// Copyright 1998-2019 Epic Games, Inc. All Rights Reserved.

#include "NavigationSystem.h"
#include "Misc/ScopeLock.h"
#include "Stats/StatsMisc.h"
#include "Modules/ModuleManager.h"
#include "AI/Navigation/NavAgentInterface.h"
#include "Engine/World.h"
#include "GameFramework/Controller.h"
#include "AI/Navigation/NavRelevantInterface.h"
#include "UObject/UObjectIterator.h"
#include "EngineUtils.h"
#include "Logging/MessageLog.h"
#include "ProfilingDebugging/CsvProfiler.h"
#include "NavAreas/NavArea.h"
#include "NavigationOctree.h"
#include "VisualLogger/VisualLogger.h"
#include "NavMesh/NavMeshBoundsVolume.h"
#include "NavigationInvokerComponent.h"
#include "AI/Navigation/NavigationDataChunk.h"
#include "Engine/Engine.h"
#include "UObject/Package.h"
#include "Components/PrimitiveComponent.h"
#include "UObject/UObjectThreadContext.h"

#if WITH_RECAST
#include "NavMesh/RecastNavMesh.h"
#include "NavMesh/RecastHelpers.h"
#include "NavMesh/RecastNavMeshGenerator.h"
#endif // WITH_RECAST
#if WITH_EDITOR
#include "EditorModeManager.h"
#include "EditorModes.h"
#include "Editor/GeometryMode/Public/GeometryEdMode.h"
#include "Editor/GeometryMode/Public/EditorGeometry.h"
#endif

#if WITH_HOT_RELOAD
#include "Misc/HotReloadInterface.h"
#endif

#include "NavAreas/NavArea_Null.h"
#include "NavAreas/NavArea_Obstacle.h"
#include "NavAreas/NavArea_Default.h"
#include "NavAreas/NavAreaMeta_SwitchByAgent.h"
#include "NavLinkCustomInterface.h"
#include "NavigationPath.h"
#include "AbstractNavData.h"
#include "CrowdManagerBase.h"


static const uint32 INITIAL_ASYNC_QUERIES_SIZE = 32;
static const uint32 REGISTRATION_QUEUE_SIZE = 16;	// and we'll not reallocate

#define LOCTEXT_NAMESPACE "Navigation"

DEFINE_LOG_CATEGORY_STATIC(LogNavOctree, Warning, All);


DECLARE_CYCLE_STAT(TEXT("Nav Tick: mark dirty"), STAT_Navigation_TickMarkDirty, STATGROUP_Navigation);
DECLARE_CYCLE_STAT(TEXT("Nav Tick: async build"), STAT_Navigation_TickAsyncBuild, STATGROUP_Navigation);
DECLARE_CYCLE_STAT(TEXT("Nav Tick: async pathfinding"), STAT_Navigation_TickAsyncPathfinding, STATGROUP_Navigation);
DECLARE_CYCLE_STAT(TEXT("Debug NavOctree Time"), STAT_DebugNavOctree, STATGROUP_Navigation);

//----------------------------------------------------------------------//
// Stats
//----------------------------------------------------------------------//

DEFINE_STAT(STAT_Navigation_QueriesTimeSync);
DEFINE_STAT(STAT_Navigation_RequestingAsyncPathfinding);
DEFINE_STAT(STAT_Navigation_PathfindingSync);
DEFINE_STAT(STAT_Navigation_PathfindingAsync);
DEFINE_STAT(STAT_Navigation_TileNavAreaSorting);
DEFINE_STAT(STAT_Navigation_TileGeometryExportToObjAsync);
DEFINE_STAT(STAT_Navigation_TileVoxelFilteringAsync);
DEFINE_STAT(STAT_Navigation_TileBuildAsync);
DEFINE_STAT(STAT_Navigation_TileBuildPreparationSync);
DEFINE_STAT(STAT_Navigation_BSPExportSync);
DEFINE_STAT(STAT_Navigation_GatheringNavigationModifiersSync);
DEFINE_STAT(STAT_Navigation_ActorsGeometryExportSync);
DEFINE_STAT(STAT_Navigation_ProcessingActorsForNavMeshBuilding);
DEFINE_STAT(STAT_Navigation_AdjustingNavLinks);
DEFINE_STAT(STAT_Navigation_AddingActorsToNavOctree);
DEFINE_STAT(STAT_Navigation_RecastAddGeneratedTiles);
DEFINE_STAT(STAT_Navigation_RecastTick);
DEFINE_STAT(STAT_Navigation_RecastPathfinding);
DEFINE_STAT(STAT_Navigation_RecastTestPath);
DEFINE_STAT(STAT_Navigation_RecastBuildCompressedLayers);
DEFINE_STAT(STAT_Navigation_RecastCreateHeightField);
DEFINE_STAT(STAT_Navigation_RecastRasterizeTriangles);
DEFINE_STAT(STAT_Navigation_RecastVoxelFilter);
DEFINE_STAT(STAT_Navigation_RecastFilter);
DEFINE_STAT(STAT_Navigation_RecastBuildCompactHeightField);
DEFINE_STAT(STAT_Navigation_RecastErodeWalkable);
DEFINE_STAT(STAT_Navigation_RecastBuildLayers);
DEFINE_STAT(STAT_Navigation_RecastBuildTileCache);
DEFINE_STAT(STAT_Navigation_RecastBuildPolyMesh);
DEFINE_STAT(STAT_Navigation_RecastBuildPolyDetail);
DEFINE_STAT(STAT_Navigation_RecastGatherOffMeshData);
DEFINE_STAT(STAT_Navigation_RecastCreateNavMeshData);
DEFINE_STAT(STAT_Navigation_RecastMarkAreas);
DEFINE_STAT(STAT_Navigation_RecastBuildContours);
DEFINE_STAT(STAT_Navigation_RecastBuildNavigation);
DEFINE_STAT(STAT_Navigation_RecastBuildRegions);
DEFINE_STAT(STAT_Navigation_UpdateNavOctree);
DEFINE_STAT(STAT_Navigation_CollisionTreeMemory);
DEFINE_STAT(STAT_Navigation_NavDataMemory);
DEFINE_STAT(STAT_Navigation_TileCacheMemory);
DEFINE_STAT(STAT_Navigation_OutOfNodesPath);
DEFINE_STAT(STAT_Navigation_PartialPath);
DEFINE_STAT(STAT_Navigation_CumulativeBuildTime);
DEFINE_STAT(STAT_Navigation_BuildTime);
DEFINE_STAT(STAT_Navigation_OffsetFromCorners);
DEFINE_STAT(STAT_Navigation_PathVisibilityOptimisation);
DEFINE_STAT(STAT_Navigation_ObservedPathsCount);
DEFINE_STAT(STAT_Navigation_RecastMemory);

//----------------------------------------------------------------------//
// consts
//----------------------------------------------------------------------//
namespace FNavigationSystem
{
	FORCEINLINE bool IsValidExtent(const FVector& Extent)
	{
		return Extent != INVALID_NAVEXTENT;
	}

	FCustomLinkOwnerInfo::FCustomLinkOwnerInfo(INavLinkCustomInterface* Link)
	{
		LinkInterface = Link;
		LinkOwner = Link->GetLinkOwner();
	}

	bool ShouldLoadNavigationOnClient(ANavigationData& NavData)
	{
		const UWorld* World = NavData.GetWorld();

		if (World && World->GetNavigationSystem())
		{
			const UNavigationSystemV1* NavSys = Cast<UNavigationSystemV1>(World->GetNavigationSystem());
			return NavSys && NavSys->ShouldLoadNavigationOnClient(&NavData);
		}
		else if (GEngine->NavigationSystemClass && GEngine->NavigationSystemClass->IsChildOf<UNavigationSystemV1>())
		{
			const UNavigationSystemV1* NavSysCDO = GEngine->NavigationSystemClass->GetDefaultObject<const UNavigationSystemV1>();
			return NavSysCDO && NavSysCDO->ShouldLoadNavigationOnClient(&NavData);
		}
		return false;
	}

	bool ShouldDiscardSubLevelNavData(ANavigationData& NavData)
	{
		const UWorld* World = NavData.GetWorld();

		if (World && World->GetNavigationSystem())
		{
			const UNavigationSystemV1* NavSys = Cast<UNavigationSystemV1>(World->GetNavigationSystem());
			if (NavSys)
			{
				return NavSys->ShouldDiscardSubLevelNavData(&NavData);
			}
		}

		const UNavigationSystemV1* NavSysCDO = (*GEngine->NavigationSystemClass != nullptr)
			? (GEngine->NavigationSystemClass->GetDefaultObject<const UNavigationSystemV1>())
			: (const UNavigationSystemV1*)nullptr;
		return NavSysCDO == nullptr || NavSysCDO->ShouldDiscardSubLevelNavData(&NavData);
	}

	void MakeAllComponentsNeverAffectNav(AActor& Actor)
	{
		const TSet<UActorComponent*> Components = Actor.GetComponents();
		for (UActorComponent* ActorComp : Components)
		{
			ActorComp->SetCanEverAffectNavigation(false);
		}
	}
}

namespace NavigationDebugDrawing
{
	const float PathLineThickness = 3.f;
	const FVector PathOffset(0,0,15);
	const FVector PathNodeBoxExtent(16.f);
}

//----------------------------------------------------------------------//
// FNavigationInvoker
//----------------------------------------------------------------------//
FNavigationInvoker::FNavigationInvoker()
: Actor(nullptr)
, GenerationRadius(0)
, RemovalRadius(0)
{

}

FNavigationInvoker::FNavigationInvoker(AActor& InActor, float InGenerationRadius, float InRemovalRadius)
: Actor(&InActor)
, GenerationRadius(InGenerationRadius)
, RemovalRadius(InRemovalRadius)
{

}

//----------------------------------------------------------------------//
// helpers
//----------------------------------------------------------------------//
namespace
{
#if ENABLE_VISUAL_LOG
	void NavigationDataDump(const UObject* Object, const FName& CategoryName, const ELogVerbosity::Type Verbosity, const FBox& Box, const UWorld& World, FVisualLogEntry& CurrentEntry)
	{
		const ANavigationData* MainNavData = FNavigationSystem::GetCurrent<UNavigationSystemV1>(&World)->GetDefaultNavDataInstance();
		const FNavDataGenerator* Generator = MainNavData ? MainNavData->GetGenerator() : nullptr;
		if (Generator)
		{
			Generator->GrabDebugSnapshot(&CurrentEntry, FMath::IsNearlyZero(Box.GetVolume()) ? MainNavData->GetBounds().ExpandBy(FVector(20, 20, 20)) : Box, CategoryName, Verbosity);
		}
	}
#endif // ENABLE_VISUAL_LOG
}
//----------------------------------------------------------------------//
// UNavigationSystemV1                                                                
//----------------------------------------------------------------------//
bool UNavigationSystemV1::bNavigationAutoUpdateEnabled = true;
TMap<INavLinkCustomInterface*, FWeakObjectPtr> UNavigationSystemV1::PendingCustomLinkRegistration;
FCriticalSection UNavigationSystemV1::CustomLinkRegistrationSection;
#if !(UE_BUILD_SHIPPING || UE_BUILD_TEST)
FNavigationSystemExec UNavigationSystemV1::ExecHandler;
#endif // !UE_BUILD_SHIPPING

/** called after navigation influencing event takes place*/
UNavigationSystemV1::FOnNavigationDirty UNavigationSystemV1::NavigationDirtyEvent;

bool UNavigationSystemV1::bUpdateNavOctreeOnComponentChange = true;
bool UNavigationSystemV1::bStaticRuntimeNavigation = false;
bool UNavigationSystemV1::bIsPIEActive = false;
//----------------------------------------------------------------------//
// life cycle stuff                                                                
//----------------------------------------------------------------------//

UNavigationSystemV1::UNavigationSystemV1(const FObjectInitializer& ObjectInitializer)
	: Super(ObjectInitializer)
	, bTickWhilePaused(false)
	, bWholeWorldNavigable(false)
	, bSkipAgentHeightCheckWhenPickingNavData(false)
	, DirtyAreasUpdateFreq(60)
	, OperationMode(FNavigationSystemRunMode::InvalidMode)
	, NavOctree(NULL)
	, NavBuildingLockFlags(0)
	, InitialNavBuildingLockFlags(0)
	, bNavOctreeLock(false)
	, bInitialSetupHasBeenPerformed(false)
	, bInitialLevelsAdded(false)
	, bWorldInitDone(false)
	, CurrentlyDrawnNavDataIndex(0)
	, DirtyAreasUpdateTime(0)
{
#if WITH_EDITOR
	NavUpdateLockFlags = 0;
#endif
	struct FDelegatesInitializer
	{
		FDelegatesInitializer()
		{
			UNavigationSystemBase::UpdateActorDataDelegate().BindStatic(&UNavigationSystemV1::UpdateActorInNavOctree);
			UNavigationSystemBase::UpdateComponentDataDelegate().BindStatic(&UNavigationSystemV1::UpdateComponentInNavOctree);
			UNavigationSystemBase::UpdateComponentDataAfterMoveDelegate().BindLambda([](USceneComponent& Comp) { UNavigationSystemV1::UpdateNavOctreeAfterMove(&Comp); });
			UNavigationSystemBase::OnActorBoundsChangedDelegate().BindLambda([](AActor& Actor) { UNavigationSystemV1::UpdateNavOctreeBounds(&Actor); });
			UNavigationSystemBase::OnPostEditActorMoveDelegate().BindLambda([](AActor& Actor) {
				// update actor and all its components in navigation system after finishing move
				// USceneComponent::UpdateNavigationData works only in game world
				UNavigationSystemV1::UpdateNavOctreeBounds(&Actor);

				TArray<AActor*> ParentedActors;
				Actor.GetAttachedActors(ParentedActors);
				for (int32 Idx = 0; Idx < ParentedActors.Num(); Idx++)
				{
					UNavigationSystemV1::UpdateNavOctreeBounds(ParentedActors[Idx]);
				}

				// not doing manual update of all attached actors since UpdateActorAndComponentsInNavOctree should take care of it
				UNavigationSystemV1::UpdateActorAndComponentsInNavOctree(Actor);
			});
			UNavigationSystemBase::OnComponentTransformChangedDelegate().BindLambda([](USceneComponent& Comp) {
				if (UNavigationSystemV1::ShouldUpdateNavOctreeOnComponentChange())
				{
					UWorld* World = Comp.GetWorld();
					UNavigationSystemV1* NavSys = FNavigationSystem::GetCurrent<UNavigationSystemV1>(World);
					if (NavSys != nullptr
						&& (NavSys->ShouldAllowClientSideNavigation() || !World->IsNetMode(ENetMode::NM_Client)))
					{
						// use propagated component's transform update in editor OR server game with additional navsys check
						UNavigationSystemV1::UpdateNavOctreeAfterMove(&Comp);
					}
				}
			});
			UNavigationSystemBase::OnActorRegisteredDelegate().BindLambda([](AActor& Actor) { UNavigationSystemV1::OnActorRegistered(&Actor); });
			UNavigationSystemBase::OnActorUnregisteredDelegate().BindLambda([](AActor& Actor) { UNavigationSystemV1::OnActorUnregistered(&Actor); });
			UNavigationSystemBase::OnComponentRegisteredDelegate().BindLambda([](UActorComponent& Comp) { UNavigationSystemV1::OnComponentRegistered(&Comp); });
			UNavigationSystemBase::OnComponentUnregisteredDelegate().BindLambda([](UActorComponent& Comp) { UNavigationSystemV1::OnComponentUnregistered(&Comp); });
			UNavigationSystemBase::RemoveActorDataDelegate().BindLambda([](AActor& Actor) { UNavigationSystemV1::ClearNavOctreeAll(&Actor); });
			UNavigationSystemBase::HasComponentDataDelegate().BindLambda([](UActorComponent& Comp) {
				UNavigationSystemV1* NavSys = FNavigationSystem::GetCurrent<UNavigationSystemV1>(Comp.GetWorld());
				return (NavSys && (NavSys->GetObjectsNavOctreeId(Comp) || NavSys->HasPendingObjectNavOctreeId(&Comp)));
			});
			UNavigationSystemBase::GetDefaultSupportedAgentDelegate().BindStatic(&UNavigationSystemV1::GetDefaultSupportedAgent);
			UNavigationSystemBase::UpdateActorAndComponentDataDelegate().BindStatic(&UNavigationSystemV1::UpdateActorAndComponentsInNavOctree);
			UNavigationSystemBase::OnComponentBoundsChangedDelegate().BindLambda([](UActorComponent& Comp, const FBox& NewBounds, const FBox& DirtyArea) {
				UNavigationSystemV1* NavSys = FNavigationSystem::GetCurrent<UNavigationSystemV1>(Comp.GetWorld());
				if (NavSys)
				{
					NavSys->UpdateNavOctreeElementBounds(&Comp, NewBounds, DirtyArea);
				}
			});
			//UNavigationSystemBase::GetNavDataForPropsDelegate();
			UNavigationSystemBase::GetNavDataForActorDelegate().BindStatic(&UNavigationSystemV1::GetNavDataForActor);

#if WITH_RECAST
			UNavigationSystemBase::GetDefaultNavDataClassDelegate().BindLambda([]() { return ARecastNavMesh::StaticClass(); });
#endif // WITH_RECAST
			UNavigationSystemBase::VerifyNavigationRenderingComponentsDelegate().BindLambda([](UWorld& World, const bool bShow) {
				UNavigationSystemV1* NavSys = FNavigationSystem::GetCurrent<UNavigationSystemV1>(&World);
				if (NavSys)
				{
					NavSys->VerifyNavigationRenderingComponents(bShow);
				}
			});
			UNavigationSystemBase::BuildDelegate().BindLambda([](UWorld& World) {
				UNavigationSystemV1* NavSys = FNavigationSystem::GetCurrent<UNavigationSystemV1>(&World);
				if (NavSys)
				{
					NavSys->Build();
				}
			});
#if WITH_EDITOR
			UNavigationSystemBase::OnPIEStartDelegate().BindLambda([](UWorld& World) {
				UNavigationSystemV1* NavSys = FNavigationSystem::GetCurrent<UNavigationSystemV1>(&World);
				if (NavSys)
				{
					NavSys->OnPIEStart();
				}
			});
			UNavigationSystemBase::OnPIEEndDelegate().BindLambda([](UWorld& World) {
				UNavigationSystemV1* NavSys = FNavigationSystem::GetCurrent<UNavigationSystemV1>(&World);
				if (NavSys)
				{
					NavSys->OnPIEEnd();
				}
			});
			UNavigationSystemBase::UpdateLevelCollisionDelegate().BindLambda([](ULevel& Level) {
				UNavigationSystemV1* NavSys = FNavigationSystem::GetCurrent<UNavigationSystemV1>(&Level);
				if (NavSys)
				{
					NavSys->UpdateLevelCollision(&Level);
				}
			});
			UNavigationSystemBase::SetNavigationAutoUpdateEnableDelegate().BindStatic(&UNavigationSystemV1::SetNavigationAutoUpdateEnabled);
				/*.BindLambda([](const bool bNewEnable, UNavigationSystemBase* InNavigationSystem) {

			})*/
			UNavigationSystemBase::AddNavigationUpdateLockDelegate().BindLambda([](UWorld& World, uint8 Flags) {
				UNavigationSystemV1* NavSys = FNavigationSystem::GetCurrent<UNavigationSystemV1>(&World);
				if (NavSys)
				{
					NavSys->AddNavigationUpdateLock(Flags);
				}
			});
			UNavigationSystemBase::RemoveNavigationUpdateLockDelegate().BindLambda([](UWorld& World, uint8 Flags) {
				UNavigationSystemV1* NavSys = FNavigationSystem::GetCurrent<UNavigationSystemV1>(&World);
				if (NavSys)
				{
					NavSys->RemoveNavigationUpdateLock(Flags);
				}
			});
#endif // WITH_EDITOR

#if ENABLE_VISUAL_LOG
			FVisualLogger::NavigationDataDumpDelegate.AddStatic(&NavigationDataDump);
#endif // ENABLE_VISUAL_LOG
		}
	};
	static FDelegatesInitializer DelegatesInitializer;
	
	// @hack, trying to load AIModule's CrowdManager
	UClass* Class = StaticLoadClass(UCrowdManagerBase::StaticClass(), nullptr, TEXT("/Script/AIModule.CrowdManager"));
	CrowdManagerClass = Class ? Class : UCrowdManagerBase::StaticClass();
	
	// active tiles
	NextInvokersUpdateTime = 0.f;
	ActiveTilesUpdateInterval = 1.f;
	bGenerateNavigationOnlyAroundNavigationInvokers = false;
	DataGatheringMode = ENavDataGatheringModeConfig::Instant;
	bCanAccumulateDirtyAreas = true;
	bShouldDiscardSubLevelNavData = true;
#if !UE_BUILD_SHIPPING
	bDirtyAreasReportedWhileAccumulationLocked = false;
#endif // !UE_BUILD_SHIPPING

	if (HasAnyFlags(RF_ClassDefaultObject) == false)
	{
		// reserve some arbitrary size
		AsyncPathFindingQueries.Reserve( INITIAL_ASYNC_QUERIES_SIZE );
		NavDataRegistrationQueue.Reserve( REGISTRATION_QUEUE_SIZE );
	
		FWorldDelegates::LevelAddedToWorld.AddUObject(this, &UNavigationSystemV1::OnLevelAddedToWorld);
		FWorldDelegates::LevelRemovedFromWorld.AddUObject(this, &UNavigationSystemV1::OnLevelRemovedFromWorld);
#if !UE_BUILD_SHIPPING
		FCoreDelegates::OnGetOnScreenMessages.AddUObject(this, &UNavigationSystemV1::GetOnScreenMessages);
#endif // !UE_BUILD_SHIPPING
	}
	else if (GetClass() == UNavigationSystemV1::StaticClass())
	{
		SetDefaultWalkableArea(UNavArea_Default::StaticClass());
		SetDefaultObstacleArea(UNavArea_Obstacle::StaticClass());
		
		const FTransform RecastToUnrealTransfrom(Recast2UnrealMatrix());
		SetCoordTransform(ENavigationCoordSystem::Navigation, ENavigationCoordSystem::Unreal, RecastToUnrealTransfrom);
	}

