UnrealEngineUWP/Engine/Plugins/Runtime/StateTree/Source/StateTreeModule/Private/StateTreeExecutionContext.cpp

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

#include "StateTreeExecutionContext.h"
#include "StateTreeTaskBase.h"
#include "StateTreeEvaluatorBase.h"
#include "StateTreeConditionBase.h"
#include "Containers/StaticArray.h"
#include "Debugger/StateTreeTrace.h"
#include "Debugger/StateTreeTraceTypes.h"
#include "Misc/ScopeExit.h"
#include "VisualLogger/VisualLogger.h"
#include "ProfilingDebugging/CsvProfiler.h"
#include "Logging/LogScopedVerbosityOverride.h"

#define STATETREE_LOG(Verbosity, Format, ...) UE_VLOG_UELOG(GetOwner(), LogStateTree, Verbosity, TEXT("%s: ") Format, *GetInstanceDescription(), ##__VA_ARGS__)
#define STATETREE_CLOG(Condition, Verbosity, Format, ...) UE_CVLOG_UELOG((Condition), GetOwner(), LogStateTree, Verbosity, TEXT("%s: ") Format, *GetInstanceDescription(), ##__VA_ARGS__)

#define STATETREE_LOG_AND_TRACE(Verbosity, Format, ...) \
	UE_VLOG_UELOG(GetOwner(), LogStateTree, Verbosity, TEXT("%s: ") Format, *GetInstanceDescription(), ##__VA_ARGS__); \
	STATETREE_TRACE_LOG_EVENT(Format, ##__VA_ARGS__)

#if WITH_STATETREE_DEBUGGER
	#define ID_NAME PREPROCESSOR_JOIN(InstanceId,__LINE__) \

	#define STATETREE_TRACE_SCOPED_PHASE(Phase) \
		FStateTreeInstanceDebugId ID_NAME = GetInstanceDebugId(); \
		TRACE_STATETREE_PHASE_EVENT(ID_NAME, Phase, EStateTreeTraceEventType::Push, FStateTreeStateHandle::Invalid) \
		ON_SCOPE_EXIT { TRACE_STATETREE_PHASE_EVENT(ID_NAME, Phase, EStateTreeTraceEventType::Pop, FStateTreeStateHandle::Invalid) }

	#define STATETREE_TRACE_SCOPED_STATE(StateHandle) \
		FStateTreeInstanceDebugId ID_NAME = GetInstanceDebugId(); \
		TRACE_STATETREE_PHASE_EVENT(ID_NAME, EStateTreeUpdatePhase::Unset, EStateTreeTraceEventType::Push, StateHandle) \
		ON_SCOPE_EXIT { TRACE_STATETREE_PHASE_EVENT(ID_NAME, EStateTreeUpdatePhase::Unset, EStateTreeTraceEventType::Pop, StateHandle) }

	#define STATETREE_TRACE_SCOPED_STATE_PHASE(StateHandle, Phase) \
		FStateTreeInstanceDebugId ID_NAME = GetInstanceDebugId(); \
		TRACE_STATETREE_PHASE_EVENT(ID_NAME, Phase, EStateTreeTraceEventType::Push, StateHandle) \
		ON_SCOPE_EXIT { TRACE_STATETREE_PHASE_EVENT(ID_NAME, Phase, EStateTreeTraceEventType::Pop, StateHandle) }

	#define STATETREE_TRACE_INSTANCE_EVENT(EventType)						TRACE_STATETREE_INSTANCE_EVENT(GetInstanceDebugId(), GetStateTree(), *GetInstanceDescription(), EventType);
	#define STATETREE_TRACE_ACTIVE_STATES_EVENT(ActiveStates)				TRACE_STATETREE_ACTIVE_STATES_EVENT(GetInstanceDebugId(), ActiveStates);
	#define STATETREE_TRACE_LOG_EVENT(Format, ...)							TRACE_STATETREE_LOG_EVENT(GetInstanceDebugId(), Format, ##__VA_ARGS__)
	#define STATETREE_TRACE_STATE_EVENT(StateHandle, EventType)				TRACE_STATETREE_STATE_EVENT(GetInstanceDebugId(), StateHandle, EventType, EStateTreeStateSelectionBehavior::None);
	#define STATETREE_TRACE_TASK_EVENT(Index, DataView, EventType, Status)	TRACE_STATETREE_TASK_EVENT(GetInstanceDebugId(), FStateTreeIndex16(Index), DataView, EventType, Status);
	#define STATETREE_TRACE_EVALUATOR_EVENT(Index, DataView, EventType)		TRACE_STATETREE_EVALUATOR_EVENT(GetInstanceDebugId(), FStateTreeIndex16(Index), DataView, EventType);
	#define STATETREE_TRACE_CONDITION_EVENT(Index, DataView, EventType)		TRACE_STATETREE_CONDITION_EVENT(GetInstanceDebugId(), FStateTreeIndex16(Index), DataView, EventType);	
	#define STATETREE_TRACE_TRANSITION_EVENT(Source, EventType)				TRACE_STATETREE_TRANSITION_EVENT(GetInstanceDebugId(), Source, EventType);
#else
	#define STATETREE_TRACE_SCOPED_PHASE(Phase)
	#define STATETREE_TRACE_SCOPED_STATE(StateHandle)
	#define STATETREE_TRACE_SCOPED_STATE_PHASE(StateHandle, Phase)
	#define STATETREE_TRACE_INSTANCE_EVENT(EventType)
	#define STATETREE_TRACE_ACTIVE_STATES_EVENT(ActiveStates)
	#define STATETREE_TRACE_LOG_EVENT(Format, ...)
	#define STATETREE_TRACE_STATE_EVENT(StateHandle, EventType)
	#define STATETREE_TRACE_TASK_EVENT(Index, DataView, EventType, Status)
	#define STATETREE_TRACE_EVALUATOR_EVENT(Index, DataView, EventType)
	#define STATETREE_TRACE_CONDITION_EVENT(Index, DataView, EventType)
	#define STATETREE_TRACE_TRANSITION_EVENT(Source, EventType)
#endif // WITH_STATETREE_DEBUGGER

namespace UE::StateTree
{
	constexpr int32 DebugIndentSize = 2;	// Debug printing indent for hierarchical data.
}; // UE::StateTree

FStateTreeExecutionContext::FStateTreeExecutionContext(UObject& InOwner, const UStateTree& InStateTree, FStateTreeInstanceData& InInstanceData)
	: Owner(InOwner)
	, RootStateTree(InStateTree)
	, InstanceData(InInstanceData)
{
	if (InStateTree.IsReadyToRun())
	{
		// Initialize data views for all possible items.
		ContextDataViews.SetNum(RootStateTree.GetNumContextDataViews());
		
		// Set data views associated to the parameters using the default values
		SetDefaultParameters();

		InstanceDataStorage = &InstanceData.GetMutableStorage();
		check(InstanceDataStorage);
	}
	else
	{
		STATETREE_LOG(Warning, TEXT("%hs: StateTree asset is not valid ('%s' using StateTree '%s')"),
			__FUNCTION__, *GetNameSafe(&Owner), *GetFullNameSafe(&RootStateTree));
	}
}

