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

namespace Ant.Service.Utility
{
    public class IdGenerator
    {
        #region Fields

        private static readonly string digits = "0123456789abcdefghijklmnopqrstuvwxyz";

        private static readonly char[] characters = digits.ToCharArray();

        private static Random random = new Random();

        private static readonly long startTicks = new DateTime(2017, 1, 1).Ticks;

        #endregion Fields

        /// <summary>
        /// Generate a short id
        /// </summary>
        /// <returns></returns>
        public static string NewId()
        {
            long current = DateTime.Now.Ticks - startTicks;
            string strRadix = ConvertToRadix(current, characters.Length);

            StringBuilder sb = new StringBuilder(strRadix);
            for (int i = 0; i < 6; i++)
            {
                sb.Append(characters[random.Next(characters.Length)]);
            }
            return sb.ToString().ToUpper();
        }

        public static string NewId(string prefix)
        {
            return $"{prefix}{NewId()}";
        }

        public static Guid NewGUId()
        {
            return Guid.NewGuid();
        }

        public static string NewUUId()
        {
            return Guid.NewGuid().ToString("N");
        }

        private static string ConvertToRadix(long value, int radix)
        {
            StringBuilder sb = new StringBuilder();
            while (value > 0)
            {
                sb.Insert(0, characters[value % radix]);
                value /= radix;
            }
            return sb.ToString();
        }
    }
}