using System;
using System.Diagnostics;
using System.Runtime.InteropServices;
using System.Threading;
using System.Threading.Tasks;
using Microsoft.UI.Dispatching;
using Microsoft.UI.Xaml;
using Microsoft.Windows.AppLifecycle;

namespace Wino.Mail.WinUI;

public class Program
{
    [STAThread]
    static int Main(string[] args)
    {
        WinRT.ComWrappersSupport.InitializeComWrappers();
        bool isRedirect = DecideRedirection();

        if (!isRedirect)
        {
            Application.Start((p) =>
            {
                var context = new DispatcherQueueSynchronizationContext(
                    DispatcherQueue.GetForCurrentThread());
                SynchronizationContext.SetSynchronizationContext(context);
                _ = new App();
            });
        }

        return 0;
    }

    private static bool DecideRedirection()
    {
        bool isRedirect = false;
        AppActivationArguments args = AppInstance.GetCurrent().GetActivatedEventArgs();
        ExtendedActivationKind kind = args.Kind;
        AppInstance keyInstance = AppInstance.FindOrRegisterForKey("WinoMailSingleInstance");

        if (keyInstance.IsCurrent)
        {
            keyInstance.Activated += OnActivated;
        }
        else
        {
            isRedirect = true;
            RedirectActivationTo(args, keyInstance);
        }

        return isRedirect;
    }

    [DllImport("kernel32.dll", CharSet = CharSet.Unicode)]
    private static extern IntPtr CreateEvent(
        IntPtr lpEventAttributes, bool bManualReset,
        bool bInitialState, string lpName);

    [DllImport("kernel32.dll")]
    private static extern bool SetEvent(IntPtr hEvent);

    [DllImport("ole32.dll")]
    private static extern uint CoWaitForMultipleObjects(
        uint dwFlags, uint dwMilliseconds, ulong nHandles,
        IntPtr[] pHandles, out uint dwIndex);

    [DllImport("user32.dll")]
    static extern bool SetForegroundWindow(IntPtr hWnd);

    private static IntPtr redirectEventHandle = IntPtr.Zero;

    // Do the redirection on another thread, and use a non-blocking
    // wait method to wait for the redirection to complete.
    public static void RedirectActivationTo(AppActivationArguments args,
                                            AppInstance keyInstance)
    {
        redirectEventHandle = CreateEvent(IntPtr.Zero, true, false, null!);
        Task.Run(() =>
        {
            keyInstance.RedirectActivationToAsync(args).AsTask().Wait();
            SetEvent(redirectEventHandle);
        });

        uint CWMO_DEFAULT = 0;
        uint INFINITE = 0xFFFFFFFF;
        _ = CoWaitForMultipleObjects(
           CWMO_DEFAULT, INFINITE, 1,
           [redirectEventHandle], out uint handleIndex);

        // Bring the window to the foreground
        Process process = Process.GetProcessById((int)keyInstance.ProcessId);
        SetForegroundWindow(process.MainWindowHandle);
    }

    private static void OnActivated(object? sender, AppActivationArguments args)
    {
        // When a new instance tries to launch, this event fires in the existing instance.
        // We need to notify the App to handle the activation (e.g., bring window to front, handle protocol).
        if (Application.Current is App app)
        {
            app.HandleRedirectedActivation(args);
        }
    }
}