using System.IO.Pipes;
using MxGateway.Contracts;
using MxGateway.Contracts.Proto;
using MxGateway.Server.Workers;

namespace MxGateway.Tests.Gateway.Workers;

public sealed class WorkerClientTests
{
    private const string SessionId = "session-worker-client";
    private const string Nonce = "nonce-worker-client";
    private const int WorkerProcessId = 4321;
    private static readonly TimeSpan TestTimeout = TimeSpan.FromSeconds(5);

    [Fact]
    public async Task StartAsync_WithWorkerHelloAndReady_EntersReadyState()
    {
        await using PipePair pipePair = await PipePair.CreateAsync();
        await using WorkerClient client = CreateClient(pipePair);

        await CompleteHandshakeAsync(client, pipePair);

        Assert.Equal(WorkerClientState.Ready, client.State);
        Assert.Equal(WorkerProcessId, client.ProcessId);
    }

    [Fact]
    public async Task InvokeAsync_WithMatchingReply_CompletesPendingCommand()
    {
        await using PipePair pipePair = await PipePair.CreateAsync();
        await using WorkerClient client = CreateClient(pipePair);
        await CompleteHandshakeAsync(client, pipePair);

        Task<WorkerCommandReply> invokeTask = client.InvokeAsync(
            CreateCommand(MxCommandKind.Ping),
            TestTimeout,
            CancellationToken.None);

        WorkerEnvelope commandEnvelope = await pipePair.WorkerReader.ReadAsync().AsTask().WaitAsync(TestTimeout);
        Assert.Equal(WorkerEnvelope.BodyOneofCase.WorkerCommand, commandEnvelope.BodyCase);
        Assert.False(string.IsNullOrWhiteSpace(commandEnvelope.CorrelationId));

        await pipePair.WorkerWriter.WriteAsync(
            CreateCommandReplyEnvelope(commandEnvelope.CorrelationId, MxCommandKind.Ping));

        WorkerCommandReply reply = await invokeTask.WaitAsync(TestTimeout);

        Assert.Equal(commandEnvelope.CorrelationId, reply.Reply.CorrelationId);
        Assert.Equal(MxCommandKind.Ping, reply.Reply.Kind);
    }

    [Fact]
    public async Task InvokeAsync_WithLateReply_IgnoresLateReplyAndKeepsClientReady()
    {
        await using PipePair pipePair = await PipePair.CreateAsync();
        await using WorkerClient client = CreateClient(pipePair);
        await CompleteHandshakeAsync(client, pipePair);

        Task<WorkerCommandReply> timedOutInvokeTask = client.InvokeAsync(
            CreateCommand(MxCommandKind.Ping),
            TimeSpan.FromMilliseconds(50),
            CancellationToken.None);
        WorkerEnvelope timedOutCommand = await pipePair.WorkerReader.ReadAsync().AsTask().WaitAsync(TestTimeout);

        WorkerClientException exception = await Assert.ThrowsAsync<WorkerClientException>(
            async () => await timedOutInvokeTask);
        Assert.Equal(WorkerClientErrorCode.CommandTimeout, exception.ErrorCode);

        await pipePair.WorkerWriter.WriteAsync(
            CreateCommandReplyEnvelope(timedOutCommand.CorrelationId, MxCommandKind.Ping));
        await Task.Delay(TimeSpan.FromMilliseconds(50));

        Task<WorkerCommandReply> secondInvokeTask = client.InvokeAsync(
            CreateCommand(MxCommandKind.GetWorkerInfo),
            TestTimeout,
            CancellationToken.None);
        WorkerEnvelope secondCommand = await pipePair.WorkerReader.ReadAsync().AsTask().WaitAsync(TestTimeout);
        await pipePair.WorkerWriter.WriteAsync(
            CreateCommandReplyEnvelope(secondCommand.CorrelationId, MxCommandKind.GetWorkerInfo));

        WorkerCommandReply reply = await secondInvokeTask.WaitAsync(TestTimeout);

        Assert.Equal(WorkerClientState.Ready, client.State);
        Assert.Equal(MxCommandKind.GetWorkerInfo, reply.Reply.Kind);
    }

    [Fact]
    public async Task ReadEventsAsync_WithWorkerEvents_YieldsEventsInPipeOrder()
    {
        await using PipePair pipePair = await PipePair.CreateAsync();
        await using WorkerClient client = CreateClient(pipePair);
        await CompleteHandshakeAsync(client, pipePair);
        using CancellationTokenSource cancellationTokenSource = new(TestTimeout);

        await using IAsyncEnumerator<WorkerEvent> events =
            client.ReadEventsAsync(cancellationTokenSource.Token).GetAsyncEnumerator(cancellationTokenSource.Token);

        await pipePair.WorkerWriter.WriteAsync(
            CreateEventEnvelope(sequence: 11, MxEventFamily.OnDataChange));
        await pipePair.WorkerWriter.WriteAsync(
            CreateEventEnvelope(sequence: 12, MxEventFamily.OperationComplete));

