PepApi.Core/PepLib.Core/IO/DrawingDxfExporter.cs

using ACadSharp;
using ACadSharp.IO;
using ACadSharp.Tables;
using CSMath;
using PepLib.Codes;
using PepLib.Enums;
using PepLib.Geometry;
using PepLib.Models;
using AcadArc = ACadSharp.Entities.Arc;
using AcadCircle = ACadSharp.Entities.Circle;
using AcadLine = ACadSharp.Entities.Line;

namespace PepLib.IO;

public static class DrawingDxfExporter
{
    public static Stream Export(Drawing drawing)
    {
        var doc = new CadDocument();

        foreach (var loop in drawing.Loops)
        {
            var layer = new Layer(loop.Name);
            doc.Layers.Add(layer);

            var pos = new Vector();

            foreach (var code in loop)
            {
                switch (code.CodeType())
                {
                    case CodeType.RapidMove:
                        pos = Advance(pos, ((RapidMove)code).EndPoint, loop.Mode);
                        break;

                    case CodeType.LinearMove:
                        var lm = (LinearMove)code;
                        var lineEnd = Advance(pos, lm.EndPoint, loop.Mode);
                        doc.Entities.Add(new AcadLine
                        {
                            StartPoint = ToXYZ(pos),
                            EndPoint = ToXYZ(lineEnd),
                            Layer = layer
                        });
                        pos = lineEnd;
                        break;

                    case CodeType.CircularMove:
                        var cm = (CircularMove)code;
                        var arcEnd = Advance(pos, cm.EndPoint, loop.Mode);
                        var arcCenter = Advance(pos, cm.CenterPoint, loop.Mode);

                        var dx = pos.X - arcCenter.X;
                        var dy = pos.Y - arcCenter.Y;
                        var radius = Math.Sqrt(dx * dx + dy * dy);

                        var startAngle = Math.Atan2(pos.Y - arcCenter.Y, pos.X - arcCenter.X);
                        var endAngle = Math.Atan2(arcEnd.Y - arcCenter.Y, arcEnd.X - arcCenter.X);

                        if (cm.Rotation == RotationType.CW)
                        {
                            (startAngle, endAngle) = (endAngle, startAngle);
                        }

                        if (Math.Abs(startAngle - endAngle) < 1e-10) // full circle
                        {
                            doc.Entities.Add(new AcadCircle
                            {
                                Center = ToXYZ(arcCenter),
                                Radius = radius,
                                Layer = layer
                            });
                        }
                        else
                        {
                            doc.Entities.Add(new AcadArc
                            {
                                Center = ToXYZ(arcCenter),
                                Radius = radius,
                                StartAngle = startAngle * (180.0 / Math.PI),
                                EndAngle = endAngle * (180.0 / Math.PI),
                                Layer = layer
                            });
                        }

                        pos = arcEnd;
                        break;
                }
            }
        }

        var buffer = new MemoryStream();
        using (var writer = new DxfWriter(buffer, doc, false))
        {
            writer.Write();
        }

        var stream = new MemoryStream(buffer.ToArray());
        return stream;
    }

    private static Vector Advance(Vector current, Vector offset, ProgrammingMode mode) =>
        mode == ProgrammingMode.Incremental ? current + offset : offset;

    private static XYZ ToXYZ(Vector v) => new XYZ(v.X, v.Y, 0);
}