From 641734ba70492b83750faeb8a333b9627dbf6646 Mon Sep 17 00:00:00 2001
From: AJ Isaacs <ajisaacs27@gmail.com>
Date: Tue, 17 Mar 2026 08:00:11 -0400
Subject: [PATCH] feat(core): add RingShape

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
---
 OpenNest.Core/Shapes/RingShape.cs       | 22 +++++++++++++++
 OpenNest.Tests/Shapes/RingShapeTests.cs | 37 +++++++++++++++++++++++++
 2 files changed, 59 insertions(+)
 create mode 100644 OpenNest.Core/Shapes/RingShape.cs
 create mode 100644 OpenNest.Tests/Shapes/RingShapeTests.cs

diff --git a/OpenNest.Core/Shapes/RingShape.cs b/OpenNest.Core/Shapes/RingShape.cs
new file mode 100644
index 0000000..2b22783
--- /dev/null
+++ b/OpenNest.Core/Shapes/RingShape.cs
@@ -0,0 +1,22 @@
+using System.Collections.Generic;
+using OpenNest.Geometry;
+
+namespace OpenNest.Shapes
+{
+    public class RingShape : ShapeDefinition
+    {
+        public double OuterDiameter { get; set; }
+        public double InnerDiameter { get; set; }
+
+        public override Drawing GetDrawing()
+        {
+            var entities = new List<Entity>
+            {
+                new Circle(0, 0, OuterDiameter / 2.0),
+                new Circle(0, 0, InnerDiameter / 2.0)
+            };
+
+            return CreateDrawing(entities);
+        }
+    }
+}
diff --git a/OpenNest.Tests/Shapes/RingShapeTests.cs b/OpenNest.Tests/Shapes/RingShapeTests.cs
new file mode 100644
index 0000000..acbedd7
--- /dev/null
+++ b/OpenNest.Tests/Shapes/RingShapeTests.cs
@@ -0,0 +1,37 @@
+using OpenNest.Shapes;
+
+namespace OpenNest.Tests.Shapes;
+
+public class RingShapeTests
+{
+    [Fact]
+    public void GetDrawing_BoundingBoxMatchesOuterDiameter()
+    {
+        var shape = new RingShape { OuterDiameter = 20, InnerDiameter = 10 };
+        var drawing = shape.GetDrawing();
+
+        var bbox = drawing.Program.BoundingBox();
+        Assert.Equal(20, bbox.Width, 0.01);
+        Assert.Equal(20, bbox.Length, 0.01);
+    }
+
+    [Fact]
+    public void GetDrawing_AreaExcludesInnerHole()
+    {
+        var shape = new RingShape { OuterDiameter = 20, InnerDiameter = 10 };
+        var drawing = shape.GetDrawing();
+
+        // Area = pi * (10^2 - 5^2) = pi * 75
+        var expectedArea = System.Math.PI * 75;
+        Assert.Equal(expectedArea, drawing.Area, 0.5);
+    }
+
+    [Fact]
+    public void GetDrawing_DefaultName_IsRing()
+    {
+        var shape = new RingShape { OuterDiameter = 20, InnerDiameter = 10 };
+        var drawing = shape.GetDrawing();
+
+        Assert.Equal("Ring", drawing.Name);
+    }
+}