using System.Collections.Concurrent;
using System.Diagnostics;
using Google.Protobuf.WellKnownTypes;
using Grpc.Core;
using Microsoft.Extensions.Logging;
using Microsoft.Extensions.Options;
using MxGateway.Contracts;
using MxGateway.Contracts.Proto;
using MxGateway.Server.Configuration;
using MxGateway.Server.Grpc;
using MxGateway.Server.Metrics;
using MxGateway.Server.Security.Authorization;
using MxGateway.Server.Sessions;
using MxGateway.Server.Workers;
using Xunit.Abstractions;

namespace MxGateway.IntegrationTests;

public sealed class WorkerLiveMxAccessSmokeTests(ITestOutputHelper output)
{
    private static readonly TimeSpan CommandTimeout = TimeSpan.FromSeconds(15);
    private static readonly TimeSpan StreamShutdownTimeout = TimeSpan.FromSeconds(10);

    [LiveMxAccessFact]
    [Trait("Category", "LiveMxAccess")]
    public async Task GatewaySession_WithLiveWorker_RegistersAdvisesStreamsDataAndCloses()
    {
        string workerExecutablePath = IntegrationTestEnvironment.ResolveLiveMxAccessWorkerExecutablePath();
        Assert.True(
            File.Exists(workerExecutablePath),
            $"Live MXAccess worker executable was not found at {workerExecutablePath}. Build the worker or set {IntegrationTestEnvironment.LiveMxAccessWorkerExecutableVariableName}.");

        TestWorkerProcessFactory processFactory = new(output);
        await using GatewayServiceFixture fixture = new(workerExecutablePath, processFactory, output);

        string? sessionId = null;
        RecordingServerStreamWriter<MxEvent>? eventWriter = null;
        Task? streamTask = null;

        try
        {
            OpenSessionReply openReply = await fixture.Service.OpenSession(
                new OpenSessionRequest
                {
                    ClientSessionName = "live-mxaccess-smoke",
                    ClientCorrelationId = "live-open",
                    CommandTimeout = Duration.FromTimeSpan(CommandTimeout),
                },
                new TestServerCallContext()).ConfigureAwait(false);

            sessionId = openReply.SessionId;
            output.WriteLine($"OpenSession status={openReply.ProtocolStatus.Code} session={sessionId} worker_pid={openReply.WorkerProcessId}");
            Assert.Equal(ProtocolStatusCode.Ok, openReply.ProtocolStatus.Code);
            Assert.True(openReply.WorkerProcessId > 0);

            eventWriter = new RecordingServerStreamWriter<MxEvent>();
            streamTask = fixture.Service.StreamEvents(
                new StreamEventsRequest { SessionId = sessionId },
                eventWriter,
                new TestServerCallContext());

            MxCommandReply registerReply = await fixture.Service.Invoke(
                CreateRegisterRequest(sessionId),
                new TestServerCallContext()).ConfigureAwait(false);
            LogReply("Register", registerReply);
            Assert.Equal(ProtocolStatusCode.Ok, registerReply.ProtocolStatus.Code);
            Assert.True(registerReply.Register.ServerHandle > 0);

            MxCommandReply addItemReply = await fixture.Service.Invoke(
                CreateAddItemRequest(sessionId, registerReply.Register.ServerHandle),
                new TestServerCallContext()).ConfigureAwait(false);
            LogReply("AddItem", addItemReply);
            Assert.Equal(ProtocolStatusCode.Ok, addItemReply.ProtocolStatus.Code);
            Assert.True(addItemReply.AddItem.ItemHandle > 0);

            MxCommandReply adviseReply = await fixture.Service.Invoke(
                CreateAdviseRequest(
                    sessionId,
                    registerReply.Register.ServerHandle,
                    addItemReply.AddItem.ItemHandle),
                new TestServerCallContext()).ConfigureAwait(false);
            LogReply("Advise", adviseReply);
            Assert.Equal(ProtocolStatusCode.Ok, adviseReply.ProtocolStatus.Code);

            MxEvent dataChange = await eventWriter
                .WaitForFirstMessageAsync(IntegrationTestEnvironment.LiveMxAccessEventTimeout)
                .ConfigureAwait(false);
            LogEvent(dataChange);

