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

#include "SequencerCommonHelpers.h"

#include "Algo/Reverse.h"
#include "EntitySystem/IMovieSceneBlenderSystemSupport.h"
#include "EntitySystem/MovieSceneBlenderSystem.h"
#include "FrameNumberDetailsCustomization.h"
#include "IDetailsView.h"
#include "ISequencerSection.h"
#include "IStructureDetailsView.h"
#include "MVVM/Extensions/ITrackAreaExtension.h"
#include "MVVM/ViewModels/ChannelModel.h"
#include "MVVM/ViewModels/FolderModel.h"
#include "MVVM/ViewModels/LayerBarModel.h"
#include "MVVM/ViewModels/ViewModelIterators.h"
#include "MVVM/ViewModels/ObjectBindingModel.h"
#include "MVVM/ViewModels/SectionModel.h"
#include "MVVM/ViewModels/TrackModel.h"
#include "MVVM/ViewModels/ViewModel.h"
#include "MVVM/ViewModels/OutlinerViewModel.h"
#include "MVVM/ViewModels/SequencerEditorViewModel.h"
#include "MVVM/ViewModels/VirtualTrackArea.h"
#include "MVVM/Views/ITrackAreaHotspot.h"
#include "MVVM/Selection/Selection.h"
#include "Modules/ModuleManager.h"
#include "MovieScene.h"
#include "MovieSceneSectionDetailsCustomization.h"
#include "MovieSceneSequence.h"
#include "Sections/MovieSceneSubSection.h"
#include "PropertyEditorModule.h"
#include "PropertyPermissionList.h"
#include "SSequencer.h"
#include "Sequencer.h"
#include "SequencerContextMenus.h"
#include "SequencerSelectedKey.h"
#include "SequencerUtilities.h"
#include "Styling/CoreStyle.h"
#include "Conditions/MovieSceneDirectorBlueprintConditionCustomization.h"
#include "Conditions/MovieSceneConditionCustomization.h"

void SequencerHelpers::GetAllChannels(TSharedPtr<FViewModel> DataModel, TSet<TSharedPtr<UE::Sequencer::FChannelModel>>& Channels)
{
	using namespace UE::Sequencer;

	if (DataModel)
	{
		constexpr bool bIncludeThis = true;
		for (const FViewModelPtr& Child : DataModel->GetDescendants(bIncludeThis))
		{
			if (TSharedPtr<ITrackAreaExtension> TrackArea = Child.ImplicitCast())
			{
				for (const FViewModelPtr& TrackAreaModel : TrackArea->GetTrackAreaModelList())
				{
					if (TViewModelPtr<FChannelModel> Channel = TrackAreaModel.ImplicitCast())
					{
						Channels.Add(Channel);
					}
				}
			}
			else if (TSharedPtr<FChannelModel> Channel = Child.ImplicitCast())
			{
				Channels.Add(Channel);
			}
		}
	}
}

void SequencerHelpers::GetAllKeyAreas(TSharedPtr<FViewModel> DataModel, TSet<TSharedPtr<IKeyArea>>& Channels)
{
	using namespace UE::Sequencer;

	if (DataModel)
	{
		constexpr bool bIncludeThis = true;
		for (const FViewModelPtr& Child : DataModel->GetDescendants(bIncludeThis))
		{
			if (TSharedPtr<ITrackAreaExtension> TrackArea = Child.ImplicitCast())
			{
				for (const FViewModelPtr& TrackAreaModel : TrackArea->GetTrackAreaModelList())
				{
					if (TViewModelPtr<FChannelModel> Channel = TrackAreaModel.ImplicitCast())
					{
						Channels.Add(Channel->GetKeyArea());
					}
				}
			}
			else if (TSharedPtr<FChannelModel> Channel = Child.ImplicitCast())
			{
				Channels.Add(Channel->GetKeyArea());
			}
		}
	}
}

void SequencerHelpers::GetAllSections(TSharedPtr<FViewModel> DataModel, TSet<TWeakObjectPtr<UMovieSceneSection>>& Sections)
{
	using namespace UE::Sequencer;

	if (DataModel)
	{
		constexpr bool bIncludeThis = true;
		for (TSharedPtr<FSectionModel> Section : TParentFirstChildIterator<FSectionModel>(DataModel, bIncludeThis))
		{
			Sections.Add(Section->GetSection());
		}
	}
}

int32 SequencerHelpers::GetSectionFromTime(TArrayView<UMovieSceneSection* const> InSections, FFrameNumber Time)
{
	FFrameNumber ClosestLowerBound = TNumericLimits<int32>::Max();
	TOptional<int32> MaxOverlapPriority, MaxProximalPriority;

	int32 MostRelevantIndex = INDEX_NONE;

	for (int32 Index = 0; Index < InSections.Num(); ++Index)
	{
		const UMovieSceneSection* Section = InSections[Index];
		if (Section)
		{
			const int32 ThisSectionPriority = Section->GetOverlapPriority();
			TRange<FFrameNumber> SectionRange = Section->GetRange();