        Assert.True(await events.MoveNextAsync());
        Assert.Equal((ulong)11, events.Current.Event.WorkerSequence);
        Assert.Equal(MxEventFamily.OnDataChange, events.Current.Event.Family);

        Assert.True(await events.MoveNextAsync());
        Assert.Equal((ulong)12, events.Current.Event.WorkerSequence);
        Assert.Equal(MxEventFamily.OperationComplete, events.Current.Event.Family);
    }

    [Fact]
    public async Task ReadLoop_WhenEventQueueOverflows_FaultsClient()
    {
        await using PipePair pipePair = await PipePair.CreateAsync();
        await using WorkerClient client = CreateClient(
            pipePair,
            new WorkerClientOptions
            {
                EventChannelCapacity = 1,
                HeartbeatGrace = TimeSpan.FromSeconds(30),
                HeartbeatCheckInterval = TimeSpan.FromSeconds(30),
            });
        await CompleteHandshakeAsync(client, pipePair);

        await pipePair.WorkerWriter.WriteAsync(
            CreateEventEnvelope(sequence: 11, MxEventFamily.OnDataChange));
        await pipePair.WorkerWriter.WriteAsync(
            CreateEventEnvelope(sequence: 12, MxEventFamily.OnDataChange));

        await WaitUntilAsync(
            () => client.State == WorkerClientState.Faulted,
            TestTimeout);

        Assert.Equal(WorkerClientState.Faulted, client.State);
    }

    [Fact]
    public async Task ReadLoop_WhenPipeDisconnects_FaultsClient()
    {
        await using PipePair pipePair = await PipePair.CreateAsync();
        await using WorkerClient client = CreateClient(pipePair);
        await CompleteHandshakeAsync(client, pipePair);

        await pipePair.DisposeWorkerSideAsync();

        await WaitUntilAsync(
            () => client.State == WorkerClientState.Faulted,
            TestTimeout);

        Assert.Equal(WorkerClientState.Faulted, client.State);
    }

    [Fact]
    public async Task HeartbeatMonitor_WhenHeartbeatExpires_FaultsClient()
    {
        await using PipePair pipePair = await PipePair.CreateAsync();
        await using WorkerClient client = CreateClient(
            pipePair,
            new WorkerClientOptions
            {
                HeartbeatGrace = TimeSpan.FromMilliseconds(80),
                HeartbeatCheckInterval = TimeSpan.FromMilliseconds(20),
                EventChannelCapacity = 8,
            });
        await CompleteHandshakeAsync(client, pipePair);

        await WaitUntilAsync(
            () => client.State == WorkerClientState.Faulted,
            TestTimeout);

        Assert.Equal(WorkerClientState.Faulted, client.State);
    }

    private static WorkerClient CreateClient(
        PipePair pipePair,
        WorkerClientOptions? options = null)
    {
        WorkerFrameProtocolOptions frameOptions = new(SessionId);
        WorkerClientConnection connection = new(
            SessionId,
            Nonce,
            pipePair.GatewayStream,
            frameOptions);

        return new WorkerClient(connection, options);
    }

    private static async Task CompleteHandshakeAsync(
        WorkerClient client,
        PipePair pipePair)
    {
        Task startTask = client.StartAsync(CancellationToken.None);

        WorkerEnvelope gatewayHello = await pipePair.WorkerReader.ReadAsync().AsTask().WaitAsync(TestTimeout);
        Assert.Equal(WorkerEnvelope.BodyOneofCase.GatewayHello, gatewayHello.BodyCase);
        Assert.Equal(Nonce, gatewayHello.GatewayHello.Nonce);
        Assert.Equal(GatewayContractInfo.WorkerProtocolVersion, gatewayHello.GatewayHello.SupportedProtocolVersion);

        await pipePair.WorkerWriter.WriteAsync(CreateWorkerHelloEnvelope());
        await pipePair.WorkerWriter.WriteAsync(CreateWorkerReadyEnvelope());
        await startTask.WaitAsync(TestTimeout);
    }

    private static WorkerCommand CreateCommand(MxCommandKind kind)
    {
        return new WorkerCommand
        {
            Command = new MxCommand
            {
                Kind = kind,
            },
        };
    }