#if WITH_EDITOR
	if (GIsEditor && HasAnyFlags(RF_ClassDefaultObject) == false)
	{
		FEditorDelegates::EditorModeEnter.AddUObject(this, &UNavigationSystemV1::OnEditorModeChanged, true);
		FEditorDelegates::EditorModeExit.AddUObject(this, &UNavigationSystemV1::OnEditorModeChanged, false);
	}
#endif // WITH_EDITOR
}

UNavigationSystemV1::~UNavigationSystemV1()
{
	CleanUp(FNavigationSystem::ECleanupMode::CleanupUnsafe);

#if WITH_EDITOR
	if (GIsEditor)
	{
		FEditorDelegates::EditorModeEnter.RemoveAll(this);
		FEditorDelegates::EditorModeExit.RemoveAll(this);
	}
#endif // WITH_EDITOR

#if !UE_BUILD_SHIPPING
	FCoreDelegates::OnGetOnScreenMessages.RemoveAll(this);
#endif // !UE_BUILD_SHIPPING
}

void UNavigationSystemV1::ConfigureAsStatic()
{
	bStaticRuntimeNavigation = true;
	SetWantsComponentChangeNotifies(false);
}

void UNavigationSystemV1::SetUpdateNavOctreeOnComponentChange(bool bNewUpdateOnComponentChange)
{
	bUpdateNavOctreeOnComponentChange = bNewUpdateOnComponentChange;
}

void UNavigationSystemV1::DoInitialSetup()
{
	if (bInitialSetupHasBeenPerformed)
	{
		return;
	}
	
	UpdateAbstractNavData();
	CreateCrowdManager();

	bInitialSetupHasBeenPerformed = true;
}

void UNavigationSystemV1::UpdateAbstractNavData()
{
	if (AbstractNavData != nullptr && !AbstractNavData->IsPendingKill())
	{
		return;
	}

	// spawn abstract nav data separately
	// it's responsible for direct paths and shouldn't be picked for any agent type as default one
	UWorld* NavWorld = GetWorld();
	for (TActorIterator<AAbstractNavData> It(NavWorld); It; ++It)
	{
		AAbstractNavData* Nav = (*It);
		if (Nav && !Nav->IsPendingKill())
		{
			AbstractNavData = Nav;
			break;
		}
	}

	if (AbstractNavData == NULL)
	{
		FNavDataConfig DummyConfig;
		DummyConfig.NavigationDataClass = AAbstractNavData::StaticClass();
		AbstractNavData = CreateNavigationDataInstance(DummyConfig);
		if (AbstractNavData)
		{
			AbstractNavData->SetFlags(RF_Transient);
		}
	}
}

void UNavigationSystemV1::SetSupportedAgentsNavigationClass(int32 AgentIndex, TSubclassOf<ANavigationData> NavigationDataClass)
{
	check(SupportedAgents.IsValidIndex(AgentIndex));
	SupportedAgents[AgentIndex].NavigationDataClass = NavigationDataClass;

	// keep preferred navigation data class in sync with actual class
	// this will be passed to navigation data actor and will be required
	// for comparisons done in DoesSupportAgent calls
	//
	// "Any" navigation data preference is valid only for instanced agents
	SupportedAgents[AgentIndex].SetPreferredNavData(NavigationDataClass);

	if (NavigationDataClass != nullptr)
	{
		SupportedAgents[AgentIndex].NavigationDataClassName = FSoftClassPath::GetOrCreateIDForClass(NavigationDataClass);
	}
	else
	{
		SupportedAgents[AgentIndex].NavigationDataClassName.Reset();
	}

#if WITH_EDITOR
	if (GIsEditor)
	{
		if (HasAnyFlags(RF_ClassDefaultObject) == false)
		{
			// set it at CDO to properly show up in project settings
			// @hack the reason for doing it this way is that engine doesn't handle default TSubclassOf properties
			//	set to game-specific classes;
			UNavigationSystemV1* NavigationSystemCDO = GetMutableDefault<UNavigationSystemV1>(GetClass());
			NavigationSystemCDO->SetSupportedAgentsNavigationClass(AgentIndex, NavigationDataClass);
		}
	}
#endif // WITH_EDITOR
}

void UNavigationSystemV1::PostInitProperties()
{
	Super::PostInitProperties();

	if (HasAnyFlags(RF_ClassDefaultObject) == false)
	{
		// Populate our NavAreaClasses list with all known nav area classes.
		// If more are loaded after this they will be registered as they come
		TArray<UClass*> CurrentNavAreaClasses;
		GetDerivedClasses(UNavArea::StaticClass(), CurrentNavAreaClasses);
		for (UClass* NavAreaClass : CurrentNavAreaClasses)
		{
			RegisterNavAreaClass(NavAreaClass);
		}

		// make sure there's at least one supported navigation agent size
		if (SupportedAgents.Num() == 0)
		{
			SupportedAgents.Add(FNavDataConfig(FNavigationSystem::FallbackAgentRadius, FNavigationSystem::FallbackAgentHeight));
		}
		else
		{
			for (int32 AgentIndex = 0; AgentIndex < SupportedAgents.Num(); ++AgentIndex)
			{
				FNavDataConfig& SupportedAgentConfig = SupportedAgents[AgentIndex];
				// a piece of legacy maintanance 
				if (SupportedAgentConfig.NavigationDataClass != nullptr && SupportedAgentConfig.NavigationDataClassName.IsValid() == false)
				{
					// fill NavigationDataClassName
					SupportedAgentConfig.NavigationDataClassName = FSoftClassPath(SupportedAgentConfig.NavigationDataClass);
				}
				else
				{
					TSubclassOf<ANavigationData> NavigationDataClass = SupportedAgentConfig.NavigationDataClassName.IsValid()
						? LoadClass<ANavigationData>(NULL, *SupportedAgentConfig.NavigationDataClassName.ToString(), NULL, LOAD_None, NULL)
						: nullptr;

					SetSupportedAgentsNavigationClass(AgentIndex, NavigationDataClass);
				}
			}
		}
	
		if (bInitialBuildingLocked)
		{
			InitialNavBuildingLockFlags |= ENavigationBuildLock::InitialLock;
		}

		uint8 UseLockFlags = InitialNavBuildingLockFlags;

		AddNavigationBuildLock(UseLockFlags);

		// register for any actor move change
#if WITH_EDITOR
		if ( GIsEditor )
		{
			GEngine->OnActorMoved().AddUObject(this, &UNavigationSystemV1::OnActorMoved);
		}
#endif
		FCoreUObjectDelegates::PostLoadMapWithWorld.AddUObject(this, &UNavigationSystemV1::OnPostLoadMap);
		UNavigationSystemV1::NavigationDirtyEvent.AddUObject(this, &UNavigationSystemV1::OnNavigationDirtied);

#if WITH_HOT_RELOAD
		IHotReloadInterface& HotReloadSupport = FModuleManager::LoadModuleChecked<IHotReloadInterface>("HotReload");
		HotReloadDelegateHandle = HotReloadSupport.OnHotReload().AddUObject(this, &UNavigationSystemV1::OnHotReload);
#endif
	}
}

bool UNavigationSystemV1::ConditionalPopulateNavOctree()
{
	// Discard all navigation updates caused by octree construction
	TGuardValue<TArray<FNavigationDirtyArea>> DirtyGuard(DirtyAreas, TArray<FNavigationDirtyArea>());

	// We are going to fully re-populate NavOctree so all pending update request are outdated
	PendingOctreeUpdates.Empty(32);
	
	// Discard current octree
	DestroyNavOctree();
	
	// See if any of registered navigation data need navoctree
	bSupportRebuilding = RequiresNavOctree();

	if (bSupportRebuilding)
	{
		NavOctree = MakeShareable(new FNavigationOctree(FVector(0,0,0), 64000));
		NavOctree->SetDataGatheringMode(DataGatheringMode);
		
		const ERuntimeGenerationType RuntimeGenerationType = GetRuntimeGenerationType();
		const bool bStoreNavGeometry = (RuntimeGenerationType == ERuntimeGenerationType::Dynamic);
		NavOctree->SetNavigableGeometryStoringMode(bStoreNavGeometry ? FNavigationOctree::StoreNavGeometry : FNavigationOctree::SkipNavGeometry);
		if (bStoreNavGeometry)
		{
#if WITH_RECAST
			NavOctree->ComponentExportDelegate = FNavigationOctree::FNavigableGeometryComponentExportDelegate::CreateStatic(&FRecastNavMeshGenerator::ExportComponentGeometry);
#endif // WITH_RECAST
		}

		if (!IsNavigationOctreeLocked())
		{
			UWorld* World = GetWorld();
			check(World);

			// now process all actors on all levels
			for (int32 LevelIndex = 0; LevelIndex < World->GetNumLevels(); ++LevelIndex)
			{
				ULevel* Level = World->GetLevel(LevelIndex);
				AddLevelCollisionToOctree(Level);

				for (int32 ActorIndex = 0; ActorIndex < Level->Actors.Num(); ActorIndex++)
				{
					AActor* Actor = Level->Actors[ActorIndex];

					const bool bLegalActor = Actor && !Actor->IsPendingKill();
					if (bLegalActor)
					{
						UpdateActorAndComponentsInNavOctree(*Actor);
					}
				}
			}
		}
	}
	
	// Add all found elements to octree, this will not add new dirty areas to navigation
	if (PendingOctreeUpdates.Num())
	{
		for (TSet<FNavigationDirtyElement>::TIterator It(PendingOctreeUpdates); It; ++It)
		{
			AddElementToNavOctree(*It);
		}
		PendingOctreeUpdates.Empty(32);
	}

	return bSupportRebuilding;
}

#if WITH_EDITOR
void UNavigationSystemV1::PostEditChangeChainProperty(FPropertyChangedChainEvent& PropertyChangedEvent)
{
	static const FName NAME_NavigationDataClass = GET_MEMBER_NAME_CHECKED(FNavDataConfig, NavigationDataClass);
	static const FName NAME_SupportedAgents = GET_MEMBER_NAME_CHECKED(UNavigationSystemV1, SupportedAgents);
	static const FName NAME_AllowClientSideNavigation = GET_MEMBER_NAME_CHECKED(UNavigationSystemV1, bAllowClientSideNavigation);

	Super::PostEditChangeChainProperty(PropertyChangedEvent);

	if (PropertyChangedEvent.Property)
	{
		FName PropName = PropertyChangedEvent.Property->GetFName();
		if (PropName == NAME_NavigationDataClass)
		{
			int32 SupportedAgentIndex = PropertyChangedEvent.GetArrayIndex(NAME_SupportedAgents.ToString());
			if (SupportedAgents.IsValidIndex(SupportedAgentIndex))
			{
				// reflect the change to SupportedAgent's 
				TSubclassOf<ANavigationData> NavClass = SupportedAgents[SupportedAgentIndex].NavigationDataClass.Get();
				SetSupportedAgentsNavigationClass(SupportedAgentIndex, NavClass);
				SaveConfig();
			}
		}
		else if (PropName == NAME_AllowClientSideNavigation && HasAnyFlags(RF_ClassDefaultObject))
		{
			for (FObjectIterator It(UNavigationSystemModuleConfig::StaticClass()); It; ++It)
			{
				((UNavigationSystemModuleConfig*)*It)->UpdateWithNavSysCDO(*this);
			}
		}
	}
}

void UNavigationSystemV1::PostEditChangeProperty(FPropertyChangedEvent& PropertyChangedEvent)
{
	static const FName NAME_EnableActiveTiles = GET_MEMBER_NAME_CHECKED(UNavigationSystemV1, bGenerateNavigationOnlyAroundNavigationInvokers);

	Super::PostEditChangeProperty(PropertyChangedEvent);

	if (PropertyChangedEvent.Property)
	{
		FName PropName = PropertyChangedEvent.Property->GetFName();
		if (PropName == NAME_EnableActiveTiles)
		{
			if (NavOctree.IsValid())
			{
				NavOctree->SetDataGatheringMode(DataGatheringMode);
			}

			for (auto NavData : NavDataSet)
			{
				if (NavData)
				{
					NavData->RestrictBuildingToActiveTiles(bGenerateNavigationOnlyAroundNavigationInvokers);
				}
			}
		}
	}
}
#endif // WITH_EDITOR

void UNavigationSystemV1::OnInitializeActors()
{
	
}

void UNavigationSystemV1::OnWorldInitDone(FNavigationSystemRunMode Mode)
{
	static const bool bSkipRebuildInEditor = true;
	OperationMode = Mode;
	DoInitialSetup();
	
	UWorld* World = GetWorld();

	if (IsThereAnywhereToBuildNavigation() == false
		// Simulation mode is a special case - better not do it in this case
		&& OperationMode != FNavigationSystemRunMode::SimulationMode)
	{
		// remove all navigation data instances
		for (TActorIterator<ANavigationData> It(World); It; ++It)
		{
			ANavigationData* Nav = (*It);
			if (Nav != NULL && Nav->IsPendingKill() == false && Nav != GetAbstractNavData())
			{
				UnregisterNavData(Nav);
				Nav->CleanUpAndMarkPendingKill();
				bNavDataRemovedDueToMissingNavBounds = true;
			}
		}

		if (OperationMode == FNavigationSystemRunMode::EditorMode)
		{
			RemoveNavigationBuildLock(InitialNavBuildingLockFlags, bSkipRebuildInEditor);
		}
	}
	else
	{
		// Discard all bounds updates that was submitted during world initialization, 
		// to avoid navigation rebuild right after map is loaded
		PendingNavBoundsUpdates.Empty();
		
		// gather navigable bounds
		GatherNavigationBounds();

		// gather all navigation data instances and register all not-yet-registered
		// (since it's quite possible navigation system was not ready by the time
		// those instances were serialized-in or spawned)
		RegisterNavigationDataInstances();

		if (bAutoCreateNavigationData == true)
		{
			SpawnMissingNavigationData();
			// in case anything spawned has registered
			ProcessRegistrationCandidates();
		}
		else
		{
			const bool bIsBuildLocked = IsNavigationBuildingLocked();
			const bool bAllowRebuild = !bIsBuildLocked && GetIsAutoUpdateEnabled();

			if (GetDefaultNavDataInstance(FNavigationSystem::DontCreate) != NULL)
			{
				// trigger navmesh update
				for (TActorIterator<ANavigationData> It(World); It; ++It)
				{
					ANavigationData* NavData = (*It);
					if (NavData != NULL)
					{
						ERegistrationResult Result = RegisterNavData(NavData);

						if (Result == RegistrationSuccessful)
						{
							if (bAllowRebuild)
							{
								NavData->RebuildAll();
							}
						}
						else if (Result != RegistrationFailed_DataPendingKill
							&& Result != RegistrationFailed_AgentNotValid
							)
						{
							NavData->CleanUpAndMarkPendingKill();
						}
					}
				}
			}
		}

		if (OperationMode == FNavigationSystemRunMode::EditorMode)
		{
			// don't lock navigation building in editor
			RemoveNavigationBuildLock(InitialNavBuildingLockFlags, bSkipRebuildInEditor);
		}

		// See if any of registered navigation data needs NavOctree
		ConditionalPopulateNavOctree();

		// All navigation actors are registered
		// Add NavMesh parts from all sub-levels that were streamed in prior NavMesh registration
		const auto& Levels = World->GetLevels();
		for (ULevel* Level : Levels)
		{
			if (!Level->IsPersistentLevel() && Level->bIsVisible)
			{
				for (ANavigationData* NavData : NavDataSet)
				{
					if (NavData)
					{
						NavData->OnStreamingLevelAdded(Level, World);
					}
				}
			}
		}
	}

#if	WITH_EDITOR
	if (Mode == FNavigationSystemRunMode::EditorMode)
	{
		// make sure this static get applied to this instance
		bNavigationAutoUpdateEnabled = !bNavigationAutoUpdateEnabled; 
		SetNavigationAutoUpdateEnabled(!bNavigationAutoUpdateEnabled, this);
		
		// update navigation invokers
		if (bGenerateNavigationOnlyAroundNavigationInvokers)
		{
			for (TObjectIterator<UNavigationInvokerComponent> It; It; ++It)
			{
				if (World == It->GetWorld())
				{
					It->RegisterWithNavigationSystem(*this);
				}
			}
		}

		// update navdata after loading world
		if (GetIsAutoUpdateEnabled())
		{
			const bool bIsLoadTime = true;
			RebuildAll(bIsLoadTime);
		}
	}
#endif

	if (!bCanAccumulateDirtyAreas)
	{
		DirtyAreas.Empty();
	}

	bWorldInitDone = true;
	OnNavigationInitDone.Broadcast();
}

void UNavigationSystemV1::RegisterNavigationDataInstances()
{
	UWorld* World = GetWorld();

	bool bProcessRegistration = false;
	for (TActorIterator<ANavigationData> It(World); It; ++It)
	{
		ANavigationData* Nav = (*It);
		if (Nav != NULL && Nav->IsPendingKill() == false && Nav->IsRegistered() == false)
		{
			RequestRegistration(Nav, false);
			bProcessRegistration = true;
		}
	}
	if (bProcessRegistration == true)
	{
		ProcessRegistrationCandidates();
	}
}

void UNavigationSystemV1::CreateCrowdManager()
{
	UClass* CrowdManagerClassInstance = CrowdManagerClass.Get();
	if (CrowdManagerClassInstance)
	{
		UCrowdManagerBase* ManagerInstance = NewObject<UCrowdManagerBase>(this, CrowdManagerClassInstance);
		// creating an instance when we have a valid class should never fail
		check(ManagerInstance);
		SetCrowdManager(ManagerInstance);
	}
}

void UNavigationSystemV1::SetCrowdManager(UCrowdManagerBase* NewCrowdManager)
{
	if (NewCrowdManager == CrowdManager.Get())
	{
		return;
	}

	if (CrowdManager.IsValid())
	{
		CrowdManager->RemoveFromRoot();
	}
	CrowdManager = NewCrowdManager;
	if (NewCrowdManager != NULL)
	{
		CrowdManager->AddToRoot();
	}
}

void UNavigationSystemV1::Tick(float DeltaSeconds)
{
	SET_DWORD_STAT(STAT_Navigation_ObservedPathsCount, 0);

	UWorld* World = GetWorld();

	if (World == nullptr 
		|| (bTickWhilePaused == false && World->IsPaused())
#if WITH_EDITOR
		|| (bIsPIEActive && !World->IsGameWorld())
#endif // WITH_EDITOR
		)
	{
		return;
	}

	const bool bIsGame = World->IsGameWorld();
	
	if (PendingCustomLinkRegistration.Num())
	{
		ProcessCustomLinkPendingRegistration();
	}

	if (PendingNavBoundsUpdates.Num() > 0)
	{
		PerformNavigationBoundsUpdate(PendingNavBoundsUpdates);
		PendingNavBoundsUpdates.Reset();
	}

	if (PendingOctreeUpdates.Num() > 0)
	{
		SCOPE_CYCLE_COUNTER(STAT_Navigation_AddingActorsToNavOctree);

		SCOPE_CYCLE_COUNTER(STAT_Navigation_BuildTime)
		STAT(double ThisTime = 0);
		{
			SCOPE_SECONDS_COUNTER(ThisTime);
			for (TSet<FNavigationDirtyElement>::TIterator It(PendingOctreeUpdates); It; ++It)
			{
				AddElementToNavOctree(*It);
			}
			PendingOctreeUpdates.Empty(32);
		}
		INC_FLOAT_STAT_BY(STAT_Navigation_CumulativeBuildTime,(float)ThisTime*1000);
	}
	
	if (bGenerateNavigationOnlyAroundNavigationInvokers)
	{
		UpdateInvokers();
	}

	{
		SCOPE_CYCLE_COUNTER(STAT_Navigation_TickMarkDirty);

		DirtyAreasUpdateTime += DeltaSeconds;
		const float DirtyAreasUpdateDeltaTime = 1.0f / DirtyAreasUpdateFreq;
		const bool bCanRebuildNow = (DirtyAreasUpdateTime >= DirtyAreasUpdateDeltaTime) || !bIsGame;
		const bool bIsLocked = IsNavigationBuildingLocked();

		if (DirtyAreas.Num() > 0 && bCanRebuildNow && !bIsLocked)
		{
			for (int32 NavDataIndex = 0; NavDataIndex < NavDataSet.Num(); ++NavDataIndex)
			{
				ANavigationData* NavData = NavDataSet[NavDataIndex];
				if (NavData)
				{
					NavData->RebuildDirtyAreas(DirtyAreas);
				}
			}

			DirtyAreasUpdateTime = 0;
			DirtyAreas.Reset();
		}
	}

	// Tick navigation mesh async builders
	if (!bAsyncBuildPaused)
	{
		SCOPE_CYCLE_COUNTER(STAT_Navigation_TickAsyncBuild);

		for (ANavigationData* NavData : NavDataSet)
		{
			if (NavData)
			{
				NavData->TickAsyncBuild(DeltaSeconds);
			}
		}
	}

	if (AsyncPathFindingQueries.Num() > 0)
	{
		SCOPE_CYCLE_COUNTER(STAT_Navigation_TickAsyncPathfinding);
		TriggerAsyncQueries(AsyncPathFindingQueries);
		AsyncPathFindingQueries.Reset();
	}

	if (CrowdManager.IsValid())
	{
		CrowdManager->Tick(DeltaSeconds);
	}
}

void UNavigationSystemV1::AddReferencedObjects(UObject* InThis, FReferenceCollector& Collector)
{
	UNavigationSystemV1* This = CastChecked<UNavigationSystemV1>(InThis);
	UCrowdManagerBase* CrowdManager = This->GetCrowdManager();
	Collector.AddReferencedObject(CrowdManager, InThis);

