Add bounded per-type enum lookup cache for GetEnumStringValue

Caches attribute resolution per enum Type (not per value), so growth is bounded by the number of distinct enum types in the app. Flags combinations and undefined values fall through to ToString() without polluting the cache.

Author: niemyjski

src/Foundatio.Repositories.Elasticsearch/Utility/FieldValueHelper.cs

@@ -1,4 +1,6 @@
 using System;
+using System.Collections.Concurrent;
+using System.Collections.Generic;
 using System.Reflection;
 using System.Runtime.Serialization;
 using System.Text.Json.Serialization;
@@ -8,6 +10,8 @@ namespace Foundatio.Repositories.Elasticsearch.Utility;
 
 public static class FieldValueHelper
 {
+    private static readonly ConcurrentDictionary<Type, Dictionary<string, string>> _enumTypeLookup = new();
+
     public static FieldValue ToFieldValue(object? value)
     {
         return value switch
@@ -35,18 +39,27 @@ public static FieldValue ToFieldValue(object? value)
 
     private static string GetEnumStringValue(Enum value)
     {
-        var field = value.GetType().GetField(value.ToString());
-        if (field is not null)
+        var lookup = _enumTypeLookup.GetOrAdd(value.GetType(), static type =>
         {
-            var jsonAttr = field.GetCustomAttribute<JsonStringEnumMemberNameAttribute>();
-            if (jsonAttr is not null)
-                return jsonAttr.Name;
+            var map = new Dictionary<string, string>();
+            foreach (var field in type.GetFields(BindingFlags.Public | BindingFlags.Static))
+            {
+                var jsonAttr = field.GetCustomAttribute<JsonStringEnumMemberNameAttribute>();
+                if (jsonAttr is not null)
+                {
+                    map[field.Name] = jsonAttr.Name;
+                    continue;
+                }
+
+                var enumMemberAttr = field.GetCustomAttribute<EnumMemberAttribute>();
+                if (enumMemberAttr?.Value is not null)
+                    map[field.Name] = enumMemberAttr.Value;
+            }
 
-            var enumMemberAttr = field.GetCustomAttribute<EnumMemberAttribute>();
-            if (enumMemberAttr?.Value is not null)
-                return enumMemberAttr.Value;
-        }
+            return map;
+        });
 
-        return value.ToString();
+        var name = value.ToString();
+        return lookup.TryGetValue(name, out var resolved) ? resolved : name;
     }
 }