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

namespace DG.Core
{
    public class LongValidationAttribute : ValidationAttribute
    {
        public int? Length { get; }
        private bool LengthError { get; set; }

        public LongValidationAttribute()
        {
        }

        public LongValidationAttribute(int? length)
        {
            Length = length;
        }

        /// <summary>
        /// IsValid 为 false 时，提示得 error 信息
        /// </summary>
        /// <param name="name"></param>
        /// <returns></returns>
        public override string FormatErrorMessage(string name)
        {
            var lengthMessage = LengthError ? $"，且长度不能超过{Length}" : "";
            return $"{name}必须输入数字{lengthMessage}，请重新输入！";
        }

        /// <summary>
        /// 验证当前字段得结果
        /// </summary>
        /// <param name="value"></param>
        /// <returns></returns>
        public override bool IsValid(object? value)
        {
            if (value == null) return true;
            if (long.TryParse(Convert.ToString(value), out long num))
            {
                if (Length != null && num.ToString().Length > Length)
                {
                    LengthError = true;
                    return false;
                }
                return true;
            }
            else
            {
                return false;
            }
        }
    }
}