using OpenCvSharp;

namespace WebApp;

public class ImageGenerator
{
    public byte[] GenerateImage3(RequestBody requestBody)
    {
        var start = DateTime.Now;
        string[] inputs = requestBody.CanvasRect.Split(":");
        double scale = requestBody.OutputScale;
        Coordinate a1 = new Coordinate("A1");
        Mat a1Mat = new Mat(a1.Path);
        int width = a1Mat.Width;
        int height = a1Mat.Height;
        if (scale < 1)
        {
            width = (int)(width * scale);
            height = (int)(height * scale);
            a1Mat = a1Mat.Resize(new Size(width, height));
        }
        
        Coordinate coord0 = new Coordinate(inputs[0]);
        Coordinate coord1 = new Coordinate(inputs[1]);

        (var matrix, int rowCount, int colCount) = GenerateMatrix(coord0, coord1);
        
        Rect canvasRect = GenerateInitialRectCanvas(a1Mat, rowCount, colCount);
        
        //Determine cropping region
        var globalRoI = GenerateGlobalRoI(requestBody.CropOffset, requestBody.CropSize, canvasRect.Width,
            canvasRect.Height);
        
        Mat canvas = new Mat(globalRoI.Height, globalRoI.Width, a1Mat.Type());

        Parallel.ForEach(matrix, item =>
        {
            try
            {
                Mat mat = new Mat(item.Path);
                if (scale < 1)
                {
                    mat = mat.Resize(new Size(width, height));
                }

                Rect origin = new Rect((item.Col - 1) * a1Mat.Cols, (item.Row - 1) * a1Mat.Rows, a1Mat.Cols, a1Mat.Rows);
                var offset = origin.Location;
                var roi = origin.Intersect(globalRoI);
                if (roi.Width == 0 || roi.Height == 0) return;
                
                Rect placement = roi.Subtract(globalRoI.Location);
                var localRoi = roi.Subtract(offset);
                var subMat = mat.SubMat(localRoi);
                subMat.CopyTo(canvas[placement]);
            }
            catch (Exception e)
            {
                Console.WriteLine( $"Error {item}, {e.Message}" );
            }
        });

        var result = canvas.ImEncode();
        var end = DateTime.Now;
        var elapsed = end - start;
        Console.WriteLine($"Elapsed: {elapsed.TotalMilliseconds} ms");
        return result;
    }

    private (List<Coordinate> Matrix, int RowCount, int ColCount) GenerateMatrix(Coordinate coordinate1, Coordinate coordinate2)
    {
        int minRow = Math.Min(coordinate1.Row, coordinate2.Row);
        int maxRow = Math.Max(coordinate1.Row, coordinate2.Row);
        int minCol = Math.Min(coordinate1.Col, coordinate2.Col);
        int maxCol = Math.Max(coordinate1.Col, coordinate2.Col);

        int rowCount = maxRow - minRow + 1;
        int colCount = maxCol - minCol + 1;
        
        // Initialize collections
        List<Coordinate> results = new List<Coordinate>(rowCount*colCount);
        for (int i = 1; i <= rowCount; i++)
        {
            for (int j = 1; j <= colCount; j++)
            {
                results.Add(new Coordinate(i,j));
            }
        }

        return (results, rowCount, colCount);
    }

    private Rect GenerateInitialRectCanvas(Mat reference, int rowCount, int colCount)
    {
        int width = reference.Width * colCount;
        int height = reference.Height * rowCount;
        return new Rect(0, 0, width, height);
    }

    private Rect GenerateGlobalRoI(float[] cropOffset, float[] cropSize, int width, int height)
    {
        int x = (int)(cropOffset[0] * width);
        int y = (int)(cropOffset[1] * height);
        width = (int)(cropSize[0] * width);
        height = (int)(cropSize[1] * height);
        
        Point location = new Point(x, y);
        Size size = new Size(width, height);
        Rect cropRegion = new Rect( location, size);
        return cropRegion;
    }
}