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

namespace Link.Common
{
    /// <summary>
    /// 地址工具
    /// </summary>
    public class LinkUtil
    {
        /// <summary>
        /// 基础62位字符
        /// </summary>
        private const string _baseKeys = "ABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789abcdefghijklmnopqrstuvwxyz";

        /// <summary>
        /// 幂数
        /// </summary>
        private static readonly int _exponent = _baseKeys.Length;

        /// <summary>
        /// 十进制转62进制
        /// </summary>
        /// <param name="value"></param>
        /// <returns></returns>
        public static string ConvertTo64(long value)
        {
            string result = string.Empty;
            do
            {
                long index = value % _exponent;
                result = _baseKeys[(int)index] + result;
                value = (value - index) / _exponent;
            }
            while (value > 0);

            return result;
        }

        /// <summary>
        /// 混淆十进制转62进制
        /// </summary>
        /// <param name="value"></param>
        /// <returns></returns>
        public static string MixValueConvertTo64(long value)
        {
            long mixValue = InsertRandomBitPer5Bits(value);
            string result = string.Empty;
            do
            {
                long index = mixValue % _exponent;
                result = _baseKeys[(int)index] + result;
                mixValue = (mixValue - index) / _exponent;
            }
            while (mixValue > 0);

            return result;
        }

        /// <summary>
        /// 62进制转10进制
        /// </summary>
        /// <param name="value"></param>
        /// <returns></returns>
        public static decimal ConvertTo10(string value)
        {
            decimal result = 0;
            for (int i = 0; i < value.Length; i++)
            {
                int x = value.Length - i - 1;
                result += _baseKeys.IndexOf(value[i]) * Pow(_exponent, x);
            }
            return result;
        }

        /// <summary>
        /// 一个数据的N次方
        /// </summary>
        /// <param name="baseNo"></param>
        /// <param name="x"></param>
        /// <returns></returns>
        private static decimal Pow(decimal baseNo, decimal x)
        {
            //1 will be the result for any number's power 0.
            decimal value = 1;
            while (x > 0)
            {
                value = value * baseNo;
                x--;
            }
            return value;
        }

        /// <summary>
        /// 每5位插一个随机位
        /// </summary>
        /// <param name="val"></param>
        /// <returns></returns>
        private static long InsertRandomBitPer5Bits(long val)
        {
            long result = val;
            long high = val;
            for (int i = 0; i < 10; i++)
            {
                if (high == 0)
                {
                    break;
                }
                Random random = new Random();
                long num = random.Next(0, 2);
                int pos = 5 + 5 * i + i;
                high = result >> pos;
                result = ((high << 1 | num) << pos) | (result & RightMove(-1L, 64 - pos));
            }

            return result;
        }

        /// <summary>
        /// 无符号右移, 相当于java里的 value>>>pos
        /// </summary>
        /// <param name="value"></param>
        /// <param name="pos"></param>
        /// <returns></returns>
        public static long RightMove(long value, int pos)
        {
            //移动 0 位时直接返回原值
            if (pos != 0)
            {
                // int.MaxValue = 0x7FFFFFFF 整数最大值
                long mask = long.MaxValue;
                //无符号整数最高位不表示正负但操作数还是有符号的，有符号数右移1位，正数时高位补0，负数时高位补1
                value = value >> 1;
                //和整数最大值进行逻辑与运算，运算后的结果为忽略表示正负值的最高位
                value = value & mask;
                //逻辑运算后的值无符号，对无符号的值直接做右移运算，计算剩下的位
                value = value >> pos - 1;
            }

            return value;
        }
    }
}