	// don't reference NavAreaClasses in editor (unless PIE is active)
	if (This->OperationMode != FNavigationSystemRunMode::EditorMode)
	{
		Collector.AddReferencedObjects(This->NavAreaClasses, InThis);
	}
}

#if WITH_EDITOR
void UNavigationSystemV1::SetNavigationAutoUpdateEnabled(bool bNewEnable, UNavigationSystemBase* InNavigationSystemBase)
{
	if (bNewEnable != bNavigationAutoUpdateEnabled)
	{
		bNavigationAutoUpdateEnabled = bNewEnable;

		UNavigationSystemV1* NavSystem = Cast<UNavigationSystemV1>(InNavigationSystemBase);
		if (NavSystem)
		{
			const bool bCurrentIsEnabled = NavSystem->GetIsAutoUpdateEnabled();
			NavSystem->bCanAccumulateDirtyAreas = bCurrentIsEnabled
				|| (NavSystem->OperationMode != FNavigationSystemRunMode::EditorMode && NavSystem->OperationMode != FNavigationSystemRunMode::InvalidMode);

			if (bCurrentIsEnabled)
			{
				const bool bSkipRebuildsInEditor = false;
				NavSystem->RemoveNavigationBuildLock(ENavigationBuildLock::NoUpdateInEditor, bSkipRebuildsInEditor);
			}
			else
			{
#if !UE_BUILD_SHIPPING
				NavSystem->bDirtyAreasReportedWhileAccumulationLocked = false;
#endif // !UE_BUILD_SHIPPING
				NavSystem->AddNavigationBuildLock(ENavigationBuildLock::NoUpdateInEditor);
			}
		}
	}
}
#endif // WITH_EDITOR

//----------------------------------------------------------------------//
// Public querying interface                                                                
//----------------------------------------------------------------------//
FPathFindingResult UNavigationSystemV1::FindPathSync(const FNavAgentProperties& AgentProperties, FPathFindingQuery Query, EPathFindingMode::Type Mode)
{
	SCOPE_CYCLE_COUNTER(STAT_Navigation_PathfindingSync);

	if (Query.NavData.IsValid() == false)
	{
		Query.NavData = GetNavDataForProps(AgentProperties);
	}

	FPathFindingResult Result(ENavigationQueryResult::Error);
	if (Query.NavData.IsValid())
	{
		if (Mode == EPathFindingMode::Hierarchical)
		{
			Result = Query.NavData->FindHierarchicalPath(AgentProperties, Query);
		}
		else
		{
			Result = Query.NavData->FindPath(AgentProperties, Query);
		}
	}

	return Result;
}

FPathFindingResult UNavigationSystemV1::FindPathSync(FPathFindingQuery Query, EPathFindingMode::Type Mode)
{
	SCOPE_CYCLE_COUNTER(STAT_Navigation_PathfindingSync);

	if (Query.NavData.IsValid() == false)
	{
		Query.NavData = GetDefaultNavDataInstance(FNavigationSystem::DontCreate);
	}
	
	FPathFindingResult Result(ENavigationQueryResult::Error);
	if (Query.NavData.IsValid())
	{
		if (Mode == EPathFindingMode::Regular)
		{
			Result = Query.NavData->FindPath(Query.NavAgentProperties, Query);
		}
		else // EPathFindingMode::Hierarchical
		{
			Result = Query.NavData->FindHierarchicalPath(Query.NavAgentProperties, Query);
		}
	}

	return Result;
}

bool UNavigationSystemV1::TestPathSync(FPathFindingQuery Query, EPathFindingMode::Type Mode, int32* NumVisitedNodes) const
{
	SCOPE_CYCLE_COUNTER(STAT_Navigation_PathfindingSync);

	if (Query.NavData.IsValid() == false)
	{
		Query.NavData = GetDefaultNavDataInstance();
	}
	
	bool bExists = false;
	if (Query.NavData.IsValid())
	{
		if (Mode == EPathFindingMode::Hierarchical)
		{
			bExists = Query.NavData->TestHierarchicalPath(Query.NavAgentProperties, Query, NumVisitedNodes);
		}
		else
		{
			bExists = Query.NavData->TestPath(Query.NavAgentProperties, Query, NumVisitedNodes);
		}
	}

	return bExists;
}

void UNavigationSystemV1::AddAsyncQuery(const FAsyncPathFindingQuery& Query)
{
	check(IsInGameThread());
	AsyncPathFindingQueries.Add(Query);
}

uint32 UNavigationSystemV1::FindPathAsync(const FNavAgentProperties& AgentProperties, FPathFindingQuery Query, const FNavPathQueryDelegate& ResultDelegate, EPathFindingMode::Type Mode)
{
	SCOPE_CYCLE_COUNTER(STAT_Navigation_RequestingAsyncPathfinding);

	if (Query.NavData.IsValid() == false)
	{
		Query.NavData = GetNavDataForProps(AgentProperties);
	}

	if (Query.NavData.IsValid())
	{
		FAsyncPathFindingQuery AsyncQuery(Query, ResultDelegate, Mode);

		if (AsyncQuery.QueryID != INVALID_NAVQUERYID)
		{
			AddAsyncQuery(AsyncQuery);
		}

		return AsyncQuery.QueryID;
	}

	return INVALID_NAVQUERYID;
}

void UNavigationSystemV1::AbortAsyncFindPathRequest(uint32 AsynPathQueryID)
{
	check(IsInGameThread());
	FAsyncPathFindingQuery* Query = AsyncPathFindingQueries.GetData();
	for (int32 Index = 0; Index < AsyncPathFindingQueries.Num(); ++Index, ++Query)
	{
		if (Query->QueryID == AsynPathQueryID)
		{
			AsyncPathFindingQueries.RemoveAtSwap(Index);
			break;
		}
	}
}

FAutoConsoleTaskPriority CPrio_TriggerAsyncQueries(
	TEXT("TaskGraph.TaskPriorities.NavTriggerAsyncQueries"),
	TEXT("Task and thread priority for UNavigationSystemV1::PerformAsyncQueries."),
	ENamedThreads::BackgroundThreadPriority, // if we have background priority task threads, then use them...
	ENamedThreads::NormalTaskPriority, // .. at normal task priority
	ENamedThreads::NormalTaskPriority // if we don't have background threads, then use normal priority threads at normal task priority instead
	);


void UNavigationSystemV1::TriggerAsyncQueries(TArray<FAsyncPathFindingQuery>& PathFindingQueries)
{
	DECLARE_CYCLE_STAT(TEXT("FSimpleDelegateGraphTask.NavigationSystem batched async queries"),
		STAT_FSimpleDelegateGraphTask_NavigationSystemBatchedAsyncQueries,
		STATGROUP_TaskGraphTasks);

	FSimpleDelegateGraphTask::CreateAndDispatchWhenReady(
		FSimpleDelegateGraphTask::FDelegate::CreateUObject(this, &UNavigationSystemV1::PerformAsyncQueries, PathFindingQueries),
		GET_STATID(STAT_FSimpleDelegateGraphTask_NavigationSystemBatchedAsyncQueries), nullptr, CPrio_TriggerAsyncQueries.Get());
}

static void AsyncQueryDone(FAsyncPathFindingQuery Query)
{
	Query.OnDoneDelegate.ExecuteIfBound(Query.QueryID, Query.Result.Result, Query.Result.Path);
}

void UNavigationSystemV1::PerformAsyncQueries(TArray<FAsyncPathFindingQuery> PathFindingQueries)
{
	SCOPE_CYCLE_COUNTER(STAT_Navigation_PathfindingAsync);

	if (PathFindingQueries.Num() == 0)
	{
		return;
	}
	
	for (FAsyncPathFindingQuery& Query : PathFindingQueries)
	{
		// @todo this is not necessarily the safest way to use UObjects outside of main thread. 
		//	think about something else.
		const ANavigationData* NavData = Query.NavData.IsValid() ? Query.NavData.Get() : GetDefaultNavDataInstance(FNavigationSystem::DontCreate);

		// perform query
		if (NavData)
		{
			if (Query.Mode == EPathFindingMode::Hierarchical)
			{
				Query.Result = NavData->FindHierarchicalPath(Query.NavAgentProperties, Query);
			}
			else
			{
				Query.Result = NavData->FindPath(Query.NavAgentProperties, Query);
			}
		}
		else
		{
			Query.Result = ENavigationQueryResult::Error;
		}

		// @todo make it return more informative results (bResult == false)
		// trigger calling delegate on main thread - otherwise it may depend too much on stuff being thread safe
		DECLARE_CYCLE_STAT(TEXT("FSimpleDelegateGraphTask.Async nav query finished"),
			STAT_FSimpleDelegateGraphTask_AsyncNavQueryFinished,
			STATGROUP_TaskGraphTasks);

		FSimpleDelegateGraphTask::CreateAndDispatchWhenReady(
			FSimpleDelegateGraphTask::FDelegate::CreateStatic(AsyncQueryDone, Query),
			GET_STATID(STAT_FSimpleDelegateGraphTask_AsyncNavQueryFinished), NULL, ENamedThreads::GameThread);
	}
}

bool UNavigationSystemV1::GetRandomPoint(FNavLocation& ResultLocation, ANavigationData* NavData, FSharedConstNavQueryFilter QueryFilter)
{
	SCOPE_CYCLE_COUNTER(STAT_Navigation_QueriesTimeSync);

	if (NavData == NULL)
	{
		NavData = MainNavData;
	}

	if (NavData != NULL)
	{
		ResultLocation = NavData->GetRandomPoint(QueryFilter);
		return true;
	}

	return false;
}

bool UNavigationSystemV1::GetRandomReachablePointInRadius(const FVector& Origin, float Radius, FNavLocation& ResultLocation, ANavigationData* NavData, FSharedConstNavQueryFilter QueryFilter) const
{
	SCOPE_CYCLE_COUNTER(STAT_Navigation_QueriesTimeSync);

	if (NavData == nullptr)
	{
		NavData = MainNavData;
	}

	return NavData != nullptr && NavData->GetRandomReachablePointInRadius(Origin, Radius, ResultLocation, QueryFilter);
}

bool UNavigationSystemV1::GetRandomPointInNavigableRadius(const FVector& Origin, float Radius, FNavLocation& ResultLocation, ANavigationData* NavData, FSharedConstNavQueryFilter QueryFilter) const
{
	SCOPE_CYCLE_COUNTER(STAT_Navigation_QueriesTimeSync);

	if (NavData == nullptr)
	{
		NavData = MainNavData;
	}

	return NavData != nullptr && NavData->GetRandomPointInNavigableRadius(Origin, Radius, ResultLocation, QueryFilter);
}

ENavigationQueryResult::Type UNavigationSystemV1::GetPathCost(const FVector& PathStart, const FVector& PathEnd, float& OutPathCost, const ANavigationData* NavData, FSharedConstNavQueryFilter QueryFilter) const
{
	SCOPE_CYCLE_COUNTER(STAT_Navigation_QueriesTimeSync);

	if (NavData == NULL)
	{
		NavData = GetDefaultNavDataInstance();
	}

	return NavData != NULL ? NavData->CalcPathCost(PathStart, PathEnd, OutPathCost, QueryFilter) : ENavigationQueryResult::Error;
}

ENavigationQueryResult::Type UNavigationSystemV1::GetPathLength(const FVector& PathStart, const FVector& PathEnd, float& OutPathLength, const ANavigationData* NavData, FSharedConstNavQueryFilter QueryFilter) const
{
	SCOPE_CYCLE_COUNTER(STAT_Navigation_QueriesTimeSync);

	if (NavData == NULL)
	{
		NavData = GetDefaultNavDataInstance();
	}

	return NavData != NULL ? NavData->CalcPathLength(PathStart, PathEnd, OutPathLength, QueryFilter) : ENavigationQueryResult::Error;
}

ENavigationQueryResult::Type UNavigationSystemV1::GetPathLengthAndCost(const FVector& PathStart, const FVector& PathEnd, float& OutPathLength, float& OutPathCost, const ANavigationData* NavData, FSharedConstNavQueryFilter QueryFilter) const
{
	SCOPE_CYCLE_COUNTER(STAT_Navigation_QueriesTimeSync);

	if (NavData == NULL)
	{
		NavData = GetDefaultNavDataInstance();
	}

	return NavData != NULL ? NavData->CalcPathLengthAndCost(PathStart, PathEnd, OutPathLength, OutPathCost, QueryFilter) : ENavigationQueryResult::Error;
}

bool UNavigationSystemV1::ProjectPointToNavigation(const FVector& Point, FNavLocation& OutLocation, const FVector& Extent, const ANavigationData* NavData, FSharedConstNavQueryFilter QueryFilter) const
{
	SCOPE_CYCLE_COUNTER(STAT_Navigation_QueriesTimeSync);

	if (NavData == NULL)
	{
		NavData = GetDefaultNavDataInstance();
	}

	return NavData != NULL && NavData->ProjectPoint(Point, OutLocation
		, FNavigationSystem::IsValidExtent(Extent) ? Extent : NavData->GetConfig().DefaultQueryExtent
		, QueryFilter);
}

UNavigationPath* UNavigationSystemV1::FindPathToActorSynchronously(UObject* WorldContextObject, const FVector& PathStart, AActor* GoalActor, float TetherDistance, AActor* PathfindingContext, TSubclassOf<UNavigationQueryFilter> FilterClass)
{
	if (GoalActor == NULL)
	{
		return NULL; 
	}

	INavAgentInterface* NavAgent = Cast<INavAgentInterface>(GoalActor);
	UNavigationPath* GeneratedPath = FindPathToLocationSynchronously(WorldContextObject, PathStart, NavAgent ? NavAgent->GetNavAgentLocation() : GoalActor->GetActorLocation(), PathfindingContext, FilterClass);
	if (GeneratedPath != NULL && GeneratedPath->GetPath().IsValid() == true)
	{
		GeneratedPath->GetPath()->SetGoalActorObservation(*GoalActor, TetherDistance);
	}

	return GeneratedPath;
}

UNavigationPath* UNavigationSystemV1::FindPathToLocationSynchronously(UObject* WorldContextObject, const FVector& PathStart, const FVector& PathEnd, AActor* PathfindingContext, TSubclassOf<UNavigationQueryFilter> FilterClass)
{
	UWorld* World = NULL;

	if (WorldContextObject != NULL)
	{
		World = GEngine->GetWorldFromContextObject(WorldContextObject, EGetWorldErrorMode::LogAndReturnNull);
	}
	if (World == NULL && PathfindingContext != NULL)
	{
		World = GEngine->GetWorldFromContextObject(PathfindingContext, EGetWorldErrorMode::LogAndReturnNull);
	}

	UNavigationPath* ResultPath = NULL;

	UNavigationSystemV1* NavSys = FNavigationSystem::GetCurrent<UNavigationSystemV1>(World);

	if (NavSys != nullptr && NavSys->GetDefaultNavDataInstance() != nullptr)
	{
		ResultPath = NewObject<UNavigationPath>(NavSys);
		bool bValidPathContext = false;
		const ANavigationData* NavigationData = NULL;

		if (PathfindingContext != NULL)
		{
			INavAgentInterface* NavAgent = Cast<INavAgentInterface>(PathfindingContext);
			
			if (NavAgent != NULL)
			{
				const FNavAgentProperties& AgentProps = NavAgent->GetNavAgentPropertiesRef();
				NavigationData = NavSys->GetNavDataForProps(AgentProps);
				bValidPathContext = true;
			}
			else if (Cast<ANavigationData>(PathfindingContext))
			{
				NavigationData = (ANavigationData*)PathfindingContext;
				bValidPathContext = true;
			}
		}
		if (bValidPathContext == false)
		{
			// just use default
			NavigationData = NavSys->GetDefaultNavDataInstance();
		}

		check(NavigationData);

		const FPathFindingQuery Query(PathfindingContext, *NavigationData, PathStart, PathEnd, UNavigationQueryFilter::GetQueryFilter(*NavigationData, PathfindingContext, FilterClass));
		const FPathFindingResult Result = NavSys->FindPathSync(Query, EPathFindingMode::Regular);
		if (Result.IsSuccessful())
		{
			ResultPath->SetPath(Result.Path);
		}
	}

	return ResultPath;
}

bool UNavigationSystemV1::NavigationRaycast(UObject* WorldContextObject, const FVector& RayStart, const FVector& RayEnd, FVector& HitLocation, TSubclassOf<UNavigationQueryFilter> FilterClass, AController* Querier)
{
	UWorld* World = NULL;

	if (WorldContextObject != NULL)
	{
		World = GEngine->GetWorldFromContextObject(WorldContextObject, EGetWorldErrorMode::LogAndReturnNull);
	}
	if (World == NULL && Querier != NULL)
	{
		World = GEngine->GetWorldFromContextObject(Querier, EGetWorldErrorMode::LogAndReturnNull);
	}

	// blocked, i.e. not traversable, by default
	bool bRaycastBlocked = true;
	HitLocation = RayStart;

	const UNavigationSystemV1* NavSys = FNavigationSystem::GetCurrent<UNavigationSystemV1>(World);

	if (NavSys)
	{
		// figure out which navigation data to use
		const ANavigationData* NavData = NULL;
		INavAgentInterface* MyNavAgent = Cast<INavAgentInterface>(Querier);
		if (MyNavAgent)
		{
			const FNavAgentProperties& AgentProps = MyNavAgent->GetNavAgentPropertiesRef();
			NavData = NavSys->GetNavDataForProps(AgentProps);
		}
		if (NavData == NULL)
		{
			NavData = NavSys->GetDefaultNavDataInstance();
		}

		if (NavData != NULL)
		{
			bRaycastBlocked = NavData->Raycast(RayStart, RayEnd, HitLocation, UNavigationQueryFilter::GetQueryFilter(*NavData, Querier, FilterClass));
		}
	}

	return bRaycastBlocked;
}

void UNavigationSystemV1::GetNavAgentPropertiesArray(TArray<FNavAgentProperties>& OutNavAgentProperties) const
{
	AgentToNavDataMap.GetKeys(OutNavAgentProperties);
}

ANavigationData* UNavigationSystemV1::GetNavDataForProps(const FNavAgentProperties& AgentProperties)
{
	const UNavigationSystemV1* ConstThis = AsConst(this);
	return const_cast<ANavigationData*>(ConstThis->GetNavDataForProps(AgentProperties));
}

// @todo could optimize this by having "SupportedAgentIndex" in FNavAgentProperties
const ANavigationData* UNavigationSystemV1::GetNavDataForProps(const FNavAgentProperties& AgentProperties) const
{
	if (SupportedAgents.Num() <= 1)
	{
		return MainNavData;
	}
	
	const TWeakObjectPtr<ANavigationData>* NavDataForAgent = AgentToNavDataMap.Find(AgentProperties);
	const ANavigationData* NavDataInstance = NavDataForAgent ? NavDataForAgent->Get() : nullptr;

	if (NavDataInstance == nullptr)
	{
		TArray<FNavAgentProperties> AgentPropertiesList;
		AgentToNavDataMap.GenerateKeyArray(AgentPropertiesList);
		
		FNavAgentProperties BestFitNavAgent;
		float BestExcessHeight = -FLT_MAX;
		float BestExcessRadius = -FLT_MAX;
		float ExcessRadius = -FLT_MAX;
		float ExcessHeight = -FLT_MAX;
		const float AgentHeight = bSkipAgentHeightCheckWhenPickingNavData ? 0.f : AgentProperties.AgentHeight;

		for (TArray<FNavAgentProperties>::TConstIterator It(AgentPropertiesList); It; ++It)
		{
			const FNavAgentProperties& NavIt = *It;
			const bool bNavClassMatch = NavIt.IsNavDataMatching(AgentProperties);
			if (!bNavClassMatch)
			{
				continue;
			}

			ExcessRadius = NavIt.AgentRadius - AgentProperties.AgentRadius;
			ExcessHeight = bSkipAgentHeightCheckWhenPickingNavData ? 0.f : (NavIt.AgentHeight - AgentHeight);

			const bool bExcessRadiusIsBetter = ((ExcessRadius == 0) && (BestExcessRadius != 0)) 
				|| ((ExcessRadius > 0) && (BestExcessRadius < 0))
				|| ((ExcessRadius > 0) && (BestExcessRadius > 0) && (ExcessRadius < BestExcessRadius))
				|| ((ExcessRadius < 0) && (BestExcessRadius < 0) && (ExcessRadius > BestExcessRadius));
			const bool bExcessHeightIsBetter = ((ExcessHeight == 0) && (BestExcessHeight != 0))
				|| ((ExcessHeight > 0) && (BestExcessHeight < 0))
				|| ((ExcessHeight > 0) && (BestExcessHeight > 0) && (ExcessHeight < BestExcessHeight))
				|| ((ExcessHeight < 0) && (BestExcessHeight < 0) && (ExcessHeight > BestExcessHeight));
			const bool bBestIsValid = (BestExcessRadius >= 0) && (BestExcessHeight >= 0);
			const bool bRadiusEquals = (ExcessRadius == BestExcessRadius);
			const bool bHeightEquals = (ExcessHeight == BestExcessHeight);

			bool bValuesAreBest = ((bExcessRadiusIsBetter || bRadiusEquals) && (bExcessHeightIsBetter || bHeightEquals));
			if (!bValuesAreBest && !bBestIsValid)
			{
				bValuesAreBest = bExcessRadiusIsBetter || (bRadiusEquals && bExcessHeightIsBetter);
			}

			if (bValuesAreBest)
			{
				BestFitNavAgent = NavIt;
				BestExcessHeight = ExcessHeight;
				BestExcessRadius = ExcessRadius;
			}
		}

		if (BestFitNavAgent.IsValid())
		{
			NavDataForAgent = AgentToNavDataMap.Find(BestFitNavAgent);
			NavDataInstance = NavDataForAgent ? NavDataForAgent->Get() : nullptr;
		}
	}

	return NavDataInstance ? NavDataInstance : MainNavData;
}

ANavigationData* UNavigationSystemV1::GetDefaultNavDataInstance(FNavigationSystem::ECreateIfMissing CreateNewIfNoneFound)
{
	checkSlow(IsInGameThread() == true);

	if (MainNavData == NULL || MainNavData->IsPendingKill())
	{
		MainNavData = NULL;

