using System.Net;
using FinalFactory.Rendezvous.Client;
using FinalFactory.Rendezvous.Contracts;
using FinalFactory.Rendezvous.Server.JoinAttempts;
using FinalFactory.Rendezvous.Server.State;
using FinalFactory.Rendezvous.Server.Transport;
using FinalFactory.Rendezvous.Tests.JoinAttempts;
using LiteNetLib;
using Microsoft.Extensions.Logging.Abstractions;
using Microsoft.Extensions.Options;

namespace FinalFactory.Rendezvous.Tests.Client;

public sealed class RendezvousCoordinatorIntegrationTests
{
    [Fact]
    public async Task CallerOwnedManagersCompleteAuthenticatedDirectConnectionAndRejectTicketReplay()
    {
        using CancellationTokenSource timeout = new(TimeSpan.FromSeconds(8));
        using JoinAttemptFixture fixture = new();
        (RegisterSessionResponse registration, _) = fixture.CreateHost();
        CreateJoinAttemptResponse created = fixture.Create(registration.ListingId, "sdk-direct-connect");
        HostJoinAttempt hostAttempt = fixture.Service.BrowseForHost(
            registration.ListingId,
            ContractLimits.ContractVersion,
            registration.LeaseToken,
            ContractLimits.BrowserPageMaxItems,
            null).Value!.Items.Single(item => item.AttemptId == created.AttemptId);
        NatMediationProcessor processor = new(
            fixture.Sessions.Store,
            fixture.Sessions.Capabilities,
            fixture.Service);
        using UdpMediatorService mediatorService = new(
            Options.Create(new UdpMediatorOptions
            {
                ListenAddress = IPAddress.Loopback.ToString(),
                Port = 0,
                PollIntervalMilliseconds = 1,
            }),
            NullLogger<UdpMediatorService>.Instance,
            processor);
        await mediatorService.StartAsync(timeout.Token);

        RendezvousNetListener hostEvents = new();
        RendezvousNetListener clientEvents = new();
        bool gameplayConnectionRequestHandled = false;
        hostEvents.GameplayEvents.ConnectionRequestEvent += _ =>
            gameplayConnectionRequestHandled = true;
        EventBasedNatPunchListener hostPunch = hostEvents.PunchEvents;
        EventBasedNatPunchListener clientPunch = clientEvents.PunchEvents;
        NetManager hostManager = hostEvents.CreateManager();
        NetManager clientManager = clientEvents.CreateManager();
        string? introductionToken = null;
        string? hostIntroductionToken = null;
        clientPunch.NatIntroductionSuccess += (_, _, token) => introductionToken = token;
        hostPunch.NatIntroductionSuccess += (_, _, token) => hostIntroductionToken = token;

        try
        {
            Assert.True(hostManager.Start(0));
            Assert.True(clientManager.Start(0));
            IPEndPoint mediator = Assert.IsType<IPEndPoint>(mediatorService.LocalEndpoint);
            FakeJoinClient joinClient = new([hostAttempt]);
            FixedCoordinatorClock clock = new(fixture.Sessions.Clock.UtcNow);
            using ConnectionTicketValidator tickets = new(1_024, clock);
            using RendezvousHostCoordinator host = new(
                hostManager,
                hostEvents,
                mediator,
                new PublishedSession(registration),
                joinClient,
                FastOptions(),
                clock,
                tickets);
            using RendezvousClientCoordinator client = new(
                clientManager,
                clientEvents,
                mediator,
                created,
                FastOptions(),
                clock);
            List<RendezvousHostAttemptCompletedEventArgs> hostCompletions = [];
            List<RendezvousConnectionCompletedEventArgs> clientCompletions = [];
            host.AttemptCompleted += (_, completion) => hostCompletions.Add(completion);
            client.Completed += (_, completion) => clientCompletions.Add(completion);
            Assert.True((await host.RefreshJoinAttemptsAsync(timeout.Token)).IsSuccess);

            while ((!client.IsCompleted || hostCompletions.Count == 0)
                   && !timeout.IsCancellationRequested)
            {
                host.Poll();
                client.Poll();
                await Task.Delay(2);
            }

