Faster enum -> string resolution

src/CodeGeneration/ApiGenerator/Views/Enums.Generated.cshtml

@@ -1,8 +1,8 @@
+@using System
 @using System.Collections.Generic
 @using System.Linq
 @using ApiGenerator.Domain
 @using ApiGenerator
-
 @functions {
 	private const string RawSize = "Raw";
 	private const string SizeEnum = "Size";
@@ -14,75 +14,149 @@
 	}
 	private string CreateCase(string e, string o)
 	{
-		var enumValue = (e == SizeEnum && o == string.Empty) ? RawSize : o.ToPascalCase(true);
+		var enumValue = GetEnumValue(e, o);
 		return string.Format("case {0}.{1}: return \"{2}\";", e, enumValue, o);
 	}
 	private bool IsFlag(string name)
 	{
-		return (name.EndsWith("Metric")) || name.EndsWith("Feature");
+		return name.EndsWith("Metric") || name.EndsWith("Feature");
+	}
+
+	private string CreateEnumKeyValue(string enumName, string value, int index)
+	{
+		var enumValue = GetEnumValue(enumName, value);
+		return string.Format("{3}{{ {0}.{1}, \"{2}\" }},", enumName, enumValue, value, index == 0 ? "\t\t\t\t" : string.Empty);
+	}
+
+	private string GetEnumValue(string enumName, string value)
+	{
+		return enumName == SizeEnum && value == string.Empty 
+			? RawSize 
+			: value.ToPascalCase(true);
 	}
 }
 using System;
 using System.Collections.Generic;
+using System.Collections.Concurrent;
 using System.Linq;
 using System.Text;
+using System.Reflection;
 using System.Runtime.Serialization;
 
 ///This file contains all the typed enums that the client rest api spec exposes.
 ///This file is automatically generated from https://github.com/elastic/elasticsearch/tree/@Model.Commit/rest-api-spec
 ///Generated of commit @Model.Commit
 namespace Elasticsearch.Net
 {
-	@foreach (EnumDescription e in Model.EnumsInTheSpec)
-	{
-		var isFlag = IsFlag(e.Name);
+@foreach (EnumDescription e in Model.EnumsInTheSpec)
+{
+	var isFlag = IsFlag(e.Name);
 	<text>
-	@(isFlag ? "[Flags]" : string.Empty)public enum @e.Name 
+	@(isFlag ? "[Flags]" : string.Empty)public enum @e.Name
 	{
-		@Raw(string.Join(",\r\n\t\t", e.Options.OrderBy(s=>s == "_all" ? 1 : 0).Select((s, i) => CreateEnum(e.Name, s, isFlag ? (int?)i : null ))))
-	}
-	</text>
-	}
+	@Raw(string.Join(",\r\n\t\t", e.Options.OrderBy(s => s == "_all" ? 1 : 0).Select((s, i) => CreateEnum(e.Name, s, isFlag ? (int?)i : null))))
+	}</text>
+}
 
