using System;
using System.Text;
using System.Linq;

namespace AllBase
{

    /// <summary>
    /// 实现Base64加密解密
    /// 作者：周公
    /// 时间：2007
    /// </summary>
    public static class Base64Encode
    {
        /// <summary>
        /// Base64加密
        /// </summary>
        /// <param name="codeName">加密采用的编码方式</param>
        /// <param name="source">待加密的明文</param>
        /// <returns></returns>
        public static string EncodeBase64(Encoding encode, string source)
        {
            byte[] bytes = encode.GetBytes(source);
            try
            {
                string code = Convert.ToBase64String(bytes);
                return code;
            }
            catch
            {
                return source;
            }
            
        }

        /// <summary>
        /// Base64加密，采用utf8编码方式加密
        /// </summary>
        /// <param name="source">待加密的明文</param>
        /// <returns>加密后的字符串</returns>
        public static string EncodeBase64(string source)
        {
            return EncodeBase64(Encoding.UTF8, source);
        }

        /// <summary>
        /// Base64解密
        /// </summary>
        /// <param name="codeName">解密采用的编码方式，注意和加密时采用的方式一致</param>
        /// <param name="result">待解密的密文</param>
        /// <returns>解密后的字符串</returns>
        public static string DecodeBase64(Encoding encode, string result)
        {
            string decode = "";
            try
            {
                byte[] bytes = Convert.FromBase64String(result);
                decode = encode.GetString(bytes);
            }
            catch
            {
                decode = result;
            }
            return decode;
        }

        /// <summary>
        /// Base64解密，采用utf8编码方式解密
        /// </summary>
        /// <param name="result">待解密的密文</param>
        /// <returns>解密后的字符串</returns>
        public static string DecodeBase64(string result)
        {
            return DecodeBase64(Encoding.UTF8, result);
        }


        #region 判断是否是base64
        /// <summary>
        /// 是否base64字符串
        /// </summary>
        /// <param name="base64Str">要判断的字符串</param>
        /// <returns></returns>
        public static bool IsBase64(string base64Str)
        {
            byte[] bytes = null;
            return IsBase64(base64Str, out bytes);
        }


        private static char[] base64CodeArray = new char[]
        {
            'A', 'B', 'C', 'D', 'E', 'F', 'G', 'H', 'I', 'J', 'K', 'L', 'M', 'N', 'O', 'P', 'Q', 'R', 'S', 'T', 'U', 'V', 'W', 'X', 'Y', 'Z',
            'a', 'b', 'c', 'd', 'e', 'f', 'g', 'h', 'i', 'j', 'k', 'l', 'm', 'n', 'o', 'p', 'q', 'r', 's', 't', 'u', 'v', 'w', 'x', 'y', 'z',
            '0', '1', '2', '3', '4',  '5', '6', '7', '8', '9', '+', '/', '='
        };


        /// <summary>
        /// 是否base64字符串
        /// </summary>
        /// <param name="base64Str">要判断的字符串</param>
        /// <param name="bytes">字符串转换成的字节数组</param>
        /// <returns></returns>
        public static bool IsBase64(string base64Str, out byte[] bytes)
        {
            //string strRegex = "^([A-Za-z0-9+/]{4})*([A-Za-z0-9+/]{4}|[A-Za-z0-9+/]{3}=|[A-Za-z0-9+/]{2}==)$";
            bytes = null;
            if (string.IsNullOrEmpty(base64Str))
                return false;
            else
            {
                if (base64Str.Contains(","))
                    base64Str = base64Str.Split(',')[1];
                if (base64Str.Length % 4 != 0)
                    return false;
                if (base64Str.Any(c => !base64CodeArray.Contains(c)))
                    return false;
            }
            try
            {
                bytes = Convert.FromBase64String(base64Str);
                return true;
            }
            catch (FormatException)
            {
                return false;
            }
        }

        #endregion
    }
}