using DNS.Protocol;
using System;
using System.Linq;
using System.Threading.Tasks;

namespace Netch
{
    public class Resolver : DNS.Client.RequestResolver.IRequestResolver
    {
        public Task<IResponse> Resolve(IRequest request)
        {
            IResponse response = Response.FromRequest(request);

            foreach (var question in response.Questions)
            {
                if (question.Type == RecordType.A)
                {
                    var client = new DnsClient.LookupClient(DnsClient.NameServer.GooglePublicDns);
                    client.UseTcpOnly = true;
                    client.UseCache = true;

                    try
                    {
                        var result = client.Query(question.Name.ToString(), DnsClient.QueryType.A);
                        foreach (var item in result.Answers.ARecords())
                        {
                            response.AnswerRecords.Add(new DNS.Protocol.ResourceRecords.IPAddressResourceRecord(question.Name, item.Address));
                        }
                    }
                    catch (Exception)
                    {
                        // 跳过
                    }
                }
                else if (question.Type == RecordType.AAAA)
                {
                    var client = new DnsClient.LookupClient(DnsClient.NameServer.GooglePublicDns);
                    client.UseTcpOnly = true;
                    client.UseCache = true;

                    try
                    {
                        var result = client.Query(question.Name.ToString(), DnsClient.QueryType.AAAA);
                        foreach (var item in result.Answers.AaaaRecords())
                        {
                            response.AnswerRecords.Add(new DNS.Protocol.ResourceRecords.IPAddressResourceRecord(question.Name, item.Address));
                        }
                    }
                    catch (Exception)
                    {
                        // 跳过
                    }
                }
            }

            return Task.FromResult(response);
        }
    }
}