namespace OcrDaemon;

using System.Drawing;
using System.Drawing.Imaging;
using OpenCvSharp;
using OpenCvSharp.Extensions;

class TemplateMatchHandler
{
    public object HandleTemplateMatch(Request req)
    {
        if (string.IsNullOrEmpty(req.Path))
            return new ErrorResponse("match-template command requires 'path' (template image file)");

        if (!System.IO.File.Exists(req.Path))
            return new ErrorResponse($"Template file not found: {req.Path}");

        using var screenshot = ScreenCapture.CaptureOrLoad(req.File, req.Region);
        using var screenMat = BitmapConverter.ToMat(screenshot);
        using var template = Cv2.ImRead(req.Path, ImreadModes.Color);

        if (template.Empty())
            return new ErrorResponse($"Failed to load template image: {req.Path}");

        // Convert screenshot from BGRA to BGR if needed
        using var screenBgr = new Mat();
        if (screenMat.Channels() == 4)
            Cv2.CvtColor(screenMat, screenBgr, ColorConversionCodes.BGRA2BGR);
        else
            screenMat.CopyTo(screenBgr);

        // Template must fit within screenshot
        if (template.Rows > screenBgr.Rows || template.Cols > screenBgr.Cols)
            return new TemplateMatchResponse { Found = false };

        using var result = new Mat();
        Cv2.MatchTemplate(screenBgr, template, result, TemplateMatchModes.CCoeffNormed);

        Cv2.MinMaxLoc(result, out _, out double maxVal, out _, out OpenCvSharp.Point maxLoc);

        double threshold = req.Threshold > 0 ? req.Threshold / 100.0 : 0.7;

        if (maxVal < threshold)
            return new TemplateMatchResponse { Found = false, Confidence = maxVal };

        // Calculate center coordinates — offset by region origin if provided
        int offsetX = req.Region?.X ?? 0;
        int offsetY = req.Region?.Y ?? 0;

        return new TemplateMatchResponse
        {
            Found = true,
            X = offsetX + maxLoc.X + template.Cols / 2,
            Y = offsetY + maxLoc.Y + template.Rows / 2,
            Width = template.Cols,
            Height = template.Rows,
            Confidence = maxVal,
        };
    }
}