meeting-assistant/MeetingAssistant/Hotkeys/GlobalHotkeyService.cs

using System.Runtime.InteropServices;
using System.Threading;
using MeetingAssistant.LaunchProfiles;
using MeetingAssistant.Recording;

namespace MeetingAssistant.Hotkeys;

public sealed class GlobalHotkeyService : BackgroundService
{
    private const int HotkeyIdBase = 0x4D41;
    private const int WmHotkey = 0x0312;
    private const int WmQuit = 0x0012;
    private readonly ILaunchProfileOptionsProvider launchProfiles;
    private readonly MeetingRecordingCoordinator coordinator;
    private readonly ILogger<GlobalHotkeyService> logger;
    private readonly Dictionary<int, string> hotkeyProfiles = [];
    private TaskCompletionSource? messageLoopCompletion;
    private uint messageThreadId;

    public GlobalHotkeyService(
        ILaunchProfileOptionsProvider launchProfiles,
        MeetingRecordingCoordinator coordinator,
        ILogger<GlobalHotkeyService> logger)
    {
        this.launchProfiles = launchProfiles;
        this.coordinator = coordinator;
        this.logger = logger;
    }

    protected override Task ExecuteAsync(CancellationToken stoppingToken)
    {
        if (!OperatingSystem.IsWindows())
        {
            logger.LogInformation("Global hotkey registration is only supported on Windows");
            return Task.CompletedTask;
        }

        messageLoopCompletion = new TaskCompletionSource(TaskCreationOptions.RunContinuationsAsynchronously);
        var messageThread = new Thread(() =>
        {
            try
            {
                RunMessageLoop(stoppingToken);
                messageLoopCompletion.TrySetResult();
            }
            catch (Exception exception)
            {
                messageLoopCompletion.TrySetException(exception);
            }
        })
        {
            IsBackground = true,
            Name = "Meeting Assistant Hotkey Loop"
        };

        messageThread.Start();
        return messageLoopCompletion.Task;
    }

    private void RunMessageLoop(CancellationToken stoppingToken)
    {
        var hotkeys = launchProfiles.GetHotkeys();
        messageThreadId = GetCurrentThreadId();
        using var stoppingRegistration = stoppingToken.Register(() => PostQuitToMessageThread());

        for (var index = 0; index < hotkeys.Count; index++)
        {
            var profileHotkey = hotkeys[index];
            var hotkey = HotkeyDefinition.Parse(profileHotkey.Toggle);
            var hotkeyId = HotkeyIdBase + index;
            if (!RegisterHotKey(IntPtr.Zero, hotkeyId, (uint)hotkey.Modifiers, hotkey.VirtualKey))
            {
                logger.LogWarning(
                    "Could not register global hotkey {Hotkey} for launch profile {LaunchProfile}",
                    profileHotkey.Toggle,
                    profileHotkey.ProfileName);
                continue;
            }

            hotkeyProfiles[hotkeyId] = profileHotkey.ProfileName;
            logger.LogInformation(
                "Registered global hotkey {Hotkey} for launch profile {LaunchProfile}",
                profileHotkey.Toggle,
                profileHotkey.ProfileName);
        }

        try
        {
            while (!stoppingToken.IsCancellationRequested && GetMessage(out var message, IntPtr.Zero, 0, 0) > 0)
            {
                if (message.Message == WmHotkey && hotkeyProfiles.TryGetValue((int)message.WParam, out var profileName))
                {
                    _ = Task.Run(() => ToggleRecordingAsync(profileName), CancellationToken.None);
                }
            }
        }
        finally
        {
            foreach (var hotkeyId in hotkeyProfiles.Keys)
            {
                UnregisterHotKey(IntPtr.Zero, hotkeyId);
            }

            hotkeyProfiles.Clear();
            messageThreadId = 0;
        }
    }

    public override Task StopAsync(CancellationToken cancellationToken)
    {
        PostQuitToMessageThread();
        return base.StopAsync(cancellationToken);
    }

    private async Task ToggleRecordingAsync(string profileName)
    {
        try
        {
            var status = await coordinator.ToggleAsync(profileName, CancellationToken.None);
            logger.LogInformation(
                "Hotkey toggled recording for launch profile {LaunchProfile}. IsRecording={IsRecording}",
                profileName,
                status.IsRecording);
        }
        catch (Exception exception)
        {
            logger.LogError(exception, "Hotkey toggle failed");
        }
    }

    private void PostQuitToMessageThread()
    {
        var threadId = messageThreadId;
        if (threadId != 0)
        {
            PostThreadMessage(threadId, WmQuit, UIntPtr.Zero, IntPtr.Zero);
        }
    }

    [DllImport("user32.dll", SetLastError = true)]
    private static extern bool RegisterHotKey(IntPtr hWnd, int id, uint fsModifiers, uint vk);

    [DllImport("user32.dll", SetLastError = true)]
    private static extern bool UnregisterHotKey(IntPtr hWnd, int id);

    [DllImport("user32.dll")]
    private static extern int GetMessage(out NativeMessage lpMsg, IntPtr hWnd, uint wMsgFilterMin, uint wMsgFilterMax);

    [DllImport("kernel32.dll")]
    private static extern uint GetCurrentThreadId();

    [DllImport("user32.dll", SetLastError = true)]
    private static extern bool PostThreadMessage(uint idThread, int msg, UIntPtr wParam, IntPtr lParam);

    [StructLayout(LayoutKind.Sequential)]
    private struct NativeMessage
    {
        public IntPtr Hwnd;
        public int Message;
        public UIntPtr WParam;
        public IntPtr LParam;
        public uint Time;
        public NativePoint Point;
    }

    [StructLayout(LayoutKind.Sequential)]
    private struct NativePoint
    {
        public int X;
        public int Y;
    }
}