OpenNest/OpenNest.IO/Bending/BendRepair.cs

using System;
using System.Collections.Generic;
using System.Linq;
using OpenNest.Bending;
using OpenNest.Geometry;

namespace OpenNest.IO.Bending
{
    public enum BendRepairUnits { Unspecified, Inches, Millimeters }

    /// <summary>Explicit opt-in. Distances are physical millimeters, not drawing coordinates.</summary>
    public sealed class BendRepairOptions
    {
        public BendRepairUnits DrawingUnits { get; set; }
        public double MaxEndpointMovementMillimeters { get; set; }
    }

    public sealed record BendRepairReport(int BendIndex, string Status, string Reason,
        Vector OriginalStart, Vector OriginalEnd, Vector Start, Vector End);

    /// <summary>Conservative, atomic repair. Never edits cut entities or unassociated marks.</summary>
    public static class BendRepair
    {
        public static List<BendRepairReport> Apply(List<Entity> entities, List<Bend> bends, BendRepairOptions options)
        {
            var reports = new List<BendRepairReport>();
            if (options == null) return reports;
            var scale = options.DrawingUnits == BendRepairUnits.Inches ? 1 / 25.4 : 1.0;
            var tolerance = 0.001 * scale;
            var limit = options.MaxEndpointMovementMillimeters * scale;
            var valid = (options.DrawingUnits == BendRepairUnits.Inches || options.DrawingUnits == BendRepairUnits.Millimeters)
                && double.IsFinite(limit) && limit > tolerance && options.MaxEndpointMovementMillimeters <= 3.175;
            var original = bends.Select(b => (b.StartPoint, b.EndPoint)).ToArray();
            var marks = entities.OfType<Line>().Where(IsMark).ToList();
            var cuts = entities.Where(IsCut).ToList();
            // ShapeBuilder may reverse/weld its inputs; isolate it from all source geometry.
            var shapes = ShapeBuilder.GetShapes(cuts.CloneAll(), tolerance);
            var boundaries = shapes.Where(s => s.IsClosed()).SelectMany(s => s.Entities).ToList();
            var polygons = shapes.Where(s => s.IsClosed()).Select(s => s.ToPolygonWithTolerance(tolerance / 10)).ToList();
            bool InMaterial(Vector point) => polygons.Count(p => p.ContainsPoint(point)) % 2 == 1;