		// @TODO this should be done a differently. There should be specified a "default agent"
		for (int32 NavDataIndex = 0; NavDataIndex < NavDataSet.Num(); ++NavDataIndex)
		{
			ANavigationData* NavData = NavDataSet[NavDataIndex];
			if (NavData && !NavData->IsPendingKill() && NavData->CanBeMainNavData())
			{
				MainNavData = NavData;
				break;
			}
		}

#if WITH_RECAST
		if ( /*GIsEditor && */(MainNavData == NULL) && CreateNewIfNoneFound == FNavigationSystem::Create )
		{
			// Spawn a new one if we're in the editor.  In-game, either we loaded one or we don't get one.
			MainNavData = GetWorld()->SpawnActor<ANavigationData>(ARecastNavMesh::StaticClass());
		}
#endif // WITH_RECAST
		// either way make sure it's registered. Registration stores unique
		// navmeshes, so we have nothing to lose
		RegisterNavData(MainNavData);
	}

	return MainNavData;
}

FSharedNavQueryFilter UNavigationSystemV1::CreateDefaultQueryFilterCopy() const 
{ 
	return MainNavData ? MainNavData->GetDefaultQueryFilter()->GetCopy() : NULL; 
}

bool UNavigationSystemV1::IsNavigationBuilt(const AWorldSettings* Settings) const
{
	if (Settings == nullptr || Settings->IsNavigationSystemEnabled() == false || IsThereAnywhereToBuildNavigation() == false)
	{
		return true;
	}

	bool bIsBuilt = true;

	for (int32 NavDataIndex = 0; NavDataIndex < NavDataSet.Num(); ++NavDataIndex)
	{
		ANavigationData* NavData = NavDataSet[NavDataIndex];
		if (NavData != NULL && NavData->GetWorldSettings() == Settings)
		{
			FNavDataGenerator* Generator = NavData->GetGenerator();
			if ((NavData->GetRuntimeGenerationMode() != ERuntimeGenerationType::Static
#if WITH_EDITOR
				|| GEditor != NULL
#endif // WITH_EDITOR
				) && (Generator == NULL || Generator->IsBuildInProgress(/*bCheckDirtyToo=*/true) == true))
			{
				bIsBuilt = false;
				break;
			}
		}
	}

	return bIsBuilt;
}

bool UNavigationSystemV1::IsThereAnywhereToBuildNavigation() const
{
	// not check if there are any volumes or other structures requiring/supporting navigation building
	if (bWholeWorldNavigable == true)
	{
		return true;
	}

	for (const FNavigationBounds& Bounds : RegisteredNavBounds)
	{
		if (Bounds.AreaBox.IsValid)
		{
			return true;
		}
	}

	// @TODO this should be made more flexible to be able to trigger this from game-specific 
	// code (like Navigation System's subclass maybe)
	bool bCreateNavigation = false;

	for (TActorIterator<ANavMeshBoundsVolume> It(GetWorld()); It; ++It)
	{
		ANavMeshBoundsVolume const* const V = (*It);
		if (V != NULL && !V->IsPendingKill())
		{
			bCreateNavigation = true;
			break;
		}
	}

	return bCreateNavigation;
}

bool UNavigationSystemV1::IsNavigationRelevant(const AActor* TestActor) const
{
	const INavRelevantInterface* NavInterface = Cast<const INavRelevantInterface>(TestActor);
	if (NavInterface && NavInterface->IsNavigationRelevant())
	{
		return true;
	}

	if (TestActor)
	{
		TInlineComponentArray<UActorComponent*> Components;
		for (int32 Idx = 0; Idx < Components.Num(); Idx++)
		{
			NavInterface = Cast<const INavRelevantInterface>(Components[Idx]);
			if (NavInterface && NavInterface->IsNavigationRelevant())
			{
				return true;
			}
		}
	}

	return false;
}

FBox UNavigationSystemV1::GetWorldBounds() const
{
	checkSlow(IsInGameThread() == true);

	NavigableWorldBounds = FBox(ForceInit);

	if (GetWorld() != nullptr)
	{
		if (bWholeWorldNavigable == false)
		{
			for (const FNavigationBounds& Bounds : RegisteredNavBounds)
			{
				NavigableWorldBounds += Bounds.AreaBox;
			}
		}
		else
		{
			// @TODO - super slow! Need to ask tech guys where I can get this from
			for (FActorIterator It(GetWorld()); It; ++It)
			{
				if (IsNavigationRelevant(*It))
				{
					NavigableWorldBounds += (*It)->GetComponentsBoundingBox();
				}
			}
		}
	}

	return NavigableWorldBounds;
}

FBox UNavigationSystemV1::GetLevelBounds(ULevel* InLevel) const
{
	FBox NavigableLevelBounds(ForceInit);

	if (InLevel)
	{
		AActor** Actor = InLevel->Actors.GetData();
		const int32 ActorCount = InLevel->Actors.Num();
		for (int32 ActorIndex = 0; ActorIndex < ActorCount; ++ActorIndex, ++Actor)
		{
			if (IsNavigationRelevant(*Actor))
			{
				NavigableLevelBounds += (*Actor)->GetComponentsBoundingBox();
			}
		}
	}

	return NavigableLevelBounds;
}

const TSet<FNavigationBounds>& UNavigationSystemV1::GetNavigationBounds() const
{
	return RegisteredNavBounds;
}

void UNavigationSystemV1::ApplyWorldOffset(const FVector& InOffset, bool bWorldShift)
{
	// Attempt at generation of new nav mesh after the shift
	// dynamic navmesh, we regenerate completely
	if (GetRuntimeGenerationType() == ERuntimeGenerationType::Dynamic)
	{
		//stop generators from building navmesh
		CancelBuild();

		ConditionalPopulateNavOctree();
		Build();

		for (ANavigationData* NavData : NavDataSet)
		{
			if (NavData)
			{
				NavData->ConditionalConstructGenerator();
				ARecastNavMesh* RecastNavMesh = Cast<ARecastNavMesh>(NavData);
				if (RecastNavMesh)
				{
					RecastNavMesh->RequestDrawingUpdate();
				}
			}
		}
	}
	else // static navmesh
	{
		//not sure what happens when we shift farther than the extents of the NavOctree are
		for (ANavigationData* NavData : NavDataSet)
		{
			if (NavData)
			{
				NavData->ApplyWorldOffset(InOffset, bWorldShift);
			}
		}
	}
}

//----------------------------------------------------------------------//
// Bookkeeping 
//----------------------------------------------------------------------//
void UNavigationSystemV1::RequestRegistration(ANavigationData* NavData, bool bTriggerRegistrationProcessing)
{
	FScopeLock RegistrationLock(&NavDataRegistrationSection);

	if (NavDataRegistrationQueue.Num() < REGISTRATION_QUEUE_SIZE)
	{
		NavDataRegistrationQueue.AddUnique(NavData);

		// checking if bWorldInitDone since requesting out-of-order registration
		// processing when we're still setting up can result in odd cases,
		// like initializing navmesh generators while the nav system doesn't have
		// the navmesh bounds collected yet.
		if (bTriggerRegistrationProcessing && bWorldInitDone)
		{
			// trigger registration candidates processing
			DECLARE_CYCLE_STAT(TEXT("FSimpleDelegateGraphTask.Process registration candidates"),
				STAT_FSimpleDelegateGraphTask_ProcessRegistrationCandidates,
				STATGROUP_TaskGraphTasks);

			FSimpleDelegateGraphTask::CreateAndDispatchWhenReady(
				FSimpleDelegateGraphTask::FDelegate::CreateUObject(this, &UNavigationSystemV1::ProcessRegistrationCandidates),
				GET_STATID(STAT_FSimpleDelegateGraphTask_ProcessRegistrationCandidates), NULL, ENamedThreads::GameThread);
		}
	}
	else
	{
		UE_LOG(LogNavigation, Error, TEXT("Navigation System: registration queue full!"));
	}
}

void UNavigationSystemV1::ProcessRegistrationCandidates()
{
	//if (FUObjectThreadContext::Get().IsRoutingPostLoad)
	//{
	//	// postopne
	//	return;
	//}

	FScopeLock RegistrationLock(&NavDataRegistrationSection);

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

	ANavigationData** NavDataPtr = NavDataRegistrationQueue.GetData();
	const int CandidatesCount = NavDataRegistrationQueue.Num();

	for (int32 CandidateIndex = 0; CandidateIndex < CandidatesCount; ++CandidateIndex, ++NavDataPtr)
	{
		if (*NavDataPtr != NULL)
		{
			ERegistrationResult Result = RegisterNavData(*NavDataPtr);

			if (Result == RegistrationSuccessful)
			{
				continue;
			}
			else if (Result != RegistrationFailed_DataPendingKill)
			{
				(*NavDataPtr)->CleanUpAndMarkPendingKill();
				if ((*NavDataPtr) == MainNavData)
				{
					MainNavData = NULL;
				}
			}
		}
	}

	MainNavData = GetDefaultNavDataInstance(FNavigationSystem::DontCreate);
	
	// we processed all candidates so clear the queue
	NavDataRegistrationQueue.Reset();
}

void UNavigationSystemV1::ProcessCustomLinkPendingRegistration()
{
	FScopeLock AccessLock(&CustomLinkRegistrationSection);

	TMap<INavLinkCustomInterface*, FWeakObjectPtr> TempPending = PendingCustomLinkRegistration;
	PendingCustomLinkRegistration.Empty();

	for (TMap<INavLinkCustomInterface*, FWeakObjectPtr>::TIterator It(TempPending); It; ++It)
	{
		INavLinkCustomInterface* ILink = It.Key();
		FWeakObjectPtr LinkOb = It.Value();
		
		if (LinkOb.IsValid() && ILink)
		{
			RegisterCustomLink(*ILink);
		}
	}
}

UNavigationSystemV1::ERegistrationResult UNavigationSystemV1::RegisterNavData(ANavigationData* NavData)
{
	if (NavData == NULL)
	{
		return RegistrationError;
	}
	else if (NavData->IsPendingKill() == true)
	{
		return RegistrationFailed_DataPendingKill;
	}
	// still to be seen if this is really true, but feels right
	else if (NavData->IsRegistered() == true)
	{
		return RegistrationSuccessful;
	}

	FScopeLock Lock(&NavDataRegistration);

	UNavigationSystemV1::ERegistrationResult Result = RegistrationError;

	// find out which, if any, navigation agents are supported by this nav data
	// if none then fail the registration
	FNavDataConfig NavConfig = NavData->GetConfig();

	// not discarding navmesh when there's only one Supported Agent
	if (NavConfig.IsValid() == false && SupportedAgents.Num() == 1)
	{
		// fill in AgentProps with whatever is the instance's setup
		NavConfig = SupportedAgents[0];
		NavData->SetConfig(SupportedAgents[0]);
		NavData->SetSupportsDefaultAgent(true);	
		NavData->ProcessNavAreas(NavAreaClasses, 0);
	}

	if (NavConfig.IsValid() == true)
	{
		// check if this kind of agent has already its navigation implemented
		TWeakObjectPtr<ANavigationData>* NavDataForAgent = AgentToNavDataMap.Find(NavConfig);
		ANavigationData* NavDataInstanceForAgent = NavDataForAgent ? NavDataForAgent->Get() : nullptr;

		if (NavDataInstanceForAgent == nullptr)
		{
			if (NavData->IsA(AAbstractNavData::StaticClass()) == false)
			{
				// ok, so this navigation agent doesn't have its navmesh registered yet, but do we want to support it?
				bool bAgentSupported = false;

				for (int32 AgentIndex = 0; AgentIndex < SupportedAgents.Num(); ++AgentIndex)
				{
					if (NavData->GetClass() == SupportedAgents[AgentIndex].NavigationDataClass && SupportedAgents[AgentIndex].IsEquivalent(NavConfig) == true)
					{
						// it's supported, then just in case it's not a precise match (IsEquivalent succeeds with some precision) 
						// update NavData with supported Agent
						bAgentSupported = true;

						NavData->SetConfig(SupportedAgents[AgentIndex]);
						AgentToNavDataMap.Add(SupportedAgents[AgentIndex], NavData);
						NavData->SetSupportsDefaultAgent(AgentIndex == 0);
						NavData->ProcessNavAreas(NavAreaClasses, AgentIndex);

						OnNavDataRegisteredEvent.Broadcast(NavData);

						NavDataSet.AddUnique(NavData);
						NavData->OnRegistered();

						break;
					}
				}
				Result = bAgentSupported == true ? RegistrationSuccessful : RegistrationFailed_AgentNotValid;
			}
			else
			{
				// fake registration since it's a special navigation data type 
				// and it would get discarded for not implementing any particular
				// navigation agent
				// Node that we don't add abstract navigation data to NavDataSet
				NavData->OnRegistered();

				Result = RegistrationSuccessful;
			}
		}
		else if (NavDataInstanceForAgent == NavData)
		{
			ensure(NavDataSet.Find(NavData) != INDEX_NONE);
			// let's treat double registration of the same nav data with the same agent as a success
			Result = RegistrationSuccessful;
		}
		else
		{
			// otherwise specified agent type already has its navmesh implemented, fail redundant instance
			Result = RegistrationFailed_AgentAlreadySupported;
		}
	}
	else
	{
		Result = RegistrationFailed_AgentNotValid;
	}

	// @todo else might consider modifying this NavData to implement navigation for one of the supported agents
	// care needs to be taken to not make it implement navigation for agent who's real implementation has 
	// not been loaded yet.

	return Result;
}

void UNavigationSystemV1::UnregisterNavData(ANavigationData* NavData)
{
	NavDataSet.RemoveSingle(NavData);

	if (NavData == NULL)
	{
		return;
	}

	FScopeLock Lock(&NavDataRegistration);
	NavData->OnUnregistered();
}

void UNavigationSystemV1::RegisterCustomLink(INavLinkCustomInterface& CustomLink)
{
	uint32 LinkId = CustomLink.GetLinkId();

	// if there's already a link with that Id registered, assign new Id and mark dirty area
	// this won't fix baked data in static navmesh (in game), but every other case will regenerate affected tiles 
	if (CustomLinksMap.Contains(LinkId))
	{
		LinkId = INavLinkCustomInterface::GetUniqueId();
		CustomLink.UpdateLinkId(LinkId);

		UObject* CustomLinkOb = CustomLink.GetLinkOwner();
		UActorComponent* OwnerComp = Cast<UActorComponent>(CustomLinkOb);
		AActor* OwnerActor = OwnerComp ? OwnerComp->GetOwner() : Cast<AActor>(CustomLinkOb);

		if (OwnerActor)
		{
			ENavLinkDirection::Type DummyDir = ENavLinkDirection::BothWays;
			FVector RelativePtA, RelativePtB;
			CustomLink.GetLinkData(RelativePtA, RelativePtB, DummyDir);

			const FTransform OwnerActorTM = OwnerActor->GetTransform();
			const FVector WorldPtA = OwnerActorTM.TransformPosition(RelativePtA);
			const FVector WorldPtB = OwnerActorTM.TransformPosition(RelativePtB);

			FBox LinkBounds(ForceInitToZero);
			LinkBounds += WorldPtA;
			LinkBounds += WorldPtB;

			AddDirtyArea(LinkBounds, OctreeUpdate_Modifiers);
		}
	}

	CustomLinksMap.Add(LinkId, FNavigationSystem::FCustomLinkOwnerInfo(&CustomLink));
}

void UNavigationSystemV1::UnregisterCustomLink(INavLinkCustomInterface& CustomLink)
{
	CustomLinksMap.Remove(CustomLink.GetLinkId());
}

INavLinkCustomInterface* UNavigationSystemV1::GetCustomLink(uint32 UniqueLinkId) const
{
	const FNavigationSystem::FCustomLinkOwnerInfo* LinkInfo = CustomLinksMap.Find(UniqueLinkId);
	return (LinkInfo && LinkInfo->IsValid()) ? LinkInfo->LinkInterface : nullptr;
}

void UNavigationSystemV1::UpdateCustomLink(const INavLinkCustomInterface* CustomLink)
{
	for (TMap<FNavAgentProperties, TWeakObjectPtr<ANavigationData> >::TIterator It(AgentToNavDataMap); It; ++It)
	{
		ANavigationData* NavData = It.Value().Get();
		if (NavData)
		{
			NavData->UpdateCustomLink(CustomLink);
		}
	}
}

void UNavigationSystemV1::RequestCustomLinkRegistering(INavLinkCustomInterface& CustomLink, UObject* OwnerOb)
{
	UNavigationSystemV1* NavSys = FNavigationSystem::GetCurrent<UNavigationSystemV1>(OwnerOb);
	if (NavSys)
	{
		NavSys->RegisterCustomLink(CustomLink);
	}
	else
	{
		FScopeLock AccessLock(&CustomLinkRegistrationSection);
		PendingCustomLinkRegistration.Add(&CustomLink, OwnerOb);
	}
}

void UNavigationSystemV1::RequestCustomLinkUnregistering(INavLinkCustomInterface& CustomLink, UObject* OwnerOb)
{
	UNavigationSystemV1* NavSys = FNavigationSystem::GetCurrent<UNavigationSystemV1>(OwnerOb);
	if (NavSys)
	{
		NavSys->UnregisterCustomLink(CustomLink);
	}
	else
	{
		FScopeLock AccessLock(&CustomLinkRegistrationSection);
		PendingCustomLinkRegistration.Remove(&CustomLink);
	}
}

void UNavigationSystemV1::RequestAreaUnregistering(UClass* NavAreaClass)
{
	for (TObjectIterator<UNavigationSystemV1> NavSysIt; NavSysIt; ++NavSysIt)
	{
		NavSysIt->UnregisterNavAreaClass(NavAreaClass);
	}
}

void UNavigationSystemV1::UnregisterNavAreaClass(UClass* NavAreaClass)
{
	// remove from known areas
	if (NavAreaClasses.Remove(NavAreaClass) > 0)
	{
		// notify navigation data
		// notify existing nav data
		OnNavigationAreaEvent(NavAreaClass, ENavAreaEvent::Unregistered);
	}
}

void UNavigationSystemV1::RequestAreaRegistering(UClass* NavAreaClass)
{
	for (TObjectIterator<UNavigationSystemV1> NavSysIt; NavSysIt; ++NavSysIt)
	{
		NavSysIt->RegisterNavAreaClass(NavAreaClass);
	}
}

void UNavigationSystemV1::RegisterNavAreaClass(UClass* AreaClass)
{
	// can't be null
	if (AreaClass == NULL)
	{
		return;
	}

	// can't be abstract
	if (AreaClass->HasAnyClassFlags(CLASS_Abstract))
	{
		return;
	}

	// special handling of blueprint based areas
	if (AreaClass->HasAnyClassFlags(CLASS_CompiledFromBlueprint))
	{
		// can't be skeleton of blueprint class
		if (AreaClass->GetName().Contains(TEXT("SKEL_")))
		{
			return;
		}

		// can't be class from Developers folder (won't be saved properly anyway)
		const UPackage* Package = AreaClass->GetOutermost();
		if (Package && Package->GetName().Contains(TEXT("/Developers/")))
		{
			return;
		}
	}

	if (NavAreaClasses.Contains(AreaClass))
	{
		// Already added
		return;
	}

	UNavArea* AreaClassCDO = GetMutableDefault<UNavArea>(AreaClass);
	check(AreaClassCDO);

	// initialize flags
	AreaClassCDO->InitializeArea();

	// add to know areas
	NavAreaClasses.Add(AreaClass);

	// notify existing nav data
	OnNavigationAreaEvent(AreaClass, ENavAreaEvent::Registered);

#if WITH_EDITOR
	UNavAreaMeta_SwitchByAgent* SwitchByAgentCDO = Cast<UNavAreaMeta_SwitchByAgent>(AreaClassCDO);
	// update area properties
	if (SwitchByAgentCDO)
	{
		SwitchByAgentCDO->UpdateAgentConfig();
	}
#endif
}

void UNavigationSystemV1::OnNavigationAreaEvent(UClass* AreaClass, ENavAreaEvent::Type Event)
{
	// notify existing nav data
	for (auto NavigationData : NavDataSet)
	{
		if (NavigationData != NULL && NavigationData->IsPendingKillPending() == false)
		{
			NavigationData->OnNavAreaEvent(AreaClass, Event);
		}
	}
}

int32 UNavigationSystemV1::GetSupportedAgentIndex(const ANavigationData* NavData) const
{
	if (SupportedAgents.Num() < 2)
	{
		return 0;
	}

	const FNavDataConfig& TestConfig = NavData->GetConfig();
	for (int32 AgentIndex = 0; AgentIndex < SupportedAgents.Num(); AgentIndex++)
	{
		if (SupportedAgents[AgentIndex].IsEquivalent(TestConfig))
		{
			return AgentIndex;
		}
	}
	
	return INDEX_NONE;
}

int32 UNavigationSystemV1::GetSupportedAgentIndex(const FNavAgentProperties& NavAgent) const
{
	if (SupportedAgents.Num() < 2)
	{
		return 0;
	}

	for (int32 AgentIndex = 0; AgentIndex < SupportedAgents.Num(); AgentIndex++)
	{
		if (SupportedAgents[AgentIndex].IsEquivalent(NavAgent))
		{
			return AgentIndex;
		}
	}

	return INDEX_NONE;
}

void UNavigationSystemV1::DescribeFilterFlags(UEnum* FlagsEnum) const
{
#if WITH_EDITOR
	TArray<FString> FlagDesc;
	FString EmptyStr;
	FlagDesc.Init(EmptyStr, 16);

	const int32 NumEnums = FMath::Min(16, FlagsEnum->NumEnums() - 1);	// skip _MAX
	for (int32 FlagIndex = 0; FlagIndex < NumEnums; FlagIndex++)
	{
		FlagDesc[FlagIndex] = FlagsEnum->GetDisplayNameTextByIndex(FlagIndex).ToString();
	}

