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

namespace XdCxRhDW.Dto.Attribute
{
    /// <summary>
    /// 2的N次方限制
    /// </summary>
    public class Pow2Attribute : ValidationAttribute
    {
        /// <summary>
        /// 是否包含零,默认不包含
        /// </summary>
        public bool IncludeZero { get; set; } = false;

        /// <summary>
        /// 
        /// </summary>
        public Pow2Attribute()
        {
        }
        /// <summary>
        /// 2的N次方验证
        /// </summary>
        /// <param name="value"></param>
        /// <returns></returns>
        /// <exception cref="Exception"></exception>
        public override bool IsValid(object value)
        {
            ErrorMessage = "字段 {0} 必须是2的N次方";
            if (IncludeZero)
            {
                ErrorMessage += "或者0";
            }
            if (value.GetType() == typeof(double))
            {
                double val = (double)value;
                int ivalue = (int)val;
                return IsPow2(ivalue);
            }
            else if (value.GetType() == typeof(int))
            {
                int val = (int)value;
                return IsPow2(val);
            }
            else
            {
                throw new Exception($"{nameof(Pow2Attribute)}只能用于int或double类型!");
            }

        }

        private bool IsPow2(int val)
        {
            var res = val & (val - 1);
            return res == 0;
        }
    }
}