FStateTreeExecutionContext::~FStateTreeExecutionContext()
{
}

void FStateTreeExecutionContext::SetDefaultParameters()
{
	if (ContextDataViews.IsValidIndex(RootStateTree.ParametersDataHandle.GetIndex()))
	{
		// @todo: Handle constness correctly.
		const FConstStructView ConstParameters = RootStateTree.GetDefaultParameters().GetValue();
		ContextDataViews[RootStateTree.ParametersDataHandle.GetIndex()] = FStateTreeDataView(ConstParameters.GetScriptStruct(), const_cast<uint8*>(ConstParameters.GetMemory()));	
	}
}

void FStateTreeExecutionContext::SetParameters(const FInstancedPropertyBag& Parameters)
{
	if (ensureMsgf(RootStateTree.GetDefaultParameters().GetPropertyBagStruct() == Parameters.GetPropertyBagStruct(),
		TEXT("Parameters must be of the same struct type. Make sure to migrate the provided parameters to the same type as the StateTree default parameters."))
		&& ContextDataViews.IsValidIndex(RootStateTree.ParametersDataHandle.GetIndex()))
	{
		// @todo: Handle constness correctly.
		const FConstStructView ConstParameters = Parameters.GetValue();
		ContextDataViews[RootStateTree.ParametersDataHandle.GetIndex()] = FStateTreeDataView(ConstParameters.GetScriptStruct(), const_cast<uint8*>(ConstParameters.GetMemory()));	
	}
}

bool FStateTreeExecutionContext::AreExternalDataViewsValid() const
{
	if (!IsValid())
	{
		return false;
	}
	
	bool bResult = true;
	for (const FStateTreeExternalDataDesc& DataDesc : RootStateTree.ExternalDataDescs)
	{
		const FStateTreeDataView& DataView = ContextDataViews[DataDesc.Handle.DataHandle.GetIndex()];
			
		auto IsAssignmentValid = [](const FStateTreeExternalDataDesc& DataDesc, const FStateTreeDataView& DataView)
		{	
			const UClass* DataDescClass = Cast<UClass>(DataDesc.Struct);
			const UClass* DataViewClass = Cast<UClass>(DataView.GetStruct());
			return DataView.GetStruct()->IsChildOf(DataDesc.Struct) || (DataViewClass && DataDescClass && DataViewClass->ImplementsInterface(DataDescClass));
		};

		if (DataDesc.Requirement == EStateTreeExternalDataRequirement::Required)
		{
			// Required items must have valid pointer of the expected type.  
			if (!DataView.IsValid() || !IsAssignmentValid(DataDesc, DataView))
			{
				bResult = false;
				break;
			}
		}
		else
		{
			// Optional items must have same type if they are set.
			if (DataView.IsValid() && !IsAssignmentValid(DataDesc, DataView))
			{
				bResult = false;
				break;
			}
		}
	}

	for (const FStateTreeExternalDataDesc& DataDesc : RootStateTree.GetContextDataDescs())
	{
		const FStateTreeDataView& DataView = ContextDataViews[DataDesc.Handle.DataHandle.GetIndex()];

		// Items must have valid pointer of the expected type.  
		if (!DataView.IsValid() || !DataView.GetStruct()->IsChildOf(DataDesc.Struct))
		{
			bResult = false;
			break;
		}
	}
	return bResult;
}

EStateTreeRunStatus FStateTreeExecutionContext::Start()
{
	CSV_SCOPED_TIMING_STAT_EXCLUSIVE(StateTree_Start);

	if (!IsValid())
	{
		STATETREE_LOG(Warning, TEXT("%hs: StateTree context is not initialized properly ('%s' using StateTree '%s')"),
			__FUNCTION__, *GetNameSafe(&Owner), *GetFullNameSafe(&RootStateTree));
		return EStateTreeRunStatus::Failed;
	}

	if (InstanceData.IsValid())
	{
		const FStateTreeExecutionState& Exec = GetExecState();
		if (!ensureMsgf(Exec.CurrentPhase == EStateTreeUpdatePhase::Unset, TEXT("%hs can't be called while already in %s ('%s' using StateTree '%s')."),
				__FUNCTION__, *UEnum::GetDisplayValueAsText(Exec.CurrentPhase).ToString(), *GetNameSafe(&Owner), *GetFullNameSafe(&RootStateTree)))
		{
			return EStateTreeRunStatus::Failed;
		}

		// Stop if still running previous state.
		if (Exec.TreeRunStatus == EStateTreeRunStatus::Running)
		{
			Stop();
		}
	}

	// Initialize instance data. No active states yet, so we'll initialize the evals and global tasks.
	InstanceData.Reset();

	FStateTreeExecutionState& Exec = GetExecState();

	// Initialize for the init frame.
	FStateTreeExecutionFrame& InitFrame = Exec.ActiveFrames.AddDefaulted_GetRef();
	InitFrame.StateTree = &RootStateTree;
	InitFrame.RootState = FStateTreeStateHandle::Root;
	InitFrame.ActiveStates = {};
	InitFrame.bIsGlobalFrame = true;
	
	UpdateInstanceData({}, Exec.ActiveFrames);
	if (!InstanceData.IsValid())
	{
		STATETREE_LOG(Warning, TEXT("%hs: Failed to initialize instance data on '%s' using StateTree '%s'. Try to recompile the StateTree asset."),
			__FUNCTION__, *GetNameSafe(&Owner), *GetFullNameSafe(&RootStateTree));
		return EStateTreeRunStatus::Failed;
	}

	// Must sent instance creation event first 
	STATETREE_TRACE_INSTANCE_EVENT(EStateTreeTraceEventType::Push);
	
	// Set scoped phase only for properly initialized context with valid Instance data
	// since we need it to output the InstanceId
	STATETREE_TRACE_SCOPED_PHASE(EStateTreeUpdatePhase::StartTree);

	// From this point any calls to Stop should be deferred.
	Exec.CurrentPhase = EStateTreeUpdatePhase::StartTree;

	// Start evaluators and global tasks. Fail the execution if any global task fails.
	FStateTreeIndex16 LastInitializedTaskIndex;
	const EStateTreeRunStatus GlobalTasksRunStatus = StartEvaluatorsAndGlobalTasks(LastInitializedTaskIndex);
	if (GlobalTasksRunStatus == EStateTreeRunStatus::Running)
	{
		// First tick.
		// Tasks are not ticked here, since their behavior is that EnterState() (called above) is treated as a tick.  
		TickEvaluatorsAndGlobalTasks(0.0f, /*bTickGlobalTasks*/false);

		// Initialize to unset running state.
		Exec.TreeRunStatus = EStateTreeRunStatus::Running;
		Exec.LastTickStatus = EStateTreeRunStatus::Unset;

		static const FStateTreeStateHandle RootState = FStateTreeStateHandle(0);

		TArray<FStateTreeExecutionFrame, TFixedAllocator<MaxExecutionFrames>> NextActiveFrames;
		if (SelectState(InitFrame, RootState, NextActiveFrames))
		{
			check(!NextActiveFrames.IsEmpty());
			if (NextActiveFrames.Last().ActiveStates.Last().IsCompletionState())
			{
				// Transition to a terminal state (succeeded/failed).
				STATETREE_LOG(Warning, TEXT("%hs: Tree %s at StateTree start on '%s' using StateTree '%s'."),
					__FUNCTION__, NextActiveFrames.Last().ActiveStates.Last() == FStateTreeStateHandle::Succeeded ? TEXT("succeeded") : TEXT("failed"), *GetNameSafe(&Owner), *GetFullNameSafe(&RootStateTree));
				Exec.TreeRunStatus = NextActiveFrames.Last().ActiveStates.Last().ToCompletionStatus();
			}
			else
			{
				// Enter state tasks can fail/succeed, treat it same as tick.
				FStateTreeTransitionResult Transition;
				Transition.TargetState = RootState;
				Transition.CurrentRunStatus = Exec.LastTickStatus;
				Transition.NextActiveFrames = NextActiveFrames; // Enter state will update Exec.ActiveFrames.
				const EStateTreeRunStatus LastTickStatus = EnterState(Transition);
			
				Exec.LastTickStatus = LastTickStatus;

				// Report state completed immediately.
				if (Exec.LastTickStatus != EStateTreeRunStatus::Running)
				{
					StateCompleted();
				}
			}
		}

		if (Exec.LastTickStatus == EStateTreeRunStatus::Unset)
		{
			// Should not happen. This may happen if initial state could not be selected.
			STATETREE_LOG(Error, TEXT("%hs: Failed to select initial state on '%s' using StateTree '%s'. This should not happen, check that the StateTree logic can always select a state at start."),
				__FUNCTION__, *GetNameSafe(&Owner), *GetFullNameSafe(&RootStateTree));
			Exec.TreeRunStatus = EStateTreeRunStatus::Failed;
		}
	}
	else
	{
		StopEvaluatorsAndGlobalTasks(GlobalTasksRunStatus, LastInitializedTaskIndex);

		STATETREE_LOG(VeryVerbose, TEXT("%hs: Global tasks completed the StateTree %s on start in status '%s'."),
			__FUNCTION__, *GetNameSafe(&Owner), *GetFullNameSafe(&RootStateTree), *UEnum::GetDisplayValueAsText(GlobalTasksRunStatus).ToString());

		// No active states or global tasks anymore, reset frames.
		Exec.ActiveFrames.Reset();
		
