BansheeEngine/BansheeCore/Include/BsPrefabDiff.h

#pragma once

#include "BsCorePrerequisites.h"
#include "BsIReflectable.h"
#include "BsGameObject.h"
#include "BsVector3.h"
#include "BsQuaternion.h"

namespace BansheeEngine
{
	/**
	 * @brief	Contains differences between two components of the same type.
	 *
	 * @see		PrefabDiff
	 */
	struct BS_CORE_EXPORT PrefabComponentDiff : public IReflectable
	{
		INT32 id;
		SPtr<SerializedObject> data;

		/************************************************************************/
		/* 								RTTI		                     		*/
		/************************************************************************/

	public:
		friend class PrefabComponentDiffRTTI;
		static RTTITypeBase* getRTTIStatic();
		virtual RTTITypeBase* getRTTI() const override;
	};

	/**
	 * @brief	Flags that mark which portion of a scene-object is modified.
	 */
	enum class SceneObjectDiffFlags
	{
		Name = 0x01,
		Position = 0x02,
		Rotation = 0x04,
		Scale = 0x08,
		Active = 0x10
	};

	/**
	 * @brief	Contains a set of prefab differences for a single scene object.
	 *
	 * @see		PrefabDiff
	 */
	struct BS_CORE_EXPORT PrefabObjectDiff : public IReflectable
	{
		UINT32 id = 0;

		String name;
		Vector3 position;
		Quaternion rotation;
		Vector3 scale;
		bool isActive = false;
		UINT32 soFlags = 0;

		Vector<SPtr<PrefabComponentDiff>> componentDiffs;
		Vector<UINT32> removedComponents;
		Vector<SPtr<SerializedObject>> addedComponents;

		Vector<SPtr<PrefabObjectDiff>> childDiffs;
		Vector<UINT32> removedChildren;
		Vector<SPtr<SerializedObject>> addedChildren;

		/************************************************************************/
		/* 								RTTI		                     		*/
		/************************************************************************/

	public:
		friend class PrefabObjectDiffRTTI;
		static RTTITypeBase* getRTTIStatic();
		virtual RTTITypeBase* getRTTI() const override;
	};

	/**
	 * @brief	Contains modifications between an prefab and its instance. The modifications are a set of
	 *			added/removed children or components and per-field "diffs" of their components.
	 */
	class BS_CORE_EXPORT PrefabDiff : public IReflectable
	{
	public:
		/**
		 * @brief	Creates a new prefab diff by comparing the provided instanced scene object hierarchy
		 *			with the prefab scene object hierarchy.
		 */
		static SPtr<PrefabDiff> create(const HSceneObject& prefab, const HSceneObject& instance);

		/**
		 * @brief	Applies the internal prefab diff to the provided object. The object should have
		 *			similar hierarchy as the prefab the diff was created for, otherwise the results are
		 *			undefined.
		 */
		void apply(const HSceneObject& object);

	private:
		/**
		 * @brief	A reference to a renamed game object instance data, and its original ID
		 *			so it may be restored later.
		 */
		struct RenamedGameObject
		{
			GameObjectInstanceDataPtr instanceData;
			UINT64 originalId;
		};

		/**
		 * @brief	Recurses over every scene object in the prefab a generates differences between itself
		 *			and the instanced version.
		 *
		 * @see		create
		 */
		static SPtr<PrefabObjectDiff> generateDiff(const HSceneObject& prefab, const HSceneObject& instance);

		/**
		 * @brief	Recursively applies a per-object set of prefab differences to a specific object.
		 *
		 * @see		apply			
		 */
		static void applyDiff(const SPtr<PrefabObjectDiff>& diff, const HSceneObject& object);

		/**
		 * @brief	Renames all game objects in the provided instance so that IDs of the objects will match
		 *			the IDs of their counterparts in the prefab. 
		 *
		 * @note	This is a temporary action and should be undone by calling "restoreInstanceIds" and providing 
		 *			it with the output of this method. 
		 * @par		By doing this before calling ::generateDiff we ensure that any game object handles pointing to objects 
		 *			within the prefab instance hierarchy aren't recorded by the diff system, since we want those to 
		 *			remain as they are after applying the diff.
		 */
		static void renameInstanceIds(const HSceneObject& prefab, const HSceneObject& instance, Vector<RenamedGameObject>& output);

		/**
		 * @brief	Restores any instance IDs that were modified by the "renameInstanceIds" method.
		 *
		 * @see		renameInstanceIds;
		 */
		static void restoreInstanceIds(const Vector<RenamedGameObject>& renamedObjects);

		SPtr<PrefabObjectDiff> mRoot;

		/************************************************************************/
		/* 								RTTI		                     		*/
		/************************************************************************/

	public:
		friend class PrefabDiffRTTI;
		static RTTITypeBase* getRTTIStatic();
		virtual RTTITypeBase* getRTTI() const override;
	};
}