using System.IO.Pipes;
using Microsoft.Extensions.Logging;
using Microsoft.Extensions.Options;
using MxGateway.Contracts;
using MxGateway.Contracts.Proto;
using MxGateway.Server.Configuration;
using MxGateway.Server.Metrics;
using MxGateway.Server.Workers;

namespace MxGateway.Server.Sessions;

public sealed class SessionWorkerClientFactory : ISessionWorkerClientFactory
{
    private readonly IWorkerProcessLauncher _workerProcessLauncher;
    private readonly GatewayMetrics _metrics;
    private readonly TimeProvider _timeProvider;
    private readonly ILoggerFactory _loggerFactory;
    private readonly GatewayOptions _options;

    public SessionWorkerClientFactory(
        IWorkerProcessLauncher workerProcessLauncher,
        IOptions<GatewayOptions> options,
        GatewayMetrics metrics,
        ILoggerFactory loggerFactory,
        TimeProvider? timeProvider = null)
    {
        _workerProcessLauncher = workerProcessLauncher ?? throw new ArgumentNullException(nameof(workerProcessLauncher));
        ArgumentNullException.ThrowIfNull(options);
        _metrics = metrics ?? throw new ArgumentNullException(nameof(metrics));
        _loggerFactory = loggerFactory ?? throw new ArgumentNullException(nameof(loggerFactory));
        _timeProvider = timeProvider ?? TimeProvider.System;
        _options = options.Value;
    }

    public async Task<IWorkerClient> CreateAsync(
        GatewaySession session,
        CancellationToken cancellationToken)
    {
        ArgumentNullException.ThrowIfNull(session);

        NamedPipeServerStream? pipe = CreatePipe(session.PipeName);
        WorkerProcessHandle? processHandle = null;
        IWorkerClient? workerClient = null;
        try
        {
            session.TransitionTo(SessionState.StartingWorker);
            processHandle = await _workerProcessLauncher
                .LaunchAsync(
                    new WorkerProcessLaunchRequest(
                        session.SessionId,
                        session.PipeName,
                        GatewayContractInfo.WorkerProtocolVersion,
                        session.Nonce,
                        pipe),
                    cancellationToken)
                .ConfigureAwait(false);

            session.TransitionTo(SessionState.WaitingForPipe);
            await WaitForPipeConnectionAsync(pipe, session.StartupTimeout, cancellationToken).ConfigureAwait(false);

            session.TransitionTo(SessionState.Handshaking);
            WorkerFrameProtocolOptions frameOptions = new(
                session.SessionId,
                GatewayContractInfo.WorkerProtocolVersion,
                _options.Worker.MaxMessageBytes);
            WorkerClientConnection connection = new(
                session.SessionId,
                session.Nonce,
                pipe,
                frameOptions,
                processHandle);
            WorkerClientOptions clientOptions = new()
            {
                HeartbeatGrace = TimeSpan.FromSeconds(_options.Worker.HeartbeatGraceSeconds),
                HeartbeatCheckInterval = TimeSpan.FromSeconds(_options.Worker.HeartbeatIntervalSeconds),
                EventChannelCapacity = _options.Events.QueueCapacity,
            };

            workerClient = new WorkerClient(
                connection,
                clientOptions,
                _metrics,
                _timeProvider,
                _loggerFactory.CreateLogger<WorkerClient>());

            pipe = null;
            processHandle = null;

            session.TransitionTo(SessionState.InitializingWorker);
            await workerClient.StartAsync(cancellationToken).ConfigureAwait(false);

            return workerClient;
        }
        catch
        {
            if (workerClient is not null)
            {
                await workerClient.DisposeAsync().ConfigureAwait(false);
            }
            else
            {
                if (processHandle is not null)
                {
                    try
                    {
                        if (!processHandle.Process.HasExited)
                        {
                            processHandle.Process.Kill(entireProcessTree: true);
                            _metrics.WorkerKilled("OpenSessionFailed");
                        }
                    }
                    finally
                    {
                        processHandle.Dispose();
                    }
                }

                pipe?.Dispose();
            }

            throw;
        }
    }

    private static NamedPipeServerStream CreatePipe(string pipeName)
    {
        return new NamedPipeServerStream(
            pipeName,
            PipeDirection.InOut,
            maxNumberOfServerInstances: 1,
            PipeTransmissionMode.Byte,
            PipeOptions.Asynchronous);
    }

    private static async Task WaitForPipeConnectionAsync(
        NamedPipeServerStream pipe,
        TimeSpan startupTimeout,
        CancellationToken cancellationToken)
    {
        using CancellationTokenSource timeout = CancellationTokenSource.CreateLinkedTokenSource(cancellationToken);
        timeout.CancelAfter(startupTimeout);
        await pipe.WaitForConnectionAsync(timeout.Token).ConfigureAwait(false);
    }
}