personal-toolbox/src/PersonalToolbox/App.xaml.cs

using System.Configuration;
using System.Data;
using System.IO;
using System.IO.Pipes;
using System.Text;
using System.Windows;
using System.Threading;

namespace PersonalToolbox;

/// <summary>
/// Interaction logic for App.xaml
/// </summary>
public partial class App : System.Windows.Application
{
    private const string ActivatePipeName = "PersonalToolbox.Activate";

    private FileStream? _instanceLockFile;
    private CancellationTokenSource? _activationPipeCancellation;
    private MainWindow? _mainWindow;

    protected override async void OnStartup(StartupEventArgs e)
    {
        base.OnStartup(e);

        ShutdownMode = ShutdownMode.OnExplicitShutdown;

        if (!TryAcquireInstanceLock())
        {
            SignalExistingInstance();
            Environment.Exit(0);
            return;
        }

        var mainWindow = new MainWindow();
        _mainWindow = mainWindow;
        MainWindow = mainWindow;
        StartActivationPipe();

        await mainWindow.InitializeShellAsync();
        if (!mainWindow.StartHiddenToTray)
        {
            mainWindow.ShowMainWindow();
        }
        else
        {
            mainWindow.RefreshTrayMenu();
        }

        await mainWindow.RunStartupTasksAsync();
    }

    protected override void OnExit(ExitEventArgs e)
    {
        _activationPipeCancellation?.Cancel();
        _activationPipeCancellation?.Dispose();
        _instanceLockFile?.Dispose();
        base.OnExit(e);
    }

    private bool TryAcquireInstanceLock()
    {
        try
        {
            var appData = Environment.GetFolderPath(Environment.SpecialFolder.ApplicationData);
            var configDirectory = Path.Combine(appData, "PersonalToolbox");
            Directory.CreateDirectory(configDirectory);
            var lockPath = Path.Combine(configDirectory, "PersonalToolbox.lock");

            _instanceLockFile = new FileStream(lockPath, FileMode.OpenOrCreate, FileAccess.ReadWrite, FileShare.None);
            _instanceLockFile.SetLength(0);
            var processId = Encoding.UTF8.GetBytes(Environment.ProcessId.ToString());
            _instanceLockFile.Write(processId, 0, processId.Length);
            _instanceLockFile.Flush();
            return true;
        }
        catch (IOException)
        {
            return false;
        }
        catch (UnauthorizedAccessException)
        {
            return false;
        }
    }

    private static void SignalExistingInstance()
    {
        for (var attempt = 0; attempt < 3; attempt++)
        {
            try
            {
                using var pipe = new NamedPipeClientStream(".", ActivatePipeName, PipeDirection.Out);
                pipe.Connect(800);
                using var writer = new StreamWriter(pipe, Encoding.UTF8)
                {
                    AutoFlush = true
                };
                writer.WriteLine("show");
                return;
            }
            catch (IOException)
            {
            }
            catch (TimeoutException)
            {
            }

            Thread.Sleep(150);
        }
    }

    private void StartActivationPipe()
    {
        _activationPipeCancellation = new CancellationTokenSource();
        _ = Task.Run(() => ListenForActivationAsync(_activationPipeCancellation.Token));
    }

    private async Task ListenForActivationAsync(CancellationToken cancellationToken)
    {
        while (!cancellationToken.IsCancellationRequested)
        {
            try
            {
                await using var pipe = new NamedPipeServerStream(
                    ActivatePipeName,
                    PipeDirection.In,
                    1,
                    PipeTransmissionMode.Byte,
                    PipeOptions.Asynchronous);

                await pipe.WaitForConnectionAsync(cancellationToken);
                using var reader = new StreamReader(pipe, Encoding.UTF8);
                _ = await reader.ReadLineAsync(cancellationToken);

                await Dispatcher.BeginInvoke(() => _mainWindow?.ShowMainWindow());
            }
            catch (OperationCanceledException)
            {
                return;
            }
            catch (IOException)
            {
            }
        }
    }
}