naps2/NAPS2.Lib.WinForms/Platform/Windows/WindowsApplicationLifecycle.cs

using System.Security.Principal;
using System.Windows.Forms;
using NAPS2.Remoting;

namespace NAPS2.Platform.Windows;

// TODO: Can we add tests for this somehow?
public class WindowsApplicationLifecycle : ApplicationLifecycle
{
    private readonly StillImage _sti;
    private readonly WindowsEventLogger _windowsEventLogger;
    private readonly ProcessCoordinator _processCoordinator;

    private bool _shouldCreateEventSource;
    private int _returnCode;

    public WindowsApplicationLifecycle(StillImage sti, WindowsEventLogger windowsEventLogger,
        ProcessCoordinator processCoordinator, Naps2Config config) : base(processCoordinator, config)
    {
        _sti = sti;
        _windowsEventLogger = windowsEventLogger;
        _processCoordinator = processCoordinator;
    }

    /// <summary>
    /// Parses the NAPS2 GUI command-line arguments.
    /// </summary>
    /// <param name="args"></param>
    public override void ParseArgs(string[] args)
    {
        bool silent = args.Any(x => x.Equals("/Silent", StringComparison.InvariantCultureIgnoreCase));
        bool noElevation = args.Any(x => x.Equals("/NoElevation", StringComparison.InvariantCultureIgnoreCase));
        bool failedUpdate = args.Any(x => x.Equals("/FailedUpdate", StringComparison.InvariantCultureIgnoreCase));

        // Utility function to send a message to the user (if /Silent is not specified)
        void Out(string message)
        {
            if (!silent)
            {
                MessageBox.Show(message);
            }
        }

        // Utility function to run the given action, elevating to admin permissions if necessary (and /NoElevation is not specified)
        bool ElevationRequired(Action action)
        {
            try
            {
                action();
                return true;
            }
            catch (Exception)
            {
                if (!noElevation && !IsElevated)
                {
                    RelaunchAsElevated();
                    return false;
                }
                throw;
            }
        }

        if (failedUpdate)
        {
            Out(MiscResources.UpdateError);
        }

        // Let StillImage figure out what it should do from the command-line args
        _sti.ParseArgs(args);

        // Actually do any specified StillImage actions
        if (_sti.ShouldRegister)
        {
            try
            {
                if (ElevationRequired(_sti.Register))
                {
                    Out("Successfully registered STI. A reboot may be needed.");
                }
            }
            catch (Exception ex)
            {
                Log.ErrorException("Error registering STI", ex);
                Out("Error registering STI. Maybe run as administrator?");
                _returnCode = 1;
            }
        }
        else if (_sti.ShouldUnregister)
        {
            try
            {
                if (ElevationRequired(_sti.Unregister))
                {
                    Out("Successfully unregistered STI. A reboot may be needed.");
                }
            }
            catch (Exception ex)
            {
                Log.ErrorException("Error unregistering STI", ex);
                Out("Error unregistering STI. Maybe run as administrator?");
                _returnCode = 1;
            }
        }

        _shouldCreateEventSource =
            args.Any(x => x.Equals("/CreateEventSource", StringComparison.InvariantCultureIgnoreCase));
        if (_shouldCreateEventSource)
        {
            try
            {
                if (ElevationRequired(_windowsEventLogger.CreateEventSource))
                {
                    Out("Successfully created event source.");
                }
            }
            catch (Exception ex)
            {
                Log.ErrorException("Error creating event source", ex);
                Out("Error creating event source. Maybe run as administrator?");
                _returnCode = 1;
            }
        }
    }

    private bool IsElevated
    {
        get
        {
            var identity = WindowsIdentity.GetCurrent();
            if (identity == null)
            {
                return false;
            }
            var pricipal = new WindowsPrincipal(identity);
            return pricipal.IsInRole(WindowsBuiltInRole.Administrator);
        }
    }

    private void RelaunchAsElevated()
    {
        Process.Start(new ProcessStartInfo
        {
            Verb = "runas",
            FileName = AssemblyHelper.EntryFile,
            Arguments = string.Join(" ", Environment.GetCommandLineArgs().Skip(1)) + " /NoElevation"
        });
    }

    /// <summary>
    /// May terminate the NAPS2 GUI based on the command-line arguments and running processes, sending messages to other processes if appropriate.
    /// </summary>
    public override void ExitIfRedundant()
    {
        if (_sti.ShouldRegister || _sti.ShouldUnregister || _shouldCreateEventSource)
        {
            // Was just started by the user to (un)register STI
            Environment.Exit(_returnCode);
        }

        // If this instance of NAPS2 was spawned by STI, then there may be another instance of NAPS2 we want to get the scan signal instead
        if (_sti.ShouldScan)
        {
            // Try each possible process in turn until one receives the message (most recently started first)
            foreach (var process in GetOtherNaps2Processes())
            {
                // Another instance of NAPS2 is running, so send it the "Scan" signal
                SetMainWindowToForeground(process);
                if (_processCoordinator.ScanWithDevice(process, 100, _sti.DeviceID!))
                {
                    // Successful, so this instance can be closed before showing any UI
                    Environment.Exit(0);
                }
            }
        }

        base.ExitIfRedundant();
    }

    protected override void SetMainWindowToForeground(Process process)
    {
        if (process.MainWindowHandle != IntPtr.Zero)
        {
            Win32.SetForegroundWindow(process.MainWindowHandle);
        }
    }

    private static IEnumerable<Process> GetOtherNaps2Processes()
    {
        Process currentProcess = Process.GetCurrentProcess();
        var otherProcesses = Process.GetProcessesByName(currentProcess.ProcessName)
            .Where(x => x.Id != currentProcess.Id)
            .OrderByDescending(x => x.StartTime);
        return otherProcesses;
    }
}