using DnsClient;
using Masuit.Tools.Config;
using System.ComponentModel.DataAnnotations;
using System.Linq;
using System.Net;
using System.Text.RegularExpressions;

namespace Masuit.Tools.Core.Validator;

/// <summary>
/// 邮箱校验
/// </summary>
public class IsEmailAttribute : ValidationAttribute
{
    private readonly bool _valid;
    private readonly string _customMessage;

    /// <summary>
    /// 域白名单
    /// </summary>
    private string[] WhiteList { get; set; }

    /// <summary>
    /// 域黑名单
    /// </summary>
    private string[] BlockList { get; set; }

    /// <summary>
    /// 是否允许为空
    /// </summary>
    public bool AllowEmpty { get; set; }

    /// <summary>
    /// 可在配置文件AppSetting节中添加EmailDomainWhiteList配置邮箱域名白名单，EmailDomainBlockList配置邮箱域名黑名单，英文分号(;)或感叹号(!)或逗号(,)分隔，每个单独的元素支持正则表达式
    /// </summary>
    /// <param name="validDns">是否检查邮箱DNS记录的有效性</param>
    /// <param name="customMessage">自定义错误消息</param>
    public IsEmailAttribute(bool validDns = true, string customMessage = null)
    {
        _valid = validDns;
        _customMessage = customMessage;
    }

    /// <summary>
    /// 邮箱校验
    /// </summary>
    /// <param name="value"></param>
    /// <returns></returns>
    public override bool IsValid(object value)
    {
        WhiteList = ConfigHelper.Get<string[]>("EmailDomainWhiteList") ?? [];
        BlockList = ConfigHelper.Get<string[]>("EmailDomainBlockList") ?? [];
        if (AllowEmpty)
        {
            switch (value)
            {
                case null:
                case string s when string.IsNullOrEmpty(s):
                    return true;
            }
        }

        if (value == null)
        {
            ErrorMessage = _customMessage ?? "邮箱不能为空！";
            return false;
        }

        var email = (string)value;
        if (email.Length < 7)
        {
            ErrorMessage = _customMessage ?? "您输入的邮箱格式不正确！";
            return false;
        }

        if (email.Length > 256)
        {
            ErrorMessage = _customMessage ?? "您输入的邮箱无效，请使用真实有效的邮箱地址！";
            return false;
        }

        if (WhiteList.Any(item => Regex.IsMatch(email, item)))
        {
            return true;
        }

        if (BlockList.Any(item => Regex.IsMatch(email, item)))
        {
            ErrorMessage = _customMessage ?? "您输入的邮箱无效，请使用真实有效的邮箱地址！";
            return false;
        }

        var isMatch = email.MatchEmail().isMatch;
        if (isMatch && _valid)
        {
            var nslookup = new LookupClient();
            var records = nslookup.Query(email.Split('@')[1], QueryType.MX).Answers.MxRecords().ToList();
            if (records.Exists(r => BlockList.Any(item => Regex.IsMatch(r.Exchange.Value, item))))
            {
                ErrorMessage = _customMessage ?? "您输入的邮箱无效，请使用真实有效的邮箱地址！";
                return false;
            }

            var task = records.SelectAsync(r => Dns.GetHostAddressesAsync(r.Exchange.Value).ContinueWith(t =>
            {
                if (t.IsCanceled || t.IsFaulted)
                {
                    return [IPAddress.Loopback];
                }

                return t.Result;
            }));
            isMatch = task.Result.SelectMany(a => a).Any(ip => !ip.IsPrivateIP());
        }
        if (isMatch)
        {
            return true;
        }

        ErrorMessage = _customMessage ?? "您输入的邮箱格式不正确！";
        return false;
    }
}