            Assert.Equal(MxEventFamily.OnDataChange, dataChange.Family);
            Assert.Equal(sessionId, dataChange.SessionId);
            Assert.Equal(registerReply.Register.ServerHandle, dataChange.ServerHandle);
            Assert.Equal(addItemReply.AddItem.ItemHandle, dataChange.ItemHandle);
        }
        finally
        {
            try
            {
                if (!string.IsNullOrWhiteSpace(sessionId))
                {
                    await CloseSessionAsync(fixture, sessionId).ConfigureAwait(false);
                }

                if (streamTask is not null)
                {
                    await streamTask.WaitAsync(StreamShutdownTimeout).ConfigureAwait(false);
                }
            }
            finally
            {
                await processFactory.WaitForProcessesAsync(StreamShutdownTimeout).ConfigureAwait(false);
            }
        }
    }

    private static MxCommandRequest CreateRegisterRequest(string sessionId)
    {
        return new MxCommandRequest
        {
            SessionId = sessionId,
            ClientCorrelationId = "live-register",
            Command = new MxCommand
            {
                Kind = MxCommandKind.Register,
                Register = new RegisterCommand
                {
                    ClientName = IntegrationTestEnvironment.LiveMxAccessClientName,
                },
            },
        };
    }

    private static MxCommandRequest CreateAddItemRequest(
        string sessionId,
        int serverHandle)
    {
        return new MxCommandRequest
        {
            SessionId = sessionId,
            ClientCorrelationId = "live-add-item",
            Command = new MxCommand
            {
                Kind = MxCommandKind.AddItem,
                AddItem = new AddItemCommand
                {
                    ServerHandle = serverHandle,
                    ItemDefinition = IntegrationTestEnvironment.LiveMxAccessItem,
                },
            },
        };
    }

    private static MxCommandRequest CreateAdviseRequest(
        string sessionId,
        int serverHandle,
        int itemHandle)
    {
        return new MxCommandRequest
        {
            SessionId = sessionId,
            ClientCorrelationId = "live-advise",
            Command = new MxCommand
            {
                Kind = MxCommandKind.Advise,
                Advise = new AdviseCommand
                {
                    ServerHandle = serverHandle,
                    ItemHandle = itemHandle,
                },
            },
        };
    }

    private async Task CloseSessionAsync(
        GatewayServiceFixture fixture,
        string sessionId)
    {
        CloseSessionReply closeReply = await fixture.Service.CloseSession(
            new CloseSessionRequest
            {
                SessionId = sessionId,
                ClientCorrelationId = "live-close",
            },
            new TestServerCallContext()).ConfigureAwait(false);

        output.WriteLine($"CloseSession status={closeReply.ProtocolStatus.Code} final_state={closeReply.FinalState}");
    }

    private void LogReply(
        string method,
        MxCommandReply reply)
    {
        output.WriteLine(
            $"{method} status={reply.ProtocolStatus.Code} hresult={reply.Hresult} diagnostic={reply.DiagnosticMessage}");

        foreach (MxStatusProxy status in reply.Statuses)
        {
            output.WriteLine(
                $"{method} mxstatus success={status.Success} category={status.Category} detail={status.Detail} text={status.DiagnosticText}");
        }
    }

    private void LogEvent(MxEvent dataChange)
    {
        output.WriteLine(
            $"Event family={dataChange.Family} worker_sequence={dataChange.WorkerSequence} server_handle={dataChange.ServerHandle} item_handle={dataChange.ItemHandle} quality={dataChange.Quality}");
        output.WriteLine(
            $"Event value_type={dataChange.Value?.DataType} raw_status={dataChange.RawStatus}");
    }

    private sealed class GatewayServiceFixture : IAsyncDisposable
    {
        private readonly GatewayMetrics _metrics = new();
        private readonly SessionRegistry _registry = new();
        private readonly ILoggerFactory _loggerFactory;