	DescribeFilterFlags(FlagDesc);
#endif
}

void UNavigationSystemV1::DescribeFilterFlags(const TArray<FString>& FlagsDesc) const
{
#if WITH_EDITOR
	const int32 MaxFlags = 16;
	TArray<FString> UseDesc = FlagsDesc;

	FString EmptyStr;
	while (UseDesc.Num() < MaxFlags)
	{
		UseDesc.Add(EmptyStr);
	}

	// get special value from recast's navmesh
#if WITH_RECAST
	uint16 NavLinkFlag = ARecastNavMesh::GetNavLinkFlag();
	for (int32 FlagIndex = 0; FlagIndex < MaxFlags; FlagIndex++)
	{
		if ((NavLinkFlag >> FlagIndex) & 1)
		{
			UseDesc[FlagIndex] = TEXT("Navigation link");
			break;
		}
	}
#endif

	// setup properties
	UStructProperty* StructProp1 = FindField<UStructProperty>(UNavigationQueryFilter::StaticClass(), TEXT("IncludeFlags"));
	UStructProperty* StructProp2 = FindField<UStructProperty>(UNavigationQueryFilter::StaticClass(), TEXT("ExcludeFlags"));
	check(StructProp1);
	check(StructProp2);

	UStruct* Structs[] = { StructProp1->Struct, StructProp2->Struct };
	const FString CustomNameMeta = TEXT("DisplayName");

	for (int32 StructIndex = 0; StructIndex < ARRAY_COUNT(Structs); StructIndex++)
	{
		for (int32 FlagIndex = 0; FlagIndex < MaxFlags; FlagIndex++)
		{
			FString PropName = FString::Printf(TEXT("bNavFlag%d"), FlagIndex);
			UProperty* Prop = FindField<UProperty>(Structs[StructIndex], *PropName);
			check(Prop);

			if (UseDesc[FlagIndex].Len())
			{
				Prop->SetPropertyFlags(CPF_Edit);
				Prop->SetMetaData(*CustomNameMeta, *UseDesc[FlagIndex]);
			}
			else
			{
				Prop->ClearPropertyFlags(CPF_Edit);
			}
		}
	}

#endif
}

void UNavigationSystemV1::ResetCachedFilter(TSubclassOf<UNavigationQueryFilter> FilterClass)
{
	for (int32 NavDataIndex = 0; NavDataIndex < NavDataSet.Num(); NavDataIndex++)
	{
		if (NavDataSet[NavDataIndex])
		{
			NavDataSet[NavDataIndex]->RemoveQueryFilter(FilterClass);
		}
	}
}

UNavigationSystemV1* UNavigationSystemV1::CreateNavigationSystem(UWorld* WorldOwner)
{
	UNavigationSystemV1* NavSys = NULL;

	// create navigation system for editor and server targets, but remove it from game clients
	if (WorldOwner && (*GEngine->NavigationSystemClass != nullptr) 
		&& (GEngine->NavigationSystemClass->GetDefaultObject<UNavigationSystemV1>()->bAllowClientSideNavigation || WorldOwner->GetNetMode() != NM_Client))
	{
		AWorldSettings* WorldSettings = WorldOwner->GetWorldSettings();
		if (WorldSettings == NULL || WorldSettings->IsNavigationSystemEnabled())
		{
			NavSys = NewObject<UNavigationSystemV1>(WorldOwner, GEngine->NavigationSystemClass);		
			WorldOwner->SetNavigationSystem(NavSys);
		}
	}

	return NavSys;
}

void UNavigationSystemV1::InitializeForWorld(UWorld& World, FNavigationSystemRunMode Mode)
{
	OnWorldInitDone(Mode);
}

UNavigationSystemV1* UNavigationSystemV1::GetCurrent(UWorld* World)
{
	return FNavigationSystem::GetCurrent<UNavigationSystemV1>(World);
}

UNavigationSystemV1* UNavigationSystemV1::GetCurrent(UObject* WorldContextObject)
{
	return FNavigationSystem::GetCurrent<UNavigationSystemV1>(WorldContextObject);
}

ANavigationData* UNavigationSystemV1::GetNavDataWithID(const uint16 NavDataID) const
{
	for (int32 NavDataIndex = 0; NavDataIndex < NavDataSet.Num(); ++NavDataIndex)
	{
		const ANavigationData* NavData = NavDataSet[NavDataIndex];
		if (NavData != NULL && NavData->GetNavDataUniqueID() == NavDataID)
		{
			return const_cast<ANavigationData*>(NavData);
		}
	}

	return NULL;
}

void UNavigationSystemV1::AddDirtyArea(const FBox& NewArea, int32 Flags)
{
	if (Flags > 0 && bCanAccumulateDirtyAreas && NewArea.IsValid)
	{
		DirtyAreas.Add(FNavigationDirtyArea(NewArea, Flags));
	}
#if !UE_BUILD_SHIPPING
	bDirtyAreasReportedWhileAccumulationLocked = bDirtyAreasReportedWhileAccumulationLocked || (Flags > 0 && !bCanAccumulateDirtyAreas);
#endif // !UE_BUILD_SHIPPING
}

void UNavigationSystemV1::AddDirtyAreas(const TArray<FBox>& NewAreas, int32 Flags)
{ 
	for (int32 NewAreaIndex = 0; NewAreaIndex < NewAreas.Num(); NewAreaIndex++)
	{
		AddDirtyArea(NewAreas[NewAreaIndex], Flags);
	}
}

bool UNavigationSystemV1::HasDirtyAreasQueued() const
{
	return DirtyAreas.Num() > 0;
}

int32 GetDirtyFlagHelper(int32 UpdateFlags, int32 DefaultValue)
{
	return ((UpdateFlags & UNavigationSystemV1::OctreeUpdate_Geometry) != 0) ? ENavigationDirtyFlag::All :
		((UpdateFlags & UNavigationSystemV1::OctreeUpdate_Modifiers) != 0) ? ENavigationDirtyFlag::DynamicModifier :		
		DefaultValue;
}

FSetElementId UNavigationSystemV1::RegisterNavOctreeElement(UObject* ElementOwner, INavRelevantInterface* ElementInterface, int32 UpdateFlags)
{
	FSetElementId SetId;

#if WITH_EDITOR
	if (IsNavigationRegisterLocked())
	{
		return SetId;
	}
#endif

	if (NavOctree.IsValid() == false || ElementOwner == NULL || ElementInterface == NULL)
	{
		return SetId;
	}

	if (IsNavigationOctreeLocked())
	{
		UE_LOG(LogNavOctree, Log, TEXT("IGNORE(RegisterNavOctreeElement) %s"), *GetPathNameSafe(ElementOwner));
		return SetId;
	}

	const bool bIsRelevant = ElementInterface->IsNavigationRelevant();
	UE_LOG(LogNavOctree, Log, TEXT("REG %s %s"), *GetNameSafe(ElementOwner), bIsRelevant ? TEXT("[relevant]") : TEXT(""));

	if (bIsRelevant)
	{
		bool bCanAdd = false;

		UObject* ParentNode = ElementInterface->GetNavigationParent();
		if (ParentNode)
		{
			OctreeChildNodesMap.AddUnique(ParentNode, FWeakObjectPtr(ElementOwner));
			bCanAdd = true;
		}
		else
		{
			const FOctreeElementId* ElementId = GetObjectsNavOctreeId(*ElementOwner);
			bCanAdd = (ElementId == NULL);
		}

		if (bCanAdd)
		{
			FNavigationDirtyElement UpdateInfo(ElementOwner, ElementInterface, GetDirtyFlagHelper(UpdateFlags, 0));

			SetId = PendingOctreeUpdates.FindId(UpdateInfo);
			if (SetId.IsValidId())
			{
				// make sure this request stays, in case it has been invalidated already
				PendingOctreeUpdates[SetId] = UpdateInfo;
			}
			else
			{
				SetId = PendingOctreeUpdates.Add(UpdateInfo);
			}
		}
	}

	return SetId;
}

void UNavigationSystemV1::AddElementToNavOctree(const FNavigationDirtyElement& DirtyElement)
{
	// handle invalidated requests first
	if (DirtyElement.bInvalidRequest)
	{
		if (DirtyElement.bHasPrevData)
		{
			AddDirtyArea(DirtyElement.PrevBounds, DirtyElement.PrevFlags);
		}
		
		return;
	}

	UObject* ElementOwner = DirtyElement.Owner.Get();
	if (ElementOwner == NULL || ElementOwner->IsPendingKill() || DirtyElement.NavInterface == NULL)
	{
		return;
	}

	FNavigationOctreeElement GeneratedData(*ElementOwner);
	const FBox ElementBounds = DirtyElement.NavInterface->GetNavigationBounds();

	UObject* NavigationParent = DirtyElement.NavInterface->GetNavigationParent();
	if (NavigationParent)
	{
		// check if parent node is waiting in queue
		const FSetElementId ParentRequestId = PendingOctreeUpdates.FindId(FNavigationDirtyElement(NavigationParent));
		const FOctreeElementId* ParentId = GetObjectsNavOctreeId(*NavigationParent);
		if (ParentRequestId.IsValidId() && ParentId == NULL)
		{
			FNavigationDirtyElement& ParentNode = PendingOctreeUpdates[ParentRequestId];
			AddElementToNavOctree(ParentNode);

			// mark as invalid so it won't be processed twice
			ParentNode.bInvalidRequest = true;
		}

		const FOctreeElementId* UseParentId = ParentId ? ParentId : GetObjectsNavOctreeId(*NavigationParent);
		if (UseParentId && NavOctree->IsValidElementId(*UseParentId))
		{
			UE_LOG(LogNavOctree, Log, TEXT("ADD %s to %s"), *GetNameSafe(ElementOwner), *GetNameSafe(NavigationParent));
			NavOctree->AppendToNode(*UseParentId, DirtyElement.NavInterface, ElementBounds, GeneratedData);
		}
		else 
		{
			UE_LOG(LogNavOctree, Warning, TEXT("Can't add node [%s] - parent [%s] not found in octree!"), *GetNameSafe(ElementOwner), *GetNameSafe(NavigationParent));
		}
	}
	else
	{
		UE_LOG(LogNavOctree, Log, TEXT("ADD %s"), *GetNameSafe(ElementOwner));
		NavOctree->AddNode(ElementOwner, DirtyElement.NavInterface, ElementBounds, GeneratedData);
	}

	const FBox BBox = GeneratedData.Bounds.GetBox();
	const bool bValidBBox = BBox.IsValid && !BBox.GetSize().IsNearlyZero();

	if (bValidBBox && !GeneratedData.IsEmpty())
	{
		const int32 DirtyFlag = DirtyElement.FlagsOverride ? DirtyElement.FlagsOverride : GeneratedData.Data->GetDirtyFlag();
		AddDirtyArea(BBox, DirtyFlag);
	}
}

bool UNavigationSystemV1::GetNavOctreeElementData(const UObject& NodeOwner, int32& DirtyFlags, FBox& DirtyBounds)
{
	const FOctreeElementId* ElementId = GetObjectsNavOctreeId(NodeOwner);
	if (ElementId != NULL)
	{
		if (NavOctree->IsValidElementId(*ElementId))
		{
			// mark area occupied by given actor as dirty
			FNavigationOctreeElement& ElementData = NavOctree->GetElementById(*ElementId);
			DirtyFlags = ElementData.Data->GetDirtyFlag();
			DirtyBounds = ElementData.Bounds.GetBox();
			return true;
		}
	}

	return false;
}

void UNavigationSystemV1::UnregisterNavOctreeElement(UObject* ElementOwner, INavRelevantInterface* ElementInterface, int32 UpdateFlags)
{
#if WITH_EDITOR
	if (IsNavigationUnregisterLocked())
	{
		return;
	}
#endif

	if (NavOctree.IsValid() == false || ElementOwner == NULL || ElementInterface == NULL)
	{
		return;
	}

	if (IsNavigationOctreeLocked())
	{
		UE_LOG(LogNavOctree, Log, TEXT("IGNORE(UnregisterNavOctreeElement) %s"), *GetPathNameSafe(ElementOwner));
		return;
	}

	const FOctreeElementId* ElementId = GetObjectsNavOctreeId(*ElementOwner);
	UE_LOG(LogNavOctree, Log, TEXT("UNREG %s %s"), *GetNameSafe(ElementOwner), ElementId ? TEXT("[exists]") : TEXT(""));

	if (ElementId != NULL)
	{
		RemoveNavOctreeElementId(*ElementId, UpdateFlags);
		RemoveObjectsNavOctreeId(*ElementOwner);
	}
	else
	{
		const bool bCanRemoveChildNode = (UpdateFlags & OctreeUpdate_ParentChain) == 0;
		UObject* ParentNode = ElementInterface->GetNavigationParent();
		if (ParentNode && bCanRemoveChildNode)
		{
			// if node has navigation parent (= doesn't exists in octree on its own)
			// and it's not part of parent chain update
			// remove it from map and force update on parent to rebuild octree element

			OctreeChildNodesMap.RemoveSingle(ParentNode, FWeakObjectPtr(ElementOwner));
			UpdateNavOctreeParentChain(ParentNode);
		}
	}

	// mark pending update as invalid, it will be dirtied according to currently active settings
	const bool bCanInvalidateQueue = (UpdateFlags & OctreeUpdate_Refresh) == 0;
	if (bCanInvalidateQueue)
	{
		const FSetElementId RequestId = PendingOctreeUpdates.FindId(FNavigationDirtyElement(ElementOwner));
		if (RequestId.IsValidId())
		{
			PendingOctreeUpdates[RequestId].bInvalidRequest = true;
		}
	}
}

void UNavigationSystemV1::RemoveNavOctreeElementId(const FOctreeElementId& ElementId, int32 UpdateFlags)
{
	if (NavOctree->IsValidElementId(ElementId))
	{
		const FNavigationOctreeElement& ElementData = NavOctree->GetElementById(ElementId);
		const int32 DirtyFlag = GetDirtyFlagHelper(UpdateFlags, ElementData.Data->GetDirtyFlag());
		// mark area occupied by given actor as dirty
		AddDirtyArea(ElementData.Bounds.GetBox(), DirtyFlag);
		NavOctree->RemoveNode(ElementId);
	}
}

const FNavigationRelevantData* UNavigationSystemV1::GetDataForObject(const UObject& Object) const
{
	check(NavOctree.IsValid());

	const FOctreeElementId* OctreeID = GetObjectsNavOctreeId(Object);

	if (OctreeID != nullptr && OctreeID->IsValidId() == true)
	{
		return NavOctree->GetDataForID(*OctreeID);
	}

	return nullptr;
}

void UNavigationSystemV1::UpdateActorInNavOctree(AActor& Actor)
{
	if (IsNavigationSystemStatic())
	{
		return;
	}
	SCOPE_CYCLE_COUNTER(STAT_DebugNavOctree);

	INavRelevantInterface* NavElement = Cast<INavRelevantInterface>(&Actor);
	if (NavElement)
	{
		UNavigationSystemV1* NavSys = FNavigationSystem::GetCurrent<UNavigationSystemV1>(Actor.GetWorld());
		if (NavSys)
		{
			NavSys->UpdateNavOctreeElement(&Actor, NavElement, OctreeUpdate_Default);
		}
	}
}

void UNavigationSystemV1::UpdateComponentInNavOctree(UActorComponent& Comp)
{
	SCOPE_CYCLE_COUNTER(STAT_DebugNavOctree);

	if (ShouldUpdateNavOctreeOnComponentChange() == false)
	{
		return;
	}

	// special case for early out: use cached nav relevancy
	if (Comp.bNavigationRelevant == true)
	{
		INavRelevantInterface* NavElement = Cast<INavRelevantInterface>(&Comp);
		if (NavElement)
		{
			AActor* OwnerActor = Comp.GetOwner();
			if (OwnerActor)
			{
				UNavigationSystemV1* NavSys = FNavigationSystem::GetCurrent<UNavigationSystemV1>(OwnerActor->GetWorld());
				if (NavSys)
				{
					if (OwnerActor->IsComponentRelevantForNavigation(&Comp))
					{
						NavSys->UpdateNavOctreeElement(&Comp, NavElement, OctreeUpdate_Default);
					}
					else
					{
						NavSys->UnregisterNavOctreeElement(&Comp, NavElement, OctreeUpdate_Default);
					}
				}
			}
		}
	}
	else if (Comp.CanEverAffectNavigation()) 
	{
		// could have been relevant before and not it isn't. Need to check if there's an octree element ID for it
		INavRelevantInterface* NavElement = Cast<INavRelevantInterface>(&Comp);
		if (NavElement)
		{
			AActor* OwnerActor = Comp.GetOwner();
			if (OwnerActor)
			{
				UNavigationSystemV1* NavSys = FNavigationSystem::GetCurrent<UNavigationSystemV1>(OwnerActor->GetWorld());
				if (NavSys)
				{
					NavSys->UnregisterNavOctreeElement(&Comp, NavElement, OctreeUpdate_Default);
				}
			}
		}
	}
}

void UNavigationSystemV1::UpdateActorAndComponentsInNavOctree(AActor& Actor, bool bUpdateAttachedActors)
{
	UpdateActorInNavOctree(Actor);
		
	for (UActorComponent* Component : Actor.GetComponents())
	{
		if (Component)
		{
			UpdateComponentInNavOctree(*Component);
		}
	}

	if (bUpdateAttachedActors)
	{
		UpdateAttachedActorsInNavOctree(Actor);
	}
}

void UNavigationSystemV1::UpdateNavOctreeAfterMove(USceneComponent* Comp)
{
	AActor* OwnerActor = Comp->GetOwner();
	if (OwnerActor && OwnerActor->GetRootComponent() == Comp)
	{
		UpdateActorAndComponentsInNavOctree(*OwnerActor, true);
	}
}

void UNavigationSystemV1::UpdateAttachedActorsInNavOctree(AActor& RootActor)
{
	TArray<AActor*> UniqueAttachedActors;
	UniqueAttachedActors.Add(&RootActor);

	TArray<AActor*> TempAttachedActors;
	for (int32 ActorIndex = 0; ActorIndex < UniqueAttachedActors.Num(); ++ActorIndex)
	{
		check(UniqueAttachedActors[ActorIndex]);
		// find all attached actors
		UniqueAttachedActors[ActorIndex]->GetAttachedActors(TempAttachedActors);
		
		for (int32 AttachmentIndex = 0; AttachmentIndex < TempAttachedActors.Num(); ++AttachmentIndex)
		{
			// and store the ones we don't know about yet
			UniqueAttachedActors.AddUnique(TempAttachedActors[AttachmentIndex]);
		}
	}
	
	// skipping the first item since that's the root, and we just care about the attached actors
	for (int32 ActorIndex = 1; ActorIndex < UniqueAttachedActors.Num(); ++ActorIndex)
	{
		UpdateActorAndComponentsInNavOctree(*UniqueAttachedActors[ActorIndex], /*bUpdateAttachedActors = */false);
	}
}

void UNavigationSystemV1::UpdateNavOctreeBounds(AActor* Actor)
{
	for (UActorComponent* Component : Actor->GetComponents())
	{
		INavRelevantInterface* NavElement = Cast<INavRelevantInterface>(Component);
		if (NavElement)
		{
			NavElement->UpdateNavigationBounds();
		}
	}
}

void UNavigationSystemV1::ClearNavOctreeAll(AActor* Actor)
{
	if (Actor)
	{
		OnActorUnregistered(Actor);

		TInlineComponentArray<UActorComponent*> Components;
		Actor->GetComponents(Components);

		for (int32 Idx = 0; Idx < Components.Num(); Idx++)
		{
			OnComponentUnregistered(Components[Idx]);
		}
	}
}

void UNavigationSystemV1::UpdateNavOctreeElement(UObject* ElementOwner, INavRelevantInterface* ElementInterface, int32 UpdateFlags)
{
	INC_DWORD_STAT(STAT_Navigation_UpdateNavOctree);

	if (IsNavigationOctreeLocked())
	{
		UE_LOG(LogNavOctree, Log, TEXT("IGNORE(UpdateNavOctreeElement) %s"), *GetPathNameSafe(ElementOwner));
		return;
	}
	else if (ElementOwner == nullptr)
	{
		return;
	}

	// grab existing octree data
	FBox CurrentBounds;
	int32 CurrentFlags;
	const bool bAlreadyExists = GetNavOctreeElementData(*ElementOwner, CurrentFlags, CurrentBounds);

	// don't invalidate pending requests
	UpdateFlags |= OctreeUpdate_Refresh;

	// always try to unregister, even if element owner doesn't exists in octree (parent nodes)
	UnregisterNavOctreeElement(ElementOwner, ElementInterface, UpdateFlags);

	const FSetElementId RequestId = RegisterNavOctreeElement(ElementOwner, ElementInterface, UpdateFlags);

	// add original data to pending registration request
	// so it could be dirtied properly when system receive unregister request while actor is still queued
	if (RequestId.IsValidId())
	{
		FNavigationDirtyElement& UpdateInfo = PendingOctreeUpdates[RequestId];
		UpdateInfo.PrevFlags = CurrentFlags;
		if (UpdateInfo.PrevBounds.IsValid)
		{
			// Is we have something stored already we want to 
			// sum it up, since we care about the whole bounding
			// box of changes that potentially took place
			UpdateInfo.PrevBounds += CurrentBounds;
		}
		else
		{
			UpdateInfo.PrevBounds = CurrentBounds;
		}
		UpdateInfo.bHasPrevData = bAlreadyExists;
	}

	UpdateNavOctreeParentChain(ElementOwner, /*bSkipElementOwnerUpdate=*/ true);
}

void UNavigationSystemV1::UpdateNavOctreeParentChain(UObject* ElementOwner, bool bSkipElementOwnerUpdate)
{
	const int32 UpdateFlags = OctreeUpdate_ParentChain | OctreeUpdate_Refresh;

