refactor(engine): extract AngleCandidateBuilder from DefaultNestEngine

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

OpenNest.Tests/AngleCandidateBuilderTests.cs

@@ -0,0 +1,83 @@
+using OpenNest.Geometry;
+
+namespace OpenNest.Tests;
+
+public class AngleCandidateBuilderTests
+{
+    private static Drawing MakeRectDrawing(double w, double h)
+    {
+        var pgm = new OpenNest.CNC.Program();
+        pgm.Codes.Add(new OpenNest.CNC.RapidMove(new Vector(0, 0)));
+        pgm.Codes.Add(new OpenNest.CNC.LinearMove(new Vector(w, 0)));
+        pgm.Codes.Add(new OpenNest.CNC.LinearMove(new Vector(w, h)));
+        pgm.Codes.Add(new OpenNest.CNC.LinearMove(new Vector(0, h)));
+        pgm.Codes.Add(new OpenNest.CNC.LinearMove(new Vector(0, 0)));
+        return new Drawing("rect", pgm);
+    }
+
+    [Fact]
+    public void Build_ReturnsAtLeastTwoAngles()
+    {
+        var builder = new AngleCandidateBuilder();
+        var item = new NestItem { Drawing = MakeRectDrawing(20, 10) };
+        var workArea = new Box(0, 0, 100, 100);
+
+        var angles = builder.Build(item, 0, workArea);
+
+        Assert.True(angles.Count >= 2);
+    }
+
+    [Fact]
+    public void Build_NarrowWorkArea_ProducesMoreAngles()
+    {
+        var builder = new AngleCandidateBuilder();
+        var item = new NestItem { Drawing = MakeRectDrawing(20, 10) };
+        var wideArea = new Box(0, 0, 100, 100);
+        var narrowArea = new Box(0, 0, 100, 8); // narrower than part's longest side
+
+        var wideAngles = builder.Build(item, 0, wideArea);
+        var narrowAngles = builder.Build(item, 0, narrowArea);
+
+        Assert.True(narrowAngles.Count > wideAngles.Count,
+            $"Narrow ({narrowAngles.Count}) should have more angles than wide ({wideAngles.Count})");
+    }
+
+    [Fact]
+    public void ForceFullSweep_ProducesFullSweep()
+    {
+        var builder = new AngleCandidateBuilder { ForceFullSweep = true };
+        var item = new NestItem { Drawing = MakeRectDrawing(5, 5) };
+        var workArea = new Box(0, 0, 100, 100);
+
+        var angles = builder.Build(item, 0, workArea);
+
+        // Full sweep at 5deg steps = ~36 angles (0 to 175), plus base angles
+        Assert.True(angles.Count > 10);
+    }
+
+    [Fact]
+    public void RecordProductive_PrunesSubsequentBuilds()
+    {
+        var builder = new AngleCandidateBuilder { ForceFullSweep = true };
+        var item = new NestItem { Drawing = MakeRectDrawing(20, 10) };
+        var workArea = new Box(0, 0, 100, 8);
+
+        // First build — full sweep
+        var firstAngles = builder.Build(item, 0, workArea);
+
+        // Record some as productive
+        var productive = new List<AngleResult>
+        {
+            new AngleResult { AngleDeg = 0, PartCount = 5 },
+            new AngleResult { AngleDeg = 45, PartCount = 3 },
+        };
+        builder.RecordProductive(productive);
+
+        // Second build — should be pruned to known-good + base angles
+        builder.ForceFullSweep = false;
+        var secondAngles = builder.Build(item, 0, workArea);
+
+        Assert.True(secondAngles.Count < firstAngles.Count,
+            $"Pruned ({secondAngles.Count}) should be fewer than full ({firstAngles.Count})");
+    }
+}