using System;
using System.Diagnostics;
using System.Runtime.InteropServices;

namespace ScreenConnect;

public class LowLevelKeyboardHooker : IDisposable
{
	private WindowsNative.HOOKPROC keyboardProc;

	private IntPtr hookHandle;

	public event EventHandler<LowLevelKeyboardHookCalledEventArgs> HookCalled;

	public LowLevelKeyboardHooker()
	{
		IntPtr hMod = default(IntPtr);
		using (Process process = Process.GetCurrentProcess())
		{
			using ProcessModule processModule = process.MainModule;
			hMod = WindowsNative.GetModuleHandle(processModule.ModuleName);
		}
		keyboardProc = LowLevelKeyboardProc;
		hookHandle = WindowsNative.SetWindowsHookEx(WindowsNative.WH.KEYBOARD_LL, keyboardProc, hMod, 0u);
	}

	public void Dispose()
	{
		if (hookHandle != IntPtr.Zero)
		{
			WindowsNative.UnhookWindowsHookEx(hookHandle);
		}
	}

	protected virtual bool OnHookCalled(WindowsNative.KBDLLHOOKSTRUCT keyInfo)
	{
		LowLevelKeyboardHookCalledEventArgs e = new LowLevelKeyboardHookCalledEventArgs
		{
			KeyInfo = keyInfo
		};
		this.RaiseEvent(HookCalled, e);
		return e.ShouldEat;
	}

	private IntPtr LowLevelKeyboardProc(int code, IntPtr wParam, IntPtr lParam)
	{
		WindowsNative.WM wM = (WindowsNative.WM)(int)wParam;
		if (wM == WindowsNative.WM.KEYDOWN || wM == WindowsNative.WM.KEYUP || wM == WindowsNative.WM.SYSKEYDOWN || wM == WindowsNative.WM.SYSKEYUP)
		{
			WindowsNative.KBDLLHOOKSTRUCT keyInfo = (WindowsNative.KBDLLHOOKSTRUCT)Marshal.PtrToStructure(lParam, typeof(WindowsNative.KBDLLHOOKSTRUCT));
			if (OnHookCalled(keyInfo))
			{
				return (IntPtr)1;
			}
		}
		return WindowsNative.CallNextHookEx(IntPtr.Zero, code, wParam, lParam);
	}
}