            for (var i = 0; i < bends.Count; i++)
            {
                var bend = bends[i];
                var (start, end) = original[i];
                var reason = "";
                var status = "Skipped";
                if (!valid) reason = "Specify drawing units and a finite movement limit above 0.001 and at most 3.175 mm.";
                else if (!Finite(start) || !Finite(end) || start.DistanceTo(end) <= 2 * limit)
                    reason = "Invalid or too-short bend axis.";
                else
                {
                    var axis = (end - start) / start.DistanceTo(end);
                    var first = marks.Where(m => Associated(m, start, end, tolerance, scale)).ToList();
                    var last = marks.Where(m => Associated(m, end, start, tolerance, scale)).ToList();
                    if (first.Count != 1 || last.Count != 1 || ReferenceEquals(first[0], last[0]))
                        reason = "Missing or ambiguous collinear ticks at both original endpoints.";
                    else if (original.Where((_, j) => j != i).Any(b =>
                        Associated(first[0], b.StartPoint, b.EndPoint, tolerance, scale) ||
                        Associated(first[0], b.EndPoint, b.StartPoint, tolerance, scale) ||
                        Associated(last[0], b.StartPoint, b.EndPoint, tolerance, scale) ||
                        Associated(last[0], b.EndPoint, b.StartPoint, tolerance, scale)))
                        reason = "Tick is shared with another bend.";
                    else
                    {
                        var probe = new Line(start - axis * limit, end + axis * limit);
                        var hits = new List<Vector>();
                        var uncertain = shapes.Where(s => !s.IsClosed()).Any(s => s.Intersects(probe));
                        foreach (var edge in boundaries)
                        {
                            if (edge is Line line && OnAxis(line.StartPoint, start, axis, tolerance)
                                && OnAxis(line.EndPoint, start, axis, tolerance)
                                && System.Math.Max(Dot(line.StartPoint - start, axis), Dot(line.EndPoint - start, axis)) >= -limit
                                && System.Math.Min(Dot(line.StartPoint - start, axis), Dot(line.EndPoint - start, axis)) <= bend.Length + limit)
                                uncertain = true;
                            if (edge.Intersects(probe, out var points))
                                foreach (var p in points)
                                    if (Finite(p) && !hits.Any(h => h.DistanceTo(p) <= tolerance)) hits.Add(p);
                        }
                        var nearStart = hits.Where(p => p.DistanceTo(start) <= limit).ToList();
                        var nearEnd = hits.Where(p => p.DistanceTo(end) <= limit).ToList();
                        if (uncertain || hits.Count != 2 || nearStart.Count != 1 || nearEnd.Count != 1)
                            reason = "Missing/ambiguous closed cut boundaries, interior crossing, or movement exceeds limit.";
                        else
                        {
                            // Project the intersection back onto the existing axis; never rotate a bend.
                            var newStart = start + axis * Dot(nearStart[0] - start, axis);
                            var newEnd = start + axis * Dot(nearEnd[0] - start, axis);
                            var sample = axis * (10 * tolerance);
                            if (!InMaterial((newStart + newEnd) / 2)
                                || !InMaterial(newStart + sample) || !InMaterial(newEnd - sample)
                                || InMaterial(newStart - sample) || InMaterial(newEnd + sample))
                                reason = "Endpoints do not bound an unambiguous material interval (possible tangent).";
                            else if (Dot(newEnd - newStart, axis) <= first[0].Length + last[0].Length + tolerance)
                                reason = "Repaired ticks would overlap or reverse the bend.";
                            else if (newStart.DistanceTo(start) <= tolerance && newEnd.DistanceTo(end) <= tolerance)
                            {
                                status = "Unchanged";
                                reason = "Already on cut boundaries.";
                            }
                            else
                            {
                                // Prepare both replacements before committing either endpoint or entity list.
                                var a = (Line)first[0].Clone();
                                var b = (Line)last[0].Clone();
                                a.Offset(newStart - start);
                                b.Offset(newEnd - end);
                                var ai = entities.IndexOf(first[0]);
                                var bi = entities.IndexOf(last[0]);
                                if (ai < 0 || bi < 0) reason = "Tick was already consumed; unchanged.";
                                else
                                {
                                    entities[ai] = a;
                                    entities[bi] = b;
                                    bend.StartPoint = newStart;
                                    bend.EndPoint = newEnd;
                                    status = "Repaired";
                                    reason = "Both endpoints snapped along axis; only their two associated ticks replaced.";
                                }
                            }
                        }
                    }
                }
                reports.Add(new BendRepairReport(i, status, reason, start, end, bend.StartPoint, bend.EndPoint));
            }
            return reports;
        }

        private static bool Finite(Vector p) => double.IsFinite(p.X) && double.IsFinite(p.Y);
        private static double Dot(Vector a, Vector b) => a.X * b.X + a.Y * b.Y;
        private static bool OnAxis(Vector p, Vector origin, Vector axis, double tolerance) =>
            System.Math.Abs((p.X - origin.X) * axis.Y - (p.Y - origin.Y) * axis.X) <= tolerance;
        private static bool Continuous(Entity e) => string.IsNullOrEmpty(e.LineTypeName)
            || string.Equals(e.LineTypeName, "Continuous", StringComparison.OrdinalIgnoreCase)
            || string.Equals(e.LineTypeName, "ByLayer", StringComparison.OrdinalIgnoreCase);
        private static bool IsMark(Entity e) => Continuous(e) &&
            (string.Equals(e.Layer?.Name, "ETCH", StringComparison.OrdinalIgnoreCase)
            || string.Equals(e.Layer?.Name, "SCRIBE", StringComparison.OrdinalIgnoreCase));
        private static bool IsCut(Entity e) => Continuous(e) &&
            (e.Layer?.Name == "0" || string.Equals(e.Layer?.Name, "CUT", StringComparison.OrdinalIgnoreCase))
            && (e is Line || e is Arc || e is Circle);
        private static bool Associated(Line mark, Vector endpoint, Vector other, double tolerance, double scale)
        {
            var length = endpoint.DistanceTo(other);
            if (!Finite(endpoint) || !Finite(other) || length <= tolerance || !Finite(mark.StartPoint) || !Finite(mark.EndPoint)
                || mark.Length <= tolerance || mark.Length > 25.4 * scale + tolerance || mark.Length >= length / 3) return false;
            var axis = (other - endpoint) / length;
            if (!OnAxis(mark.StartPoint, endpoint, axis, tolerance) || !OnAxis(mark.EndPoint, endpoint, axis, tolerance)) return false;
            var a = Dot(mark.StartPoint - endpoint, axis);
            var b = Dot(mark.EndPoint - endpoint, axis);
            return System.Math.Abs(System.Math.Min(a, b)) <= tolerance && System.Math.Max(a, b) > tolerance;
        }
    }
}