From 439fbb1433c31504bee2b79072062bbb66ae4e7a Mon Sep 17 00:00:00 2001
From: ADAM David Alan Martin <adam@recursive.engineer>
Date: Tue, 26 Oct 2021 05:10:40 -0400
Subject: [PATCH] StaticValue helper.

Incorporated into `Testing`, for now.  Semi-threadsafe statics,
initialize them before going multithreaded.
---
 Testing/test.h        | 12 +++++------
 Utility/StaticValue.h | 47 +++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 53 insertions(+), 6 deletions(-)
 create mode 100644 Utility/StaticValue.h

diff --git a/Testing/test.h b/Testing/test.h
index e0654e9..e7fe23a 100644
--- a/Testing/test.h
+++ b/Testing/test.h
@@ -15,6 +15,8 @@ static_assert( __cplusplus > 201700, "C++17 Required" );
 
 #include <Alepha/console.h>
 #include <Alepha/types.h>
+#include <Alepha/Utility/evaluation.h>
+#include <Alepha/Utility/StaticValue.h>
 
 namespace Alepha::Hydrogen::Testing
 {
@@ -34,6 +36,8 @@ namespace Alepha::Hydrogen::Testing
 		}
 
 		using namespace std::literals::string_literals;
+		using namespace Utility::exports::evaluation;
+		using namespace Utility::exports::static_value;
 
 		struct TestName
 		{
@@ -65,12 +69,8 @@ namespace Alepha::Hydrogen::Testing
 			}
 		}
 
-		inline auto &
-		registry()
-		{
-			static std::vector< std::tuple< std::string, bool, std::function< void() > > > registry;
-			return registry;
-		}
+		StaticValue< std::vector< std::tuple< std::string, bool, std::function< void() > > > > registry;
+		auto initRegistry= enroll <=registry;
 
 		// It is okay to discard this, if making tests in an enroll block.
 		inline auto
diff --git a/Utility/StaticValue.h b/Utility/StaticValue.h
new file mode 100644
index 0000000..d80bb99
--- /dev/null
+++ b/Utility/StaticValue.h
@@ -0,0 +1,47 @@
+static_assert( __cplusplus > 201700, "C++17 Required" );
+
+#pragma once
+
+namespace Alepha::Hydrogen::Utility
+{
+	inline namespace exports { inline namespace static_value {} }
+
+	namespace detail::static_value
+	{
+		inline namespace exports {}
+
+		template< typename T >
+		struct default_init
+		{
+			T *operator()() const { return new T{}; }
+		};
+
+		namespace exports
+		{
+			template< typename T, typename Init= default_init< T > >
+			struct StaticValue;
+		}
+
+		template< typename T, typename Init >
+		struct exports::StaticValue
+		{
+			private:
+				T *storage= nullptr;
+
+			public:
+				decltype( auto )
+				get()
+				{
+					if( not storage ) storage= Init{}();
+					return *storage;
+				}
+
+				decltype( auto ) operator ()() { return get(); }
+		};
+	}
+
+	namespace exports::static_value
+	{
+		using namespace detail::static_value::exports;
+	}
+}