using System;
using System.IO;
using System.IO.Pipes;
using System.Threading;
using System.Threading.Tasks;
using Google.Protobuf.WellKnownTypes;
using MxGateway.Contracts;
using MxGateway.Contracts.Proto;
using MxGateway.Worker.Bootstrap;
using MxGateway.Worker.Ipc;
using MxGateway.Worker.Tests.TestSupport;

namespace MxGateway.Worker.Tests.Ipc;

public sealed class WorkerPipeClientTests
{
    /// <summary>Verifies that worker client connects and completes handshake.</summary>
    [Fact]
    public async Task RunAsync_ConnectsToPipeAndCompletesHandshake()
    {
        string pipeName = $"mxaccess-gateway-test-{Guid.NewGuid():N}";
        WorkerOptions workerOptions = new(
            "session-1",
            pipeName,
            GatewayContractInfo.WorkerProtocolVersion,
            "nonce-secret");
        WorkerFrameProtocolOptions frameOptions = new(workerOptions);

        using NamedPipeServerStream server = new(
            pipeName,
            PipeDirection.InOut,
            1,
            PipeTransmissionMode.Byte,
            PipeOptions.Asynchronous);

        WorkerPipeClient client = new(
            connectTimeoutMilliseconds: 5000,
            (stream, options) => CreateSession(stream, options));
        Task clientTask = client.RunAsync(workerOptions);

        await Task.Factory.FromAsync(server.BeginWaitForConnection, server.EndWaitForConnection, null);

        WorkerFrameReader reader = new(server, frameOptions);
        WorkerFrameWriter writer = new(server, frameOptions);

        await writer.WriteAsync(new WorkerEnvelope
        {
            ProtocolVersion = GatewayContractInfo.WorkerProtocolVersion,
            SessionId = "session-1",
            Sequence = 1,
            GatewayHello = new GatewayHello
            {
                SupportedProtocolVersion = GatewayContractInfo.WorkerProtocolVersion,
                Nonce = "nonce-secret",
                GatewayVersion = "test-gateway",
            },
        });

        WorkerEnvelope hello = await reader.ReadAsync();
        Assert.Equal(WorkerEnvelope.BodyOneofCase.WorkerHello, hello.BodyCase);
        Assert.Equal("nonce-secret", hello.WorkerHello.Nonce);

        WorkerEnvelope ready = await reader.ReadAsync();
        Assert.Equal(WorkerEnvelope.BodyOneofCase.WorkerReady, ready.BodyCase);

        await writer.WriteAsync(new WorkerEnvelope
        {
            ProtocolVersion = GatewayContractInfo.WorkerProtocolVersion,
            SessionId = "session-1",
            Sequence = 2,
            WorkerShutdown = new WorkerShutdown
            {
                GracePeriod = Duration.FromTimeSpan(TimeSpan.FromSeconds(1)),
                Reason = "test-complete",
            },
        });

        WorkerEnvelope shutdownAck = await ReadUntilAsync(
            reader,
            WorkerEnvelope.BodyOneofCase.WorkerShutdownAck);
        Assert.Equal(WorkerEnvelope.BodyOneofCase.WorkerShutdownAck, shutdownAck.BodyCase);
        await clientTask;
    }

    /// <summary>Verifies that worker client retries until pipe server becomes available.</summary>
    [Fact]
    public async Task RunAsync_RetriesUntilPipeServerAppears()
    {
        string pipeName = $"mxaccess-gateway-test-{Guid.NewGuid():N}";
        WorkerOptions workerOptions = new(
            "session-1",
            pipeName,
            GatewayContractInfo.WorkerProtocolVersion,
            "nonce-secret");
        WorkerFrameProtocolOptions frameOptions = new(workerOptions);

