// Copyright Epic Games, Inc. All Rights Reserved.

#pragma once

#include "CoreMinimal.h"
#include "Selection/PersistentMeshSelection.h"
#include "InteractiveToolChange.h"

#include "PersistentMeshSelectionManager.generated.h"

class UInteractiveToolsContext;
class UInteractiveToolManager;
class UPrimitiveComponent;
class UInteractiveTool;
class UPreviewGeometry;


/**
 * UPersistentMeshSelectionManager manages an active Mesh Selection.
 * The assumption is that this class will be registered with the ContextStore of an InteractiveToolsContext,
 * and the various Tool implementations will get/set the selection.
 * 
 * 
 * 
 * StoredMeshSelectionUtil.h contains various utility functions to simplify usage of this class,
 * those functions are preferable to directly using the Manager.
 * 
 */
UCLASS()
class MODELINGCOMPONENTS_API UPersistentMeshSelectionManager : public UObject
{
	GENERATED_BODY()

public:
	
	virtual void Initialize(TObjectPtr<UInteractiveToolsContext> ToolsContext);
	virtual void Shutdown();

	/** @return true if there is an active selection */
	virtual bool HasActiveSelection();

	/** @return the active selection */
	virtual UPersistentMeshSelection* GetActiveSelection();

	/** Set a new active selection. This is undoable, ie a FPersistentMeshSelectionChange will be emitted */
	virtual void SetNewActiveSelection(UPersistentMeshSelection* Selection);

	/** Clear the active selection. This is undoable, ie a FPersistentMeshSelectionChange will be emitted */
	virtual void ClearActiveSelection();


protected:
	UPROPERTY()
	TObjectPtr<UInteractiveToolsContext> ParentContext;

	UPROPERTY()
	TObjectPtr<UPersistentMeshSelection> ActiveSelection;

	UPROPERTY()
	TObjectPtr<UPreviewGeometry> SelectionDisplay;

	virtual void OnSelectionModified();

	virtual void SetNewActiveSelectionInternal(UPersistentMeshSelection* Selection);
	friend class FPersistentMeshSelectionChange;
};





/**
 * FPersistentMeshSelectionChange stores a selection change, ie before-and-after states.
 * UPersistentMeshSelectionManager emits these changes on selection modifications.
 */
class MODELINGCOMPONENTS_API FPersistentMeshSelectionChange : public FToolCommandChange
{
public:
	FGenericMeshSelection From;
	FGenericMeshSelection To;

	virtual void Apply(UObject* Object) override;
	virtual void Revert(UObject* Object) override;
	virtual bool HasExpired(UObject* Object) const override;
	virtual FString ToString() const override;
};








namespace UE
{
namespace Geometry
{
	//
	// The functions below are helper functions that simplify usage of a UPersistentMeshSelectionManager 
	// that is registered as a ContextStoreObject in an InteractiveToolsContext
	//

	/**
	 * If one does not already exist, create a new instance of UPersistentMeshSelectionManager and add it to the
	 * ToolsContext's ContextObjectStore
	 * @return true if the ContextObjectStore now has a UPersistentMeshSelectionManager (whether it already existed, or was created)
	 */
	MODELINGCOMPONENTS_API bool RegisterPersistentMeshSelectionManager(UInteractiveToolsContext* ToolsContext);

	/**
	 * Remove any existing UPersistentMeshSelectionManager from the ToolsContext's ContextObjectStore
	 * @return true if the ContextObjectStore no longer has a UPersistentMeshSelectionManager (whether it was removed, or did not exist)
	 */
	MODELINGCOMPONENTS_API bool DeregisterPersistentMeshSelectionManager(UInteractiveToolsContext* ToolsContext);


	/**
	 * Find an existing UPersistentMeshSelectionManager in the ToolsContext's ContextObjectStore
	 * @return SelectionManager pointer or nullptr if not found
	 */
	MODELINGCOMPONENTS_API UPersistentMeshSelectionManager* FindPersistentMeshSelectionManager(UInteractiveToolManager* ToolManager);


}
}