	TArray<FWeakObjectPtr> ChildNodes;
	OctreeChildNodesMap.MultiFind(ElementOwner, ChildNodes);

	if (ChildNodes.Num() == 0)
	{
		if (bSkipElementOwnerUpdate == false)
		{
			INavRelevantInterface* ElementInterface = Cast<INavRelevantInterface>(ElementOwner);
			UpdateNavOctreeElement(ElementOwner, ElementInterface, UpdateFlags);
		}
		return;
	}

	INavRelevantInterface* ElementInterface = Cast<INavRelevantInterface>(ElementOwner);
	TArray<INavRelevantInterface*> ChildNavInterfaces;
	ChildNavInterfaces.AddZeroed(ChildNodes.Num());
	
	for (int32 Idx = 0; Idx < ChildNodes.Num(); Idx++)
	{
		if (ChildNodes[Idx].IsValid())
		{
			UObject* ChildNodeOb = ChildNodes[Idx].Get();
			ChildNavInterfaces[Idx] = Cast<INavRelevantInterface>(ChildNodeOb);
			UnregisterNavOctreeElement(ChildNodeOb, ChildNavInterfaces[Idx], UpdateFlags);
		}
	}

	if (bSkipElementOwnerUpdate == false)
	{
		UnregisterNavOctreeElement(ElementOwner, ElementInterface, UpdateFlags);
		RegisterNavOctreeElement(ElementOwner, ElementInterface, UpdateFlags);
	}

	for (int32 Idx = 0; Idx < ChildNodes.Num(); Idx++)
	{
		if (ChildNodes[Idx].IsValid())
		{
			RegisterNavOctreeElement(ChildNodes[Idx].Get(), ChildNavInterfaces[Idx], UpdateFlags);
		}
	}
}

bool UNavigationSystemV1::UpdateNavOctreeElementBounds(UActorComponent* Comp, const FBox& NewBounds, const FBox& DirtyArea)
{
	if (Comp == nullptr)
	{
		return false;
	}

	const FOctreeElementId* ElementId = GetObjectsNavOctreeId(*Comp);
	if (ElementId && ElementId->IsValidId())
	{
		NavOctree->UpdateNode(*ElementId, NewBounds);
		
		// Add dirty area
		if (DirtyArea.IsValid)
		{
			ElementId = GetObjectsNavOctreeId(*Comp);
			if (ElementId && ElementId->IsValidId())
			{
				FNavigationOctreeElement& ElementData = NavOctree->GetElementById(*ElementId);
				AddDirtyArea(DirtyArea, ElementData.Data->GetDirtyFlag());
			}
		}

		return true;
	}
	
	return false;
}

void UNavigationSystemV1::OnComponentRegistered(UActorComponent* Comp)
{
	if (IsNavigationSystemStatic())
	{
		return;
	}

	SCOPE_CYCLE_COUNTER(STAT_DebugNavOctree);
	INavRelevantInterface* NavInterface = Cast<INavRelevantInterface>(Comp);
	if (NavInterface)
	{
		AActor* OwnerActor = Comp ? Comp->GetOwner() : NULL;
		if (OwnerActor && OwnerActor->IsComponentRelevantForNavigation(Comp))
		{
			UNavigationSystemV1* NavSys = FNavigationSystem::GetCurrent<UNavigationSystemV1>(OwnerActor->GetWorld());
			if (NavSys)
			{
				NavSys->RegisterNavOctreeElement(Comp, NavInterface, OctreeUpdate_Default);
			}
		}
	}
}

void UNavigationSystemV1::OnComponentUnregistered(UActorComponent* Comp)
{
	if (IsNavigationSystemStatic())
	{
		return;
	}

	SCOPE_CYCLE_COUNTER(STAT_DebugNavOctree);
	INavRelevantInterface* NavInterface = Cast<INavRelevantInterface>(Comp);
	if (NavInterface)
	{
		AActor* OwnerActor = Comp ? Comp->GetOwner() : NULL;
		if (OwnerActor)
		{
			// skip IsComponentRelevantForNavigation check, it's only for adding new stuff

			UNavigationSystemV1* NavSys = FNavigationSystem::GetCurrent<UNavigationSystemV1>(OwnerActor->GetWorld());
			if (NavSys)
			{
				NavSys->UnregisterNavOctreeElement(Comp, NavInterface, OctreeUpdate_Default);
			}
		}
	}
}

void UNavigationSystemV1::OnActorRegistered(AActor* Actor)
{
	if (IsNavigationSystemStatic())
	{
		return;
	}

	SCOPE_CYCLE_COUNTER(STAT_DebugNavOctree);
	INavRelevantInterface* NavInterface = Cast<INavRelevantInterface>(Actor);
	if (NavInterface)
	{
		UNavigationSystemV1* NavSys = FNavigationSystem::GetCurrent<UNavigationSystemV1>(Actor->GetWorld());
		if (NavSys)
		{
			NavSys->RegisterNavOctreeElement(Actor, NavInterface, OctreeUpdate_Default);
		}
	}
}

void UNavigationSystemV1::OnActorUnregistered(AActor* Actor)
{
	if (IsNavigationSystemStatic())
	{
		return;
	}

	SCOPE_CYCLE_COUNTER(STAT_DebugNavOctree);
	INavRelevantInterface* NavInterface = Cast<INavRelevantInterface>(Actor);
	if (NavInterface)
	{
		UNavigationSystemV1* NavSys = FNavigationSystem::GetCurrent<UNavigationSystemV1>(Actor->GetWorld());
		if (NavSys)
		{
			NavSys->UnregisterNavOctreeElement(Actor, NavInterface, OctreeUpdate_Default);
		}
	}
}

void UNavigationSystemV1::FindElementsInNavOctree(const FBox& QueryBox, const FNavigationOctreeFilter& Filter, TArray<FNavigationOctreeElement>& Elements)
{
	if (NavOctree.IsValid() == false)
	{
		UE_LOG(LogNavigation, Warning, TEXT("UNavigationSystemV1::FindElementsInNavOctree gets called while NavOctree is null"));
		return;
	}
	
	for (FNavigationOctree::TConstElementBoxIterator<> It(*NavOctree, QueryBox); It.HasPendingElements(); It.Advance())
	{
		const FNavigationOctreeElement& Element = It.GetCurrentElement();
		if (Element.IsMatchingFilter(Filter))
		{
			Elements.Add(Element);
		}		
	}
}

void UNavigationSystemV1::ReleaseInitialBuildingLock()
{
	RemoveNavigationBuildLock(ENavigationBuildLock::InitialLock);
}

void UNavigationSystemV1::InitializeLevelCollisions()
{
	if (IsNavigationSystemStatic())
	{
		bInitialLevelsAdded = true;
		return;
	}

	UWorld* World = GetWorld();
	if (!bInitialLevelsAdded && FNavigationSystem::GetCurrent<UNavigationSystemV1>(World) == this)
	{
		// Process all visible levels
		const auto& Levels = World->GetLevels();
		for (ULevel* Level : Levels)
		{
			if (Level->bIsVisible)
			{
				AddLevelCollisionToOctree(Level);
			}
		}

		bInitialLevelsAdded = true;
	}
}

#if WITH_EDITOR
void UNavigationSystemV1::UpdateLevelCollision(ULevel* InLevel)
{
	if (InLevel != NULL)
	{
		UWorld* World = GetWorld();
		OnLevelRemovedFromWorld(InLevel, World);
		OnLevelAddedToWorld(InLevel, World);
	}
}

void UNavigationSystemV1::OnEditorModeChanged(FEdMode* Mode, bool IsEntering)
{
	if (Mode == NULL)
	{
		return;
	}

	if (IsEntering == false && Mode->GetID() == FBuiltinEditorModes::EM_Geometry)
	{
		// check if any of modified brushes belongs to an ANavMeshBoundsVolume
		FEdModeGeometry* GeometryMode = (FEdModeGeometry*)Mode;
		for (auto GeomObjectIt = GeometryMode->GeomObjectItor(); GeomObjectIt; GeomObjectIt++)
		{
			ANavMeshBoundsVolume* Volume = Cast<ANavMeshBoundsVolume>((*GeomObjectIt)->GetActualBrush());
			if (Volume)
			{
				OnNavigationBoundsUpdated(Volume);
			}
		}
	}
}
#endif

void UNavigationSystemV1::OnNavigationBoundsUpdated(ANavMeshBoundsVolume* NavVolume)
{
	if (NavVolume == nullptr || IsNavigationSystemStatic())
	{
		return;
	}

	FNavigationBoundsUpdateRequest UpdateRequest;
	UpdateRequest.NavBounds.UniqueID = NavVolume->GetUniqueID();
	UpdateRequest.NavBounds.AreaBox = NavVolume->GetComponentsBoundingBox(true);
	UpdateRequest.NavBounds.Level = NavVolume->GetLevel();
	UpdateRequest.NavBounds.SupportedAgents = NavVolume->SupportedAgents;
	
	UpdateRequest.UpdateRequest = FNavigationBoundsUpdateRequest::Updated;
	AddNavigationBoundsUpdateRequest(UpdateRequest);
}

void UNavigationSystemV1::OnNavigationBoundsAdded(ANavMeshBoundsVolume* NavVolume)
{
	if (NavVolume == nullptr || IsNavigationSystemStatic())
	{
		return;
	}

	FNavigationBoundsUpdateRequest UpdateRequest;
	UpdateRequest.NavBounds.UniqueID = NavVolume->GetUniqueID();
	UpdateRequest.NavBounds.AreaBox = NavVolume->GetComponentsBoundingBox(true);
	UpdateRequest.NavBounds.Level = NavVolume->GetLevel();
	UpdateRequest.NavBounds.SupportedAgents = NavVolume->SupportedAgents;

	UpdateRequest.UpdateRequest = FNavigationBoundsUpdateRequest::Added;
	AddNavigationBoundsUpdateRequest(UpdateRequest);
}

void UNavigationSystemV1::OnNavigationBoundsRemoved(ANavMeshBoundsVolume* NavVolume)
{
	if (NavVolume == nullptr || IsNavigationSystemStatic())
	{
		return;
	}
	
	FNavigationBoundsUpdateRequest UpdateRequest;
	UpdateRequest.NavBounds.UniqueID = NavVolume->GetUniqueID();
	UpdateRequest.NavBounds.AreaBox = NavVolume->GetComponentsBoundingBox(true);
	UpdateRequest.NavBounds.Level = NavVolume->GetLevel();
	UpdateRequest.NavBounds.SupportedAgents = NavVolume->SupportedAgents;

	UpdateRequest.UpdateRequest = FNavigationBoundsUpdateRequest::Removed;
	AddNavigationBoundsUpdateRequest(UpdateRequest);
}

void UNavigationSystemV1::AddNavigationBoundsUpdateRequest(const FNavigationBoundsUpdateRequest& UpdateRequest)
{
	int32 ExistingIdx = PendingNavBoundsUpdates.IndexOfByPredicate([&](const FNavigationBoundsUpdateRequest& Element) {
		return UpdateRequest.NavBounds.UniqueID == Element.NavBounds.UniqueID;
	});

	if (ExistingIdx != INDEX_NONE)
	{
		// catch the case where the bounds was removed and immediately re-added with the same bounds as before
		// in that case, we can cancel any update at all
		bool bCanCancelUpdate = false;
		if (PendingNavBoundsUpdates[ExistingIdx].UpdateRequest == FNavigationBoundsUpdateRequest::Removed && UpdateRequest.UpdateRequest == FNavigationBoundsUpdateRequest::Added)
		{
			for (TSet<FNavigationBounds>::TConstIterator It(RegisteredNavBounds); It; ++It)
			{
				if (*It == UpdateRequest.NavBounds)
				{
					bCanCancelUpdate = true;
					break;
				}
			}
		}
		if (bCanCancelUpdate)
		{
			PendingNavBoundsUpdates.RemoveAt(ExistingIdx);
		}
		else
		{
			// Overwrite any previous updates
			PendingNavBoundsUpdates[ExistingIdx] = UpdateRequest;
		}
	}
	else
	{
		PendingNavBoundsUpdates.Add(UpdateRequest);
	}
}

void UNavigationSystemV1::PerformNavigationBoundsUpdate(const TArray<FNavigationBoundsUpdateRequest>& UpdateRequests)
{
	// NOTE: we used to create missing nav data first, before updating nav bounds, 
	// but some nav data classes (like RecastNavMesh) may depend on the nav bounds
	// being already known at the moment of creation or serialization, so it makes more 
	// sense to update bounds first 

	// Create list of areas that needs to be updated
	TArray<FBox> UpdatedAreas;
	for (const FNavigationBoundsUpdateRequest& Request : UpdateRequests)
	{
		FSetElementId ExistingElementId = RegisteredNavBounds.FindId(Request.NavBounds);

		switch (Request.UpdateRequest)
		{
		case FNavigationBoundsUpdateRequest::Removed:
			{
				if (ExistingElementId.IsValidId())
				{
					UpdatedAreas.Add(RegisteredNavBounds[ExistingElementId].AreaBox);
					RegisteredNavBounds.Remove(ExistingElementId);
				}
			}
			break;

		case FNavigationBoundsUpdateRequest::Added:
		case FNavigationBoundsUpdateRequest::Updated:
			{
				if (ExistingElementId.IsValidId())
				{
					const FBox ExistingBox = RegisteredNavBounds[ExistingElementId].AreaBox;
					const bool bSameArea = (Request.NavBounds.AreaBox == ExistingBox);
					if (!bSameArea)
					{
						UpdatedAreas.Add(ExistingBox);
					}

					// always assign new bounds data, it may have different properties (like supported agents)
					RegisteredNavBounds[ExistingElementId] = Request.NavBounds;
				}
				else
				{
					AddNavigationBounds(Request.NavBounds);
				}

				UpdatedAreas.Add(Request.NavBounds.AreaBox);
			}

			break;
		}
	}

	if (!IsNavigationBuildingLocked())
	{
		if (UpdatedAreas.Num())
		{
			for (ANavigationData* NavData : NavDataSet)
			{
				if (NavData)
				{
					NavData->OnNavigationBoundsChanged();	
				}
			}
		}
				
		// Propagate to generators areas that needs to be updated
		AddDirtyAreas(UpdatedAreas, ENavigationDirtyFlag::All | ENavigationDirtyFlag::NavigationBounds);
	}

	// I'm not sure why we even do the following as part of this function
	// @TODO investigate if we can extract it into a separate function and
	// call it directly
	if (NavDataSet.Num() == 0)
	{
		//TODO: will hitch when user places first navigation volume in the world 

		if (NavDataRegistrationQueue.Num() > 0)
		{
			ProcessRegistrationCandidates();
		}

		if (NavDataSet.Num() == 0 && bAutoCreateNavigationData == true)
		{
			SpawnMissingNavigationData();
			ProcessRegistrationCandidates();
		}

		ConditionalPopulateNavOctree();
	}
}

void UNavigationSystemV1::AddNavigationBounds(const FNavigationBounds& NewBounds)
{
	RegisteredNavBounds.Add(NewBounds);
}

void UNavigationSystemV1::GatherNavigationBounds()
{
	// Gather all available navigation bounds
	RegisteredNavBounds.Empty();
	for (TActorIterator<ANavMeshBoundsVolume> It(GetWorld()); It; ++It)
	{
		ANavMeshBoundsVolume* V = (*It);
		if (V != nullptr && !V->IsPendingKill())
		{
			FNavigationBounds NavBounds;
			NavBounds.UniqueID = V->GetUniqueID();
			NavBounds.AreaBox = V->GetComponentsBoundingBox(true);
			NavBounds.Level = V->GetLevel();
			NavBounds.SupportedAgents = V->SupportedAgents;

			AddNavigationBounds(NavBounds);
		}
	}
}

void UNavigationSystemV1::Build()
{
	UWorld* World = GetWorld();
	if (!World)
	{
		UE_LOG(LogNavigation, Error, TEXT("Unable to build navigation due to missing World pointer"));
		return;
	}

	FNavigationSystem::DiscardNavigationDataChunks(*World);

	const bool bHasWork = IsThereAnywhereToBuildNavigation();
	const bool bLockedIgnoreEditor = (NavBuildingLockFlags & ~ENavigationBuildLock::NoUpdateInEditor) != 0;
	if (!bHasWork || bLockedIgnoreEditor)
	{
		return;
	}

	const double BuildStartTime = FPlatformTime::Seconds();

	if (bAutoCreateNavigationData == true
#if WITH_EDITOR
		|| OperationMode == FNavigationSystemRunMode::EditorMode
#endif // WITH_EDITOR
		)
	{
		SpawnMissingNavigationData();
	}

	// make sure freshly created navigation instances are registered before we try to build them
	ProcessRegistrationCandidates();

	// and now iterate through all registered and just start building them
	RebuildAll();

	// Block until build is finished
	for (ANavigationData* NavData : NavDataSet)
	{
		if (NavData)
		{
			NavData->EnsureBuildCompletion();
		}
	}

#if !UE_BUILD_SHIPPING
	// no longer report that navmesh needs to be rebuild
	bDirtyAreasReportedWhileAccumulationLocked = false;
#endif // !UE_BUILD_SHIPPING

	UE_LOG(LogNavigation, Display, TEXT("UNavigationSystemV1::Build total execution time: %.5f"), float(FPlatformTime::Seconds() - BuildStartTime));
}

void UNavigationSystemV1::CancelBuild()
{
	for (ANavigationData* NavData : NavDataSet)
	{
		if (NavData)
		{
			if (NavData->GetGenerator())
			{
				NavData->GetGenerator()->CancelBuild();
			}
		}
	}
}

void UNavigationSystemV1::SpawnMissingNavigationData()
{
	const int32 SupportedAgentsCount = SupportedAgents.Num();
	check(SupportedAgentsCount >= 0);
	
	// Bit array might be a bit of an overkill here, but this function will be called very rarely
	TBitArray<> AlreadyInstantiated(false, SupportedAgentsCount);
	uint8 NumberFound = 0;
	UWorld* NavWorld = GetWorld();

	// 1. check whether any of required navigation data has already been instantiated
	for (TActorIterator<ANavigationData> It(NavWorld); It && NumberFound < SupportedAgentsCount; ++It)
	{
		ANavigationData* Nav = (*It);
		if (Nav != nullptr 
			&& Nav->IsPendingKill() == false
			// mz@todo the 'is level in' condition is temporary
			&& (Nav->GetTypedOuter<UWorld>() == NavWorld || NavWorld->GetLevels().Contains(Nav->GetLevel())))
		{
			// find out which one it is
			for (int32 AgentIndex = 0; AgentIndex < SupportedAgentsCount; ++AgentIndex)
			{
				if (AlreadyInstantiated[AgentIndex] == false
					&& Nav->GetClass() == SupportedAgents[AgentIndex].NavigationDataClass 
					&& Nav->DoesSupportAgent(SupportedAgents[AgentIndex]) == true)
				{
					AlreadyInstantiated[AgentIndex] = true;
					++NumberFound;
					break;
				}
			}				
		}
	}

	// 2. for any not already instantiated navigation data call creator functions
	if (NumberFound < SupportedAgentsCount)
	{
		for (int32 AgentIndex = 0; AgentIndex < SupportedAgentsCount; ++AgentIndex)
		{
			const FNavDataConfig& NavConfig = SupportedAgents[AgentIndex];
			if (AlreadyInstantiated[AgentIndex] == false && NavConfig.NavigationDataClass != nullptr)
			{
				bool bHandled = false;

				const ANavigationData* NavDataCDO = NavConfig.NavigationDataClass->GetDefaultObject<ANavigationData>();
				if (NavDataCDO == nullptr || !NavDataCDO->CanSpawnOnRebuild())
				{
					continue;
				}

				if (NavWorld->WorldType != EWorldType::Editor && NavDataCDO->GetRuntimeGenerationMode() == ERuntimeGenerationType::Static)
				{
					// if we're not in the editor, and specified navigation class is configured 
					// to be static, then we don't want to create an instance					
					UE_LOG(LogNavigation, Log, TEXT("Not spawning navigation data for %s since indivated NavigationData type is not configured for dynamic generation")
						, *NavConfig.Name.ToString());
					continue;
				}

				ANavigationData* Instance = CreateNavigationDataInstance(NavConfig);
				if (Instance)
				{
					RequestRegistration(Instance);
				}
				else
				{
					UE_LOG(LogNavigation, Warning, TEXT("Was not able to create navigation data for SupportedAgent[%d]: %s"), AgentIndex, *NavConfig.Name.ToString());
				}
			}
		}
	}
	
	if (MainNavData == nullptr || MainNavData->IsPendingKillPending())
	{
		// update 
		MainNavData = GetDefaultNavDataInstance(FNavigationSystem::DontCreate);
	}
}

ANavigationData* UNavigationSystemV1::CreateNavigationDataInstance(const FNavDataConfig& NavConfig)
{
	UWorld* World = GetWorld();
	check(World);

	FActorSpawnParameters SpawnInfo;
	if (bSpawnNavDataInNavBoundsLevel && RegisteredNavBounds.Num() > 0)
	{
		// pick the first valid level
		for (const FNavigationBounds& Bounds : RegisteredNavBounds)
		{
			if (Bounds.Level.IsValid())
			{
				SpawnInfo.OverrideLevel = Bounds.Level.Get();
				break;
			}
		}
	}
	if (SpawnInfo.OverrideLevel == nullptr)
	{
		SpawnInfo.OverrideLevel = World->PersistentLevel;
	}
	ANavigationData* Instance = World->SpawnActor<ANavigationData>(*NavConfig.NavigationDataClass, SpawnInfo);

	if (Instance != NULL)
	{
		Instance->SetConfig(NavConfig);
		if (NavConfig.Name != NAME_None)
		{
			FString StrName = FString::Printf(TEXT("%s-%s"), *(Instance->GetFName().GetPlainNameString()), *(NavConfig.Name.ToString()));
			// temporary solution to make sure we don't try to change name while there's already
			// an object with this name
			UObject* ExistingObject = StaticFindObject(/*Class=*/ NULL, Instance->GetOuter(), *StrName, true);
			if (ExistingObject != NULL)
			{
				ANavigationData* ExistingNavigationData = Cast<ANavigationData>(ExistingObject);
				if (ExistingNavigationData)
				{
					UnregisterNavData(ExistingNavigationData);
					AgentToNavDataMap.Remove(ExistingNavigationData->GetConfig());
				}

