using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace SysBaseLibs
{
    public sealed class RandomUtil
    {
        static Random _random;

        static int GetRandomSeed()
        {
            byte[] bytes = new byte[4];
            System.Security.Cryptography.RNGCryptoServiceProvider rng = new System.Security.Cryptography.RNGCryptoServiceProvider();
            rng.GetBytes(bytes);
            return BitConverter.ToInt32(bytes, 0);
        }


        public static int GetIntRandom()
        {
            if (_random == null)
            {
                _random = new Random(0x989680);
            }

            return _random.Next(0x989680, 0x5f5e0ff);
        }

        public static string GetRandom()
        {
            if (_random == null)
            {
                _random = new Random(0x989680);
            }
            int liInt = _random.Next(0x989680, 0x5f5e0ff);
            return ("R" + liInt.ToString());
        }

        public static string GetRandom1()
        {
            if (_random == null)
            {
                _random = new Random(0x989680);
            }
            int liInt = _random.Next(0x989680, 0x5f5e0ff);
            return ("+" + liInt.ToString() + " GS");
        }

        /// <summary>
        /// 从字符串里随机得到，规定个数的字符串.
        /// </summary>
        /// <param name="allChar"></param>
        /// <param name="CodeCount"></param>
        /// <returns></returns>
        public static string GetRandomCode(string allChar, int CodeCount)
        {
            //string allChar = "1,2,3,4,5,6,7,8,9,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"; 
            string[] allCharArray = allChar.Split(',');
            string RandomCode = "";
            int temp = -1;
            Random rand = new Random();
            for (int i = 0; i < CodeCount; i++)
            {
                if (temp != -1)
                {
                    rand = new Random(temp * i * ((int)DateTime.Now.Ticks));
                }

                int t = rand.Next(allCharArray.Length - 1);

                while (temp == t)
                {
                    t = rand.Next(allCharArray.Length - 1);
                }

                temp = t;
                RandomCode += allCharArray[t];
            }
            return RandomCode;
        }

        public static string GetNextDataTableName()
        {
            return ("T" + GetRandom());
        }


        public static string GetGUID()
        {
            return System.Guid.NewGuid().ToString("N");
        }
        /// <summary>
        /// 
        /// </summary>
        /// <returns></returns>
        public static string UUID()
        {
            byte[] buffer = Guid.NewGuid().ToByteArray();
            long long_guid = BitConverter.ToInt64(buffer, 0);

            string _Value = System.Math.Abs(long_guid).ToString();

            byte[] buf = new byte[_Value.Length];
            int p = 0;
            for (int i = 0; i < _Value.Length;)
            {
                byte ph = System.Convert.ToByte(_Value[i]);

                int fix = 1;
                if ((i + 1) < _Value.Length)
                {
                    byte pl = System.Convert.ToByte(_Value[i + 1]);
                    buf[p] = (byte)((ph << 4) + pl);
                    fix = 2;
                }
                else
                {
                    buf[p] = (byte)(ph);
                }

                if ((i + 3) < _Value.Length)
                {
                    if (System.Convert.ToInt16(_Value.Substring(i, 3)) < 256)
                    {
                        buf[p] = System.Convert.ToByte(_Value.Substring(i, 3));
                        fix = 3;
                    }
                }
                p++;
                i = i + fix;
            }
            byte[] buf2 = new byte[p];
            for (int i = 0; i < p; i++)
            {
                buf2[i] = buf[i];
            }
            string cRtn = System.Convert.ToBase64String(buf2);
            if (cRtn == null)
            {
                cRtn = "";
            }
            cRtn = cRtn.ToLower();
            cRtn = cRtn.Replace("/", "");
            cRtn = cRtn.Replace("+", "");
            cRtn = cRtn.Replace("=", "");
            if (cRtn.Length == 12)
            {
                return cRtn;
            }
            else
            {
                return UUID();
            }
        }

        /// <summary> 
        /// 根据GUID获取16位的唯一字符串 
        /// </summary> 
        /// <param name=\"guid\"></param> 
        /// <returns></returns> 
        public static string GuidTo16String()
        {
            long i = 1;
            foreach (byte b in Guid.NewGuid().ToByteArray())
                i *= ((int)b + 1);
            return string.Format("{0:x}", i - DateTime.Now.Ticks);
        }
        /// <summary> 
        /// 根据GUID获取19位的唯一数字序列 
        /// </summary> 
        /// <returns></returns> 
        public static long GuidToLongID()
        {
            byte[] buffer = Guid.NewGuid().ToByteArray();
            return BitConverter.ToInt64(buffer, 0);
        }
        /// <summary>
        /// 生成随机数的种子
        /// </summary>
        /// <returns></returns>
        private static int getNewSeed()
        {
            byte[] rndBytes = new byte[4];
            System.Security.Cryptography.RNGCryptoServiceProvider rng = new System.Security.Cryptography.RNGCryptoServiceProvider();
            rng.GetBytes(rndBytes);
            return BitConverter.ToInt32(rndBytes, 0);
        }     /// <summary>
              /// 生成len位随机数
              /// </summary>
              /// <param name="length"></param>
              /// <returns></returns>
        static public string GetRandomString(int len)
        {
            string s = "123456789abcdefghijklmnpqrstuvwxyzABCDEFGHIJKLMNPQRSTUVWXYZ";
            string reValue = string.Empty;
            Random rnd = new Random(getNewSeed());
            while (reValue.Length < len)
            {
                string s1 = s[rnd.Next(0, s.Length)].ToString();
                if (reValue.IndexOf(s1) == -1) reValue += s1;
            }
            return reValue;
        }
        /// <summary>
        /// 获得有序的GUID
        /// </summary>
        /// <returns></returns>
        public static Guid GenerateGuid()
        {
            byte[] guidArray = Guid.NewGuid().ToByteArray();

            var baseDate = new DateTime(1900, 1, 1);
            DateTime now = DateTime.Now;
            var days = new TimeSpan(now.Ticks - baseDate.Ticks);
            TimeSpan msecs = now.TimeOfDay;

            byte[] daysArray = BitConverter.GetBytes(days.Days);
            byte[] msecsArray = BitConverter.GetBytes((long)(msecs.TotalMilliseconds / 3.333333));

            Array.Reverse(daysArray);
            Array.Reverse(msecsArray);

            Array.Copy(daysArray, daysArray.Length - 2, guidArray, guidArray.Length - 6, 2);
            Array.Copy(msecsArray, msecsArray.Length - 4, guidArray, guidArray.Length - 4, 4);

            return new Guid(guidArray);
        }

    }
}