			// If the specified time is within the section bounds
			if (SectionRange.Contains(Time))
			{
				if (ThisSectionPriority >= MaxOverlapPriority.Get(ThisSectionPriority))
				{
					MaxOverlapPriority = ThisSectionPriority;
					MostRelevantIndex = Index;
				}
			}
			// Check for nearby sections if there is nothing overlapping
			else if (!MaxOverlapPriority.IsSet() && SectionRange.HasLowerBound())
			{
				const FFrameNumber LowerBoundValue = SectionRange.GetLowerBoundValue();
				// If this section exists beyond the current time, we can choose it if its closest to the time
				if (LowerBoundValue >= Time)
				{
					if (
						(LowerBoundValue < ClosestLowerBound) ||
						(LowerBoundValue == ClosestLowerBound && ThisSectionPriority >= MaxProximalPriority.Get(ThisSectionPriority))
						)
					{
						MostRelevantIndex = Index;
						ClosestLowerBound = LowerBoundValue;
						MaxProximalPriority = ThisSectionPriority;
					}
				}
			}
		}
	}

	// If we didn't find one, use the last one (or return -1)
	if (MostRelevantIndex == -1)
	{
		MostRelevantIndex = InSections.Num() - 1;
	}

	return MostRelevantIndex;
}

void SequencerHelpers::GetDescendantNodes(TSharedRef<FViewModel> DataModel, TSet<TSharedRef<FViewModel>>& Nodes)
{
	using namespace UE::Sequencer;

	for (TSharedPtr<FViewModel> ChildNode : DataModel->GetChildren())
	{
		if (ChildNode->IsA<IOutlinerExtension>())
		{
			Nodes.Add(ChildNode.ToSharedRef());
		}

		GetDescendantNodes(ChildNode.ToSharedRef(), Nodes);
	}
}

bool IsSectionSelectedInNode(FSequencer& Sequencer, TSharedPtr<UE::Sequencer::FViewModel> InModel)
{
	using namespace UE::Sequencer;

	const FTrackAreaSelection& Selection = Sequencer.GetViewModel()->GetSelection()->TrackArea;

	if (ITrackAreaExtension* TrackArea = InModel->CastThis<ITrackAreaExtension>())
	{
		for (TSharedPtr<FViewModel> TrackAreaModel : TrackArea->GetTrackAreaModelList())
		{
			constexpr bool bIncludeThis = true;
			for (TSharedPtr<FSectionModel> Section : TParentFirstChildIterator<FSectionModel>(TrackAreaModel, bIncludeThis))
			{
				if (Selection.IsSelected(Section))
				{
					return true;
				}
			}
		}
	}

	return false;
}

bool AreKeysSelectedInNode(FSequencer& Sequencer, TSharedPtr<UE::Sequencer::FViewModel> InModel)
{
	using namespace UE::Sequencer;

	TSet<TSharedPtr<FChannelModel>> Channels;
	SequencerHelpers::GetAllChannels(InModel, Channels);

	const FKeySelection& Selection = Sequencer.GetViewModel()->GetSelection()->KeySelection;

	for (FKeyHandle Key : Selection)
	{
		TSharedPtr<FChannelModel> Channel = Selection.GetModelForKey(Key);
		if (Channels.Contains(Channel))
		{
			return true;
		}
	}

	return false;
}


void SequencerHelpers::PerformDefaultSelection(FSequencer& Sequencer, const FPointerEvent& MouseEvent)
{
	using namespace UE::Sequencer;

	// @todo: selection in transactions
	FHotspotSelectionManager SelectionManager(&MouseEvent, &Sequencer);
	TSharedPtr<FSequencerEditorViewModel> SequencerViewModel = Sequencer.GetViewModel()->CastThisShared<FSequencerEditorViewModel>();
	TSharedPtr<ITrackAreaHotspot> Hotspot = SequencerViewModel->GetHotspot();
	if (TSharedPtr<IMouseHandlerHotspot> MouseHandler = HotspotCast<IMouseHandlerHotspot>(Hotspot))
	{
		MouseHandler->HandleMouseSelection(SelectionManager);
	}
	else
	{
		// No hotspot so clear the selection if we're not adding to it
		SelectionManager.ConditionallyClearSelection();
	}
}

TSharedPtr<SWidget> SequencerHelpers::SummonContextMenu(FSequencer& Sequencer, const FGeometry& MyGeometry, const FPointerEvent& MouseEvent)
{
	using namespace UE::Sequencer;

	// @todo sequencer replace with UI Commands instead of faking it

	// Attempt to paste into either the current node selection, or the clicked on track
	TSharedRef<SSequencer> SequencerWidget = StaticCastSharedRef<SSequencer>(Sequencer.GetSequencerWidget());
	const FFrameNumber PasteAtTime = Sequencer.GetLocalTime().Time.FrameNumber;

