BansheeEngine/Source/SBansheeEngine/BsScriptObject.h

//********************************** Banshee Engine (www.banshee3d.com) **************************************************//
//**************** Copyright (c) 2016 Marko Pintera ([email protected]). All rights reserved. **********************//
#pragma once

#include "BsScriptEnginePrerequisites.h"
#include "BsScriptMeta.h"
#include "Error/BsException.h"
#include "BsMonoManager.h"
#include "BsMonoField.h"
#include "BsMonoClass.h"

namespace bs
{
	/** @addtogroup SBansheeEngine
	 *  @{
	 */

	/**	Contains backed up interop object data. */
	struct ScriptObjectBackup
	{
		Any data;
	};

	/**
	 * Base class for all script interop objects. Interop objects form a connection between C++ and CLR classes and methods.
	 */
	class BS_SCR_BE_EXPORT ScriptObjectBase
	{
	public:
		ScriptObjectBase(MonoObject* instance);
		virtual ~ScriptObjectBase();

		/**
		 * Should the interop object persist through assembly reload. If false then the interop object will be destroyed on
		 * reload.
		 */
		virtual bool isPersistent() const { return false; }

		/**	
		 * Clears any managed instance references from the interop object. Normally called right after the assemblies are
		 * unloaded.
		 */
		virtual void _clearManagedInstance() { }

		/**	Allows persistent objects to restore their managed instances after assembly reload. */
		virtual void _restoreManagedInstance() { }

		/**	Called when the managed instance gets finalized by the CLR. */
		virtual void _onManagedInstanceDeleted();

		/**	Called before assembly reload starts to give the object a chance to back up its data. */
		virtual ScriptObjectBackup beginRefresh();

		/**
		 * Called after assembly reload starts to give the object a chance to restore the data backed up by the previous
		 * beginRefresh() call.
		 */
		virtual void endRefresh(const ScriptObjectBackup& data);
	};

	/**	Base class for all persistent interop objects. Persistent objects persist through assembly reload. */
	class BS_SCR_BE_EXPORT PersistentScriptObjectBase : public ScriptObjectBase
	{
	public:
		PersistentScriptObjectBase(MonoObject* instance);
		virtual ~PersistentScriptObjectBase();

		/** @copydoc ScriptObjectBase::isPersistent  */
		bool isPersistent() const override { return true; }
	};

	template <class Type, class Base>
	class ScriptObject;

	/** Helper class to initialize all script interop objects as soon as the library is loaded. */
	template <class Type, class Base>
	struct InitScriptObjectOnStart
	{
	public:
		InitScriptObjectOnStart()
		{
			ScriptObject<Type, Base>::_initMetaData();
		}

		void makeSureIAmInstantiated() { }
	};

	/**	Template version of ScriptObjectBase populates the object meta-data on library load. */
	template <class Type, class Base = ScriptObjectBase>
	class ScriptObject : public Base
	{
	public:
		ScriptObject(MonoObject* instance)
			:Base(instance)
		{
			initOnStart.makeSureIAmInstantiated();

			Type* param = (Type*)(Base*)this; // Needed due to multiple inheritance. Safe since Type must point to an class derived from this one.

			if(metaData.thisPtrField != nullptr)
				metaData.thisPtrField->set(instance, &param);
		}

		virtual ~ScriptObject() 
		{ }

		/**	Allows persistent objects to restore their managed instances after assembly reload. */
		void _restoreManagedInstance()
		{
			MonoObject* instance = _createManagedInstance(true);

			Type* param = (Type*)(Base*)this; // Needed due to multiple inheritance. Safe since Type must point to an class derived from this one.

			if (metaData.thisPtrField != nullptr && instance != nullptr)
				metaData.thisPtrField->set(instance, &param);
		}

		/**	Creates a new managed instance of the type wrapped by this interop object. */
		virtual MonoObject* _createManagedInstance(bool construct)
		{
			return metaData.scriptClass->createInstance(construct);
		}

		/**
		 * Converts a managed instance into a specific interop object. Caller must ensure the managed instance is of the
		 * proper type.
		 */
		static Type* toNative(MonoObject* managedInstance)
		{
			Type* nativeInstance = nullptr;

			if (metaData.thisPtrField != nullptr && managedInstance != nullptr)
				metaData.thisPtrField->get(managedInstance, &nativeInstance);

			return nativeInstance;
		}

		/** Returns the meta-data containing class and method information for the managed type. */
		static const ScriptMeta* getMetaData() { return &metaData; }

		/**
		 * Initializes the meta-data containing class and method information for the managed type. Called on library load
		 * and on assembly reload.
		 */
		static void _initMetaData()
		{
			// Need to delay init of actual metaData since it's also a static, and we can't guarantee the order
			// (if it gets initialized after this, it will just overwrite the data)
			ScriptMeta localMetaData = ScriptMeta(Type::getAssemblyName(), Type::getNamespace(), Type::getTypeName(),
					&Type::initRuntimeData);

			MonoManager::registerScriptType(&metaData, localMetaData);
		}

	protected:
		static ScriptMeta metaData;

	private:
		static InitScriptObjectOnStart<Type, Base> initOnStart;
	};

	template <typename Type, typename Base>
	InitScriptObjectOnStart<Type, Base> ScriptObject<Type, Base>::initOnStart;

	template <typename Type, typename Base>
	ScriptMeta ScriptObject<Type, Base>::metaData;

/** Helper macro to use with script interop objects that form a link between C++ and CLR. */
#define SCRIPT_OBJ(assembly, namespace, name)		\
	static String getAssemblyName() { return assembly; }	\
	static String getNamespace() { return namespace; }		\
	static String getTypeName() { return name; }			\
	static void initRuntimeData();

	/** @} */
}