            Assert.True(
                client.State == RendezvousConnectionState.Connected,
                $"Client ended in {client.State}; host pending={host.PendingAttemptCount}; "
                + $"host completions={hostCompletions.Count}; introduction={introductionToken is not null}; "
                + $"host introduction={hostIntroductionToken is not null}; "
                + $"client digest={NatIntroductionTokenCodec.MatchesDigest(introductionToken, created.ConnectionTicketDigest)}; "
                + $"host digest={NatIntroductionTokenCodec.MatchesDigest(hostIntroductionToken, hostAttempt.ConnectionTicketDigest)}.");
            Assert.NotNull(client.ConnectedPeer);
            Assert.Equal(
                RendezvousConnectionState.Connected,
                Assert.Single(clientCompletions).State);
            RendezvousHostAttemptCompletedEventArgs hostCompletion = Assert.Single(hostCompletions);
            Assert.Equal(created.AttemptId, hostCompletion.AttemptId);
            Assert.Equal(RendezvousConnectionState.Connected, hostCompletion.State);
            Assert.NotNull(hostCompletion.Peer);
            Assert.False(gameplayConnectionRequestHandled);
            Assert.True(NatIntroductionTokenCodec.TryDecode(
                introductionToken,
                out NatIntroductionToken? introduction));
            Assert.NotNull(introduction);

            EventBasedNetListener replayEvents = new();
            bool replayConnected = false;
            replayEvents.PeerConnectedEvent += _ => replayConnected = true;
            NetManager replayManager = new(replayEvents);
            try
            {
                Assert.True(replayManager.Start(0));
                replayManager.Connect(
                    new IPEndPoint(IPAddress.Loopback, hostManager.LocalPort),
                    DirectConnectionRequestCodec.Encode(
                        created.AttemptId,
                        introduction.ConnectionTicket));
                DateTime replayDeadline = DateTime.UtcNow.AddSeconds(1);
                while (DateTime.UtcNow < replayDeadline && !replayConnected)
                {
                    host.Poll();
                    replayManager.PollEvents();
                    await Task.Delay(2, timeout.Token);
                }

                Assert.False(replayConnected);
                Assert.False(gameplayConnectionRequestHandled);
                Assert.Single(hostCompletions);
            }
            finally
            {
                replayManager.Stop();
            }
        }
        finally
        {
            hostManager.Stop();
            clientManager.Stop();
            await mediatorService.StopAsync(CancellationToken.None);
        }
    }

    [Fact]
    public async Task HostDefersADirectRequestUntilTheMatchingNatIntroductionArrives()
    {
        using JoinAttemptFixture fixture = new();
        (RegisterSessionResponse registration, _) = fixture.CreateHost();
        CreateJoinAttemptResponse created = fixture.Create(registration.ListingId, "direct-before-nat");
        HostJoinAttempt hostAttempt = fixture.Service.BrowseForHost(
            registration.ListingId,
            ContractLimits.ContractVersion,
            registration.LeaseToken,
            ContractLimits.BrowserPageMaxItems,
            null).Value!.Items.Single(item => item.AttemptId == created.AttemptId);
        IntroductionEndpoints introduction = fixture.Introduce(registration, created);
        ConnectionTicketGrant grant = Assert.IsType<ConnectionTicketGrant>(
            fixture.Service.IssueConnectionTicket(introduction.Attempt).Value);
        RendezvousNetListener hostEvents = new();
        EventBasedNatPunchListener hostPunch = hostEvents.PunchEvents;
        EventBasedNetListener clientEvents = new();
        bool clientConnected = false;
        clientEvents.PeerConnectedEvent += _ => clientConnected = true;
        NetManager hostManager = hostEvents.CreateManager();
        NetManager clientManager = new(clientEvents);
        try
        {
            Assert.True(hostManager.Start(0));
            Assert.True(clientManager.Start(0));
            FixedCoordinatorClock clock = new(fixture.Sessions.Clock.UtcNow);
            FakeJoinClient joins = new([hostAttempt]);
            using ConnectionTicketValidator tickets = new(16, clock);
            using RendezvousHostCoordinator host = new(
                hostManager,
                hostEvents,
                new IPEndPoint(IPAddress.Loopback, 65_000),
                new PublishedSession(registration),
                joins,
                FastOptions(),
                clock,
                tickets);
            List<RendezvousHostAttemptCompletedEventArgs> completions = [];
            host.AttemptCompleted += (_, completion) => completions.Add(completion);
            Assert.True((await host.RefreshJoinAttemptsAsync()).IsSuccess);
            host.Poll();
            bool observedDeferredRequest = false;
            hostEvents.RendezvousConnectionRequest += _ =>
            {
                observedDeferredRequest = host.DeferredRequestCount == 1;
                ((INatPunchListener)hostPunch).OnNatIntroductionSuccess(
                    new IPEndPoint(IPAddress.Loopback, clientManager.LocalPort),
                    NatAddressType.External,
                    grant.Ticket);
            };

