From f90074adb6e78addc635667c97b2c8bd7ca0a2a3 Mon Sep 17 00:00:00 2001
From: AMZN-ScottR <24445312+AMZN-ScottR@users.noreply.github.com>
Date: Wed, 27 Oct 2021 15:54:03 -0700
Subject: [PATCH] [profiler_capture_api] added utility for reflecting
 AZ::Interfaces through the BehaviorContext

Signed-off-by: AMZN-ScottR <24445312+AMZN-ScottR@users.noreply.github.com>
---
 .../AzCore/RTTI/BehaviorInterfaceProxy.h      | 122 ++++++++++++++++++
 .../AzCore/AzCore/azcore_files.cmake          |   1 +
 2 files changed, 123 insertions(+)
 create mode 100644 Code/Framework/AzCore/AzCore/RTTI/BehaviorInterfaceProxy.h

diff --git a/Code/Framework/AzCore/AzCore/RTTI/BehaviorInterfaceProxy.h b/Code/Framework/AzCore/AzCore/RTTI/BehaviorInterfaceProxy.h
new file mode 100644
index 0000000000..430524d3a2
--- /dev/null
+++ b/Code/Framework/AzCore/AzCore/RTTI/BehaviorInterfaceProxy.h
@@ -0,0 +1,122 @@
+/*
+ * Copyright (c) Contributors to the Open 3D Engine Project.
+ * For complete copyright and license terms please see the LICENSE at the root of this distribution.
+ *
+ * SPDX-License-Identifier: Apache-2.0 OR MIT
+ *
+ */
+
+#include <AzCore/Interface/Interface.h>
+#include <AzCore/Memory/SystemAllocator.h>
+#include <AzCore/RTTI/RTTI.h>
+#include <AzCore/std/functional.h>
+#include <AzCore/std/typetraits/function_traits.h>
+
+namespace AZ
+{
+    /**
+     * Utility class for reflecting an AZ::Interface through the BehaviorContext
+     *
+     * Example:
+     *
+     * class MyInterface
+     * {
+     * public:
+     *     AZ_RTTI(MyInterface, "{BADDF000D-CDCD-CDCD-CDCD-BAAAADF0000D}");
+     *     virtual ~MyInterface() = default;
+     *
+     *     virtual AZStd::string Foo() = 0;
+     *     virtual void Bar(float x, float y) = 0;
+     * };
+     *
+     * class MySystemProxy
+     *     : public BehaviorInterfaceProxy<MyInterface>
+     * {
+     * public:
+     *     AZ_RTTI(MySystemProxy, "{CDCDCDCD-BAAD-BADD-F00D-CDCDCDCDCDCD}", BehaviorInterfaceProxy<MyInterface>);
+     * };
+     *
+     * void Reflect(AZ::ReflectContext* context)
+     * {
+     *     if (AZ::BehaviorContext* behaviorContext = azrtti_cast<AZ::BehaviorContext*>(context))
+     *     {
+     *         behaviorContext->ConstantProperty("g_MySystem", MySystemProxy::GetInstance)
+     *             ->Attribute(AZ::Script::Attributes::Scope, AZ::Script::Attributes::ScopeFlags::Common)
+     *             ->Attribute(AZ::Script::Attributes::Module, "MyModule");
+     *
+     *         behaviorContext->Class<MySystemProxy>("MySystemInterface")
+     *             ->Attribute(AZ::Script::Attributes::Scope, AZ::Script::Attributes::ScopeFlags::Common)
+     *             ->Attribute(AZ::Script::Attributes::Module, "MyModule")
+     *
+     *             ->Method("Foo", MySystemProxy::WrapMethod<&MyInterface::Foo>())
+     *             ->Method("Bar", MySystemProxy::WrapMethod<&MyInterface::Bar>());
+     *     }
+     * }
+     */
+    template<typename T>
+    class BehaviorInterfaceProxy
+    {
+    public:
+        AZ_CLASS_ALLOCATOR(BehaviorInterfaceProxy, AZ::SystemAllocator, 0);
+        AZ_RTTI(BehaviorInterfaceProxy<T>, "{E7CC8D27-4499-454E-A7DF-3F72FBECD30D}");
+
+        //! Accessor for use with ConstantProperty
+        static T* GetInstance()
+        {
+            T* interfacePtr = AZ::Interface<T>::Get();
+            AZ_Warning("BehaviorInterfaceProxy", interfacePtr,
+                "There is currently no global %s registered with an AZ Interface<T>",
+                AzTypeInfo<T>::Name()
+            );
+            // Don't delete the global instance, it is not owned by the behavior context
+            return interfacePtr;
+        }
+
+        //! Helper for attaching interface function via ClassBuilder::Method
+        template<auto Method>
+        static auto WrapMethod()
+        {
+            using FuncTraits = AZStd::function_traits<AZStd::remove_cvref_t<decltype(Method)>>;
+            return FuncTraits::template expand_args<MethodWrapper>::template WrapMethod<Method>();
+        }
+
+        BehaviorInterfaceProxy() = default;
+        virtual ~BehaviorInterfaceProxy() = default;
+
+        //! Stores the instance which will use the provided shared_ptr deleter when the reference count hits zero
+        BehaviorInterfaceProxy(AZStd::shared_ptr<T> sharedInstance)
+            : m_instance(AZStd::move(sharedInstance))
+        {
+        }
+
+        //! Stores the instance which will perform a no-op deleter when the reference count hits zero
+        BehaviorInterfaceProxy(T* rawIntance)
+            : m_instance(rawIntance, [](T*) {})
+        {
+        }
+
+        //! Returns if the m_instance shared pointer is non-nullptr
+        bool IsValid() const { return m_instance; }
+
+    private:
+        template <typename... Args>
+        struct MethodWrapper
+        {
+            template<auto Method>
+            static auto WrapMethod()
+            {
+                using return_type = AZStd::function_traits_get_result_t<AZStd::remove_cvref_t<decltype(Method)>>;
+                return [](BehaviorInterfaceProxy<T>* proxy, Args... params) -> return_type
+                {
+                    if (proxy && proxy->IsValid())
+                    {
+                        return AZStd::invoke(Method, proxy->m_instance, AZStd::forward<Args>(params)...);
+                    }
+                    return return_type();
+                };
+            }
+        };
+
+        AZStd::shared_ptr<T> m_instance;
+    };
+} // namespace AZ
diff --git a/Code/Framework/AzCore/AzCore/azcore_files.cmake b/Code/Framework/AzCore/AzCore/azcore_files.cmake
index d4a26256bf..3cd702e588 100644
--- a/Code/Framework/AzCore/AzCore/azcore_files.cmake
+++ b/Code/Framework/AzCore/AzCore/azcore_files.cmake
@@ -456,6 +456,7 @@ set(FILES
     RTTI/BehaviorContext.h
     RTTI/BehaviorContextUtilities.h
     RTTI/BehaviorContextUtilities.cpp
+    RTTI/BehaviorInterfaceProxy.h
     RTTI/BehaviorObjectSignals.h
     RTTI/TypeSafeIntegral.h
     Script/ScriptAsset.cpp