From c0977cbc0a76948c45f67d5667c9fd4fbd70dadd Mon Sep 17 00:00:00 2001
From: Jamie Reece Wilson <me@reece.sx>
Date: Tue, 17 Oct 2023 03:26:43 +0100
Subject: [PATCH] [*] Improved AuMin/AuMax - New prototype: constexpr Ret_t
 AuMin(const A &a, const B &b) [+] AuCommonType_t

---
 Include/auROXTL/auNumberUtils.hpp  | 10 ++--
 Include/auROXTL/auTemplateMeta.hpp | 76 +++++++++++++++++++++++++++++-
 2 files changed, 80 insertions(+), 6 deletions(-)

diff --git a/Include/auROXTL/auNumberUtils.hpp b/Include/auROXTL/auNumberUtils.hpp
index d1a735b..0ea5663 100644
--- a/Include/auROXTL/auNumberUtils.hpp
+++ b/Include/auROXTL/auNumberUtils.hpp
@@ -7,14 +7,16 @@
 ***/
 #pragma once
 
-template <class T>
-constexpr const T &AuMin(const T &a, const T &b)
+template <typename A, typename B, typename Ret_t = 
+    AuConditional_t<AuIsClass_v<A>, A, AuCommonType_t<A, B>>>
+constexpr Ret_t AuMin(const A &a, const B &b)
 {
     return a < b ? a : b;
 }
 
-template <class T>
-constexpr const T &AuMax(const T &a, const T &b)
+template <typename A, typename B, typename Ret_t =
+    AuConditional_t<AuIsClass_v<A>, A, AuCommonType_t<A, B>>>
+constexpr Ret_t AuMax(const A &a, const B &b)
 {
     return a < b ? b : a;
 }
diff --git a/Include/auROXTL/auTemplateMeta.hpp b/Include/auROXTL/auTemplateMeta.hpp
index 78ea28b..c36fd4d 100644
--- a/Include/auROXTL/auTemplateMeta.hpp
+++ b/Include/auROXTL/auTemplateMeta.hpp
@@ -78,7 +78,7 @@ namespace _audetail
     AuFalseType TestIsPtrConvertible(const volatile void *);
 
     template <class, typename>
-    auto TestIsBaseOf(...)->AuTrueType;
+    auto TestIsBaseOf(...) -> AuTrueType;
 
     template <class B, typename D>
     auto TestIsBaseOf(int) -> decltype(TestIsPtrConvertible<B>(static_cast<D *>(nullptr)));
@@ -361,6 +361,12 @@ using AuDecay_t = AuConditional_t<
     >
 >;
 
+template <class T>
+struct AuDecay
+{
+    using type = AuDecay_t<T>;
+};
+
 template <template <class...> class Base, typename Derived>
 struct AuIsBaseOfTemplateImpl
 {
@@ -424,6 +430,72 @@ static auto AuGetAmbiguousMethod2(Ret_t(T :: *a)(Args...))
     return a;
 }
 
+
+// I dont think I can easily implement these in templates
+// For the sake of syntax sugar, these will be macros for now
 #define AuGetAmbiguousMethod(Ret_t, Args, T, Method) AuGetAmbiguousMethod2<Ret_t, T, AU_BRACKET_SCOPE Args >(&T::Method)
 
-#define AuGetAmbiguousMethod_v AuGetAmbiguousMethod
\ No newline at end of file
+#define AuGetAmbiguousMethod_v AuGetAmbiguousMethod
+
+namespace _audetail
+{
+    // yoinking https://en.cppreference.com/w/cpp/types/common_type
+    template<class...>
+    struct common_type
+    { };
+
+    template<class T>
+    struct common_type<T> : common_type<T, T>
+    { };
+
+    namespace ctdetail
+    {
+        template<class...>
+        using void_t = void;
+        
+        template<class T1, class T2>
+        using conditional_result_t = decltype(false ? AuDeclVal<T1>() : AuDeclVal<T2>());
+        
+        template<class, class, class = void>
+        struct decay_conditional_result
+        { };
+
+        template<class T1, class T2>
+        struct decay_conditional_result<T1, T2, void_t<conditional_result_t<T1, T2>>>
+            : AuDecay<conditional_result_t<T1, T2>>
+        { };
+
+        template<class T1, class T2, class = void>
+        struct common_type_2_impl : decay_conditional_result<const T1 &, const T2 &>
+        { };
+
+        template<class T1, class T2>
+        struct common_type_2_impl<T1, T2, void_t<conditional_result_t<T1, T2>>>
+            : decay_conditional_result<T1, T2>
+        { };
+    }
+
+    template<class T1, class T2>
+    struct common_type<T1, T2>
+        : AuConditional<AuIsSame_v<T1,typename AuDecay_t<T1>> && AuIsSame_v<T2, AuDecay_t<T2>>,
+                                   ctdetail::common_type_2_impl<T1, T2>,
+                                   common_type<AuDecay_t<T1>, AuDecay_t<T2>>>::type 
+    {};
+
+    namespace ctdetail
+    {
+        template<class AlwaysVoid, class T1, class T2, class...R>
+        struct common_type_multi_impl
+        { };
+        template<class T1, class T2, class...R>
+        struct common_type_multi_impl<void_t<typename common_type<T1, T2>::type>, T1, T2, R...>
+            : common_type<typename common_type<T1, T2>::type, R...>
+        { };
+    }
+}
+
+template <class T, class T2>
+using AuCommonType = typename _audetail::common_type<T, T2>;
+
+template <class T, class T2>
+using AuCommonType_t = typename _audetail::common_type<T, T2>::type;
\ No newline at end of file