				ExistingObject->Rename(NULL, NULL, REN_DontCreateRedirectors | REN_ForceGlobalUnique | REN_DoNotDirty | REN_NonTransactional | REN_ForceNoResetLoaders);
			}

			// Set descriptive name
			Instance->Rename(*StrName, NULL, REN_DoNotDirty | REN_ForceNoResetLoaders);
#if WITH_EDITOR
			if (World->WorldType == EWorldType::Editor)
			{
				const bool bMarkDirty = false;
				Instance->SetActorLabel(StrName, bMarkDirty);
			}
#endif // WITH_EDITOR
		}
	}

	return Instance;
}

void UNavigationSystemV1::OnPIEStart()
{
	bIsPIEActive = true;
	// no updates for editor world while PIE is active
	const UWorld* MyWorld = GetWorld();
	if (MyWorld && !MyWorld->IsGameWorld())
	{
		bAsyncBuildPaused = true;
		AddNavigationBuildLock(ENavigationBuildLock::NoUpdateInEditor);
	}
}

void UNavigationSystemV1::OnPIEEnd()
{
	bIsPIEActive = false;
	const UWorld* MyWorld = GetWorld();
	if (MyWorld && !MyWorld->IsGameWorld())
	{
		bAsyncBuildPaused = false;
		// there's no need to request while navigation rebuilding just because PIE has ended
		RemoveNavigationBuildLock(ENavigationBuildLock::NoUpdateInEditor, /*bSkipRebuildInEditor=*/true);
	}
}

void UNavigationSystemV1::RemoveNavigationBuildLock(uint8 Flags, bool bSkipRebuildInEditor)
{
	const bool bWasLocked = IsNavigationBuildingLocked();

	NavBuildingLockFlags &= ~Flags;

	const bool bIsLocked = IsNavigationBuildingLocked();
	const bool bSkipRebuild = (OperationMode == FNavigationSystemRunMode::EditorMode) && bSkipRebuildInEditor;
	if (bWasLocked && !bIsLocked && !bSkipRebuild)
	{
		RebuildAll();
	}
}

void UNavigationSystemV1::RebuildAll(bool bIsLoadTime)
{
	const bool bIsInGame = GetWorld()->IsGameWorld();
	
	GatherNavigationBounds();

	// make sure that octree is up to date
	for (TSet<FNavigationDirtyElement>::TIterator It(PendingOctreeUpdates); It; ++It)
	{
		AddElementToNavOctree(*It);
	}
	PendingOctreeUpdates.Empty(32);

	// discard all pending dirty areas, we are going to rebuild navmesh anyway 
	DirtyAreas.Reset();
	PendingNavBoundsUpdates.Reset();
#if !UE_BUILD_SHIPPING
	bDirtyAreasReportedWhileAccumulationLocked = false;
#endif // !UE_BUILD_SHIPPING

	// 
	for (int32 NavDataIndex = 0; NavDataIndex < NavDataSet.Num(); ++NavDataIndex)
	{
		ANavigationData* NavData = NavDataSet[NavDataIndex];
				
		if (NavData && (!bIsLoadTime || NavData->NeedsRebuildOnLoad()) && (!bIsInGame || NavData->SupportsRuntimeGeneration()))
		{
			NavData->RebuildAll();
		}
	}
}

bool UNavigationSystemV1::IsNavigationBuildInProgress(bool bCheckDirtyToo)
{
	bool bRet = false;

	if (NavDataSet.Num() == 0)
	{
		// @todo this is wrong! Should not need to create a navigation data instance in a "getter" like function
		// update nav data. If none found this is the place to create one
		GetDefaultNavDataInstance(FNavigationSystem::DontCreate);
	}
	
	for (int32 NavDataIndex = 0; NavDataIndex < NavDataSet.Num(); ++NavDataIndex)
	{
		ANavigationData* NavData = NavDataSet[NavDataIndex];
		if (NavData != NULL && NavData->GetGenerator() != NULL 
			&& NavData->GetGenerator()->IsBuildInProgress(bCheckDirtyToo) == true)
		{
			bRet = true;
			break;
		}
	}

	return bRet;
}

void UNavigationSystemV1::OnNavigationGenerationFinished(ANavigationData& NavData)
{
	OnNavigationGenerationFinishedDelegate.Broadcast(&NavData);
}

int32 UNavigationSystemV1::GetNumRemainingBuildTasks() const
{
	int32 NumTasks = 0;
	
	for (ANavigationData* NavData : NavDataSet)
	{
		if (NavData && NavData->GetGenerator())
		{
			NumTasks+= NavData->GetGenerator()->GetNumRemaningBuildTasks();
		}
	}
	
	return NumTasks;
}

int32 UNavigationSystemV1::GetNumRunningBuildTasks() const 
{
	int32 NumTasks = 0;
	
	for (ANavigationData* NavData : NavDataSet)
	{
		if (NavData && NavData->GetGenerator())
		{
			NumTasks+= NavData->GetGenerator()->GetNumRunningBuildTasks();
		}
	}
	
	return NumTasks;
}

void UNavigationSystemV1::OnLevelAddedToWorld(ULevel* InLevel, UWorld* InWorld)
{
	if ((IsNavigationSystemStatic() == false) && (InWorld == GetWorld()))
	{
		AddLevelCollisionToOctree(InLevel);

		if (!InLevel->IsPersistentLevel())
		{
			for (ANavigationData* NavData : NavDataSet)
			{
				if (NavData)
				{
					NavData->OnStreamingLevelAdded(InLevel, InWorld);
				}
			}
		}
	}
}

void UNavigationSystemV1::OnLevelRemovedFromWorld(ULevel* InLevel, UWorld* InWorld)
{
	if ((IsNavigationSystemStatic() == false) && (InWorld == GetWorld()))
	{
		RemoveLevelCollisionFromOctree(InLevel);

		if (InLevel && !InLevel->IsPersistentLevel())
		{
			for (int32 DataIndex = NavDataSet.Num() - 1; DataIndex >= 0; --DataIndex)
			{		
				ANavigationData* NavData = NavDataSet[DataIndex];
				if (NavData)
				{
					if (NavData->GetLevel() != InLevel)
					{
						NavData->OnStreamingLevelRemoved(InLevel, InWorld);
					}
					else
					{
						NavDataSet.RemoveAt(DataIndex, 1, /*bAllowShrinking=*/false);
					}
				}
			}
		}
	}
}

void UNavigationSystemV1::AddLevelCollisionToOctree(ULevel* Level)
{
#if WITH_RECAST
	if (Level && NavOctree.IsValid() &&
		NavOctree->GetNavGeometryStoringMode() == FNavigationOctree::StoreNavGeometry)
	{
		const TArray<FVector>* LevelGeom = Level->GetStaticNavigableGeometry();
		const FOctreeElementId* ElementId = GetObjectsNavOctreeId(*Level);

		if (!ElementId && LevelGeom && LevelGeom->Num() > 0)
		{
			FNavigationOctreeElement BSPElem(*Level);
			FRecastNavMeshGenerator::ExportVertexSoupGeometry(*LevelGeom, *BSPElem.Data);

			const auto& Bounds = BSPElem.Data->Bounds;
			if (!Bounds.GetExtent().IsNearlyZero())
			{
				NavOctree->AddNode(Level, NULL, Bounds, BSPElem);
				AddDirtyArea(Bounds, ENavigationDirtyFlag::All);

				UE_LOG(LogNavOctree, Log, TEXT("ADD %s"), *GetNameSafe(Level));
			}
		}
	}
#endif// WITH_RECAST
}

void UNavigationSystemV1::RemoveLevelCollisionFromOctree(ULevel* Level)
{
	if (Level && NavOctree.IsValid())
	{
		const FOctreeElementId* ElementId = GetObjectsNavOctreeId(*Level);
		UE_LOG(LogNavOctree, Log, TEXT("UNREG %s %s"), *GetNameSafe(Level), ElementId ? TEXT("[exists]") : TEXT(""));

		if (ElementId != NULL)
		{
			if (NavOctree->IsValidElementId(*ElementId))
			{
				// mark area occupied by given actor as dirty
				FNavigationOctreeElement& ElementData = NavOctree->GetElementById(*ElementId);
				AddDirtyArea(ElementData.Bounds.GetBox(), ENavigationDirtyFlag::All);
			}

			NavOctree->RemoveNode(*ElementId);
			RemoveObjectsNavOctreeId(*Level);
		}
	}
}

void UNavigationSystemV1::OnPostLoadMap(UWorld*)
{
	UE_LOG(LogNavigation, Log, TEXT("UNavigationSystemV1::OnPostLoadMap"));

	// if map has been loaded and there are some navigation bounds volumes 
	// then create appropriate navigation structured
	ANavigationData* NavData = GetDefaultNavDataInstance(FNavigationSystem::DontCreate);

	// Do this if there's currently no navigation
	if (NavData == NULL && bAutoCreateNavigationData == true && IsThereAnywhereToBuildNavigation() == true)
	{
		NavData = GetDefaultNavDataInstance(FNavigationSystem::Create);
	}
}

#if WITH_EDITOR
void UNavigationSystemV1::OnActorMoved(AActor* Actor)
{
	if (Cast<ANavMeshBoundsVolume>(Actor) != NULL)
	{
		OnNavigationBoundsUpdated((ANavMeshBoundsVolume*)Actor);
	}
}
#endif // WITH_EDITOR

void UNavigationSystemV1::OnNavigationDirtied(const FBox& Bounds)
{
	AddDirtyArea(Bounds, ENavigationDirtyFlag::All);
}

#if WITH_HOT_RELOAD
void UNavigationSystemV1::OnHotReload(bool bWasTriggeredAutomatically)
{
	if (RequiresNavOctree() && NavOctree.IsValid() == false)
	{
		ConditionalPopulateNavOctree();

		if (bInitialBuildingLocked)
		{
			RemoveNavigationBuildLock(ENavigationBuildLock::InitialLock, /*bSkipRebuildInEditor=*/true);
		}
	}
}
#endif // WITH_HOT_RELOAD

void UNavigationSystemV1::CleanUp(FNavigationSystem::ECleanupMode Mode)
{
	UE_LOG(LogNavigation, Log, TEXT("UNavigationSystemV1::CleanUp"));

#if WITH_EDITOR
	if (GIsEditor && GEngine)
	{
		GEngine->OnActorMoved().RemoveAll(this);
	}
#endif // WITH_EDITOR

	FCoreUObjectDelegates::PostLoadMapWithWorld.RemoveAll(this);
	UNavigationSystemV1::NavigationDirtyEvent.RemoveAll(this);
	FWorldDelegates::LevelAddedToWorld.RemoveAll(this);
	FWorldDelegates::LevelRemovedFromWorld.RemoveAll(this);

#if WITH_HOT_RELOAD
	if (IHotReloadInterface* HotReloadSupport = FModuleManager::GetModulePtr<IHotReloadInterface>("HotReload"))
	{
		HotReloadSupport->OnHotReload().Remove(HotReloadDelegateHandle);
	}
#endif

	DestroyNavOctree();
	
	SetCrowdManager(NULL);

	NavDataSet.Reset();

	// reset unique link Id for new map
	const UWorld* MyWorld = (Mode == FNavigationSystem::ECleanupMode::CleanupWithWorld) ? GetWorld() : NULL;
	if (MyWorld && (MyWorld->WorldType == EWorldType::Game || MyWorld->WorldType == EWorldType::Editor))
	{
		INavLinkCustomInterface::NextUniqueId = 1;
	}
}

void UNavigationSystemV1::DestroyNavOctree()
{
	if (NavOctree.IsValid())
	{
		NavOctree->Destroy();
		NavOctree = NULL;
	}

	ObjectToOctreeId.Empty();
}

bool UNavigationSystemV1::RequiresNavOctree() const
{
	UWorld* World = GetWorld();
	check(World);
	
	// We always require navoctree in editor worlds
	if (!World->IsGameWorld())
	{
		return true;
	}
		
	for (ANavigationData* NavData : NavDataSet)
	{
		if (NavData && NavData->SupportsRuntimeGeneration())
		{
			return true;
		}
	}
	
	return false;
}

ERuntimeGenerationType UNavigationSystemV1::GetRuntimeGenerationType() const
{
	UWorld* World = GetWorld();
	check(World);
	
	// We always use ERuntimeGenerationType::Dynamic in editor worlds
	if (!World->IsGameWorld())
	{
		return ERuntimeGenerationType::Dynamic;
	}
	
	ERuntimeGenerationType RuntimeGenerationType = ERuntimeGenerationType::Static;

	for (ANavigationData* NavData : NavDataSet)
	{
		if (NavData && NavData->GetRuntimeGenerationMode() > RuntimeGenerationType)
		{
			RuntimeGenerationType = NavData->GetRuntimeGenerationMode();
		}
	}
	
	return RuntimeGenerationType;
}

//----------------------------------------------------------------------//
// Blueprint functions
//----------------------------------------------------------------------//
UNavigationSystemV1* UNavigationSystemV1::GetNavigationSystem(UObject* WorldContextObject)
{
	return GetCurrent(WorldContextObject);
}

bool UNavigationSystemV1::K2_ProjectPointToNavigation(UObject* WorldContextObject, const FVector& Point, FVector& ProjectedLocation, ANavigationData* NavData, TSubclassOf<UNavigationQueryFilter> FilterClass, const FVector QueryExtent)
{
	UWorld* World = GEngine->GetWorldFromContextObject(WorldContextObject, EGetWorldErrorMode::LogAndReturnNull);
	UNavigationSystemV1* NavSys = FNavigationSystem::GetCurrent<UNavigationSystemV1>(World);

	ProjectedLocation = Point;
	bool bResult = false;

	if (NavSys)
	{
		FNavLocation OutNavLocation;
		ANavigationData* UseNavData = NavData ? NavData : NavSys->GetDefaultNavDataInstance(FNavigationSystem::DontCreate);
		if (UseNavData)
		{
			bResult = NavSys->ProjectPointToNavigation(Point, OutNavLocation, QueryExtent, NavData
				, UNavigationQueryFilter::GetQueryFilter(*UseNavData, WorldContextObject, FilterClass));
			ProjectedLocation = OutNavLocation.Location;
		}
	}

	return bResult;
}

bool UNavigationSystemV1::K2_GetRandomReachablePointInRadius(UObject* WorldContextObject, const FVector& Origin, FVector& RandomLocation, float Radius, ANavigationData* NavData, TSubclassOf<UNavigationQueryFilter> FilterClass)
{
	FNavLocation RandomPoint(Origin);
	bool bResult = false;

	UWorld* World = GEngine->GetWorldFromContextObject(WorldContextObject, EGetWorldErrorMode::LogAndReturnNull);
	UNavigationSystemV1* NavSys = FNavigationSystem::GetCurrent<UNavigationSystemV1>(World);
	if (NavSys)
	{
		ANavigationData* UseNavData = NavData ? NavData : NavSys->GetDefaultNavDataInstance(FNavigationSystem::DontCreate);
		if (UseNavData)
		{
			bResult = NavSys->GetRandomReachablePointInRadius(Origin, Radius, RandomPoint, UseNavData, UNavigationQueryFilter::GetQueryFilter(*UseNavData, WorldContextObject, FilterClass));
			RandomLocation = RandomPoint.Location;
		}
	}

	return bResult;
}

bool UNavigationSystemV1::K2_GetRandomPointInNavigableRadius(UObject* WorldContextObject, const FVector& Origin, FVector& RandomLocation, float Radius, ANavigationData* NavData, TSubclassOf<UNavigationQueryFilter> FilterClass)
{
	FNavLocation RandomPoint(Origin);
	bool bResult = false;

	UWorld* World = GEngine->GetWorldFromContextObject(WorldContextObject, EGetWorldErrorMode::LogAndReturnNull);
	UNavigationSystemV1* NavSys = FNavigationSystem::GetCurrent<UNavigationSystemV1>(World);
	if (NavSys)
	{
		ANavigationData* UseNavData = NavData ? NavData : NavSys->GetDefaultNavDataInstance(FNavigationSystem::DontCreate);
		if (UseNavData)
		{
			bResult = NavSys->GetRandomPointInNavigableRadius(Origin, Radius, RandomPoint, UseNavData, UNavigationQueryFilter::GetQueryFilter(*UseNavData, WorldContextObject, FilterClass));
			RandomLocation = RandomPoint.Location;
		}
	}

	return bResult;
}

ENavigationQueryResult::Type UNavigationSystemV1::GetPathCost(UObject* WorldContextObject, const FVector& PathStart, const FVector& PathEnd, float& OutPathCost, ANavigationData* NavData, TSubclassOf<UNavigationQueryFilter> FilterClass)
{
	UWorld* World = GEngine->GetWorldFromContextObject(WorldContextObject, EGetWorldErrorMode::LogAndReturnNull);
	UNavigationSystemV1* NavSys = FNavigationSystem::GetCurrent<UNavigationSystemV1>(World);
	if (NavSys)
	{
		ANavigationData* UseNavData = NavData ? NavData : NavSys->GetDefaultNavDataInstance(FNavigationSystem::DontCreate);
		if (UseNavData)
		{
			return NavSys->GetPathCost(PathStart, PathEnd, OutPathCost, UseNavData, UNavigationQueryFilter::GetQueryFilter(*UseNavData, WorldContextObject, FilterClass));
		}
	}

	return ENavigationQueryResult::Error;
}

ENavigationQueryResult::Type UNavigationSystemV1::GetPathLength(UObject* WorldContextObject, const FVector& PathStart, const FVector& PathEnd, float& OutPathLength, ANavigationData* NavData, TSubclassOf<UNavigationQueryFilter> FilterClass)
{
	float PathLength = 0.f;

	UWorld* World = GEngine->GetWorldFromContextObject(WorldContextObject, EGetWorldErrorMode::LogAndReturnNull);
	UNavigationSystemV1* NavSys = FNavigationSystem::GetCurrent<UNavigationSystemV1>(World);
	if (NavSys)
	{
		ANavigationData* UseNavData = NavData ? NavData : NavSys->GetDefaultNavDataInstance(FNavigationSystem::DontCreate);
		if (UseNavData)
		{
			return NavSys->GetPathLength(PathStart, PathEnd, OutPathLength, UseNavData, UNavigationQueryFilter::GetQueryFilter(*UseNavData, WorldContextObject, FilterClass));
		}
	}

	return ENavigationQueryResult::Error;
}

bool UNavigationSystemV1::IsNavigationBeingBuilt(UObject* WorldContextObject)
{
	UWorld* World = GEngine->GetWorldFromContextObject(WorldContextObject, EGetWorldErrorMode::LogAndReturnNull);
	UNavigationSystemV1* NavSys = FNavigationSystem::GetCurrent<UNavigationSystemV1>(World);
	
	if (NavSys && !NavSys->IsNavigationBuildingPermanentlyLocked())
	{
		return NavSys->HasDirtyAreasQueued() || NavSys->IsNavigationBuildInProgress();
	}

	return false;
}

bool UNavigationSystemV1::IsNavigationBeingBuiltOrLocked(UObject* WorldContextObject)
{
	UWorld* World = GEngine->GetWorldFromContextObject(WorldContextObject, EGetWorldErrorMode::LogAndReturnNull);
	UNavigationSystemV1* NavSys = FNavigationSystem::GetCurrent<UNavigationSystemV1>(World);

	if (NavSys)
	{
		return NavSys->IsNavigationBuildingLocked() || NavSys->HasDirtyAreasQueued() || NavSys->IsNavigationBuildInProgress();
	}

	return false;
}

//----------------------------------------------------------------------//
// HACKS!!!
//----------------------------------------------------------------------//
bool UNavigationSystemV1::ShouldGeneratorRun(const FNavDataGenerator* Generator) const
{
	if (Generator != NULL && (IsNavigationSystemStatic() == false))
	{
		for (int32 NavDataIndex = 0; NavDataIndex < NavDataSet.Num(); ++NavDataIndex)
		{
			ANavigationData* NavData = NavDataSet[NavDataIndex];
			if (NavData != NULL && NavData->GetGenerator() == Generator)
			{
				return true;
			}
		}
	}

	return false;
}

bool UNavigationSystemV1::HandleCycleNavDrawnCommand( const TCHAR* Cmd, FOutputDevice& Ar )
{
	CycleNavigationDataDrawn();

	return true;
}

bool UNavigationSystemV1::HandleCountNavMemCommand()
{
	UE_LOG(LogNavigation, Warning, TEXT("Logging NavigationSystem memory usage:"));

	if (NavOctree.IsValid())
	{
		UE_LOG(LogNavigation, Warning, TEXT("NavOctree memory: %d"), NavOctree->GetSizeBytes());
	}

	for (int32 NavDataIndex = 0; NavDataIndex < NavDataSet.Num(); ++NavDataIndex)
	{
		ANavigationData* NavData = NavDataSet[NavDataIndex];
		if (NavData != NULL)
		{
			NavData->LogMemUsed();
		}
	}
	return true;
}