		// We are not considered as running yet so we only set the status without requiring a stop.
		Exec.TreeRunStatus = GlobalTasksRunStatus;
	}

	// Reset phase since we are now safe to stop.
	Exec.CurrentPhase = EStateTreeUpdatePhase::Unset;

	// Use local for resulting run state since Stop will reset the instance data.
	EStateTreeRunStatus Result = Exec.TreeRunStatus;
	
	if (Exec.RequestedStop != EStateTreeRunStatus::Unset)
	{
		STATETREE_LOG_AND_TRACE(VeryVerbose, TEXT("Processing Deferred Stop"));
		Result = Stop(Exec.RequestedStop);
	}
	
	return Result;
}

EStateTreeRunStatus FStateTreeExecutionContext::Stop(EStateTreeRunStatus CompletionStatus)
{
	CSV_SCOPED_TIMING_STAT_EXCLUSIVE(StateTree_Stop);

	if (!IsValid())
	{
		STATETREE_LOG(Warning, TEXT("%hs: StateTree context is not initialized properly ('%s' using StateTree '%s')"),
			__FUNCTION__, *GetNameSafe(&Owner), *GetFullNameSafe(&RootStateTree));
		return EStateTreeRunStatus::Failed;
	}
	
	if (!InstanceData.IsValid())
	{
		return EStateTreeRunStatus::Failed;
	}

	// Set scoped phase only for properly initialized context with valid Instance data
	// since we need it to output the InstanceId 
	STATETREE_TRACE_SCOPED_PHASE(EStateTreeUpdatePhase::StopTree);

	// Make sure that we return a valid completion status (i.e. Succeeded, Failed or Stopped)
	if (CompletionStatus == EStateTreeRunStatus::Unset
		|| CompletionStatus == EStateTreeRunStatus::Running)
	{
		CompletionStatus = EStateTreeRunStatus::Stopped;
	}

	FStateTreeExecutionState& Exec = GetExecState();

	// A reentrant call to Stop or a call from Start or Tick must be deferred.
	if (Exec.CurrentPhase != EStateTreeUpdatePhase::Unset)
	{
		STATETREE_LOG_AND_TRACE(VeryVerbose, TEXT("Deferring Stop at end of %s"), *UEnum::GetDisplayValueAsText(Exec.CurrentPhase).ToString());

		Exec.RequestedStop = CompletionStatus;
		return EStateTreeRunStatus::Running;
	}

	// No need to clear on exit since we reset all the instance data before leaving the function.
	Exec.CurrentPhase = EStateTreeUpdatePhase::StopTree;

	EStateTreeRunStatus Result = Exec.TreeRunStatus;
	
	// Capture events added between ticks.
	FStateTreeEventQueue& EventQueue = InstanceData.GetMutableEventQueue();
	EventsToProcess = EventQueue.GetEvents();
	EventQueue.Reset();

	// Exit states if still in some valid state.
	if (Exec.TreeRunStatus == EStateTreeRunStatus::Running)
	{
		// Transition to Succeeded state.
		FStateTreeTransitionResult Transition;
		Transition.TargetState = FStateTreeStateHandle::FromCompletionStatus(CompletionStatus);
		Transition.CurrentRunStatus = CompletionStatus;
		FStateTreeExecutionFrame& NewFrame = Transition.NextActiveFrames.AddDefaulted_GetRef();
		NewFrame.StateTree = &RootStateTree;
		NewFrame.RootState = FStateTreeStateHandle::Root;
		NewFrame.ActiveStates = {};
		
		if (Exec.TreeRunStatus == EStateTreeRunStatus::Running)
		{
			ExitState(Transition);
		}

		// Stop evaluators and global tasks.
		StopEvaluatorsAndGlobalTasks(CompletionStatus);

		// No active states or global tasks anymore, reset frames.
		Exec.ActiveFrames.Reset();

		Result = CompletionStatus;
	}

	// Trace before resetting the instance data since it is required to provide all the event information
	STATETREE_TRACE_ACTIVE_STATES_EVENT(FStateTreeActiveStates());
	STATETREE_TRACE_INSTANCE_EVENT(EStateTreeTraceEventType::Pop);

	// Destruct all allocated instance data (does not shrink the buffer). This will invalidate Exec too.
	InstanceData.Reset();

	return Result;
}

EStateTreeRunStatus FStateTreeExecutionContext::Tick(const float DeltaTime)
{
	CSV_SCOPED_TIMING_STAT_EXCLUSIVE(StateTree_Tick);
	STATETREE_TRACE_SCOPED_PHASE(EStateTreeUpdatePhase::TickStateTree);

	if (!IsValid())
	{
		STATETREE_LOG(Warning, TEXT("%hs: StateTree context is not initialized properly ('%s' using StateTree '%s')"),
			__FUNCTION__, *GetNameSafe(&Owner), *GetFullNameSafe(&RootStateTree));
		return EStateTreeRunStatus::Failed;
	}

	if (!InstanceData.IsValid())
	{
		STATETREE_LOG(Error, TEXT("%hs: Tick called on %s using StateTree %s with invalid instance data. Start() must be called before Tick()."),
			__FUNCTION__, *GetNameSafe(&Owner), *GetFullNameSafe(&RootStateTree));
		return EStateTreeRunStatus::Failed;
	}

	FStateTreeEventQueue& EventQueue = InstanceData.GetMutableEventQueue();
	FStateTreeExecutionState& Exec = GetExecState();

	// No ticking if the tree is done or stopped.
	if (Exec.TreeRunStatus != EStateTreeRunStatus::Running)
	{
		return Exec.TreeRunStatus;
	}

	if (!ensureMsgf(Exec.CurrentPhase == EStateTreeUpdatePhase::Unset, TEXT("%hs can't be called while already in %s ('%s' using StateTree '%s')."),
			__FUNCTION__, *UEnum::GetDisplayValueAsText(Exec.CurrentPhase).ToString(), *GetNameSafe(&Owner), *GetFullNameSafe(&RootStateTree)))
	{
		return EStateTreeRunStatus::Failed;
	}

	// From this point any calls to Stop should be deferred.
	Exec.CurrentPhase = EStateTreeUpdatePhase::TickStateTree;
	
	// Capture events added between ticks.
	EventsToProcess = EventQueue.GetEvents();
	EventQueue.Reset();
	
	// Update the delayed transitions.
	for (FStateTreeTransitionDelayedState& DelayedState : Exec.DelayedTransitions)
	{
		DelayedState.TimeLeft -= DeltaTime;
	}

	// Tick global evaluators and tasks.
	const EStateTreeRunStatus EvalAndGlobalTaskStatus = TickEvaluatorsAndGlobalTasks(DeltaTime);
	if (EvalAndGlobalTaskStatus == EStateTreeRunStatus::Running)
	{
		if (Exec.LastTickStatus == EStateTreeRunStatus::Running)
		{
			// Tick tasks on active states.
			Exec.LastTickStatus = TickTasks(DeltaTime);

			// Report state completed immediately.
			if (Exec.LastTickStatus != EStateTreeRunStatus::Running)
			{
				StateCompleted();
			}
		}

		// The state selection is repeated up to MaxIteration time. This allows failed EnterState() to potentially find a new state immediately.
		// This helps event driven StateTrees to not require another event/tick to find a suitable state.
		static constexpr int32 MaxIterations = 5;
		for (int32 Iter = 0; Iter < MaxIterations; Iter++)
		{
			// Append events accumulated during the tick, so that transitions can immediately act on them.
			// We'll consume the events only if they lead to state change below (EnterState is treated the same as Tick),
			// or let them be processed next frame if no transition.
			EventsToProcess.Append(EventQueue.GetEvents());

			// Trigger conditional transitions or state succeed/failed transitions. First tick transition is handled here too.
			if (TriggerTransitions())
			{
				STATETREE_TRACE_SCOPED_PHASE(EStateTreeUpdatePhase::ApplyTransitions);
				STATETREE_TRACE_TRANSITION_EVENT(NextTransitionSource, EStateTreeTraceEventType::OnTransition);
				NextTransitionSource.Reset();

				// We have committed to state change, consume events that were accumulated during the tick above.
				EventQueue.Reset();

				ExitState(NextTransition);

				// Tree succeeded or failed.
				if (NextTransition.TargetState.IsCompletionState())
				{
					// Transition to a terminal state (succeeded/failed), or default transition failed.
					Exec.TreeRunStatus = NextTransition.TargetState.ToCompletionStatus();