    private static WorkerEnvelope CreateWorkerHelloEnvelope()
    {
        return CreateWorkerEnvelope(
            correlationId: string.Empty,
            sequence: 1,
            envelope => envelope.WorkerHello = new WorkerHello
            {
                ProtocolVersion = GatewayContractInfo.WorkerProtocolVersion,
                Nonce = Nonce,
                WorkerProcessId = WorkerProcessId,
                WorkerVersion = "fake-worker",
            });
    }

    private static WorkerEnvelope CreateWorkerReadyEnvelope()
    {
        return CreateWorkerEnvelope(
            correlationId: string.Empty,
            sequence: 2,
            envelope => envelope.WorkerReady = new WorkerReady
            {
                WorkerProcessId = WorkerProcessId,
                MxaccessProgid = "LMXProxy.LMXProxyServer.1",
                MxaccessClsid = "{C30B52F5-2CB5-4760-AF0A-3A344A7EB5DC}",
            });
    }

    private static WorkerEnvelope CreateCommandReplyEnvelope(
        string correlationId,
        MxCommandKind kind)
    {
        return CreateWorkerEnvelope(
            correlationId,
            sequence: 10,
            envelope => envelope.WorkerCommandReply = new WorkerCommandReply
            {
                Reply = new MxCommandReply
                {
                    SessionId = SessionId,
                    CorrelationId = correlationId,
                    Kind = kind,
                },
            });
    }

    private static WorkerEnvelope CreateEventEnvelope(
        ulong sequence,
        MxEventFamily family)
    {
        return CreateWorkerEnvelope(
            correlationId: string.Empty,
            sequence,
            envelope => envelope.WorkerEvent = new WorkerEvent
            {
                Event = new MxEvent
                {
                    SessionId = SessionId,
                    Family = family,
                    WorkerSequence = sequence,
                },
            });
    }

    private static WorkerEnvelope CreateWorkerEnvelope(
        string correlationId,
        ulong sequence,
        Action<WorkerEnvelope> setBody)
    {
        WorkerEnvelope envelope = new()
        {
            ProtocolVersion = GatewayContractInfo.WorkerProtocolVersion,
            SessionId = SessionId,
            Sequence = sequence,
            CorrelationId = correlationId,
        };
        setBody(envelope);

        return envelope;
    }

    private static async Task WaitUntilAsync(
        Func<bool> predicate,
        TimeSpan timeout)
    {
        using CancellationTokenSource cancellationTokenSource = new(timeout);
        while (!predicate())
        {
            await Task.Delay(TimeSpan.FromMilliseconds(10), cancellationTokenSource.Token);
        }
    }

    private sealed class PipePair : IAsyncDisposable
    {
        private readonly NamedPipeClientStream _workerStream;
        private bool _workerSideDisposed;

        private PipePair(
            NamedPipeServerStream gatewayStream,
            NamedPipeClientStream workerStream)
        {
            GatewayStream = gatewayStream;
            _workerStream = workerStream;
            WorkerReader = new WorkerFrameReader(_workerStream, new WorkerFrameProtocolOptions(SessionId));
            WorkerWriter = new WorkerFrameWriter(_workerStream, new WorkerFrameProtocolOptions(SessionId));
        }

        public NamedPipeServerStream GatewayStream { get; }

        public WorkerFrameReader WorkerReader { get; }

        public WorkerFrameWriter WorkerWriter { get; }

        public static async Task<PipePair> CreateAsync()
        {
            string pipeName = $"mxaccessgw-workerclient-tests-{Guid.NewGuid():N}";
            NamedPipeServerStream gatewayStream = new(
                pipeName,
                PipeDirection.InOut,
                maxNumberOfServerInstances: 1,
                PipeTransmissionMode.Byte,
                PipeOptions.Asynchronous);
            NamedPipeClientStream workerStream = new(
                ".",
                pipeName,
                PipeDirection.InOut,
                PipeOptions.Asynchronous);

            Task waitForConnectionTask = gatewayStream.WaitForConnectionAsync();
            await workerStream.ConnectAsync();
            await waitForConnectionTask;

            return new PipePair(gatewayStream, workerStream);
        }

        public async ValueTask DisposeWorkerSideAsync()
        {
            if (_workerSideDisposed)
            {
                return;
            }

            await _workerStream.DisposeAsync();
            _workerSideDisposed = true;
        }

        public async ValueTask DisposeAsync()
        {
            await DisposeWorkerSideAsync();
            await GatewayStream.DisposeAsync();
        }
    }
}