	// The menu are generated through reflection and sometime the API exposes some recursivity (think about a Widget returning it parent which is also a Widget). Just by reflection
	// it is not possible to determine when the root object is reached. It needs a kind of simulation which is not implemented. Also, even if the recursivity was correctly handled, the possible
	// permutations tend to grow exponentially. Until a clever solution is found, the simple approach is to disable recursively searching those menus. User can still search the current one though.
	// See UE-131257
	const bool bInRecursivelySearchable = false;

	const bool bShouldCloseWindowAfterMenuSelection = true;

	TSharedPtr<FExtender> MenuExtender = MakeShared<FExtender>();

	FMenuBuilder MenuBuilder(bShouldCloseWindowAfterMenuSelection, Sequencer.GetCommandBindings(), MenuExtender, false, &FCoreStyle::Get(), true, NAME_None, bInRecursivelySearchable);

	TSharedPtr<FSequencerEditorViewModel> SequencerViewModel = Sequencer.GetViewModel()->CastThisShared<FSequencerEditorViewModel>();
	TSharedPtr<ITrackAreaHotspot> Hotspot = SequencerViewModel->GetHotspot();

	if (Hotspot.IsValid() && Hotspot->PopulateContextMenu(MenuBuilder, MenuExtender, PasteAtTime))
	{
		return MenuBuilder.MakeWidget();
	}
	else if (Sequencer.GetClipboardStack().Num() != 0)
	{
		const TWeakPtr<FSequencer> WeakSequencer = StaticCastWeakPtr<FSequencer>(Sequencer.AsWeak());
		TSharedPtr<FPasteContextMenu> PasteMenu = FPasteContextMenu::CreateMenu(WeakSequencer, SequencerWidget->GeneratePasteArgs(PasteAtTime));
		if (PasteMenu.IsValid() && PasteMenu->IsValidPaste())
		{
			PasteMenu->PopulateMenu(MenuBuilder, MenuExtender);

			return MenuBuilder.MakeWidget();
		}
	}

	return nullptr;
}

/** A widget which wraps the section details view which is an FNotifyHook which is used to forward
	changes to the section to sequencer. */
class SSectionDetailsNotifyHookWrapper : public SCompoundWidget, public FNotifyHook
{
public:
	SLATE_BEGIN_ARGS(SSectionDetailsNotifyHookWrapper) {}
	SLATE_END_ARGS();

	void Construct(FArguments InArgs) { }

	void SetDetailsAndSequencer(TSharedRef<SWidget> InDetailsPanel, TWeakPtr<ISequencer> InWeakSequencer)
	{
		ChildSlot
		[
			InDetailsPanel
		];
		WeakSequencer = InWeakSequencer;
	}

	//~ FNotifyHook interface
	virtual void NotifyPostChange(const FPropertyChangedEvent& PropertyChangedEvent, FProperty* PropertyThatChanged) override
	{
		if (const TSharedPtr<ISequencer> Sequencer = WeakSequencer.Pin())
		{
			if (PropertyThatChanged && PropertyThatChanged->GetName() == TEXT("Condition"))
			{
				// Rebuild hierarchy on changing a condition so the indicators have a chance to refresh
				Sequencer->NotifyMovieSceneDataChanged(EMovieSceneDataChangeType::MovieSceneStructureItemsChanged);
			}
			else
			{
				Sequencer->NotifyMovieSceneDataChanged(EMovieSceneDataChangeType::TrackValueChanged);
			}
		}
	}

private:
	TWeakPtr<ISequencer> WeakSequencer;
};

void SequencerHelpers::BuildNewSectionMenu(const TWeakPtr<FSequencer>& InWeakSequencer
	, const int32 InRowIndex
	, const TWeakObjectPtr<UMovieSceneTrack>& InTrackWeak
	, FMenuBuilder& MenuBuilder)
{
	using namespace UE::Sequencer;

	MenuBuilder.AddSubMenu(
		NSLOCTEXT("Sequencer", "AddSection", "Add Section"),
		FText(),
		FNewMenuDelegate::CreateLambda([InWeakSequencer, InRowIndex, InTrackWeak](FMenuBuilder& SubMenuBuilder)
		{
			if (const TSharedPtr<ISequencer> Sequencer = InWeakSequencer.Pin())
			{
				FSequencerUtilities::PopulateMenu_CreateNewSection(SubMenuBuilder, InRowIndex, InTrackWeak.Get(), Sequencer);
			}
		}));
}

void SequencerHelpers::BuildEditSectionMenu(const TWeakPtr<FSequencer>& InWeakSequencer
	, const TArray<TWeakObjectPtr<>>& InWeakSections
	, FMenuBuilder& MenuBuilder
	, const bool bInSubMenu)
{
	using namespace UE::Sequencer;

	if (InWeakSections.Num() == 0)
	{
		return;
	}

	auto BuildSection = [InWeakSequencer, InWeakSections](FMenuBuilder& LambdaMenuBuilder)
	{
		const TSharedPtr<FSequencer> Sequencer = InWeakSequencer.Pin();
		if (!Sequencer)
		{
			return;
		}