					// Stop evaluators and global tasks.
					StopEvaluatorsAndGlobalTasks(Exec.TreeRunStatus);

					// No active states or global tasks anymore, reset frames.
					Exec.ActiveFrames.Reset();

					break;
				}

				// Append and consume the events accumulated during the state exit.
				EventsToProcess.Append(EventQueue.GetEvents());
				EventQueue.Reset();

				// Enter state tasks can fail/succeed, treat it same as tick.
				const EStateTreeRunStatus LastTickStatus = EnterState(NextTransition);

				NextTransition.Reset();

				Exec.LastTickStatus = LastTickStatus;

				// Consider events so far processed. Events sent during EnterState went into EventQueue, and are processed in next iteration.
				EventsToProcess.Reset();

				// Report state completed immediately.
				if (Exec.LastTickStatus != EStateTreeRunStatus::Running)
				{
					StateCompleted();
				}
			}

			// Stop as soon as have found a running state.
			if (Exec.LastTickStatus == EStateTreeRunStatus::Running)
			{
				break;
			}
		}
	}
	else
	{
		// If global tasks succeed or fail, stop the tree.
		Exec.RequestedStop = EvalAndGlobalTaskStatus;
	}

	EventsToProcess.Reset();

	// Reset phase since we are now safe to stop.
	Exec.CurrentPhase = EStateTreeUpdatePhase::Unset;

	// Use local for resulting run state since Stop will reset the instance data.
	EStateTreeRunStatus Result = Exec.TreeRunStatus;
	
	if (Exec.RequestedStop != EStateTreeRunStatus::Unset)
	{
		STATETREE_LOG_AND_TRACE(VeryVerbose, TEXT("Processing Deferred Stop"));
		Result = Stop(Exec.RequestedStop);
	}

	return Result;
}

EStateTreeRunStatus FStateTreeExecutionContext::GetStateTreeRunStatus() const
{
	if (!IsValid())
	{
		STATETREE_LOG(Warning, TEXT("%hs: StateTree context is not initialized properly ('%s' using StateTree '%s')"),
			__FUNCTION__, *GetNameSafe(&Owner), *GetFullNameSafe(&RootStateTree));
		return EStateTreeRunStatus::Failed;
	}

	if (const FStateTreeExecutionState* Exec = InstanceData.GetExecutionState())
	{
		return Exec->TreeRunStatus;
	}
	
	return EStateTreeRunStatus::Failed;
}

void FStateTreeExecutionContext::SendEvent(const FStateTreeEvent& Event) const
{
	SendEvent(Event.Tag, Event.Payload, Event.Origin);
}

void FStateTreeExecutionContext::SendEvent(const FGameplayTag Tag, const FConstStructView Payload, const FName Origin) const
{
	CSV_SCOPED_TIMING_STAT_EXCLUSIVE(StateTree_SendEvent);

	if (!IsValid())
	{
		STATETREE_LOG(Warning, TEXT("%hs: StateTree context is not initialized properly ('%s' using StateTree '%s')"),
			__FUNCTION__, *GetNameSafe(&Owner), *GetFullNameSafe(&RootStateTree));
		return;
	}

	if (!InstanceData.IsValid())
	{
		STATETREE_LOG(Error, TEXT("%hs: SendEvent called on %s using StateTree %s with invalid instance data. Start() must be called before sending events."),
			__FUNCTION__, *GetNameSafe(&Owner), *GetFullNameSafe(&RootStateTree));
		return;
	}

	STATETREE_LOG_AND_TRACE(Verbose, TEXT("Send Event '%s'"), *Tag.ToString());

	FStateTreeEventQueue& EventQueue = InstanceData.GetMutableEventQueue();
	EventQueue.SendEvent(&Owner, Tag, Payload, Origin);
}

void FStateTreeExecutionContext::RequestTransition(const FStateTreeTransitionRequest& Request)
{
	CSV_SCOPED_TIMING_STAT_EXCLUSIVE(StateTree_RequestTransition);

	if (!IsValid())
	{
		STATETREE_LOG(Warning, TEXT("%hs: StateTree context is not initialized properly ('%s' using StateTree '%s')"),
			__FUNCTION__, *GetNameSafe(&Owner), *GetFullNameSafe(&RootStateTree));
		return;
	}

	if (!InstanceData.IsValid())
	{
		STATETREE_LOG(Error, TEXT("%hs: RequestTransition called on %s using StateTree %s with invalid instance data. Start() must be called before requesting transition."),
			__FUNCTION__, *GetNameSafe(&Owner), *GetFullNameSafe(&RootStateTree));
		return;
	}

	FStateTreeExecutionState& Exec = GetExecState();

	if (bAllowDirectTransitions)
	{
		checkf(CurrentlyProcessedFrame, TEXT("Expecting CurrentlyProcessedFrame to be valid when called during TriggerTransitions()."));
		
		STATETREE_LOG(Verbose, TEXT("Request transition to '%s' at priority %s"), *GetSafeStateName(*CurrentlyProcessedFrame, Request.TargetState), *UEnum::GetDisplayValueAsText(Request.Priority).ToString());

		if (RequestTransition(*CurrentlyProcessedFrame, Request.TargetState, Request.Priority))
		{
			NextTransitionSource = FStateTreeTransitionSource(EStateTreeTransitionSourceType::ExternalRequest, Request.TargetState, Request.Priority);
		}
	}
	else
	{
		const FStateTreeExecutionFrame* RootFrame = &Exec.ActiveFrames[0];
		if (CurrentlyProcessedFrame)
		{
			RootFrame = CurrentlyProcessedFrame;
		}

		if (!RootFrame)
		{
			STATETREE_LOG(Warning, TEXT("%hs: RequestTransition called on %s using StateTree %s without active state. Start() must be called before requesting transition."),
				__FUNCTION__, *GetNameSafe(&Owner), *GetFullNameSafe(&RootStateTree));
			return;
		}
		
		STATETREE_LOG(Verbose, TEXT("Request transition to '%s' at priority %s"), *GetSafeStateName(*RootFrame, Request.TargetState), *UEnum::GetDisplayValueAsText(Request.Priority).ToString());

		FStateTreeTransitionRequest RequestWithSource = Request;
		RequestWithSource.SourceStateTree = RootFrame->StateTree;
		RequestWithSource.SourceRootState = RootFrame->ActiveStates[0];
		RequestWithSource.SourceState = CurrentlyProcessedState;
		
		InstanceData.AddTransitionRequest(&Owner, RequestWithSource);
	}
}

#if WITH_STATETREE_DEBUGGER
FStateTreeInstanceDebugId FStateTreeExecutionContext::GetInstanceDebugId() const
{
	FStateTreeInstanceDebugId& InstanceDebugId = GetExecState().InstanceDebugId; 
	if (!InstanceDebugId.IsValid())
	{
		static std::atomic<uint32> SerialNumber = 0;
		InstanceDebugId = FStateTreeInstanceDebugId(GetTypeHash(GetInstanceDescription()), ++SerialNumber); 
	}
	return InstanceDebugId;
}
#endif // WITH_STATETREE_DEBUGGER

void FStateTreeExecutionContext::UpdateInstanceData(TConstArrayView<FStateTreeExecutionFrame> CurrentActiveFrames, TArrayView<FStateTreeExecutionFrame> NextActiveFrames)
{
	// Estimate how many new instance data items we might have.
	int32 EstimatedNumStructs = 0;
	for (int32 FrameIndex = 0; FrameIndex < NextActiveFrames.Num(); FrameIndex++)
	{
		const FStateTreeExecutionFrame& NextFrame = NextActiveFrames[FrameIndex];
		if (NextFrame.bIsGlobalFrame)
		{
			EstimatedNumStructs += NextFrame.StateTree->NumGlobalInstanceData;
		}
		// States
		for (int32 StateIndex = 0; StateIndex < NextFrame.ActiveStates.Num(); StateIndex++)
		{
			const FStateTreeStateHandle StateHandle = NextFrame.ActiveStates[StateIndex];
			const FCompactStateTreeState& State = NextFrame.StateTree->States[StateHandle.Index];
			EstimatedNumStructs += State.InstanceDataNum;
		}
	}
	
