using Microsoft.Extensions.Options;
using System;
using System.Collections.Generic;
using System.ComponentModel.DataAnnotations;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace Myshipping.Application
{
    public class SuperShortLinkHelper
    {
        private readonly string _base62CharSet = "s9LFkgy5RovixI1aOf8UhdY3r4DMplQZJXPqebE0WSjBn7wVzmN2Gc6THCAKut";
        private readonly int _codeLength = 6;
        private readonly int _powMax = 62;

        public SuperShortLinkHelper()
        {
        }

        /// <summary>
        /// 补充0的长度
        /// </summary>
        private int ZeroLength
        {
            get
            {
                return MaxValue.ToString().Length;
            }
        }

        /// <summary>
        /// Code长度位数下能达到的最大值
        /// </summary>
        public long MaxValue
        {
            get
            {
                var max = (long)Math.Pow(_powMax, _codeLength) - 1;
                return (long)Math.Pow(10, max.ToString().Length - 1) - 1;
            }
        }

        /// <summary>
        /// 【混淆加密】转短码
        /// 1、根据自增主键id前面补0，如：00000123
        /// 2、倒转32100000
        /// 3、把倒转后的十进制转六十二进制（乱序后）
        /// </summary>
        public string Confuse(long id)
        {
            if (id > MaxValue)
            {
                throw new Exception($"转换值不能超过最大值{MaxValue}");
            }

            var idChars = id.ToString()
                   .PadLeft(ZeroLength, '0')
                   .ToCharArray()
                   .Reverse();

            var confuseId = long.Parse(string.Join("", idChars));
            var base62Str = Encode(confuseId);
            return base62Str.PadLeft(_codeLength, _base62CharSet.First());
        }

        /// <summary>
        /// 十进制 -> 62进制
        /// </summary>
        public string Encode(long value)
        {
            if (value < 0)
                throw new ArgumentOutOfRangeException("value", "value must be greater or equal to zero");

            var sb = new StringBuilder();
            do
            {
                sb.Insert(0, _base62CharSet[(int)(value % _powMax)]);
                value /= _powMax;
            } while (value > 0);

            return sb.ToString();
        }
    }

    public class ShortLinkOptions
    {

        public const string SectionName = "ShortShareLink";

        /// <summary>
        /// 短码长度
        /// </summary>
        [Range(1, int.MaxValue)]
        public int CodeLength { get; set; }

        /// <summary>
        /// 62位加密秘钥
        /// </summary>
        [Required]
        public string Secrect { get; set; }

        /// <summary>
        /// 缓存数量限制
        /// </summary>
        public int? CacheCountLimit { get; set; }

        /// <summary>
        /// 生成默认数据
        /// </summary>
        public static ShortLinkOptions GenDefault()
        {
            return new ShortLinkOptions()
            {
                CacheCountLimit = 10000
            };
        }
    }
}