		UMovieSceneSequence* Sequence = Sequencer->GetFocusedMovieSceneSequence();
		const TWeakObjectPtr<UMovieScene> CurrentScene = Sequence->GetMovieScene();

		TSharedRef<SSectionDetailsNotifyHookWrapper> DetailsNotifyWrapper = SNew(SSectionDetailsNotifyHookWrapper);
		FDetailsViewArgs DetailsViewArgs;
		{
			DetailsViewArgs.bAllowSearch = false;
			DetailsViewArgs.bCustomFilterAreaLocation = true;
			DetailsViewArgs.bCustomNameAreaLocation = true;
			DetailsViewArgs.bHideSelectionTip = true;
			DetailsViewArgs.bLockable = false;
			DetailsViewArgs.bSearchInitialKeyFocus = true;
			DetailsViewArgs.bUpdatesFromSelection = false;
			DetailsViewArgs.bShowOptions = false;
			DetailsViewArgs.bShowModifiedPropertiesOption = false;
			DetailsViewArgs.bShowScrollBar = false;
			DetailsViewArgs.NotifyHook = &DetailsNotifyWrapper.Get();
			DetailsViewArgs.ColumnWidth = 0.45f;
		}

		// We pass the current scene to the UMovieSceneSection customization so we can get the overall bounds of the section when we change a section from infinite->bounded.

		TSharedRef<IDetailsView> DetailsView = FModuleManager::GetModuleChecked<FPropertyEditorModule>("PropertyEditor").CreateDetailView(DetailsViewArgs);
		DetailsView->RegisterInstancedCustomPropertyTypeLayout("FrameNumber",
			FOnGetPropertyTypeCustomizationInstance::CreateSP(Sequencer.ToSharedRef(), &FSequencer::MakeFrameNumberDetailsCustomization));

		DetailsView->RegisterInstancedCustomPropertyLayout(UMovieSceneSection::StaticClass(),
			FOnGetDetailCustomizationInstance::CreateLambda([TypeInterface = Sequencer->GetNumericTypeInterface(), CurrentScene]()
			{
				return MakeShared<FMovieSceneSectionDetailsCustomization>(TypeInterface, CurrentScene.Get());
			}));

		DetailsView->RegisterInstancedCustomPropertyTypeLayout("MovieSceneConditionContainer", FOnGetPropertyTypeCustomizationInstance::CreateLambda([WeakSequence = TWeakObjectPtr(Sequence), InWeakSequencer]() 
		{
			return FMovieSceneConditionCustomization::MakeInstance(WeakSequence, InWeakSequencer); 
		}));

		DetailsView->RegisterInstancedCustomPropertyTypeLayout("MovieSceneDirectorBlueprintConditionData", FOnGetPropertyTypeCustomizationInstance::CreateLambda([=]() {
			return FMovieSceneDirectorBlueprintConditionCustomization::MakeInstance(CurrentScene.Get());}));
	
		DetailsView->SetIsPropertyVisibleDelegate(FIsPropertyVisible::CreateLambda([](const FPropertyAndParent& PropertyAndParent)
			{			
				return FPropertyEditorPermissionList::Get().DoesPropertyPassFilter(PropertyAndParent.Property.GetOwnerStruct(), PropertyAndParent.Property.GetFName());
			})
		);

		// Let section interfaces further customize the properties details view.
		TSharedRef<FSequencerNodeTree> SequencerNodeTree = Sequencer->GetNodeTree();
		for (TWeakObjectPtr<> Section : InWeakSections)
		{
			if (Section.IsValid())
			{
				TSharedPtr<FSectionModel> SectionHandle = SequencerNodeTree->GetSectionModel(Cast<UMovieSceneSection>(Section));
				if (SectionHandle)
				{
					TSharedPtr<ISequencerSection> SectionInterface = SectionHandle->GetSectionInterface();
					FSequencerSectionPropertyDetailsViewCustomizationParams CustomizationDetails(
						SectionInterface.ToSharedRef(), InWeakSequencer, *SectionHandle->GetParentTrackExtension()->GetTrackEditor().Get());
					TSharedPtr<FObjectBindingModel> ParentObjectBindingNode = SectionHandle->FindAncestorOfType<FObjectBindingModel>();
					if (ParentObjectBindingNode.IsValid())
					{
						CustomizationDetails.ParentObjectBindingGuid = ParentObjectBindingNode->GetObjectGuid();
					}
					SectionInterface->CustomizePropertiesDetailsView(DetailsView, CustomizationDetails);
				}
			}
		}

