feat: add RotationSlideStrategy with directional push contact algorithm

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

OpenNest.Engine/BestFit/RotationSlideStrategy.cs

@@ -0,0 +1,131 @@
+using System.Collections.Generic;
+using OpenNest.Geometry;
+using OpenNest.Math;
+
+namespace OpenNest.Engine.BestFit
+{
+    public class RotationSlideStrategy : IBestFitStrategy
+    {
+        public RotationSlideStrategy(double part2Rotation, int type, string description)
+        {
+            Part2Rotation = part2Rotation;
+            Type = type;
+            Description = description;
+        }
+
+        public double Part2Rotation { get; }
+        public int Type { get; }
+        public string Description { get; }
+
+        public List<PairCandidate> GenerateCandidates(Drawing drawing, double spacing, double stepSize)
+        {
+            var candidates = new List<PairCandidate>();
+
+            // Build part1 at origin
+            var part1 = new Part(drawing);
+            var bbox1 = part1.Program.BoundingBox();
+            part1.Offset(-bbox1.Location.X, -bbox1.Location.Y);
+            part1.UpdateBounds();
+
+            // Build part2 template with rotation, normalized to origin
+            var part2Template = new Part(drawing);
+            if (!Part2Rotation.IsEqualTo(0))
+                part2Template.Rotate(Part2Rotation);
+            var bbox2 = part2Template.Program.BoundingBox();
+            part2Template.Offset(-bbox2.Location.X, -bbox2.Location.Y);
+            part2Template.UpdateBounds();
+
+            var testNumber = 0;
+
+            // Try pushing left (horizontal slide)
+            GenerateCandidatesForAxis(
+                part1, part2Template, drawing, spacing, stepSize,
+                PushDirection.Left, candidates, ref testNumber);
+
+            // Try pushing down (vertical slide)
+            GenerateCandidatesForAxis(
+                part1, part2Template, drawing, spacing, stepSize,
+                PushDirection.Down, candidates, ref testNumber);
+
+            return candidates;
+        }
+
+        private void GenerateCandidatesForAxis(
+            Part part1, Part part2Template, Drawing drawing,
+            double spacing, double stepSize, PushDirection pushDir,
+            List<PairCandidate> candidates, ref int testNumber)
+        {
+            var bbox1 = part1.BoundingBox;
+            var bbox2 = part2Template.BoundingBox;
+            var halfSpacing = spacing / 2;
+
+            var isHorizontalPush = pushDir == PushDirection.Left || pushDir == PushDirection.Right;
+
+            // Perpendicular range: part2 slides across the full extent of part1
+            double perpMin, perpMax, pushStartOffset;
+
+            if (isHorizontalPush)
+            {
+                perpMin = -(bbox2.Height + spacing);
+                perpMax = bbox1.Height + bbox2.Height + spacing;
+                pushStartOffset = bbox1.Width + bbox2.Width + spacing * 2;
+            }
+            else
+            {
+                perpMin = -(bbox2.Width + spacing);
+                perpMax = bbox1.Width + bbox2.Width + spacing;
+                pushStartOffset = bbox1.Height + bbox2.Height + spacing * 2;
+            }
+
+            // Pre-compute part1's offset lines (half-spacing outward)
+            var part1Lines = Helper.GetOffsetPartLines(part1, halfSpacing);
+
+            for (var offset = perpMin; offset <= perpMax; offset += stepSize)
+            {
+                var part2 = (Part)part2Template.Clone();
+
+                // Place part2 far away along push axis, at perpendicular offset
+                if (isHorizontalPush)
+                    part2.Offset(pushStartOffset, offset);
+                else
+                    part2.Offset(offset, pushStartOffset);
+
+                // Get part2's offset lines (half-spacing outward)
+                var part2Lines = Helper.GetOffsetPartLines(part2, halfSpacing);
+
+                // Find contact distance
+                var slideDist = Helper.DirectionalDistance(part2Lines, part1Lines, pushDir);
+
+                if (slideDist >= double.MaxValue || slideDist < 0)
+                    continue;
+
+                // Move part2 to contact position
+                var pushVector = GetPushVector(pushDir, slideDist);
+                var finalPosition = part2.Location + pushVector;
+
+                candidates.Add(new PairCandidate
+                {
+                    Drawing = drawing,
+                    Part1Rotation = 0,
+                    Part2Rotation = Part2Rotation,
+                    Part2Offset = finalPosition,
+                    StrategyType = Type,
+                    TestNumber = testNumber++,
+                    Spacing = spacing
+                });
+            }
+        }
+
+        private static Vector GetPushVector(PushDirection direction, double distance)
+        {
+            switch (direction)
+            {
+                case PushDirection.Left: return new Vector(-distance, 0);
+                case PushDirection.Right: return new Vector(distance, 0);
+                case PushDirection.Down: return new Vector(0, -distance);
+                case PushDirection.Up: return new Vector(0, distance);
+                default: return Vector.Zero;
+            }
+        }
+    }
+}

OpenNest.Engine/OpenNest.Engine.csproj

@@ -40,6 +40,7 @@
     <Compile Include="BestFit\PairCandidate.cs" />
     <Compile Include="BestFit\BestFitResult.cs" />
     <Compile Include="BestFit\IBestFitStrategy.cs" />
+    <Compile Include="BestFit\RotationSlideStrategy.cs" />
     <Compile Include="CirclePacking\Bin.cs" />
     <Compile Include="CirclePacking\FillEndEven.cs" />
     <Compile Include="CirclePacking\FillEndOdd.cs" />