKCS7
            };

            ICryptoTransform cTransform = rDel.CreateDecryptor();
            byte[] resultArray = cTransform.TransformFinalBlock(toEncryptArray, 0,
                    toEncryptArray.Length);
            return Encoding.ASCII.GetString(resultArray);
        }

        /// <summary>
        /// Byte array to convert 16 hex string
        /// </summary>
        /// <param name="bytes">byte array</param>
        /// <returns>16 hex string</returns>
        public static string BytesToHexString(byte[] bytes)
        {
            StringBuilder returnStr = new StringBuilder();
            if (bytes != null)
            {
                foreach (var t in bytes)
                {
                    returnStr.Append(t.ToString("X2"));
                }
            }
            return returnStr.ToString();
        }

        /// <summary>
        /// 16 hex string converted to byte array
        /// </summary>
        /// <param name="hexString">16 hex string</param>
        /// <returns>byte array</returns>
        public static byte[] HexStringToBytes(string hexString)
        {
            if (hexString == null || hexString.Equals(""))
            {
                return null;
            }
            int length = hexString.Length / 2;
            if (hexString.Length % 2 != 0)
            {
                return null;
            }
            byte[] d = new byte[length];
            for (int i = 0; i < length; i++)
            {
                d[i] = Convert.ToByte(hexString.Substring(i * 2, 2), 16);
            }
            return d;
        }
    }
}