		Sequencer->OnInitializeDetailsPanel().Broadcast(DetailsView, Sequencer.ToSharedRef());
		DetailsView->SetObjects(InWeakSections);

		DetailsNotifyWrapper->SetDetailsAndSequencer(DetailsView, InWeakSequencer);
		DetailsNotifyWrapper->SetEnabled(!Sequencer->IsReadOnly());

		LambdaMenuBuilder.BeginSection(TEXT("TrackSection"));
        {
			LambdaMenuBuilder.AddWidget(DetailsNotifyWrapper, FText::GetEmpty(), true);
        }
        LambdaMenuBuilder.EndSection();
	};

	if (bInSubMenu)
	{
		const FText MenuLabel = InWeakSections.Num() > 1
			? NSLOCTEXT("Sequencer", "BatchEditSections", "Batch Edit Sections")
			: NSLOCTEXT("Sequencer", "EditSection", "Edit Section");

		MenuBuilder.AddSubMenu(
			MenuLabel,
			FText(),
			FNewMenuDelegate::CreateLambda([BuildSection](FMenuBuilder& SubMenuBuilder)
			{
				BuildSection(SubMenuBuilder);
			}));
	}
	else
	{
		BuildSection(MenuBuilder);
	}
}

void SequencerHelpers::BuildEditTrackMenu(const TWeakPtr<FSequencer>& InWeakSequencer
	, const TArray<TWeakObjectPtr<>>& InWeakTracks
	, FMenuBuilder& MenuBuilder
	, const bool bInSubMenu)
{
	using namespace UE::Sequencer;

	if (InWeakTracks.Num() == 0)
	{
		return;
	}

	auto BuildTrack = [InWeakSequencer, InWeakTracks](FMenuBuilder& LambdaMenuBuilder)
	{
		const TSharedPtr<FSequencer> Sequencer = InWeakSequencer.Pin();
		if (!Sequencer)
		{
			return;
		}

		TSharedRef<SSectionDetailsNotifyHookWrapper> DetailsNotifyWrapper = SNew(SSectionDetailsNotifyHookWrapper);
		FDetailsViewArgs DetailsViewArgs;
		{
			DetailsViewArgs.bAllowSearch = false;
			DetailsViewArgs.bCustomFilterAreaLocation = true;
			DetailsViewArgs.bCustomNameAreaLocation = true;
			DetailsViewArgs.bHideSelectionTip = true;
			DetailsViewArgs.bLockable = false;
			DetailsViewArgs.bSearchInitialKeyFocus = true;
			DetailsViewArgs.bUpdatesFromSelection = false;
			DetailsViewArgs.bShowOptions = false;
			DetailsViewArgs.bShowModifiedPropertiesOption = false;
			DetailsViewArgs.bShowScrollBar = false;
			DetailsViewArgs.NotifyHook = &DetailsNotifyWrapper.Get();
			DetailsViewArgs.ColumnWidth = 0.45f;
		}

		// We pass the current scene to the UMovieSceneSection customization so we can get the overall bounds of the section when we change a section from infinite->bounded.
		UMovieSceneSequence* Sequence = Sequencer->GetFocusedMovieSceneSequence();
		UMovieScene* CurrentScene = Sequence->GetMovieScene();

		TSharedRef<IDetailsView> DetailsView = FModuleManager::GetModuleChecked<FPropertyEditorModule>("PropertyEditor").CreateDetailView(DetailsViewArgs);

		DetailsView->RegisterInstancedCustomPropertyTypeLayout("MovieSceneConditionContainer", FOnGetPropertyTypeCustomizationInstance::CreateLambda([Sequence, InWeakSequencer]() {
			return FMovieSceneConditionCustomization::MakeInstance(Sequence, InWeakSequencer); }));

		DetailsView->RegisterInstancedCustomPropertyTypeLayout("MovieSceneDirectorBlueprintConditionData", FOnGetPropertyTypeCustomizationInstance::CreateLambda([=]() {
			return FMovieSceneDirectorBlueprintConditionCustomization::MakeInstance(CurrentScene); }));

		DetailsView->SetIsPropertyVisibleDelegate(FIsPropertyVisible::CreateLambda([](const FPropertyAndParent& PropertyAndParent)
			{
				return FPropertyEditorPermissionList::Get().DoesPropertyPassFilter(PropertyAndParent.Property.GetOwnerStruct(), PropertyAndParent.Property.GetFName());
			})
		);

		Sequencer->OnInitializeDetailsPanel().Broadcast(DetailsView, Sequencer.ToSharedRef());
		DetailsView->SetObjects(InWeakTracks);

		DetailsNotifyWrapper->SetDetailsAndSequencer(DetailsView, Sequencer);
		DetailsNotifyWrapper->SetEnabled(!Sequencer->IsReadOnly());

