// Copyright (c) 2025 Nikolai Papin
//
// This file is part of the Auto Attendance app that looks for
// self-attend QR-codes during lectures and opens their URLs in your
// browser.
//
// This program is free software: you can redistribute it and/or modify
// it under the terms of the GNU General Public License as published by
// the Free Software Foundation, either version 3 of the License, or
// (at your option) any later version.
//
// This program is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See
// the GNU General Public License for more details.
//
// You should have received a copy of the GNU General Public License
// along with this program.  If not, see <https://www.gnu.org/licenses/>.

package vision

import (
	"errors"

	"git.weirdcat.su/weirdcat/auto-attendance/internal/logger"
	"github.com/makiuchi-d/gozxing"
	"github.com/makiuchi-d/gozxing/qrcode"
	"gocv.io/x/gocv"
)

type Vision interface {
	AnalyzeImage(filePath string) (data VisionData, err error)
}

type visionImpl struct {
	log *logger.Logger
}

var (
	ErrImageEmpty = errors.New("Image from file was empty")
)

// AnalyzeImage implements Vision.
func (v *visionImpl) AnalyzeImage(filePath string) (data VisionData, err error) {
	// TODO: scanning for multiple QR-codes at once
	v.log.Debug("analyzing image for qr codes", "filePath", filePath)

	img := gocv.IMRead(filePath, gocv.IMReadColor)
	if img.Empty() {
		v.log.Error("could not read image file", "filePath", filePath)
		return VisionData{}, ErrImageEmpty
	}
	defer img.Close()

	// Convert to grayscale for QR code detection
	gray := gocv.NewMat()
	defer gray.Close()
	gocv.CvtColor(img, &gray, gocv.ColorBGRToGray)

	// Convert gocv.Mat to image.Image for gozxing
	imgGray, err := gray.ToImage()
	if err != nil {
		v.log.Error("failed to convert image", "error", err)
		return VisionData{}, err
	}

	// Create a binary bitmap from the image
	bmp, err := gozxing.NewBinaryBitmapFromImage(imgGray)
	if err != nil {
		v.log.Error("failed to create binary bitmap", "error", err)
		return VisionData{}, err
	}

	reader := qrcode.NewQRCodeReader()
	result, err := reader.Decode(bmp, nil)
	if err != nil {
		v.log.Debug("no qr code found in image", "filePath", filePath)
		return VisionData{}, nil
	}

	v.log.Info("QR code decoded successfully", "content", result.GetText())

	data = VisionData{result.GetText()}
	return data, nil
}

func NewVision(log *logger.Logger) Vision {
	return &visionImpl{log: log}
}