	TArray<FConstStructView, TConcurrentLinearArrayAllocator<FDefaultBlockAllocationTag>> InstanceStructs;
	InstanceStructs.Reserve(EstimatedNumStructs);

	// Find next instance data sources and find common/existing section of instance data at start.
	int32 CurrentGlobalInstanceIndexBase = 0;
	int32 NumCommonInstanceData = 0;

	const UStruct* NextStateParameterDataStruct = nullptr;
	FStateTreeIndex16 NextStateParameterDataIndex = FStateTreeIndex16::Invalid; 
	
	bool bAreCommon = true;
	for (int32 FrameIndex = 0; FrameIndex < NextActiveFrames.Num(); FrameIndex++)
	{
		const bool bIsCurrentFrameValid = CurrentActiveFrames.IsValidIndex(FrameIndex)
						&& CurrentActiveFrames[FrameIndex].IsSameFrame(NextActiveFrames[FrameIndex]);

		bAreCommon &= bIsCurrentFrameValid;

		const FStateTreeExecutionFrame* CurrentFrame = bIsCurrentFrameValid ? &CurrentActiveFrames[FrameIndex] : nullptr;
		FStateTreeExecutionFrame& NextFrame = NextActiveFrames[FrameIndex];

		check(NextFrame.StateTree);

		if (NextFrame.bIsGlobalFrame)
		{
			// Global Evals
			const int32 BaseIndex = InstanceStructs.Num();

			NextFrame.GlobalInstanceIndexBase = FStateTreeIndex16(BaseIndex);
			NextFrame.ActiveInstanceIndexBase = FStateTreeIndex16(BaseIndex);
			CurrentGlobalInstanceIndexBase = BaseIndex;
			
			InstanceStructs.AddDefaulted(NextFrame.StateTree->NumGlobalInstanceData);
			
			for (int32 EvalIndex = NextFrame.StateTree->EvaluatorsBegin; EvalIndex < (NextFrame.StateTree->EvaluatorsBegin + NextFrame.StateTree->EvaluatorsNum); EvalIndex++)
			{
				const FStateTreeEvaluatorBase& Eval =  NextFrame.StateTree->Nodes[EvalIndex].Get<const FStateTreeEvaluatorBase>();
				const FConstStructView EvalInstanceData = NextFrame.StateTree->DefaultInstanceData.GetStruct(Eval.InstanceTemplateIndex.Get());
				InstanceStructs[BaseIndex + Eval.InstanceDataHandle.GetIndex()] = EvalInstanceData;
			}

			// Global tasks
			for (int32 TaskIndex = NextFrame.StateTree->GlobalTasksBegin; TaskIndex < (NextFrame.StateTree->GlobalTasksBegin + NextFrame.StateTree->GlobalTasksNum); TaskIndex++)
			{
				const FStateTreeTaskBase& Task =  NextFrame.StateTree->Nodes[TaskIndex].Get<const FStateTreeTaskBase>();
				const FConstStructView TaskInstanceData = NextFrame.StateTree->DefaultInstanceData.GetStruct(Task.InstanceTemplateIndex.Get());
				InstanceStructs[BaseIndex + Task.InstanceDataHandle.GetIndex()] = TaskInstanceData;
			}

			if (bAreCommon)
			{
				NumCommonInstanceData = InstanceStructs.Num();
			}
		}

		// States
		const int32 BaseIndex = InstanceStructs.Num();

		NextFrame.GlobalInstanceIndexBase = FStateTreeIndex16(CurrentGlobalInstanceIndexBase);
		NextFrame.ActiveInstanceIndexBase = FStateTreeIndex16(BaseIndex);

		for (int32 StateIndex = 0; StateIndex < NextFrame.ActiveStates.Num(); StateIndex++)
		{
			// Check if the next state is still same as current state, GetStateSafe() will return invalid state if passed out of bounds index.
			bAreCommon = bAreCommon && (CurrentFrame && CurrentFrame->ActiveStates.GetStateSafe(StateIndex) == NextFrame.ActiveStates[StateIndex]);

			const FStateTreeStateHandle StateHandle = NextFrame.ActiveStates[StateIndex];
			const FCompactStateTreeState& State = NextFrame.StateTree->States[StateHandle.Index];

			InstanceStructs.AddDefaulted(State.InstanceDataNum);

			if (State.Type == EStateTreeStateType::Linked)
			{
				// Linked state's instance data is the parameters.
				check(State.ParameterDataHandle.IsValid());
				const FConstStructView ParamsInstanceData = NextFrame.StateTree->DefaultInstanceData.GetStruct(State.ParameterTemplateIndex.Get());
				InstanceStructs[BaseIndex + State.ParameterDataHandle.GetIndex()] = ParamsInstanceData;
				
				// Store the index of the parameter data, so that we can point the linked state to it.
				check(State.ParameterDataHandle.GetSource() == EStateTreeDataSourceType::LinkedStateParameterData);
				checkf(!NextStateParameterDataIndex.IsValid(), TEXT("NextStateParameterDataIndex not should be set yet when we encounter a linked state."));
				NextStateParameterDataIndex = FStateTreeIndex16(BaseIndex + State.ParameterDataHandle.GetIndex());
				NextStateParameterDataStruct = ParamsInstanceData.GetScriptStruct();
			}
			else if (State.Type == EStateTreeStateType::Subtree)
			{
				check(State.ParameterDataHandle.IsValid());
				const FConstStructView ParamsInstanceData = NextFrame.StateTree->DefaultInstanceData.GetStruct(State.ParameterTemplateIndex.Get());
				if (!NextStateParameterDataIndex.IsValid())
				{
					// Parameters are not set by a linked state, create instance data.
					InstanceStructs[BaseIndex + State.ParameterDataHandle.GetIndex()] = ParamsInstanceData;
					NextFrame.StateParameterDataIndex = FStateTreeIndex16(BaseIndex + State.ParameterDataHandle.GetIndex());
				}
				else
				{
					// Point to the parameter block set by linked state.
					check(NextStateParameterDataStruct == ParamsInstanceData.GetScriptStruct());
					NextFrame.StateParameterDataIndex = NextStateParameterDataIndex;
					NextStateParameterDataIndex = FStateTreeIndex16(); // Mark as used.
				}
			}
	
			for (int32 TaskIndex = State.TasksBegin; TaskIndex < (State.TasksBegin + State.TasksNum); TaskIndex++)
			{
				const FStateTreeTaskBase& Task = NextFrame.StateTree->Nodes[TaskIndex].Get<const FStateTreeTaskBase>();
				const FConstStructView TaskInstanceData = NextFrame.StateTree->DefaultInstanceData.GetStruct(Task.InstanceTemplateIndex.Get());
				InstanceStructs[BaseIndex + Task.InstanceDataHandle.GetIndex()] = TaskInstanceData;
			}

			if (bAreCommon)
			{
				NumCommonInstanceData = InstanceStructs.Num();
			}
		}
	}
	
	// Common section should match.
	// @todo: put this behind a define when enough testing has been done.
	for (int32 Index = 0; Index < NumCommonInstanceData; Index++)
	{
		check(Index < InstanceData.Num());

		FConstStructView ExistingInstanceDataView = InstanceData.GetStruct(Index);
		FConstStructView NewInstanceDataView = InstanceStructs[Index]; 

		check(NewInstanceDataView.GetScriptStruct() == ExistingInstanceDataView.GetScriptStruct());

		const FStateTreeInstanceObjectWrapper* ExistingWrapper = ExistingInstanceDataView.GetPtr<const FStateTreeInstanceObjectWrapper>();
		const FStateTreeInstanceObjectWrapper* NewWrapper = ExistingInstanceDataView.GetPtr<const FStateTreeInstanceObjectWrapper>();
		if (ExistingWrapper && NewWrapper)
		{
			check(ExistingWrapper->InstanceObject && NewWrapper->InstanceObject);
			check(ExistingWrapper->InstanceObject->GetClass() == NewWrapper->InstanceObject->GetClass());
		}
	}

	// Remove instance data that was not common.
	InstanceData.ShrinkTo(NumCommonInstanceData);

	// Add new instance data.
	InstanceData.Append(Owner, MakeArrayView(InstanceStructs.GetData() + NumCommonInstanceData, InstanceStructs.Num() - NumCommonInstanceData));
}

