using Microsoft.AspNetCore.Cryptography.KeyDerivation;
using Microsoft.IdentityModel.Tokens;
using System;
using System.Collections.Generic;
using System.IdentityModel.Tokens.Jwt;
using System.Security.Claims;
using System.Security.Cryptography;
using System.Text;

namespace TEAMModelOS.SDK.Extension
{
    public class Utils
    {
        private static RNGCryptoServiceProvider _random = new RNGCryptoServiceProvider();

        public static string HashedPassword(string password, string salt)
        {
            byte[] hashBytes = KeyDerivation.Pbkdf2(
                password: password,
                salt: Encoding.UTF8.GetBytes(salt), //SHA1鹽(8-20字節)，SHA256(32字節)
                prf: KeyDerivationPrf.HMACSHA1,
                iterationCount: 10000, //hash次數，越多次代表破解難度變高，但效能會差點
                numBytesRequested: 256 / 8 //指定得出結果長度
            );

            string hashText = BitConverter.ToString(hashBytes).Replace("-", string.Empty);
            return hashText;
        }

        /// <summary>
        /// 建立真隨機字串(CSPRNG)，適用密碼、鹽
        /// </summary>
        /// <param name="stringLength">長度</param>
        /// <param name="key">要限制的字元串(長度需大於等於8)，如果為null或者小於8，預設為"abcdefghijklmnopqrstuvwxyz1234567890"</param>
        /// <returns></returns>
        public static string CreatSaltString(int stringLength, string key = null)
        {
            ReadOnlySpan<char> span;
            if (key == null || key.Length < 8)
                span = "abcdefghijklmnopqrstuvwxyz1234567890";
            else
                span = key.AsSpan();

            int length = span.Length;
            StringBuilder randomString = new StringBuilder(length);
            for (int i = 0; i < stringLength; ++i)
            {
                randomString.Append(span[SetRandomSeeds(length)]);
            }
            return randomString.ToString();
        }

        /// <summary>
        /// 建立真隨機整數數字(CSPRNG)，適用亂數、隨機編號
        /// </summary>
        /// <param name="max">最大值</param>
        public static int CreatSaltInt(int max)
        {
            var bytes = new byte[4];
            _random.GetBytes(bytes);
            int value = BitConverter.ToInt32(bytes, 0);
            value = value % (max + 1);
            if (value < 0) value = -value;
            return value;
        }

        /// <summary>
        /// 建立真隨機整數數字(CSPRNG)，適用亂數、隨機編號
        /// </summary>
        /// <param name="min">最小值</param>
        /// <param name="max">最大值</param>
        public static int CreatSaltInt(int min, int max)
        {
            int value = CreatSaltInt(max - min) + min;
            return value;
        }        

        /// <summary>
        /// 剖析連接字串
        /// </summary>
        /// <param name="connectionString"></param>
        /// <returns></returns>
        public static Dictionary<string, string> ParseConnectionString(string connectionString)
        {
            var d = new Dictionary<string, string>();
            foreach (var item in connectionString.Split(';',StringSplitOptions.RemoveEmptyEntries))
            {
                var a = item.IndexOf('=');
                d.Add(item.Substring(0, a), item.Substring(a + 1));
            }
            return d;
        }    

        private static int SetRandomSeeds(int length)
        {
            decimal maxValue = (decimal)long.MaxValue;
            byte[] array = new byte[8];
            _random.GetBytes(array);
            return (int)(Math.Abs(BitConverter.ToInt64(array, 0)) / maxValue * length);
        }


    }
}