using System.Security.Cryptography;
using System.Security.Cryptography.X509Certificates;
using VoiceCat.Crypto;
using VoiceCat.Protocol;

namespace VoiceCat.Tests;

public class TlsTests
{
    [Fact]
    public void ManagedTlsHandshakeExportsMatchingDirectionalKeys()
    {
        var (pem, key, fingerprint) = Credentials();
        using var server = TlsSession.CreateServer(pem, key);
        using var client = TlsSession.CreateClient(value => value == fingerprint);
        Assert.Throws<InvalidOperationException>(() => client.CreateMediaEncryptor());
        Handshake(client, server);
        Assert.Equal(fingerprint, client.PeerCertificateFingerprint);
        Assert.Equal(server.ExportMediaKey(0), client.ExportMediaKey(0));
        Assert.Equal(server.ExportMediaKey(1), client.ExportMediaKey(1));
        Assert.NotEqual(client.ExportMediaKey(0), client.ExportMediaKey(1));
        client.WritePlaintext("hello"u8);
        Pump(client, server);
        byte[] output = new byte[5];
        Assert.Equal(5, server.ReadPlaintext(output));
        Assert.Equal("hello"u8.ToArray(), output);
        using var encryptor = server.CreateMediaEncryptor();
        using var decryptor = client.CreateMediaDecryptor();
        byte[] packet = new byte[41];
        encryptor.Encrypt(new(MediaFrameType.Voice, 0, 0, 42, 0, 960), "hello"u8, packet);
        Assert.True(decryptor.TryDecrypt(packet, output, out _, out _));
        Assert.Equal("hello"u8.ToArray(), output);
    }

    [Fact]
    public void CertificateRejectionPreventsApplicationDataAndMediaKeys()
    {
        var (pem, key, _) = Credentials();
        using var server = TlsSession.CreateServer(pem, key);
        using var client = TlsSession.CreateClient(_ => false);
        Assert.ThrowsAny<IOException>(() => Handshake(client, server));
        Assert.False(client.IsReady);
        Assert.Throws<InvalidOperationException>(() => client.CreateMediaDecryptor());
        Assert.Throws<InvalidOperationException>(() => client.WritePlaintext("secret"u8));
    }

    [Fact]
    public void CloseNotifyEndsSessionAndAbruptEofIsRejected()
    {
        var (pem, key, fingerprint) = Credentials();
        using var server = TlsSession.CreateServer(pem, key);
        using var client = TlsSession.CreateClient(value => value == fingerprint);
        Handshake(client, server);
        client.Close();
        Pump(client, server);
        Assert.False(client.IsReady);
        Assert.False(server.IsReady);
        server.CompleteInput();
        using var incomplete = TlsSession.CreateClient(_ => true);
        Assert.ThrowsAny<IOException>(() => incomplete.CompleteInput());
    }

    [Fact]
    public void TlsTwelveCannotNegotiateWithManagedServer()
    {
        var (pem, key, _) = Credentials();
        using var server = TlsSession.CreateServer(pem, key);
        var legacy = new Org.BouncyCastle.Tls.TlsClientProtocol();
        legacy.Connect(new LegacyPeer());
        byte[] hello = new byte[legacy.GetAvailableOutputBytes()];
        legacy.ReadOutput(hello, 0, hello.Length);
        Assert.ThrowsAny<IOException>(() => server.ReceiveCiphertext(hello));
        Assert.False(server.IsReady);
        Assert.Throws<InvalidOperationException>(() => server.CreateMediaEncryptor());
    }

    private sealed class LegacyPeer() : Org.BouncyCastle.Tls.DefaultTlsClient(new Org.BouncyCastle.Tls.Crypto.Impl.BC.BcTlsCrypto())
    {
        protected override Org.BouncyCastle.Tls.ProtocolVersion[] GetSupportedVersions() => [Org.BouncyCastle.Tls.ProtocolVersion.TLSv12];
        public override Org.BouncyCastle.Tls.TlsAuthentication GetAuthentication() => throw new InvalidOperationException("TLS 1.2 must be rejected before authentication.");
    }

    internal static (string Certificate, string Key, string Fingerprint) Credentials()
    {
        using var key = ECDsa.Create(ECCurve.NamedCurves.nistP256);
        var request = new System.Security.Cryptography.X509Certificates.CertificateRequest("CN=VoiceCat TLS test", key, HashAlgorithmName.SHA256);
        using var certificate = request.CreateSelfSigned(DateTimeOffset.UtcNow.AddMinutes(-1), DateTimeOffset.UtcNow.AddDays(1));
        return (certificate.ExportCertificatePem(), key.ExportPkcs8PrivateKeyPem(), Convert.ToHexString(SHA256.HashData(certificate.RawData)));
    }

    internal static void Handshake(TlsSession client, TlsSession server)
    {
        for (int i = 0; i < 100 && (!client.IsReady || !server.IsReady); i++)
        {
            Pump(client, server);
            Pump(server, client);
        }
        Assert.True(client.IsReady);
        Assert.True(server.IsReady);
    }

    private static void Pump(TlsSession sender, TlsSession receiver)
    {
        byte[] buffer = new byte[17];
        while (sender.PendingCiphertextBytes > 0)
        {
            int count = sender.DrainCiphertext(buffer);
            receiver.ReceiveCiphertext(buffer.AsSpan(0, count));
        }
    }
}