        public GatewayServiceFixture(
            string workerExecutablePath,
            IWorkerProcessFactory processFactory,
            ITestOutputHelper output)
        {
            IOptions<GatewayOptions> options = Options.Create(CreateOptions(workerExecutablePath));
            _loggerFactory = LoggerFactory.Create(builder => builder.AddProvider(new TestOutputLoggerProvider(output)));
            WorkerProcessLauncher launcher = new(
                options,
                processFactory,
                new WorkerProcessStartedProbe(),
                _metrics);
            SessionWorkerClientFactory workerClientFactory = new(
                launcher,
                options,
                _metrics,
                _loggerFactory);
            SessionManager sessionManager = new(
                _registry,
                workerClientFactory,
                options,
                _metrics,
                logger: _loggerFactory.CreateLogger<SessionManager>());
            MxAccessGrpcMapper mapper = new();
            EventStreamService eventStreamService = new(
                sessionManager,
                options,
                mapper,
                _metrics,
                _loggerFactory.CreateLogger<EventStreamService>());

            Service = new MxAccessGatewayService(
                sessionManager,
                new GatewayRequestIdentityAccessor(),
                new MxAccessGrpcRequestValidator(),
                mapper,
                eventStreamService,
                _loggerFactory.CreateLogger<MxAccessGatewayService>());
        }

        public MxAccessGatewayService Service { get; }

        public async ValueTask DisposeAsync()
        {
            foreach (GatewaySession session in _registry.Snapshot())
            {
                await session.DisposeAsync().ConfigureAwait(false);
            }

            _loggerFactory.Dispose();
            _metrics.Dispose();
        }

        private static GatewayOptions CreateOptions(string workerExecutablePath)
        {
            return new GatewayOptions
            {
                Worker = new WorkerOptions
                {
                    ExecutablePath = workerExecutablePath,
                    StartupTimeoutSeconds = 30,
                    ShutdownTimeoutSeconds = 15,
                    HeartbeatIntervalSeconds = 5,
                    HeartbeatGraceSeconds = 15,
                    MaxMessageBytes = WorkerFrameProtocolOptions.DefaultMaxMessageBytes,
                    RequiredArchitecture = WorkerArchitecture.X86,
                },
                Sessions = new SessionOptions
                {
                    DefaultCommandTimeoutSeconds = 15,
                    MaxSessions = 1,
                },
                Events = new EventOptions
                {
                    QueueCapacity = 32,
                },
            };
        }
    }

    private sealed class RecordingServerStreamWriter<T> : IServerStreamWriter<T>
    {
        private readonly object syncRoot = new();
        private readonly TaskCompletionSource<T> firstMessage = new(TaskCreationOptions.RunContinuationsAsynchronously);
        private readonly List<T> messages = [];

        public IReadOnlyList<T> Messages
        {
            get
            {
                lock (syncRoot)
                {
                    return messages.ToArray();
                }
            }
        }

        public WriteOptions? WriteOptions { get; set; }

        public Task WriteAsync(T message)
        {
            lock (syncRoot)
            {
                messages.Add(message);
            }

            firstMessage.TrySetResult(message);
            return Task.CompletedTask;
        }

        public async Task<T> WaitForFirstMessageAsync(TimeSpan timeout)
        {
            return await firstMessage.Task.WaitAsync(timeout).ConfigureAwait(false);
        }
    }

    private sealed class TestServerCallContext(CancellationToken cancellationToken = default) : ServerCallContext
    {
        private readonly Metadata requestHeaders = [];
        private readonly Metadata responseTrailers = [];
        private readonly Dictionary<object, object> userState = [];
        private Status status;
        private WriteOptions? writeOptions;

        protected override string MethodCore => "/mxaccess_gateway.v1.MxAccessGateway/Test";

        protected override string HostCore => "localhost";

        protected override string PeerCore => "ipv4:127.0.0.1:5000";

        protected override DateTime DeadlineCore => DateTime.UtcNow.AddMinutes(1);

        protected override Metadata RequestHeadersCore => requestHeaders;

        protected override CancellationToken CancellationTokenCore => cancellationToken;

        protected override Metadata ResponseTrailersCore => responseTrailers;

        protected override Status StatusCore
        {
            get => status;
            set => status = value;
        }

        protected override WriteOptions? WriteOptionsCore
        {
            get => writeOptions;
            set => writeOptions = value;
        }