		LambdaMenuBuilder.BeginSection(TEXT("Track"));
		{
			LambdaMenuBuilder.AddWidget(DetailsNotifyWrapper, FText::GetEmpty(), true);
		}
		LambdaMenuBuilder.EndSection();
	};

	if (bInSubMenu)
	{
		const FText MenuLabel = InWeakTracks.Num() > 1
			? NSLOCTEXT("Sequencer", "BatchEditTracks", "Batch Edit Tracks")
			: NSLOCTEXT("Sequencer", "EditTrack", "Edit Track");

		MenuBuilder.AddSubMenu(
			MenuLabel,
			FText(),
			FNewMenuDelegate::CreateLambda([BuildTrack](FMenuBuilder& SubMenuBuilder)
				{
					BuildTrack(SubMenuBuilder);
				}));
	}
	else
	{
		BuildTrack(MenuBuilder);
	}
}

void SequencerHelpers::BuildBlendingMenu(const TWeakPtr<FSequencer>& InWeakSequencer
	, const TWeakObjectPtr<UMovieSceneTrack>& InTrackWeak
	, FMenuBuilder& MenuBuilder)
{
	if (!InTrackWeak.IsValid())
	{
		return;
	}

	IMovieSceneBlenderSystemSupport* const BlenderSystemSupport = Cast<IMovieSceneBlenderSystemSupport>(InTrackWeak.Get());
	if (!BlenderSystemSupport)
	{
		return;
	}

	TArray<TSubclassOf<UMovieSceneBlenderSystem>> BlenderTypes;
	BlenderSystemSupport->GetSupportedBlenderSystems(BlenderTypes);
	if (BlenderTypes.Num() < 2)
	{
		return;
	}

	MenuBuilder.AddSubMenu(
		NSLOCTEXT("Sequencer", "BlendingAlgorithmSubMenu", "Blending Algorithm"),
		FText(),
		FNewMenuDelegate::CreateLambda([InWeakSequencer, InTrackWeak](FMenuBuilder& SubMenuBuilder)
		{
			if (const TSharedPtr<ISequencer> Sequencer = InWeakSequencer.Pin())
			{
				FSequencerUtilities::PopulateMenu_BlenderSubMenu(SubMenuBuilder, InTrackWeak.Get(), Sequencer);
			}
		}));
}

TArray<TWeakObjectPtr<>> SequencerHelpers::GetSectionObjectsFromTrackAreaModels(const UE::Sequencer::FViewModelVariantIterator& InTrackAreaModels)
{
	using namespace UE::Sequencer;

	TArray<TWeakObjectPtr<>> OutWeakSectionObjects;

	for (const TViewModelPtr<FViewModel>& TrackAreaModel : InTrackAreaModels)
	{
		constexpr bool bIncludeThis = true;
		for (const TSharedPtr<FSectionModel> SectionModel : TParentFirstChildIterator<FSectionModel>(TrackAreaModel, bIncludeThis))
		{
			if (UMovieSceneSection* const SectionObject = SectionModel->GetSection())
			{
				OutWeakSectionObjects.AddUnique(SectionObject);
			}
		}
	}

	return OutWeakSectionObjects;
}

void SequencerHelpers::SortOutlinerItems(FSequencer& Sequencer
	, const TArray<UE::Sequencer::TViewModelPtr<UE::Sequencer::IOutlinerExtension>>& InItems
	, const bool bInSortByItemOrder
	, const bool bInDescending
	, const bool bInTransact)
{
	using namespace UE::Sequencer;

	if (InItems.IsEmpty())
	{
		return;
	}

	UMovieSceneSequence* const Sequence = Sequencer.GetFocusedMovieSceneSequence();
	if (!IsValid(Sequence))
	{
		return;
	}

	UMovieScene* const MovieScene = Sequence->GetMovieScene();
	if (!IsValid(Sequence))
	{
		return;
	}

	/** Represents a layer bar. Holds cached pointers for element operations. */
	struct FSortBarElement
	{
		static FSortBarElement FromTrack(FSequencer& InSequencer, const TViewModelPtr<ITrackAreaExtension>& InTrackAreaExtension)
		{
			for (const FViewModelPtr& TrackAreaModel : InTrackAreaExtension->GetTopLevelChildTrackAreaModels())
			{
				if (const TViewModelPtr<FLayerBarModel> BarModel = TrackAreaModel.ImplicitCast())
				{
					return FSortBarElement(InSequencer, BarModel);
				}
			}
			for (const TViewModelPtr<ILayerBarExtension>& TrackAreaModel : InTrackAreaExtension->GetTrackAreaModelListAs<ILayerBarExtension>())
			{
				if (const TViewModelPtr<ILayerBarExtension> BarModel = TrackAreaModel.ImplicitCast())
				{
					return FSortBarElement(InSequencer, BarModel);
				}
			}
			return FSortBarElement(InSequencer);
		}
	
