refactor: extract input sender to an interface for multiple platform support

SlidePresenter/InputSender/WindowsInputSender.cs

@@ -0,0 +1,47 @@
+using System.Runtime.InteropServices;
+using Win32Api;
+
+namespace SwitchSlidePresenter.InputSender;
+
+public class WindowsInputSender : IInputSender {
+	private const uint INPUT_KEYBOARD = 1;
+	private const ushort VK_NEXT = 0x22;
+	private const ushort VK_PRIOR = 0x21;
+	private const uint KEYEVENTF_KEYDOWN = 0x0000;
+	private const uint KEYEVENTF_KEYUP = 0x0002;
+
+	public void NextSlide() => SimulateKeyPress(VK_NEXT);
+	public void PreviousSlide() => SimulateKeyPress(VK_PRIOR);
+
+	private static void SimulateKeyPress(ushort keyCode) {
+		Input[] inputs = new Input[2];
+
+		inputs[0] = new Input {
+			type = INPUT_KEYBOARD,
+			u = new InputUnion {
+				ki = new KeyboardInput {
+					wVk = keyCode,
+					wScan = 0,
+					dwFlags = KEYEVENTF_KEYDOWN,
+					time = 0,
+					dwExtraInfo = IntPtr.Zero
+				}
+			}
+		};
+
+		inputs[1] = new Input {
+			type = INPUT_KEYBOARD,
+			u = new InputUnion {
+				ki = new KeyboardInput {
+					wVk = keyCode,
+					wScan = 0,
+					dwFlags = KEYEVENTF_KEYUP,
+					time = 0,
+					dwExtraInfo = IntPtr.Zero
+				}
+			}
+		};
+
+		Win32Api.Win32Api.SendInput((uint)inputs.Length, inputs, Marshal.SizeOf(typeof(Input)));
+	}
+}