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

namespace BF
{
    public class AesEncrypt
    {
        const int PASSWORD_LENGTH = 32; //密钥长度16，24，32
        static byte[] IV = new byte[]
        {
            0x00, 0x01, 0x02, 0x03,
            0x04, 0x05, 0x06, 0x07,
            0x08, 0x09, 0x0A, 0x0B,
            0x0C, 0x0D, 0x0E, 0x0F
        }; //只能16字节

        static AesCryptoServiceProvider aesProvider;

        static void Init(string key, bool fromBase64 = false)
        {
            if (null == aesProvider)
            {
                aesProvider = new AesCryptoServiceProvider
                {
                    // KeySize = PASSWORD_LENGTH,
                    IV = IV,
                    Mode = CipherMode.ECB,
                    Padding = PaddingMode.PKCS7,
                };
            }
            if (!string.IsNullOrEmpty(key))
            {
                if (fromBase64)
                    key = Encoding.UTF8.GetString(Convert.FromBase64String(key));
                key = GenPassWord(key);
                var keyBytes = Encoding.UTF8.GetBytes(key);
                aesProvider.Key = keyBytes;
            }
        }

        /// <summary>
        /// 纯aes加密
        /// </summary>
        static public byte[] Encrypt(byte[] buffer, string key)
        {
            Init(key);
            var encrytor = aesProvider.CreateEncryptor();
            byte[] finalArray = encrytor.TransformFinalBlock(buffer, 0, buffer.Length);
            encrytor.Dispose();
            return finalArray;
        }

        /// <summary>
        /// 纯aes解密
        /// </summary>
        static public byte[] Decrypt(byte[] buffer, string key)
        {
            Init(key);
            var decrytor = aesProvider.CreateDecryptor();
            byte[] finalArray = decrytor.TransformFinalBlock(buffer, 0, buffer.Length);
            decrytor.Dispose();
            return finalArray;
        }

        static string GenPassWord(string key)
        {
            int len = key.Length;
            if (len < PASSWORD_LENGTH)
            {
                key = key.PadRight(PASSWORD_LENGTH, 'D');
            }
            else if (len > PASSWORD_LENGTH)
            {
                key = key.Substring(0, len);
            }
            return key;
        }

        static public void Clear()
        {
            if (null != aesProvider)
            {
                aesProvider.Clear();
            }
        }
    }
}