FStateTreeDataView FStateTreeExecutionContext::GetDataView(const FStateTreeExecutionFrame& CurrentFrame, const FStateTreeDataHandle Handle) const
{
	switch (Handle.GetSource())
	{
	case EStateTreeDataSourceType::None:
		return {};

	case EStateTreeDataSourceType::GlobalInstanceData:
		return InstanceDataStorage->GetMutableStruct(CurrentFrame.GlobalInstanceIndexBase.Get() + Handle.GetIndex());
	case EStateTreeDataSourceType::GlobalInstanceDataObject:
		return InstanceDataStorage->GetMutableObject(CurrentFrame.GlobalInstanceIndexBase.Get() + Handle.GetIndex());
		
	case EStateTreeDataSourceType::ActiveInstanceData:
		return InstanceDataStorage->GetMutableStruct(CurrentFrame.ActiveInstanceIndexBase.Get() + Handle.GetIndex());
	case EStateTreeDataSourceType::ActiveInstanceDataObject:
		return InstanceDataStorage->GetMutableObject(CurrentFrame.ActiveInstanceIndexBase.Get() + Handle.GetIndex());

	case EStateTreeDataSourceType::SharedInstanceData:
		check(CurrentlyProcessedSharedInstanceStorage);
		return CurrentlyProcessedSharedInstanceStorage->GetMutableStruct(Handle.GetIndex());
	case EStateTreeDataSourceType::SharedInstanceDataObject:
		check(CurrentlyProcessedSharedInstanceStorage);
		return CurrentlyProcessedSharedInstanceStorage->GetMutableStruct(Handle.GetIndex());

	case EStateTreeDataSourceType::ContextData:
		return ContextDataViews[Handle.GetIndex()];

	case EStateTreeDataSourceType::SubtreeParameterData:
		{
			FCompactStateTreeParameters& Params = InstanceDataStorage->GetMutableStruct(CurrentFrame.StateParameterDataIndex.Get()).Get<FCompactStateTreeParameters>();
			return Params.Parameters.GetMutableValue();
		}
	case EStateTreeDataSourceType::LinkedStateParameterData:
		{
			FCompactStateTreeParameters& Params = InstanceDataStorage->GetMutableStruct(CurrentFrame.ActiveInstanceIndexBase.Get() + Handle.GetIndex()).Get<FCompactStateTreeParameters>();
			return Params.Parameters.GetMutableValue();
		}

	default:
		checkf(false, TEXT("Unhandle case %s"), *UEnum::GetValueAsString(Handle.GetSource()));
	}

	return {};
}

bool FStateTreeExecutionContext::IsHandleSourceValid(const FStateTreeExecutionFrame& CurrentFrame, const FStateTreeDataHandle Handle) const
{
	// Checks that the instance data is valid for specific handle types.
	// 
	// The CurrentFrame may not be yet properly initialized, for that reason we need to check
	// that the path to the handle makes sense (it's part of the active states) as well as that
	// we actually have instance data for the handle (index is valid).
	// 
	// The (base) indices can be invalid if the frame/state is not entered yet.
	// For active instance data we need to check that the frame is initialized for a specific state,
	// as well as that the instance data is initialized.

	switch (Handle.GetSource())
	{
	case EStateTreeDataSourceType::None:
		return true;

	case EStateTreeDataSourceType::GlobalInstanceData:
	case EStateTreeDataSourceType::GlobalInstanceDataObject:
		return CurrentFrame.GlobalInstanceIndexBase.IsValid()
			&& InstanceDataStorage->IsValidIndex(CurrentFrame.GlobalInstanceIndexBase.Get() + Handle.GetIndex());

	case EStateTreeDataSourceType::ActiveInstanceData:
	case EStateTreeDataSourceType::ActiveInstanceDataObject:
		return CurrentFrame.ActiveInstanceIndexBase.IsValid()
			&& CurrentFrame.ActiveStates.Contains(Handle.GetState())
			&& InstanceDataStorage->IsValidIndex(CurrentFrame.ActiveInstanceIndexBase.Get() + Handle.GetIndex());
		
	case EStateTreeDataSourceType::SharedInstanceData:
	case EStateTreeDataSourceType::SharedInstanceDataObject:
		return true;

	case EStateTreeDataSourceType::ContextData:
		return true;

	case EStateTreeDataSourceType::SubtreeParameterData:
		return CurrentFrame.StateParameterDataIndex.IsValid()
			&& InstanceDataStorage->IsValidIndex(CurrentFrame.StateParameterDataIndex.Get());

	case EStateTreeDataSourceType::LinkedStateParameterData:
		return CurrentFrame.ActiveInstanceIndexBase.IsValid()
			&& CurrentFrame.ActiveStates.Contains(Handle.GetState())
			&& InstanceDataStorage->IsValidIndex(CurrentFrame.ActiveInstanceIndexBase.Get() + Handle.GetIndex());

	default:
		checkf(false, TEXT("Unhandle case %s"), *UEnum::GetValueAsString(Handle.GetSource()));
	}

	return false;
}


bool FStateTreeExecutionContext::CopyBatch(const FStateTreeExecutionFrame& CurrentFrame, const FStateTreeDataView TargetView, const FStateTreeIndex16 BindingsBatch) const
{
	const FStateTreePropertyCopyBatch& Batch = CurrentFrame.StateTree->PropertyBindings.GetBatch(BindingsBatch);
	check(TargetView.GetStruct() == Batch.TargetStruct.Struct);

	bool bSucceed = true;
	for (const FStateTreePropertyCopy& Copy : CurrentFrame.StateTree->PropertyBindings.GetBatchCopies(Batch))
	{
		const FStateTreeDataView SourceView = GetDataView(CurrentFrame, Copy.SourceDataHandle);
		bSucceed &= CurrentFrame.StateTree->PropertyBindings.CopyProperty(Copy, SourceView, TargetView);
	}
	return bSucceed;
}

bool FStateTreeExecutionContext::CopyBatchWithValidation(const FStateTreeExecutionFrame& CurrentFrame, const FStateTreeDataView TargetView, const FStateTreeIndex16 BindingsBatch) const
{
	const FStateTreePropertyCopyBatch& Batch = CurrentFrame.StateTree->PropertyBindings.GetBatch(BindingsBatch);
	check(TargetView.GetStruct() == Batch.TargetStruct.Struct);

	bool bSucceed = true;
	for (const FStateTreePropertyCopy& Copy : CurrentFrame.StateTree->PropertyBindings.GetBatchCopies(Batch))
	{
		if (!IsHandleSourceValid(CurrentFrame, Copy.SourceDataHandle))
		{
			bSucceed = false;
			break;
		}

		const FStateTreeDataView SourceView = GetDataView(CurrentFrame, Copy.SourceDataHandle);
		bSucceed &= CurrentFrame.StateTree->PropertyBindings.CopyProperty(Copy, SourceView, TargetView);
	}
	return bSucceed;
}

EStateTreeRunStatus FStateTreeExecutionContext::EnterState(FStateTreeTransitionResult& Transition)
{
	CSV_SCOPED_TIMING_STAT_EXCLUSIVE(StateTree_EnterState);

	if (Transition.NextActiveFrames.IsEmpty())
	{
		return EStateTreeRunStatus::Failed;
	}

	FStateTreeExecutionState& Exec = GetExecState();

	// Allocate new tasks.
	UpdateInstanceData(Exec.ActiveFrames, Transition.NextActiveFrames);

	Exec.StateChangeCount++;
	Exec.CompletedFrameIndex = FStateTreeIndex16::Invalid;
	Exec.CompletedStateHandle = FStateTreeStateHandle::Invalid;
	Exec.EnterStateFailedFrameIndex = FStateTreeIndex16::Invalid; // This will make all tasks to be accepted.
	Exec.EnterStateFailedTaskIndex = FStateTreeIndex16::Invalid; // This will make all tasks to be accepted.
	