        WorkerPipeClient client = new(
            logger: null,
            connectTimeoutMilliseconds: 1000,
            connectAttemptTimeoutMilliseconds: 50,
            (stream, options, _) => CreateSession(stream, options));
        Task clientTask = client.RunAsync(workerOptions);

        await Task.Delay(150);

        using NamedPipeServerStream server = new(
            pipeName,
            PipeDirection.InOut,
            1,
            PipeTransmissionMode.Byte,
            PipeOptions.Asynchronous);

        await Task.Factory.FromAsync(server.BeginWaitForConnection, server.EndWaitForConnection, null);

        WorkerFrameReader reader = new(server, frameOptions);
        WorkerFrameWriter writer = new(server, frameOptions);

        await writer.WriteAsync(CreateGatewayHello());
        Assert.Equal(WorkerEnvelope.BodyOneofCase.WorkerHello, (await reader.ReadAsync()).BodyCase);
        Assert.Equal(WorkerEnvelope.BodyOneofCase.WorkerReady, (await reader.ReadAsync()).BodyCase);
        await writer.WriteAsync(CreateShutdown());

        Assert.Equal(
            WorkerEnvelope.BodyOneofCase.WorkerShutdownAck,
            (await ReadUntilAsync(reader, WorkerEnvelope.BodyOneofCase.WorkerShutdownAck)).BodyCase);
        await clientTask;
    }

    /// <summary>Verifies that worker client throws timeout if pipe never appears.</summary>
    [Fact]
    public async Task RunAsync_WhenPipeNeverAppears_ThrowsTimeoutException()
    {
        WorkerOptions workerOptions = new(
            "session-1",
            $"mxaccess-gateway-test-{Guid.NewGuid():N}",
            GatewayContractInfo.WorkerProtocolVersion,
            "nonce-secret");

        WorkerPipeClient client = new(
            logger: null,
            connectTimeoutMilliseconds: 100,
            connectAttemptTimeoutMilliseconds: 50,
            (stream, options, _) => CreateSession(stream, options));

        await Assert.ThrowsAsync<TimeoutException>(async () => await client.RunAsync(workerOptions));
    }

    /// <summary>
    ///     Reads frames until one matching the expected body case is found,
    ///     skipping interleaved heartbeats (the first heartbeat is emitted
    ///     immediately on entering the heartbeat loop — see Worker-002).
    /// </summary>
    private static async Task<WorkerEnvelope> ReadUntilAsync(
        WorkerFrameReader reader,
        WorkerEnvelope.BodyOneofCase expectedBody)
    {
        while (true)
        {
            WorkerEnvelope envelope = await reader.ReadAsync();
            if (envelope.BodyCase == expectedBody)
            {
                return envelope;
            }
        }
    }

    private static WorkerPipeSession CreateSession(
        Stream stream,
        WorkerFrameProtocolOptions options)
    {
        return new WorkerPipeSession(
            new WorkerFrameReader(stream, options),
            new WorkerFrameWriter(stream, options),
            options,
            () => 1234,
            new WorkerPipeSessionOptions
            {
                HeartbeatInterval = TimeSpan.FromSeconds(30),
                HeartbeatGrace = TimeSpan.FromSeconds(30),
            },
            () => new FakeRuntimeSession());
    }

    private static WorkerEnvelope CreateGatewayHello()
    {
        return new WorkerEnvelope
        {
            ProtocolVersion = GatewayContractInfo.WorkerProtocolVersion,
            SessionId = "session-1",
            Sequence = 1,
            GatewayHello = new GatewayHello
            {
                SupportedProtocolVersion = GatewayContractInfo.WorkerProtocolVersion,
                Nonce = "nonce-secret",
                GatewayVersion = "test-gateway",
            },
        };
    }

    private static WorkerEnvelope CreateShutdown()
    {
        return new WorkerEnvelope
        {
            ProtocolVersion = GatewayContractInfo.WorkerProtocolVersion,
            SessionId = "session-1",
            Sequence = 2,
            WorkerShutdown = new WorkerShutdown
            {
                GracePeriod = Duration.FromTimeSpan(TimeSpan.FromSeconds(1)),
                Reason = "test-complete",
            },
        };
    }
}