        protected override AuthContext AuthContextCore { get; } = new(
            string.Empty,
            new Dictionary<string, List<AuthProperty>>(StringComparer.Ordinal));

        protected override IDictionary<object, object> UserStateCore => userState;

        protected override Task WriteResponseHeadersAsyncCore(Metadata responseHeaders)
        {
            return Task.CompletedTask;
        }

        protected override ContextPropagationToken CreatePropagationTokenCore(
            ContextPropagationOptions? options)
        {
            throw new NotSupportedException();
        }
    }

    private sealed class TestWorkerProcessFactory(ITestOutputHelper output) : IWorkerProcessFactory
    {
        private readonly ConcurrentBag<TestWorkerProcess> processes = [];

        public IWorkerProcess Start(ProcessStartInfo startInfo)
        {
            startInfo.RedirectStandardError = true;
            startInfo.RedirectStandardOutput = true;
            startInfo.UseShellExecute = false;

            Process process = new()
            {
                StartInfo = startInfo,
                EnableRaisingEvents = true,
            };

            process.OutputDataReceived += (_, args) => WriteWorkerOutput("stdout", args.Data);
            process.ErrorDataReceived += (_, args) => WriteWorkerOutput("stderr", args.Data);

            if (!process.Start())
            {
                process.Dispose();
                throw new InvalidOperationException("Worker process failed to start.");
            }

            process.BeginOutputReadLine();
            process.BeginErrorReadLine();

            TestWorkerProcess workerProcess = new(process);
            processes.Add(workerProcess);
            output.WriteLine($"WorkerProcess started pid={workerProcess.Id} path={startInfo.FileName}");

            return workerProcess;
        }

        public async Task WaitForProcessesAsync(TimeSpan timeout)
        {
            foreach (TestWorkerProcess process in processes)
            {
                if (process.HasExited)
                {
                    output.WriteLine($"WorkerProcess exited pid={process.Id} exit_code={process.ExitCode}");
                    continue;
                }

                using CancellationTokenSource timeoutCancellation = new(timeout);
                await process.WaitForExitAsync(timeoutCancellation.Token).ConfigureAwait(false);
                output.WriteLine($"WorkerProcess exited pid={process.Id} exit_code={process.ExitCode}");
            }
        }

        private void WriteWorkerOutput(
            string streamName,
            string? line)
        {
            if (!string.IsNullOrWhiteSpace(line))
            {
                output.WriteLine($"worker_{streamName}: {line}");
            }
        }
    }

    private sealed class TestWorkerProcess(Process process) : IWorkerProcess
    {
        public int Id => process.Id;

        public bool HasExited => process.HasExited;

        public int? ExitCode => process.HasExited ? process.ExitCode : null;

        public async ValueTask WaitForExitAsync(CancellationToken cancellationToken)
        {
            await process.WaitForExitAsync(cancellationToken).ConfigureAwait(false);
        }

        public void Kill(bool entireProcessTree)
        {
            process.Kill(entireProcessTree);
        }

        public void Dispose()
        {
            process.Dispose();
        }
    }

    private sealed class TestOutputLoggerProvider(ITestOutputHelper output) : ILoggerProvider
    {
        public ILogger CreateLogger(string categoryName)
        {
            return new TestOutputLogger(output, categoryName);
        }

        public void Dispose()
        {
        }
    }

    private sealed class TestOutputLogger(
        ITestOutputHelper output,
        string categoryName) : ILogger
    {
        public IDisposable? BeginScope<TState>(TState state)
            where TState : notnull
        {
            return null;
        }

        public bool IsEnabled(LogLevel logLevel)
        {
            return logLevel >= LogLevel.Information;
        }

        public void Log<TState>(
            LogLevel logLevel,
            EventId eventId,
            TState state,
            Exception? exception,
            Func<TState, Exception?, string> formatter)
        {
            if (!IsEnabled(logLevel))
            {
                return;
            }

            output.WriteLine($"{logLevel} {categoryName}: {formatter(state, exception)}");
            if (exception is not null)
            {
                output.WriteLine(exception.ToString());
            }
        }
    }
}