 	public static class KnownEnums
+    { 
+        private class EnumDictionary : @(Raw("Dictionary<Enum, string>"))
+		{	
+			public EnumDictionary(int capacity) : base(capacity) {}
+			public @(Raw("Func<Enum, string>")) Resolver { get; set; }
+		}	
+
+	@foreach (EnumDescription e in Model.EnumsInTheSpec)
 	{
-		public static string UnknownEnum { get; } = "_UNKNOWN_ENUM_";
-		public static string Resolve(Enum e)
+		var isFlag = IsFlag(e.Name);
+		<text>
+		public static string GetStringValue(this @(e.Name) enumValue)
+		{
+		</text>
+		if (isFlag)
+		{
+			var allOption = e.Options.FirstOrDefault(o => o == "_all");
+			if (allOption != null)
+			{
+	        <text>if ((enumValue & @(e.Name).All) != 0) return "_all";</text>
+			}
+			<text>var list = new @(Raw("List<string>()"));</text>
+			foreach (var option in e.Options.Where(o => o != "_all"))
+			{
+			<text>if ((enumValue & @(e.Name).@(GetEnumValue(e.Name, option))) != 0) list.Add("@(option)");</text>
+			}
+			<text>return string.Join(",", list);
+		}</text>
+		}
+		else
+		{
+			<text>switch (enumValue)
+			{
+				@Raw(string.Join("\r\n\t\t\t\t", e.Options.Select(o => CreateCase(e.Name, o))))
+			}
+			throw new ArgumentException($"'{enumValue.ToString()}' is not a valid value for enum '@(e.Name)'");		
+		}</text>
+		}
+	}
+
+		private static readonly @(Raw("ConcurrentDictionary<Type, Func<Enum, string>>")) EnumStringResolvers =
+			new @(Raw("ConcurrentDictionary<Type, Func<Enum, string>>"))();
+
+		static KnownEnums()
+		{
+		@foreach (EnumDescription e in Model.EnumsInTheSpec)
+		{
+			<text>EnumStringResolvers.TryAdd(typeof(@(e.Name)), (e) => GetStringValue((@(e.Name))e));</text>
+		}
+		}
+
+		public static string GetStringValue(this Enum e)
+		{
+			var type = e.GetType();		
+			var resolver = EnumStringResolvers.GetOrAdd(type, GetEnumStringResolver);
+			return resolver(e);
+		}
+
+		private static @Raw("Func<Enum, string>") GetEnumStringResolver(Type type)
 		{
-			@foreach (EnumDescription e in Model.EnumsInTheSpec)
+			var values = Enum.GetValues(type);
+			var dictionary = new EnumDictionary(values.Length);
+
+			for (int index = 0; index < values.Length; index++)
 			{
-			var isFlag = IsFlag(e.Name);
-			<text>if (e is @e.Name)
-			{ </text>
-			if (isFlag)
+				var value = values.GetValue(index);
+#if DOTNETCORE
+				var info = type.GetTypeInfo().GetDeclaredField(value.ToString());
+#else
+				var info = type.GetField(value.ToString());
+#endif
+				var da = (EnumMemberAttribute[])info.GetCustomAttributes(typeof(EnumMemberAttribute), false);
+				var stringValue = da.Length > 0 ? da[0].Value : Enum.GetName(type, value);
+				dictionary.Add((Enum)value, stringValue);
+			}
+
+#if DOTNETCORE
+			var isFlag = type.GetTypeInfo().GetCustomAttributes(typeof(FlagsAttribute), false).Any();
+#else
+			var isFlag = type.GetCustomAttributes(typeof(FlagsAttribute), false).Length > 0;
+#endif
+
+			return (e) => 
 			{
-				<text>var list = new @(Raw("List<string>()"));</text>
-				foreach(var option in e.Options.OrderBy(s=>s == "_all" ? 1 : 0))
+				if (isFlag)
 				{
-					if (option != "_all")
+					var list = new @(Raw("List<string>()"));
+					foreach(var kv in dictionary)
 					{
-				<text>if (e.HasFlag(@(e.Name).@(option.ToPascalCase(true)))) list.Add("@(option)");</text>
-					}
-					else 
-					{
-				<text>if (e.HasFlag(@(e.Name).@(option.ToPascalCase(true)))) return "@(option)";</text>
+						if (e.HasFlag(kv.Key)) list.Add(kv.Value);
 					}
+					return string.Join(",", list);
 				}
-				<text>return string.Join(",", list);</text>
-			}
-			else 
-			{
-				<text>switch((@e.Name)e)
+				else
 				{
-					@Raw(string.Join("\r\n\t\t\t\t\t", e.Options.Select(o =>CreateCase(e.Name,o))))
-				}</text>
-			}
-			<text>
-			}
-			</text>
-			}
-			return UnknownEnum;
+					return dictionary[e];
+				}
+			};
 		}
 	}
-}
-
+}

src/Elasticsearch.Net/Connection/HttpConnection.cs

@@ -66,7 +66,7 @@ protected virtual HttpWebRequest CreateWebRequest(RequestData requestData)
 			//see: https://github.com/elasticsearch/elasticsearch-net/issues/562
 			var m = requestData.Method.GetStringValue();
 			request.Method = m;
-			if (m != "head" && m != "get" && (requestData.PostData == null))
+			if (m != "HEAD" && m != "GET" && (requestData.PostData == null))
 				request.ContentLength = 0;
 
 			return request;

src/Elasticsearch.Net/Connection/HttpMethod.cs

@@ -17,4 +17,4 @@ public enum HttpMethod
 		[EnumMember(Value = "HEAD")]
 		HEAD
 	}
-}
+}