		FSortBarElement(FSequencer& InSequencer)
			: Sequencer(InSequencer)
		{}
		FSortBarElement(FSequencer& InSequencer, const TViewModelPtr<FLayerBarModel>& InBarModel)
			: Sequencer(InSequencer)
		{
			if (const TViewModelPtr<IOutlinerExtension> LinkedOutlinerItem = InBarModel->GetLinkedOutlinerItem())
			{
				if (const TViewModelPtr<ISortableExtension> SortableExtension = LinkedOutlinerItem.ImplicitCast())
				{
					const TViewModelPtr<ISortableExtension> ParentSortableItem = LinkedOutlinerItem.AsModel()->FindAncestorOfType<ISortableExtension>();

					BarModel.Emplace<TViewModelPtr<FLayerBarModel>>(InBarModel);
					SortableItem = SortableExtension;
					ParentItem = ParentSortableItem.IsValid()? ParentSortableItem : CastViewModelChecked<ISortableExtension>(Sequencer.GetViewModel()->GetRootSequenceModel());
					Range = InBarModel->ComputeRange();
				}
			}
		}
		FSortBarElement(FSequencer& InSequencer, const TViewModelPtr<ILayerBarExtension>& InBarModel)
			: Sequencer(InSequencer)
		{
			if (const TViewModelPtr<FLinkedOutlinerExtension> LinkedOutlinerExtension = InBarModel.ImplicitCast())
			{
				if (const TViewModelPtr<IOutlinerExtension> LinkedOutlinerItem = LinkedOutlinerExtension->GetLinkedOutlinerItem())
				{
					if (const TViewModelPtr<ISortableExtension> SortableExtension = LinkedOutlinerItem.ImplicitCast())
					{
						const TViewModelPtr<ISortableExtension> ParentSortableItem = LinkedOutlinerItem.AsModel()->FindAncestorOfType<ISortableExtension>();

						BarModel.Emplace<TViewModelPtr<ILayerBarExtension>>(InBarModel);
						SortableItem = SortableExtension;
						ParentItem = ParentSortableItem.IsValid() ? ParentSortableItem : CastViewModelChecked<ISortableExtension>(Sequencer.GetViewModel()->GetRootSequenceModel());
						Range = InBarModel->GetLayerBarRange();
					}
				}
			}
		}

		bool IsValid() const
		{
			if (const TViewModelPtr<FLayerBarModel>* LayerBarModel = BarModel.TryGet<TViewModelPtr<FLayerBarModel>>())
			{
				return LayerBarModel->IsValid();
			}
			if (const TViewModelPtr<ILayerBarExtension>* LayerBarExtension = BarModel.TryGet<TViewModelPtr<ILayerBarExtension>>())
			{
				return LayerBarExtension->IsValid();
			}
			return false;
		}

		FSequencer& Sequencer;

		TVariant<TViewModelPtr<FLayerBarModel>, TViewModelPtr<ILayerBarExtension>> BarModel;

		TViewModelPtr<ISortableExtension> SortableItem;
		TViewModelPtr<ISortableExtension> ParentItem;
		TRange<FFrameNumber> Range;
	};

	// Gather all the selected folder and layer bar models from InItems so we can sort them
	TMap<TViewModelPtr<FFolderModel>, TArray<FSortBarElement>> FolderPairs;
	TMap<TViewModelPtr<ISortableExtension>, TArray<FSortBarElement>> SortItems;

	for (const TViewModelPtr<IOutlinerExtension>& TrackItem : InItems)
	{
		// Handle folders
		if (!bInSortByItemOrder)
		{
			if (const TViewModelPtr<FFolderModel> FolderModel = TrackItem.ImplicitCast())
			{
				TArray<FSortBarElement> FolderElements;

				for (const TViewModelPtr<IOutlinerExtension>& ChildTrack : FolderModel->GetChildrenOfType<IOutlinerExtension>())
				{
					if (const TViewModelPtr<ITrackAreaExtension> ChildTrackArea = ChildTrack.ImplicitCast())
					{
						FSortBarElement NewElement = FSortBarElement::FromTrack(Sequencer, ChildTrackArea);
						if (NewElement.IsValid())
						{
							FolderElements.Add(MoveTemp(NewElement));
						}
					}
				}

				if (!FolderElements.IsEmpty())
				{
					FolderPairs.Add(FolderModel, FolderElements);
				}
			}
		}

		// Handle track areas
		if (const TViewModelPtr<ITrackAreaExtension> TrackArea = TrackItem.ImplicitCast())
		{
			FSortBarElement NewElement = FSortBarElement::FromTrack(Sequencer, TrackArea);
			if (NewElement.IsValid())
			{
				SortItems.FindOrAdd(NewElement.ParentItem).Add(NewElement);
			}
		}
	}