//----------------------------------------------------------------------//
// Commands
//----------------------------------------------------------------------//
bool FNavigationSystemExec::Exec(UWorld* InWorld, const TCHAR* Cmd, FOutputDevice& Ar)
{
	UNavigationSystemV1*  NavSys = FNavigationSystem::GetCurrent<UNavigationSystemV1>(InWorld);

	if (NavSys && NavSys->NavDataSet.Num() > 0)
	{
		if (FParse::Command(&Cmd, TEXT("CYCLENAVDRAWN")))
		{
			NavSys->HandleCycleNavDrawnCommand( Cmd, Ar );
			// not returning true to enable all navigation systems to cycle their own data
			return false;
		}
		else if (FParse::Command(&Cmd, TEXT("CountNavMem")))
		{
			NavSys->HandleCountNavMemCommand();
			return false;
		}
		/** Builds the navigation mesh (or rebuilds it). **/
		else if (FParse::Command(&Cmd, TEXT("RebuildNavigation")))
		{
			NavSys->Build();
		}
	}

	return false;
}

void UNavigationSystemV1::CycleNavigationDataDrawn()
{
	++CurrentlyDrawnNavDataIndex;
	if (CurrentlyDrawnNavDataIndex >= NavDataSet.Num())
	{
		CurrentlyDrawnNavDataIndex = INDEX_NONE;
	}

	for (int32 NavDataIndex = 0; NavDataIndex < NavDataSet.Num(); ++NavDataIndex)
	{
		ANavigationData* NavData = NavDataSet[NavDataIndex];
		if (NavData != NULL)
		{
			const bool bNewEnabledDrawing = (CurrentlyDrawnNavDataIndex == INDEX_NONE) || (NavDataIndex == CurrentlyDrawnNavDataIndex);
			NavData->SetNavRenderingEnabled(bNewEnabledDrawing);
		}
	}
}

bool UNavigationSystemV1::IsNavigationDirty() const
{
#if !UE_BUILD_SHIPPING
	if (bCanAccumulateDirtyAreas == false && bDirtyAreasReportedWhileAccumulationLocked)
	{
		return true;
	}
#endif // !UE_BUILD_SHIPPING

	for (int32 NavDataIndex=0; NavDataIndex < NavDataSet.Num(); ++NavDataIndex)
	{
		if (NavDataSet[NavDataIndex] && NavDataSet[NavDataIndex]->NeedsRebuild())
		{
			return true;
		}
	}

	return false;
}

bool UNavigationSystemV1::CanRebuildDirtyNavigation() const
{
	const bool bIsInGame = GetWorld()->IsGameWorld();

	for (const ANavigationData* NavData : NavDataSet)
	{
		if (NavData)
		{
			const bool bIsDirty = NavData->NeedsRebuild();
			const bool bCanRebuild = !bIsInGame || NavData->SupportsRuntimeGeneration();

			if (bIsDirty && !bCanRebuild)
			{
				return false;
			}
		}
	}

	return true;
}

bool UNavigationSystemV1::DoesPathIntersectBox(const FNavigationPath* Path, const FBox& Box, uint32 StartingIndex, FVector* AgentExtent)
{
	return Path != NULL && Path->DoesIntersectBox(Box, StartingIndex, NULL, AgentExtent);
}

bool UNavigationSystemV1::DoesPathIntersectBox(const FNavigationPath* Path, const FBox& Box, const FVector& AgentLocation, uint32 StartingIndex, FVector* AgentExtent)
{
	return Path != NULL && Path->DoesIntersectBox(Box, AgentLocation, StartingIndex, NULL, AgentExtent);
}

void UNavigationSystemV1::SetMaxSimultaneousTileGenerationJobsCount(int32 MaxNumberOfJobs)
{
#if WITH_RECAST
	for (auto NavigationData : NavDataSet)
	{
		ARecastNavMesh* RecastNavMesh = Cast<ARecastNavMesh>(NavigationData);
		if (RecastNavMesh)
		{
			RecastNavMesh->SetMaxSimultaneousTileGenerationJobsCount(MaxNumberOfJobs);
		}
	}
#endif
}

void UNavigationSystemV1::ResetMaxSimultaneousTileGenerationJobsCount()
{
#if WITH_RECAST
	for (auto NavigationData : NavDataSet)
	{
		ARecastNavMesh* RecastNavMesh = Cast<ARecastNavMesh>(NavigationData);
		if (RecastNavMesh)
		{
			const ARecastNavMesh* CDO = RecastNavMesh->GetClass()->GetDefaultObject<ARecastNavMesh>();
			RecastNavMesh->SetMaxSimultaneousTileGenerationJobsCount(CDO->MaxSimultaneousTileGenerationJobsCount);
		}
	}
#endif
}

//----------------------------------------------------------------------//
// Active tiles
//----------------------------------------------------------------------//

void UNavigationSystemV1::RegisterNavigationInvoker(AActor& Invoker, float TileGenerationRadius, float TileRemovalRadius)
{
	UNavigationSystemV1* NavSys = FNavigationSystem::GetCurrent<UNavigationSystemV1>(Invoker.GetWorld());
	if (NavSys)
	{
		NavSys->RegisterInvoker(Invoker, TileGenerationRadius, TileRemovalRadius);
	}
}

void UNavigationSystemV1::UnregisterNavigationInvoker(AActor& Invoker)
{
	UNavigationSystemV1* NavSys = FNavigationSystem::GetCurrent<UNavigationSystemV1>(Invoker.GetWorld());
	if (NavSys)
	{
		NavSys->UnregisterInvoker(Invoker);
	}
}

void UNavigationSystemV1::SetGeometryGatheringMode(ENavDataGatheringModeConfig NewMode)
{
	DataGatheringMode = NewMode;
	if (NavOctree.IsValid())
	{
		NavOctree->SetDataGatheringMode(DataGatheringMode);
	}
}

void UNavigationSystemV1::RegisterInvoker(AActor& Invoker, float TileGenerationRadius, float TileRemovalRadius)
{
	UE_CVLOG(bGenerateNavigationOnlyAroundNavigationInvokers == false, this, LogNavigation, Warning
		, TEXT("Trying to register %s as enforcer, but NavigationSystem is not set up for enforcer-centric generation. See GenerateNavigationOnlyAroundNavigationInvokers in NavigationSystem's properties")
		, *Invoker.GetName());

	TileGenerationRadius = FMath::Clamp(TileGenerationRadius, 0.f, BIG_NUMBER);
	TileRemovalRadius = FMath::Clamp(TileRemovalRadius, TileGenerationRadius, BIG_NUMBER);

	FNavigationInvoker& Data = Invokers.FindOrAdd(&Invoker);
	Data.Actor = &Invoker;
	Data.GenerationRadius = TileGenerationRadius;
	Data.RemovalRadius = TileRemovalRadius;

	UE_VLOG_CYLINDER(this, LogNavigation, Log, Invoker.GetActorLocation(), Invoker.GetActorLocation() + FVector(0, 0, 20), TileGenerationRadius, FColorList::LimeGreen
		, TEXT("%s %.0f %.0f"), *Invoker.GetName(), TileGenerationRadius, TileRemovalRadius);
	UE_VLOG_CYLINDER(this, LogNavigation, Log, Invoker.GetActorLocation(), Invoker.GetActorLocation() + FVector(0, 0, 20), TileRemovalRadius, FColorList::IndianRed, TEXT(""));
}

void UNavigationSystemV1::UnregisterInvoker(AActor& Invoker)
{
	UE_VLOG(this, LogNavigation, Log, TEXT("Removing %s from enforcers list"), *Invoker.GetName());
	Invokers.Remove(&Invoker);
}

void UNavigationSystemV1::UpdateInvokers()
{
	UWorld* World = GetWorld();
	const float CurrentTime = World->GetTimeSeconds();
	if (CurrentTime >= NextInvokersUpdateTime)
	{
		TArray<FNavigationInvokerRaw> InvokerLocations;

		if (Invokers.Num() > 0)
		{
			QUICK_SCOPE_CYCLE_COUNTER(STAT_NavSys_Clusterize);

			const double StartTime = FPlatformTime::Seconds();

			InvokerLocations.Reserve(Invokers.Num());

			for (auto ItemIterator = Invokers.CreateIterator(); ItemIterator; ++ItemIterator)
			{
				AActor* Actor = ItemIterator->Value.Actor.Get();
				if (Actor != nullptr
#if WITH_EDITOR
					// Would like to ignore objects in transactional buffer here, but there's no flag for it
					//&& (GIsEditor == false || Item.Actor->HasAnyFlags(RF_Transactional | RF_PendingKill) == false)
#endif //WITH_EDITOR
					)
				{
					InvokerLocations.Add(FNavigationInvokerRaw(Actor->GetActorLocation(), ItemIterator->Value.GenerationRadius, ItemIterator->Value.RemovalRadius));
				}
				else
				{
					ItemIterator.RemoveCurrent();
				}
			}

#if ENABLE_VISUAL_LOG
			const double CachingFinishTime = FPlatformTime::Seconds();
			UE_VLOG(this, LogNavigation, Log, TEXT("Caching time %fms"), (CachingFinishTime - StartTime) * 1000);

			for (const auto& InvokerData : InvokerLocations)
			{
				UE_VLOG_CYLINDER(this, LogNavigation, Log, InvokerData.Location, InvokerData.Location + FVector(0, 0, 20), InvokerData.RadiusMax, FColorList::Blue, TEXT(""));
				UE_VLOG_CYLINDER(this, LogNavigation, Log, InvokerData.Location, InvokerData.Location + FVector(0, 0, 20), InvokerData.RadiusMin, FColorList::CadetBlue, TEXT(""));
			}
#endif // ENABLE_VISUAL_LOG
		}

#if WITH_RECAST
		const double UpdateStartTime = FPlatformTime::Seconds();
		for (TActorIterator<ARecastNavMesh> It(GetWorld()); It; ++It)
		{
			It->UpdateActiveTiles(InvokerLocations);
		}
		const double UpdateEndTime = FPlatformTime::Seconds();
		UE_VLOG(this, LogNavigation, Log, TEXT("Marking tiles to update %fms (%d invokers)"), (UpdateEndTime - UpdateStartTime) * 1000, InvokerLocations.Num());
#endif

		// once per second
		NextInvokersUpdateTime = CurrentTime + ActiveTilesUpdateInterval;
	}
}

void UNavigationSystemV1::RegisterNavigationInvoker(AActor* Invoker, float TileGenerationRadius, float TileRemovalRadius)
{
	if (Invoker != nullptr)
	{
		RegisterInvoker(*Invoker, TileGenerationRadius, TileRemovalRadius);
	}
}

void UNavigationSystemV1::UnregisterNavigationInvoker(AActor* Invoker)
{
	if (Invoker != nullptr)
	{
		UnregisterInvoker(*Invoker);
	}
}

//----------------------------------------------------------------------//
// DEPRECATED
//----------------------------------------------------------------------//
FVector UNavigationSystemV1::ProjectPointToNavigation(UObject* WorldContextObject, const FVector& Point, ANavigationData* NavData, TSubclassOf<UNavigationQueryFilter> FilterClass, const FVector QueryExtent)
{
	FNavLocation ProjectedPoint(Point);

	UWorld* World = GEngine->GetWorldFromContextObject(WorldContextObject, EGetWorldErrorMode::LogAndReturnNull);
	UNavigationSystemV1* NavSys = FNavigationSystem::GetCurrent<UNavigationSystemV1>(World);
	if (NavSys)
	{
		ANavigationData* UseNavData = NavData ? NavData : NavSys->GetDefaultNavDataInstance(FNavigationSystem::DontCreate);
		if (UseNavData)
		{
			NavSys->ProjectPointToNavigation(Point, ProjectedPoint, QueryExtent.IsNearlyZero() ? INVALID_NAVEXTENT : QueryExtent, UseNavData,
				UNavigationQueryFilter::GetQueryFilter(*UseNavData, WorldContextObject, FilterClass));
		}
	}

	return ProjectedPoint.Location;
}

FVector UNavigationSystemV1::GetRandomReachablePointInRadius(UObject* WorldContextObject, const FVector& Origin, float Radius, ANavigationData* NavData, TSubclassOf<UNavigationQueryFilter> FilterClass)
{
	FNavLocation RandomPoint;

	UWorld* World = GEngine->GetWorldFromContextObject(WorldContextObject, EGetWorldErrorMode::LogAndReturnNull);
	UNavigationSystemV1* NavSys = FNavigationSystem::GetCurrent<UNavigationSystemV1>(World);
	if (NavSys)
	{
		ANavigationData* UseNavData = NavData ? NavData : NavSys->GetDefaultNavDataInstance(FNavigationSystem::DontCreate);
		if (UseNavData)
		{
			NavSys->GetRandomReachablePointInRadius(Origin, Radius, RandomPoint, UseNavData, UNavigationQueryFilter::GetQueryFilter(*UseNavData, WorldContextObject, FilterClass));
		}
	}

	return RandomPoint.Location;
}

FVector UNavigationSystemV1::GetRandomPointInNavigableRadius(UObject* WorldContextObject, const FVector& Origin, float Radius, ANavigationData* NavData, TSubclassOf<UNavigationQueryFilter> FilterClass)
{
	FNavLocation RandomPoint;

	UWorld* World = GEngine->GetWorldFromContextObject(WorldContextObject, EGetWorldErrorMode::LogAndReturnNull);
	UNavigationSystemV1* NavSys = FNavigationSystem::GetCurrent<UNavigationSystemV1>(World);
	if (NavSys)
	{
		ANavigationData* UseNavData = NavData ? NavData : NavSys->GetDefaultNavDataInstance(FNavigationSystem::DontCreate);
		if (UseNavData)
		{
			NavSys->GetRandomPointInNavigableRadius(Origin, Radius, RandomPoint, UseNavData, UNavigationQueryFilter::GetQueryFilter(*UseNavData, WorldContextObject, FilterClass));
		}
	}

	return RandomPoint.Location;
}

void UNavigationSystemV1::SimpleMoveToActor(AController* Controller, const AActor* Goal)
{
	UE_LOG(LogNavigation, Error, TEXT("SimpleMoveToActor is deprecated. Use UAIBlueprintHelperLibrary::SimpleMoveToActor instead"));
}

void UNavigationSystemV1::SimpleMoveToLocation(AController* Controller, const FVector& Goal)
{
	UE_LOG(LogNavigation, Error, TEXT("SimpleMoveToLocation is deprecated. Use UAIBlueprintHelperLibrary::SimpleMoveToLocation instead"));
}

//----------------------------------------------------------------------//
// NEW STUFF!
//----------------------------------------------------------------------//
void UNavigationSystemV1::VerifyNavigationRenderingComponents(const bool bShow)
{
	// make sure nav mesh has a rendering component
	ANavigationData* const NavData = GetDefaultNavDataInstance(FNavigationSystem::DontCreate);

	if (NavData && NavData->RenderingComp == nullptr)
	{
		NavData->RenderingComp = NavData->ConstructRenderingComponent();
		if (NavData->RenderingComp)
		{
			NavData->RenderingComp->SetVisibility(bShow);
			NavData->RenderingComp->RegisterComponent();
		}
	}

	if (NavData == nullptr)
	{
		UE_LOG(LogNavigation, Warning, TEXT("No NavData found when calling UNavigationSystemV1::VerifyNavigationRenderingComponents()"));
	}
}

#if !UE_BUILD_SHIPPING
void UNavigationSystemV1::GetOnScreenMessages(TMultiMap<FCoreDelegates::EOnScreenMessageSeverity, FText>& OutMessages)
{
	// check navmesh
#if WITH_EDITOR
	const bool bIsNavigationAutoUpdateEnabled = GetIsAutoUpdateEnabled();
#else
	const bool bIsNavigationAutoUpdateEnabled = true;
#endif
	if (IsNavigationDirty()
		&& ((OperationMode == FNavigationSystemRunMode::EditorMode && !bIsNavigationAutoUpdateEnabled)
			|| !SupportsNavigationGeneration() || !CanRebuildDirtyNavigation()))
	{
		OutMessages.Add(FCoreDelegates::EOnScreenMessageSeverity::Error
			, LOCTEXT("NAVMESHERROR", "NAVMESH NEEDS TO BE REBUILT"));
	}
}
#endif // !UE_BUILD_SHIPPING

INavigationDataInterface* UNavigationSystemV1::GetNavDataForActor(const AActor& Actor)
{
	UNavigationSystemV1* NavSys = FNavigationSystem::GetCurrent<UNavigationSystemV1>(Actor.GetWorld());
	ANavigationData* NavData = nullptr;
	const INavAgentInterface* AsNavAgent = CastChecked<INavAgentInterface>(&Actor);
	if (AsNavAgent)
	{
		const FNavAgentProperties& AgentProps = AsNavAgent->GetNavAgentPropertiesRef();
		NavData = NavSys->GetNavDataForProps(AgentProps);
	}
	if (NavData == nullptr)
	{
		NavData = NavSys->GetDefaultNavDataInstance(FNavigationSystem::DontCreate);
	}

	//  Only RecastNavMesh supported
	return (INavigationDataInterface*)(Cast<ARecastNavMesh>(NavData));
}

int UNavigationSystemV1::GetNavigationBoundsForNavData(const ANavigationData& NavData, TArray<FBox>& OutBounds) const
{
	const int InitialBoundsCount = OutBounds.Num();
	OutBounds.Reserve(InitialBoundsCount + RegisteredNavBounds.Num());
	const int32 AgentIndex = GetSupportedAgentIndex(&NavData);

	for (const FNavigationBounds& NavigationBounds : RegisteredNavBounds)
	{
		if (NavigationBounds.SupportedAgents.Contains(AgentIndex))
		{
			OutBounds.Add(NavigationBounds.AreaBox);
		}
	}

	return OutBounds.Num() - InitialBoundsCount;
}

const FNavDataConfig& UNavigationSystemV1::GetDefaultSupportedAgent()
{
	static const FNavDataConfig DefaultAgent;
	const UNavigationSystemV1* NavSysCDO = GetDefault<UNavigationSystemV1>();
	check(NavSysCDO);
	return NavSysCDO->SupportedAgents.Num() > 0
		? NavSysCDO->GetDefaultSupportedAgentConfig()
		: DefaultAgent;
}

void UNavigationSystemV1::OverrideSupportedAgents(const TArray<FNavDataConfig>& NewSupportedAgents)
{
	UE_CLOG(bWorldInitDone, LogNavigation, Warning, TEXT("Trying to override NavigationSystem\'s SupportedAgents past the World\'s initialization"));

	SupportedAgents = NewSupportedAgents;
	if (SupportedAgents.Num() == 0)
	{
		SupportedAgents.Add(FNavDataConfig(FNavigationSystem::FallbackAgentRadius, FNavigationSystem::FallbackAgentHeight));
	}
}

void UNavigationSystemV1::Configure(const UNavigationSystemConfig& Config)
{

}

//----------------------------------------------------------------------//
// UNavigationSystemModuleConfig
//----------------------------------------------------------------------//
UNavigationSystemModuleConfig::UNavigationSystemModuleConfig(const FObjectInitializer& ObjectInitializer)
	: Super(ObjectInitializer)
{
}

void UNavigationSystemModuleConfig::PostInitProperties()
{
	Super::PostInitProperties();

	const UNavigationSystemV1* NavSysCDO = GetDefault<UNavigationSystemV1>();
	if (NavSysCDO)
	{
		UpdateWithNavSysCDO(*NavSysCDO);
	}
}

void UNavigationSystemModuleConfig::UpdateWithNavSysCDO(const UNavigationSystemV1& NavSysCDO)
{
	UClass* MyClass = NavigationSystemClass.ResolveClass();
	if (MyClass != nullptr && MyClass->IsChildOf(NavSysCDO.GetClass()))
	{
		bStrictlyStatic = NavSysCDO.bStaticRuntimeNavigation;
		bCreateOnClient = NavSysCDO.bAllowClientSideNavigation;
		bAutoSpawnMissingNavData = NavSysCDO.bAutoCreateNavigationData;
		bSpawnNavDataInNavBoundsLevel = NavSysCDO.bSpawnNavDataInNavBoundsLevel;
	}
}

UNavigationSystemBase* UNavigationSystemModuleConfig::CreateAndConfigureNavigationSystem(UWorld& World) const
{
	if (bCreateOnClient == false && World.GetNetMode() == NM_Client)
	{
		return nullptr;
	}

	UNavigationSystemBase* NewNavSys = Super::CreateAndConfigureNavigationSystem(World);
	UNavigationSystemV1* NavSysInstance = Cast<UNavigationSystemV1>(NewNavSys);
	UE_CLOG(NavSysInstance == nullptr && NewNavSys != nullptr, LogNavigation, Error
		, TEXT("Unable to spawn navsys instance of class %s - unable to cast to UNavigationSystemV1")
		, *NavigationSystemClass.GetAssetName()
	);
	
	if (NavSysInstance)
	{
		NavSysInstance->bAutoCreateNavigationData = bAutoSpawnMissingNavData;
		NavSysInstance->bSpawnNavDataInNavBoundsLevel = bSpawnNavDataInNavBoundsLevel;
		if (bStrictlyStatic)
		{
			NavSysInstance->ConfigureAsStatic();
		}
	}

	return NavSysInstance;
}

#if WITH_EDITOR
void UNavigationSystemModuleConfig::PostEditChangeProperty(FPropertyChangedEvent& PropertyChangedEvent)
{
	static const FName NAME_NavigationSystemClass = GET_MEMBER_NAME_CHECKED(UNavigationSystemConfig, NavigationSystemClass);

	Super::PostEditChangeProperty(PropertyChangedEvent);

	if (PropertyChangedEvent.Property)
	{
		FName PropName = PropertyChangedEvent.Property->GetFName();
		if (PropName == NAME_NavigationSystemClass)
		{
			if (NavigationSystemClass.IsValid() == false)
			{
				NavigationSystemClass = *GEngine->NavigationSystemClass;
			}
			else
			{
				NavigationSystemClass.TryLoad();
				TSubclassOf<UNavigationSystemBase> NavSysClass = NavigationSystemClass.ResolveClass();
				const UNavigationSystemV1* NavSysCDO = *NavSysClass
					? NavSysClass->GetDefaultObject<UNavigationSystemV1>()
					: (UNavigationSystemV1*)nullptr;
				if (NavSysCDO)
				{
					UpdateWithNavSysCDO(*NavSysCDO);
				}
			}
		}
	}
}
#endif // WITH_EDITOR

#undef LOCTEXT_NAMESPACE