            clientManager.Connect(
                new IPEndPoint(IPAddress.Loopback, hostManager.LocalPort),
                DirectConnectionRequestCodec.Encode(created.AttemptId, grant.Ticket));
            DateTime connectedDeadline = DateTime.UtcNow.AddSeconds(1);
            while ((!clientConnected || completions.Count == 0)
                   && DateTime.UtcNow < connectedDeadline)
            {
                host.Poll();
                clientManager.PollEvents();
                await Task.Delay(2);
            }

            Assert.True(
                clientConnected,
                $"Deferred observed={observedDeferredRequest}; deferred={host.DeferredRequestCount}; "
                + $"pending={host.PendingAttemptCount}; completions={completions.Count}.");
            Assert.True(observedDeferredRequest);
            Assert.Equal(0, host.DeferredRequestCount);
            Assert.Equal(
                RendezvousConnectionState.Connected,
                Assert.Single(completions).State);
        }
        finally
        {
            hostManager.Stop();
            clientManager.Stop();
        }
    }

    private static RendezvousCoordinatorOptions FastOptions() => new()
    {
        MaximumPunchRequests = 20,
        InitialPunchRetryDelay = TimeSpan.FromMilliseconds(10),
        MaximumPunchRetryDelay = TimeSpan.FromMilliseconds(100),
        JitterRatio = 0,
    };

    private sealed class FakeJoinClient(IReadOnlyList<HostJoinAttempt> attempts) : IRendezvousJoinClient
    {
        public Task<RendezvousClientResult<CreateJoinAttemptResponse>> CreateAsync(
            CreateJoinAttemptRequest request,
            CancellationToken cancellationToken = default) => throw new NotSupportedException();

        public Task<RendezvousClientResult<bool>> CancelAsync(
            CreateJoinAttemptResponse attempt,
            CancellationToken cancellationToken = default) => throw new NotSupportedException();

        public Task<RendezvousClientResult<BrowseHostJoinAttemptsResponse>> BrowseForHostAsync(
            PublishedSession session,
            int pageSize = ContractLimits.BrowserPageMaxItems,
            string? cursor = null,
            CancellationToken cancellationToken = default) => throw new NotSupportedException();

        public Task<RendezvousClientResult<IReadOnlyList<HostJoinAttempt>>> BrowseAllForHostAsync(
            PublishedSession session,
            int maximumPages = 100,
            CancellationToken cancellationToken = default) => Task.FromResult(
                RendezvousClientResult.Success(attempts));
    }

    private sealed class FixedCoordinatorClock(DateTimeOffset now) :
        IRendezvousCoordinatorClock,
        IConnectionTicketClock
    {
        public DateTimeOffset UtcNow { get; } = now;
    }
}