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

#pragma once

#include "CoreMinimal.h"
#include "Templates/Casts.h"
#include "UObject/WeakObjectPtr.h"
#include "EditorUndoClient.h"

class UStateTreeEditorData;
class UStateTreeState;
class UStateTree;
class FMenuBuilder;

/**
 * ModelView for editing StateTreeEditorData.
 */
class FStateTreeViewModel : public FEditorUndoClient, public TSharedFromThis<FStateTreeViewModel>
{
public:

	DECLARE_MULTICAST_DELEGATE(FOnAssetChanged);
	DECLARE_MULTICAST_DELEGATE_TwoParams(FOnStatesChanged, const TSet<UStateTreeState*>& /*AffectedStates*/, const FPropertyChangedEvent& /*PropertyChangedEvent*/);
	DECLARE_MULTICAST_DELEGATE_TwoParams(FOnStateAdded, UStateTreeState* /*ParentState*/, UStateTreeState* /*NewState*/);
	DECLARE_MULTICAST_DELEGATE_OneParam(FOnStatesRemoved, const TSet<UStateTreeState*>& /*AffectedParents*/);
	DECLARE_MULTICAST_DELEGATE_TwoParams(FOnStatesMoved, const TSet<UStateTreeState*>& /*AffectedParents*/, const TSet<UStateTreeState*>& /*MovedStates*/);
	DECLARE_MULTICAST_DELEGATE_OneParam(FOnSelectionChanged, const TArray<UStateTreeState*>& /*SelectedStates*/);

	FStateTreeViewModel();
	~FStateTreeViewModel();

	void Init(UStateTreeEditorData* InTreeData);

	//~ FEditorUndoClient
	void PostUndo(bool bSuccess);
	void PostRedo(bool bSuccess);

	// Selection handling.
	void ClearSelection();
	void SetSelection(UStateTreeState* Selected);
	void SetSelection(const TArray<UStateTreeState*>& InSelection);
	bool IsSelected(const UStateTreeState* State) const;
	bool IsChildOfSelection(const UStateTreeState* State) const;
	void GetSelectedStates(TArray<UStateTreeState*>& OutSelectedStates);

	// Returns array of routines to edit.
	TArray<UStateTreeState*>* GetRoutines();

	// Gets and sets StateTree view expansion state store in the asset.
	void GetPersistentExpandedStates(TSet<UStateTreeState*>& OutExpandedStates);
	void SetPersistentExpandedStates(TSet<UStateTreeState*>& InExpandedStates);

	// State manupulation commands
	void AddState(UStateTreeState* AfterState);
	void AddChildState(UStateTreeState* ParentState);
	void RenameState(UStateTreeState* State, FName NewName);
	void RemoveSelectedStates();
	void MoveSelectedStatesBefore(UStateTreeState* TargetState);
	void MoveSelectedStatesAfter(UStateTreeState* TargetState);
	void MoveSelectedStatesInto(UStateTreeState* TargetState);

	// Force to update the view externally.
	void NotifyAssetChangedExternally();
	void NotifyStatesChangedExternally(const TSet<UStateTreeState*>& ChangedStates, const FPropertyChangedEvent& PropertyChangedEvent);

	// Called when the whole asset is updated (i.e. undo/redo).
	FOnAssetChanged& GetOnAssetChanged() { return OnAssetChanged; }
	
	// Called when States are changed (i.e. change name or properties).
	FOnStatesChanged& GetOnStatesChanged() { return OnStatesChanged; }
	
	// Called each time a state is added.
	FOnStateAdded& GetOnStateAdded() { return OnStateAdded; }

	// Called each time a states are removed.
	FOnStatesRemoved& GetOnStatesRemoved() { return OnStatesRemoved; }

	// Called each time a state is removed.
	FOnStatesMoved& GetOnStatesMoved() { return OnStatesMoved; }

	// Called each time the selection changes.
	FOnSelectionChanged& GetOnSelectionChanged() { return OnSelectionChanged; }

protected:
	void GetExpandedStatesRecursive(UStateTreeState* State, TSet<UStateTreeState*>& ExpandedStates);
	void MoveSelectedStates(UStateTreeState* TargetState, int32 RelativeLocation);

	void HandleIdentifierChanged(const UStateTree& StateTree);
	void HandleParameterLayoutChanged(const UStateTree& StateTree);

	UStateTreeEditorData* TreeData;	// TODO: is this safe? should we used TWeakObjectPtr here istead?
	TSet<FWeakObjectPtr> SelectedStates;
	FOnAssetChanged OnAssetChanged;
	FOnStatesChanged OnStatesChanged;
	FOnStateAdded OnStateAdded;
	FOnStatesRemoved OnStatesRemoved;
	FOnStatesMoved OnStatesMoved;
	FOnSelectionChanged OnSelectionChanged;
};