From 46fe48870ce892600f5ac1389d644e678f5cc1e5 Mon Sep 17 00:00:00 2001
From: AJ Isaacs <ajisaacs27@gmail.com>
Date: Wed, 18 Mar 2026 12:57:31 -0400
Subject: [PATCH] feat(engine): add FillStrategyRegistry with reflection-based
 discovery

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
---
 .../Strategies/FillStrategyRegistry.cs        | 79 +++++++++++++++++++
 1 file changed, 79 insertions(+)
 create mode 100644 OpenNest.Engine/Strategies/FillStrategyRegistry.cs

diff --git a/OpenNest.Engine/Strategies/FillStrategyRegistry.cs b/OpenNest.Engine/Strategies/FillStrategyRegistry.cs
new file mode 100644
index 0000000..f146cdf
--- /dev/null
+++ b/OpenNest.Engine/Strategies/FillStrategyRegistry.cs
@@ -0,0 +1,79 @@
+using System;
+using System.Collections.Generic;
+using System.Diagnostics;
+using System.IO;
+using System.Linq;
+using System.Reflection;
+
+namespace OpenNest
+{
+    public static class FillStrategyRegistry
+    {
+        private static readonly List<IFillStrategy> strategies = new();
+        private static List<IFillStrategy> sorted;
+
+        static FillStrategyRegistry()
+        {
+            LoadFrom(typeof(FillStrategyRegistry).Assembly);
+        }
+
+        public static IReadOnlyList<IFillStrategy> Strategies =>
+            sorted ??= strategies.OrderBy(s => s.Order).ToList();
+
+        public static void LoadFrom(Assembly assembly)
+        {
+            foreach (var type in assembly.GetTypes())
+            {
+                if (type.IsAbstract || type.IsInterface || !typeof(IFillStrategy).IsAssignableFrom(type))
+                    continue;
+
+                var ctor = type.GetConstructor(Type.EmptyTypes);
+                if (ctor == null)
+                {
+                    Debug.WriteLine($"[FillStrategyRegistry] Skipping {type.Name}: no parameterless constructor");
+                    continue;
+                }
+
+                try
+                {
+                    var instance = (IFillStrategy)ctor.Invoke(null);
+
+                    if (strategies.Any(s => s.Name.Equals(instance.Name, StringComparison.OrdinalIgnoreCase)))
+                    {
+                        Debug.WriteLine($"[FillStrategyRegistry] Duplicate strategy '{instance.Name}' skipped");
+                        continue;
+                    }
+
+                    strategies.Add(instance);
+                    Debug.WriteLine($"[FillStrategyRegistry] Registered: {instance.Name} (Order={instance.Order})");
+                }
+                catch (Exception ex)
+                {
+                    Debug.WriteLine($"[FillStrategyRegistry] Failed to instantiate {type.Name}: {ex.Message}");
+                }
+            }
+
+            sorted = null;
+        }
+
+        public static void LoadPlugins(string directory)
+        {
+            if (!Directory.Exists(directory))
+                return;
+
+            foreach (var dll in Directory.GetFiles(directory, "*.dll"))
+            {
+                try
+                {
+                    var assembly = Assembly.LoadFrom(dll);
+                    LoadFrom(assembly);
+                    Debug.WriteLine($"[FillStrategyRegistry] Loaded plugin assembly: {Path.GetFileName(dll)}");
+                }
+                catch (Exception ex)
+                {
+                    Debug.WriteLine($"[FillStrategyRegistry] Failed to load {Path.GetFileName(dll)}: {ex.Message}");
+                }
+            }
+        }
+    }
+}