using System;
using System.Drawing;
using System.Runtime.InteropServices;

class Program {
  [StructLayout(LayoutKind.Sequential)]
  private struct RECT {
    public int Left;
    public int Top;
    public int Right;
    public int Bottom;
  }

  [DllImport("user32.dll")]
  private static extern IntPtr GetDC(IntPtr hWnd);

  [DllImport("user32.dll")]
  private static extern int GetClientRect(IntPtr hWnd, out RECT rect);

  [DllImport("user32.dll")]
  private static extern int ReleaseDC(IntPtr hWnd, IntPtr hDC);

  [DllImport("gdi32.dll")]
  private static extern IntPtr CreateCompatibleDC(IntPtr hDC);

  [DllImport("gdi32.dll")]
  private static extern IntPtr CreateCompatibleBitmap(IntPtr hDC, int width,
                                                      int height);

  [DllImport("gdi32.dll")]
  private static extern IntPtr SelectObject(IntPtr hDC, IntPtr hObject);

  [DllImport("gdi32.dll")]
  private static extern bool DeleteObject(IntPtr hObject);

  [DllImport("gdi32.dll")]
  private static extern bool DeleteDC(IntPtr hDC);

  [DllImport("user32.dll")]
  private static extern bool PrintWindow(IntPtr hwnd, IntPtr hdcBlt,
                                         uint nFlags);

  private const uint PW_RENDERFULLCONTENT = 0x00000002;

  static bool CaptureWindow(IntPtr windowHandle, string outputPath) {
    try {
      // Get the window dimensions
      GetClientRect(windowHandle, out RECT windowRect);
      int width = windowRect.Right - windowRect.Left;
      int height = windowRect.Bottom - windowRect.Top;

      // Create compatible DC and bitmap
      IntPtr sourceContext = GetDC(windowHandle);
      IntPtr destContext = CreateCompatibleDC(sourceContext);
      IntPtr bitmap = CreateCompatibleBitmap(sourceContext, width, height);

      // Select the bitmap into the DC
      IntPtr oldBitmap = SelectObject(destContext, bitmap);

      // Use PrintWindow to capture the window content
      PrintWindow(windowHandle, destContext, PW_RENDERFULLCONTENT);

      // Create the final bitmap
      using (Bitmap screenshot = Bitmap.FromHbitmap(bitmap)) {
        screenshot.Save(outputPath, System.Drawing.Imaging.ImageFormat.Png);
      }

      // Clean up
      SelectObject(destContext, oldBitmap);
      DeleteObject(bitmap);
      DeleteDC(destContext);
      ReleaseDC(windowHandle, sourceContext);

      return true;
    } catch (Exception) {
      return false;
    }
  }

  static int Main(string[] args) {
    if (args.Length != 2) {
      Console.WriteLine(
          "Usage: WindowCapture.exe <window_handle> <output_path>");
      Console.WriteLine("Example: WindowCapture.exe 123456 screenshot.png");
      return 1;
    }

    if (!IntPtr.TryParse(args[0], out IntPtr windowHandle)) {
      Console.WriteLine(
          "Invalid window handle. Please provide a valid number.");
      return 1;
    }

    string outputPath = args[1];

    if (CaptureWindow(windowHandle, outputPath)) {
      Console.WriteLine($"Screenshot saved to: {outputPath}");
      return 0;
    } else {
      Console.WriteLine("Failed to capture screenshot");
      return 1;
    }
  }
}