	// On target branch means that the state is the target of current transition or child of it.
	// States which were active before and will remain active, but are not on target branch will not get
	// EnterState called. That is, a transition is handled as "replan from this state".
	bool bOnTargetBranch = false;
	FStateTreeTransitionResult CurrentTransition = Transition;
	EStateTreeRunStatus Result = EStateTreeRunStatus::Running;

	STATETREE_LOG(Log, TEXT("Enter state '%s' (%d)"), *DebugGetStatePath(Transition.NextActiveFrames), Exec.StateChangeCount);
	STATETREE_TRACE_SCOPED_PHASE(EStateTreeUpdatePhase::EnterStates);

	// The previous active frames are needed for state enter logic.
	TArray<FStateTreeExecutionFrame, TConcurrentLinearArrayAllocator<FDefaultBlockAllocationTag>> PreviousActiveFrames;
	PreviousActiveFrames = Exec.ActiveFrames;

	// Reset the current active frames, new ones are added one by one.
	Exec.ActiveFrames.Reset();

	for (int32 FrameIndex = 0; FrameIndex < Transition.NextActiveFrames.Num() && Result != EStateTreeRunStatus::Failed; FrameIndex++)
	{
		const FStateTreeExecutionFrame& NextFrame = Transition.NextActiveFrames[FrameIndex];
		
		FStateTreeExecutionFrame& CurrentFrame = Exec.ActiveFrames.Add_GetRef(NextFrame);
		// We'll add new states one by one, so that active states contain only the states which have EnterState called.
		CurrentFrame.ActiveStates.Reset();

		// Get previous active states, they are used to calculate transition type.
		FStateTreeActiveStates PreviousActiveStates;
		if (PreviousActiveFrames.IsValidIndex(FrameIndex)
			&& PreviousActiveFrames[FrameIndex].IsSameFrame(NextFrame))
		{
			PreviousActiveStates = PreviousActiveFrames[FrameIndex].ActiveStates;
		}

		FCurrentlyProcessedFrameScope FrameScope(*this, CurrentFrame, FrameIndex);
		const UStateTree* CurrentStateTree = NextFrame.StateTree;

		for (int32 Index = 0; Index < NextFrame.ActiveStates.Num() && Result != EStateTreeRunStatus::Failed; Index++)
		{
			const FStateTreeStateHandle CurrentHandle = NextFrame.ActiveStates[Index];
			const FStateTreeStateHandle PreviousHandle = PreviousActiveStates.GetStateSafe(Index);
			const FCompactStateTreeState& State = CurrentStateTree->States[CurrentHandle.Index];

			FCurrentlyProcessedStateScope StateScope(*this, CurrentHandle);
			
			// Add only enabled States to the list of active States
			if (State.bEnabled && !CurrentFrame.ActiveStates.Push(CurrentHandle))
			{
				STATETREE_LOG(Error, TEXT("%hs: Reached max execution depth when trying to enter state '%s'.  '%s' using StateTree '%s'."),
					__FUNCTION__, *GetStateStatusString(Exec), *GetNameSafe(&Owner), *GetFullNameSafe(&RootStateTree));
				break;
			}

			if (State.Type == EStateTreeStateType::Linked)
			{
				if (State.ParameterDataHandle.IsValid()
					&& State.ParameterBindingsBatch.IsValid())
				{
					const FStateTreeDataView StateParamsDataView = GetDataView(CurrentFrame, State.ParameterDataHandle);
					CopyBatch(CurrentFrame, StateParamsDataView, State.ParameterBindingsBatch);
				}
			}

			bOnTargetBranch = bOnTargetBranch || CurrentHandle == Transition.TargetState;
			const bool bWasActive = PreviousHandle == CurrentHandle;

			// Do not enter a disabled State tasks but maintain property bindings
			const bool bIsEnteringState = (!bWasActive || bOnTargetBranch) && State.bEnabled;

			CurrentTransition.CurrentState = CurrentHandle;
			CurrentTransition.ChangeType = bWasActive ? EStateTreeStateChangeType::Sustained : EStateTreeStateChangeType::Changed;

			if (bIsEnteringState)
			{
				STATETREE_TRACE_STATE_EVENT(CurrentHandle, EStateTreeTraceEventType::OnEntering);
				STATETREE_LOG(Log, TEXT("%*sState '%s' %s"), Index*UE::StateTree::DebugIndentSize, TEXT(""),
					*DebugGetStatePath(Transition.NextActiveFrames, &NextFrame, Index),
					*UEnum::GetDisplayValueAsText(CurrentTransition.ChangeType).ToString());
			}

			// Activate tasks on current state.
			for (int32 TaskIndex = State.TasksBegin; TaskIndex < (State.TasksBegin + State.TasksNum); TaskIndex++)
			{
				const FStateTreeTaskBase& Task = NextFrame.StateTree->Nodes[TaskIndex].Get<const FStateTreeTaskBase>();
				const FStateTreeDataView TaskInstanceView = GetDataView(NextFrame, Task.InstanceDataHandle);

				// Copy bound properties.
				if (Task.BindingsBatch.IsValid())
				{
					CopyBatch(NextFrame, TaskInstanceView, Task.BindingsBatch);
				}

				// Ignore disabled task
				if (Task.bTaskEnabled == false)
				{
					STATETREE_LOG(VeryVerbose, TEXT("%*sSkipped 'EnterState' for disabled Task: '%s'"), UE::StateTree::DebugIndentSize, TEXT(""), *Task.Name.ToString());
					continue;
				}

				const bool bShouldCallStateChange = CurrentTransition.ChangeType == EStateTreeStateChangeType::Changed
													|| (CurrentTransition.ChangeType == EStateTreeStateChangeType::Sustained && Task.bShouldStateChangeOnReselect);

				if (bIsEnteringState && bShouldCallStateChange)
				{
					STATETREE_LOG(Verbose, TEXT("%*s  Task '%s'"), Index*UE::StateTree::DebugIndentSize, TEXT(""), *Task.Name.ToString());

					EStateTreeRunStatus Status = EStateTreeRunStatus::Unset;
					{
						QUICK_SCOPE_CYCLE_COUNTER(StateTree_Task_EnterState);
						CSV_SCOPED_TIMING_STAT_EXCLUSIVE(StateTree_Task_EnterState);
					
						Status = Task.EnterState(*this, CurrentTransition);
					}

					STATETREE_TRACE_TASK_EVENT(TaskIndex, TaskInstanceView, EStateTreeTraceEventType::OnEntered, Status);

					if (Status != EStateTreeRunStatus::Running)
					{
						// Store the first state that completed, will be used to decide where to trigger transitions.
						if (!Exec.CompletedStateHandle.IsValid())
						{
							Exec.CompletedFrameIndex = FStateTreeIndex16(FrameIndex);
							Exec.CompletedStateHandle = CurrentHandle;
						}
						Result = Status;
					}
					
					if (Status == EStateTreeRunStatus::Failed)
					{
						// Store how far in the enter state we got. This will be used to match the StateCompleted() and ExitState() calls.
						Exec.EnterStateFailedFrameIndex = FStateTreeIndex16(FrameIndex); 
						Exec.EnterStateFailedTaskIndex = FStateTreeIndex16(TaskIndex);
						break;
					}
				}
			}

			if (bIsEnteringState)
			{
				STATETREE_TRACE_STATE_EVENT(CurrentHandle, EStateTreeTraceEventType::OnEntered);
			}
		}
	}

#if WITH_STATETREE_DEBUGGER
	// @todo: implement support for frames in debugger
	FStateTreeActiveStates AllActiveStates;
	for (const FStateTreeExecutionFrame& ActiveFrame : Exec.ActiveFrames)
	{
		for (const FStateTreeStateHandle StateHandle : ActiveFrame.ActiveStates)
		{
			AllActiveStates.Push(StateHandle);	
		}
	}
	STATETREE_TRACE_ACTIVE_STATES_EVENT(AllActiveStates);
#endif // WITH_STATETREE_DEBUGGER

	return Result;
}

void FStateTreeExecutionContext::ExitState(const FStateTreeTransitionResult& Transition)
{
	CSV_SCOPED_TIMING_STAT_EXCLUSIVE(StateTree_ExitState);

	FStateTreeExecutionState& Exec = GetExecState();

	if (Exec.ActiveFrames.IsEmpty())
	{
		return;
	}

	// On target branch means that the state is the target of current transition or child of it.
	// States which were active before and will remain active, but are not on target branch will not get
	// EnterState called. That is, a transition is handled as "replan from this state".
	bool bOnTargetBranch = false;

	struct FExitStateCall
	{
		FExitStateCall() = default;
		FExitStateCall(const EStateTreeStateChangeType InChangeType, const bool bInShouldCall)
			: ChangeType(InChangeType)
			, bShouldCall(bInShouldCall)
		{
		}

