using FastGithub.Configuration;

using System;

using System.Collections.Concurrent;

using System.Collections.Generic;

using System.Linq;

using System.Net;

using System.Runtime.CompilerServices;

using System.Threading;

using System.Threading.Tasks;

namespace FastGithub.DomainResolve

{

/// <summary>

/// 域名解析器

/// </summary>

sealed class DomainResolver : IDomainResolver

{

private readonly DnsClient dnsClient;

private readonly ConcurrentDictionary<DnsEndPoint, IPAddressElapsedCollection> dnsEndPointAddressElapseds = new();

/// <summary>

/// 域名解析器

/// </summary>

/// <param name="dnsClient"></param>

public DomainResolver(DnsClient dnsClient)

{

this.dnsClient = dnsClient;

}

/// <summary>

/// 解析ip

/// </summary>

/// <param name="endPoint">节点</param>

/// <param name="cancellationToken"></param>

/// <returns></returns>

public async Task<IPAddress> ResolveAnyAsync(DnsEndPoint endPoint, CancellationToken cancellationToken = default)

{

await foreach (var address in this.ResolveAllAsync(endPoint, cancellationToken))

{

return address;

}

throw new FastGithubException($"解析不到{endPoint.Host}的IP");

}

/// <summary>

/// 解析域名

/// </summary>

/// <param name="endPoint">节点</param>

/// <param name="cancellationToken"></param>

/// <returns></returns>

public async IAsyncEnumerable<IPAddress> ResolveAllAsync(DnsEndPoint endPoint, [EnumeratorCancellation] CancellationToken cancellationToken)

{

if (this.dnsEndPointAddressElapseds.TryGetValue(endPoint, out var addressElapseds) && addressElapseds.IsEmpty == false)

{

foreach (var addressElapsed in addressElapseds)

{

yield return addressElapsed.Adddress;

}

}

else

{

this.dnsEndPointAddressElapseds.TryAdd(endPoint, IPAddressElapsedCollection.Empty);

await foreach (var adddress in this.dnsClient.ResolveAsync(endPoint, cancellationToken))

{

yield return adddress;

}

}

}

/// <summary>

/// 对所有节点进行测速

/// </summary>

/// <param name="cancellationToken"></param>

/// <returns></returns>

public async Task TestAllEndPointsAsync(CancellationToken cancellationToken)

{

foreach (var keyValue in this.dnsEndPointAddressElapseds)

{

if (keyValue.Value.IsEmpty || keyValue.Value.IsExpired)

{

var dnsEndPoint = keyValue.Key;

var addresses = new List<IPAddress>();

await foreach (var adddress in this.dnsClient.ResolveAsync(dnsEndPoint, cancellationToken))

{

addresses.Add(adddress);

}

var addressElapseds = IPAddressElapsedCollection.Empty;

if (addresses.Count == 1)

{

var addressElapsed = new IPAddressElapsed(addresses[0], TimeSpan.Zero);

addressElapseds = new IPAddressElapsedCollection(addressElapsed);

}

else if (addresses.Count > 1)

{

var tasks = addresses.Select(address => IPAddressElapsed.ParseAsync(address, dnsEndPoint.Port, cancellationToken));

addressElapseds = new IPAddressElapsedCollection(await Task.WhenAll(tasks));

}

this.dnsEndPointAddressElapseds[dnsEndPoint] = addressElapseds;

}

}

}

}

}