	// Begin the transaction operation
	const FText TransactionText = bInDescending
		? NSLOCTEXT("Sequencer", "SortByAscending_Transaction", "Sort Tracks (Ascending)")
		: NSLOCTEXT("Sequencer", "SortByDescending_Transaction", "Sort Tracks (Descending)");
	FScopedTransaction SortNodesTransaction(TransactionText, bInTransact);

	if (bInTransact)
	{
		MovieScene->Modify();
	}

	// Set the sort order for all selected folder children
	if (!bInSortByItemOrder)
	{
		int32 SortOrder = 0;
		for (TPair<TViewModelPtr<FFolderModel>, TArray<FSortBarElement>>& FolderModel : FolderPairs)
		{
			FolderModel.Value.Sort([bInDescending](const FSortBarElement& InLayerBarA, const FSortBarElement& InLayerBarB) -> bool
				{
					if (bInDescending)
					{
						return InLayerBarA.Range.GetLowerBoundValue() > InLayerBarB.Range.GetLowerBoundValue();
					}
					return InLayerBarA.Range.GetLowerBoundValue() < InLayerBarB.Range.GetLowerBoundValue();
				});

			SortOrder = 0;
			for (const FSortBarElement& Element : FolderModel.Value)
			{
				Element.SortableItem->SetCustomOrder(SortOrder);
				++SortOrder;
			}
		}
	}

	// Set the sort order for all items
	for (TPair<TViewModelPtr<ISortableExtension>, TArray<FSortBarElement>>& LayerBarSortItemPair : SortItems)
	{
		TViewModelPtr<ISortableExtension>& ParentSortableItem = LayerBarSortItemPair.Key;
		TArray<FSortBarElement>& Elements = LayerBarSortItemPair.Value;

		// Remove all layer models that have a descendant that is in the InItems list
		Elements.RemoveAll([&InItems](const FSortBarElement& InElement) -> bool
			{
				for (const TViewModelPtr<IOutlinerExtension>& ChildOutlinerExtension : InElement.SortableItem.AsModel()->GetDescendantsOfType<IOutlinerExtension>())
				{
					if (InItems.Contains(ChildOutlinerExtension))
					{
						return true;
					}
				}
				return false;
			});

		if (!bInSortByItemOrder)
		{
			Elements.Sort([bInDescending](const FSortBarElement& InSortItemA, const FSortBarElement& InSortItemB) -> bool
				{
					if (bInDescending)
					{
						return InSortItemA.Range.GetLowerBoundValue() > InSortItemB.Range.GetLowerBoundValue();
					}
					return InSortItemA.Range.GetLowerBoundValue() < InSortItemB.Range.GetLowerBoundValue();
				});
		}

		// Save the current sortable children and begin the re-ordering operation.
		// We will attempt to maintain any current custom ordering that exists.
		TArray<TViewModelPtr<ISortableExtension>> SortableChildren;
		ParentSortableItem.AsModel()->GetChildrenOfType<ISortableExtension>().ToArray(SortableChildren);

		// Sort to make sure we are in the correct order since the array can be out of order from what is actually displayed
		SortableChildren.Sort([](const TViewModelPtr<ISortableExtension>& InA, const TViewModelPtr<ISortableExtension>& InB) -> bool
			{
				return FSortingKey::CompareCustomOrderFirst(InA->GetSortingKey(), InB->GetSortingKey());
			});

		// Loop backwards and remove items to re-insert while also re-ordering items
		TArray<int32> ItemIndicesToReinsert;

		for (int32 Index = SortableChildren.Num() - 1; Index >= 0; --Index)
		{
			const TViewModelPtr<ISortableExtension>& SortableChild = SortableChildren[Index];
			const bool bHasItemToSort = Elements.ContainsByPredicate([&SortableChild](const FSortBarElement& InItemCache)
				{
					return InItemCache.SortableItem == SortableChild;
				});
			if (bHasItemToSort)
			{
				SortableChildren.RemoveAt(Index);
				ItemIndicesToReinsert.Add(Index);
			}
		}

		// Reverse the array since we added while looping backwards through the array
		Algo::Reverse(ItemIndicesToReinsert);

		// Insert the sorted (selected) items to the array
		int32 CurrentIndex = 0;
		for (const int32 ItemIndex : ItemIndicesToReinsert)
		{
			if (Elements.IsValidIndex(CurrentIndex))
			{
				SortableChildren.Insert(Elements[CurrentIndex].SortableItem, ItemIndex);
				++CurrentIndex;
			}
		}

		// Use the SortableChildren index to set the custom order
		int32 CustomOrder = 0;
		for (const TViewModelPtr<ISortableExtension>& SortableChild : SortableChildren)
		{
			SortableChild->SetCustomOrder(CustomOrder++);
		}
	}

	Sequencer.RefreshTree();
}