feat: add GeometrySimplifier.Analyze with incremental arc fitting

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

OpenNest.Tests/GeometrySimplifierTests.cs

@@ -40,4 +40,71 @@ public class GeometrySimplifierTests
 
         Assert.False(fitCenter.IsValid());
     }
+
+    [Fact]
+    public void Analyze_LinesFromSemicircle_FindsOneCandidate()
+    {
+        // Create 20 lines approximating a semicircle of radius 10
+        var arc = new Arc(new Vector(0, 0), 10, 0, System.Math.PI, false);
+        var points = arc.ToPoints(20);
+        var shape = new Shape();
+        for (var i = 0; i < points.Count - 1; i++)
+            shape.Entities.Add(new Line(points[i], points[i + 1]));
+
+        var simplifier = new GeometrySimplifier { Tolerance = 0.1 };
+        var candidates = simplifier.Analyze(shape);
+
+        Assert.Single(candidates);
+        Assert.Equal(0, candidates[0].StartIndex);
+        Assert.Equal(19, candidates[0].EndIndex);
+        Assert.Equal(20, candidates[0].LineCount);
+        Assert.InRange(candidates[0].FittedArc.Radius, 9.5, 10.5);
+        Assert.True(candidates[0].MaxDeviation <= 0.1);
+    }
+
+    [Fact]
+    public void Analyze_TooFewLines_ReturnsNoCandidates()
+    {
+        // Only 2 consecutive lines — below MinLines threshold
+        var shape = new Shape();
+        shape.Entities.Add(new Line(new Vector(0, 0), new Vector(1, 1)));
+        shape.Entities.Add(new Line(new Vector(1, 1), new Vector(2, 0)));
+
+        var simplifier = new GeometrySimplifier { Tolerance = 0.1, MinLines = 3 };
+        var candidates = simplifier.Analyze(shape);
+
+        Assert.Empty(candidates);
+    }
+
+    [Fact]
+    public void Analyze_MixedEntitiesWithArc_OnlyAnalyzesLines()
+    {
+        // Line, Line, Line, Arc, Line, Line, Line — should find candidates only in line runs
+        var shape = new Shape();
+        // First run: 5 lines on a curve
+        var arc1 = new Arc(new Vector(0, 0), 10, 0, System.Math.PI / 2, false);
+        var pts1 = arc1.ToPoints(5);
+        for (var i = 0; i < pts1.Count - 1; i++)
+            shape.Entities.Add(new Line(pts1[i], pts1[i + 1]));
+
+        // An existing arc entity (breaks the run)
+        shape.Entities.Add(new Arc(new Vector(20, 0), 5, 0, System.Math.PI, false));
+
+        // Second run: 4 lines on a different curve
+        var arc2 = new Arc(new Vector(30, 0), 8, 0, System.Math.PI / 3, false);
+        var pts2 = arc2.ToPoints(4);
+        for (var i = 0; i < pts2.Count - 1; i++)
+            shape.Entities.Add(new Line(pts2[i], pts2[i + 1]));
+
+        var simplifier = new GeometrySimplifier { Tolerance = 0.5, MinLines = 3 };
+        var candidates = simplifier.Analyze(shape);
+
+        Assert.Equal(2, candidates.Count);
+        // First candidate covers indices 0-4 (5 lines)
+        Assert.Equal(0, candidates[0].StartIndex);
+        Assert.Equal(4, candidates[0].EndIndex);
+        // Second candidate covers indices 6-9 (4 lines, after the arc at index 5)
+        Assert.Equal(6, candidates[1].StartIndex);
+        Assert.Equal(9, candidates[1].EndIndex);
+    }
 }