using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;


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

namespace CommonObj.common
{
    public sealed class CustomEncryption
    {
        //private static string key = "sfdjf48mdfdf3054";
        //private static string key = "sfdjf48mdfdf3054123";

        public CustomEncryption()
        {
        }
        /// <summary>
        /// Mã hóa dựa trên thuật toán mã hóa 1 chiều MD5, 
        /// Sau khi mã hóa, sử dụng thuật toán encode Base64 để lưu dưới dạng Text
        /// </summary>
        /// <param name="plainText">Chuỗi cần mã hóa</param>
        /// <returns></returns>
        public static string EncryptUseMD5(string plainText)
        {
            string encrypted = null;
            MD5CryptoServiceProvider hashmd5 = new MD5CryptoServiceProvider();
            byte[] pwdhash = hashmd5.ComputeHash(ASCIIEncoding.ASCII.GetBytes(plainText));
            encrypted = Convert.ToBase64String(pwdhash);
            return encrypted;
        }
        /// <summary>
        /// Mã hóa dựa trên thuật toán mã hóa phức hợp, có thể giải mã sử dụng hàm Decrypt, 
        /// Sau khi mã hóa, sử dụng thuật toán encode Base64 để lưu dưới dạng Text
        /// </summary>
        /// <param name="plainText">Chuỗi cần mã hóa</param>
        /// <returns></returns>
        public static string Encrypt(string clearText, string EncryptionKey)
        {
            //string EncryptionKey = "abc123";
            byte[] clearBytes = Encoding.Unicode.GetBytes(clearText);
            using (Aes encryptor = Aes.Create())
            {
                Rfc2898DeriveBytes pdb = new Rfc2898DeriveBytes(EncryptionKey, new byte[] { 0x49, 0x76, 0x61, 0x6e, 0x20, 0x4d, 0x65, 0x64, 0x76, 0x65, 0x64, 0x65, 0x76 });
                encryptor.Key = pdb.GetBytes(32);
                encryptor.IV = pdb.GetBytes(16);
                using (MemoryStream ms = new MemoryStream())
                {
                    using (CryptoStream cs = new CryptoStream(ms, encryptor.CreateEncryptor(), CryptoStreamMode.Write))
                    {
                        cs.Write(clearBytes, 0, clearBytes.Length);
                        cs.Close();
                    }
                    clearText = Convert.ToBase64String(ms.ToArray());
                }
            }
            return clearText;
        }
        public static string Decrypt(string cipherText, string EncryptionKey)
        {
            //string EncryptionKey = "abc123";
            try
            {
                cipherText = cipherText.Replace(" ", "+");
                byte[] cipherBytes = Convert.FromBase64String(cipherText);
                using (Aes encryptor = Aes.Create())
                {
                    Rfc2898DeriveBytes pdb = new Rfc2898DeriveBytes(EncryptionKey, new byte[] { 0x49, 0x76, 0x61, 0x6e, 0x20, 0x4d, 0x65, 0x64, 0x76, 0x65, 0x64, 0x65, 0x76 });
                    encryptor.Key = pdb.GetBytes(32);
                    encryptor.IV = pdb.GetBytes(16);
                    using (MemoryStream ms = new MemoryStream())
                    {
                        using (CryptoStream cs = new CryptoStream(ms, encryptor.CreateDecryptor(), CryptoStreamMode.Write))
                        {
                            cs.Write(cipherBytes, 0, cipherBytes.Length);
                            cs.Close();
                        }
                        cipherText = Encoding.Unicode.GetString(ms.ToArray());
                    }
                }
                return cipherText;
            }
            catch (Exception ex)
            {
                return "";
            }


        }
    }
}