namespace Automata.Screen;

using System.Drawing;
using System.Drawing.Imaging;
using System.Runtime.InteropServices;
using SdImageFormat = System.Drawing.Imaging.ImageFormat;

static class ImageUtils
{
    public static (byte[] gray, byte[] argb, int stride) BitmapToGrayAndArgb(Bitmap bmp)
    {
        int w = bmp.Width, h = bmp.Height;
        var data = bmp.LockBits(new Rectangle(0, 0, w, h), ImageLockMode.ReadOnly, PixelFormat.Format32bppArgb);
        byte[] argb = new byte[data.Stride * h];
        Marshal.Copy(data.Scan0, argb, 0, argb.Length);
        bmp.UnlockBits(data);
        int stride = data.Stride;

        byte[] gray = new byte[w * h];
        for (int y = 0; y < h; y++)
            for (int x = 0; x < w; x++)
            {
                int i = y * stride + x * 4;
                gray[y * w + x] = (byte)((argb[i] + argb[i + 1] + argb[i + 2]) / 3);
            }
        return (gray, argb, stride);
    }

    public static SdImageFormat GetImageFormat(string path)
    {
        var ext = Path.GetExtension(path).ToLowerInvariant();
        return ext switch
        {
            ".jpg" or ".jpeg" => SdImageFormat.Jpeg,
            ".bmp" => SdImageFormat.Bmp,
            _ => SdImageFormat.Png,
        };
    }
}