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();
        doc.Header.Version = ACadVersion.AC1018;

        // Collect loop IDs that are called as subprograms so we skip drawing them as top-level
        var subprogramIds = new HashSet<int>();
        foreach (var loop in drawing.Loops)
        {
            foreach (var code in loop)
            {
                if (code.CodeType() == CodeType.SubProgramCall)
                    subprogramIds.Add(((SubProgramCall)code).LoopId);
            }
        }

        foreach (var loop in drawing.Loops)
        {
            var loopNumber = GetLoopNumber(loop.Name);
            if (subprogramIds.Contains(loopNumber))
                continue; // drawn inline at SubProgramCall positions

            var layer = new Layer(loop.Name);
            doc.Layers.Add(layer);

            DrawLoop(doc, drawing, loop, layer, new Vector());
        }

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

        return new MemoryStream(buffer.ToArray());
    }

    private static Vector DrawLoop(CadDocument doc, Drawing drawing, Loop loop, Layer layer, Vector startPos)
    {
        var pos = startPos;

        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;
                    if (lm.Type == EntityType.Cut)
                    {
                        var lineEnd = Advance(pos, lm.EndPoint, loop.Mode);
                        doc.Entities.Add(new AcadLine
                        {
                            StartPoint = ToXYZ(pos),
                            EndPoint = ToXYZ(lineEnd),
                            Layer = layer
                        });
                        pos = lineEnd;
                    }
                    else
                    {
                        pos = Advance(pos, lm.EndPoint, loop.Mode);
                    }
                    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)
                    {
                        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,
                            EndAngle = endAngle,
                            Layer = layer
                        });
                    }

                    pos = arcEnd;
                    break;

                case CodeType.SubProgramCall:
                    var call = (SubProgramCall)code;
                    var subLoop = drawing.Loops.FirstOrDefault(l => l.Name == drawing.GetLoopName(call.LoopId));
                    if (subLoop != null)
                        DrawLoop(doc, drawing, subLoop, layer, pos);
                    // pos unchanged — subprograms are closed shapes that return to start
                    break;
            }
        }

        return pos;
    }

    private static int GetLoopNumber(string loopName)
    {
        var idx = loopName.LastIndexOf(".loop-", StringComparison.OrdinalIgnoreCase);
        if (idx < 0) return -1;
        return int.TryParse(loopName.Substring(idx + 6), out var n) ? n : -1;
    }

    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);
}