		EStateTreeStateChangeType ChangeType = EStateTreeStateChangeType::None;
		bool bShouldCall = false; 
	};

	TArray<FExitStateCall, TConcurrentLinearArrayAllocator<FDefaultBlockAllocationTag>> ExitStateCalls;
	
	for (int32 FrameIndex = 0; FrameIndex < Exec.ActiveFrames.Num(); FrameIndex++)
	{
		FStateTreeExecutionFrame& CurrentFrame = Exec.ActiveFrames[FrameIndex];
		const UStateTree* CurrentStateTree = CurrentFrame.StateTree;
		FStateTreeInstanceStorage& SharedInstanceDataStorage = CurrentStateTree->GetSharedInstanceData()->GetMutableStorage();

		FCurrentlyProcessedFrameScope FrameScope(*this, CurrentFrame, FrameIndex);

		const FStateTreeExecutionFrame* NextFrame = nullptr;
		if (Transition.NextActiveFrames.IsValidIndex(FrameIndex)
			&& Transition.NextActiveFrames[FrameIndex].IsSameFrame(CurrentFrame))
		{
			NextFrame = &Transition.NextActiveFrames[FrameIndex];
		}

		for (int32 Index = 0; Index < CurrentFrame.ActiveStates.Num(); Index++)
		{
			const FStateTreeStateHandle CurrentHandle = CurrentFrame.ActiveStates[Index];
			const FStateTreeStateHandle NextHandle = NextFrame ? NextFrame->ActiveStates.GetStateSafe(Index) : FStateTreeStateHandle::Invalid;
			const FCompactStateTreeState& State = CurrentStateTree->States[CurrentHandle.Index];

			FCurrentlyProcessedStateScope StateScope(*this, CurrentHandle);

			if (State.Type == EStateTreeStateType::Linked)
			{
				if (State.ParameterDataHandle.IsValid()
					&& State.ParameterBindingsBatch.IsValid())
				{
					const FStateTreeDataView StateParamsDataView = GetDataView(CurrentFrame, State.ParameterDataHandle);
					CopyBatch(CurrentFrame, StateParamsDataView, State.ParameterBindingsBatch);
				}
			}

			const bool bRemainsActive = NextHandle == CurrentHandle;
			bOnTargetBranch = bOnTargetBranch || NextHandle == Transition.TargetState;
			const EStateTreeStateChangeType ChangeType = bRemainsActive ? EStateTreeStateChangeType::Sustained : EStateTreeStateChangeType::Changed;
			
			// Should call ExitState() on this state.
			const bool bShouldCall = !bRemainsActive || bOnTargetBranch; 
			ExitStateCalls.Emplace(ChangeType, bShouldCall);

			// Do property copies, ExitState() is called below.
			for (int32 TaskIndex = State.TasksBegin; TaskIndex < (State.TasksBegin + State.TasksNum); TaskIndex++)
			{
				const FStateTreeTaskBase& Task = CurrentStateTree->Nodes[TaskIndex].Get<const FStateTreeTaskBase>();
				const FStateTreeDataView TaskInstanceView = GetDataView(CurrentFrame, Task.InstanceDataHandle);

				// Copy bound properties.
				if (Task.BindingsBatch.IsValid() && Task.bShouldCopyBoundPropertiesOnExitState)
				{
					CopyBatch(CurrentFrame, TaskInstanceView, Task.BindingsBatch);
				}
			}
		}
	}

	// Call in reverse order.
	STATETREE_LOG(Log, TEXT("Exit state '%s' (%d)"), *DebugGetStatePath(Exec.ActiveFrames), Exec.StateChangeCount);
	STATETREE_TRACE_SCOPED_PHASE(EStateTreeUpdatePhase::ExitStates);

	FStateTreeTransitionResult CurrentTransition = Transition;
	int32 CallIndex = ExitStateCalls.Num() - 1;

	for (int32 FrameIndex = Exec.ActiveFrames.Num() - 1; FrameIndex >= 0; FrameIndex--)
	{
		FStateTreeExecutionFrame& CurrentFrame = Exec.ActiveFrames[FrameIndex];
		const UStateTree* CurrentStateTree = CurrentFrame.StateTree;

		FCurrentlyProcessedFrameScope FrameScope(*this, CurrentFrame, FrameIndex);

		for (int32 Index = CurrentFrame.ActiveStates.Num() - 1; Index >= 0; Index--)
		{
			const FStateTreeStateHandle CurrentHandle = CurrentFrame.ActiveStates[Index];
			const FCompactStateTreeState& State = CurrentStateTree->States[CurrentHandle.Index];

			const FExitStateCall& ExitCall = ExitStateCalls[CallIndex--];
			CurrentTransition.ChangeType = ExitCall.ChangeType;

			STATETREE_LOG(Log, TEXT("%*sState '%s' %s"), Index*UE::StateTree::DebugIndentSize, TEXT(""), *DebugGetStatePath(Exec.ActiveFrames, &CurrentFrame, CurrentHandle.Index), *UEnum::GetDisplayValueAsText(CurrentTransition.ChangeType).ToString());

			STATETREE_TRACE_STATE_EVENT(CurrentHandle, EStateTreeTraceEventType::OnExiting);
				
			if (ExitCall.bShouldCall)
			{
				FCurrentlyProcessedStateScope StateScope(*this, CurrentHandle);

				// Remove any delayed transitions that belong to this state.
				Exec.DelayedTransitions.RemoveAllSwap(
					[StateTree = CurrentFrame.StateTree, Begin = State.TransitionsBegin, End = State.TransitionsBegin + State.TransitionsNum](const FStateTreeTransitionDelayedState& DelayedState)
					{
						return  DelayedState.StateTree == StateTree && DelayedState.TransitionIndex.Get() >= Begin && DelayedState.TransitionIndex.Get() < End;
					});

				CurrentTransition.CurrentState = CurrentHandle;

				// Do property copies, ExitState() is called below.
				for (int32 TaskIndex = (State.TasksBegin + State.TasksNum) - 1; TaskIndex >= State.TasksBegin; TaskIndex--)
				{

					// Call task completed only if EnterState() was called.
					// The task order in the tree (BF) allows us to use the comparison.
					// Relying here that invalid value of Exec.EnterStateFailedTaskIndex == MAX_uint16.
					if (TaskIndex <= Exec.EnterStateFailedTaskIndex.Get())
					{
						const FStateTreeTaskBase& Task = CurrentStateTree->Nodes[TaskIndex].Get<const FStateTreeTaskBase>();
						const FStateTreeDataView TaskInstanceView = GetDataView(CurrentFrame, Task.InstanceDataHandle);

						// Ignore disabled task
						if (Task.bTaskEnabled == false)
						{
							STATETREE_LOG(VeryVerbose, TEXT("%*sSkipped 'ExitState' for disabled Task: '%s'"), UE::StateTree::DebugIndentSize, TEXT(""), *Task.Name.ToString());
							continue;
						}

						const bool bShouldCallStateChange = CurrentTransition.ChangeType == EStateTreeStateChangeType::Changed
									|| (CurrentTransition.ChangeType == EStateTreeStateChangeType::Sustained && Task.bShouldStateChangeOnReselect);

						if (bShouldCallStateChange)
						{

							STATETREE_LOG(Verbose, TEXT("%*s  Task '%s'"), Index*UE::StateTree::DebugIndentSize, TEXT(""), *Task.Name.ToString());
							{
								QUICK_SCOPE_CYCLE_COUNTER(StateTree_Task_ExitState);
								CSV_SCOPED_TIMING_STAT_EXCLUSIVE(StateTree_Task_ExitState);
								Task.ExitState(*this, CurrentTransition);
							}
							STATETREE_TRACE_TASK_EVENT(TaskIndex, TaskInstanceView, EStateTreeTraceEventType::OnExited, Transition.CurrentRunStatus);
						}
					}
				}
			}

			STATETREE_TRACE_STATE_EVENT(CurrentHandle, EStateTreeTraceEventType::OnExited);
		}
	}

}

void FStateTreeExecutionContext::StateCompleted()
{
	CSV_SCOPED_TIMING_STAT_EXCLUSIVE(StateTree_StateCompleted);

	const FStateTreeExecutionState& Exec = GetExecState();

	if (Exec.ActiveFrames.IsEmpty())
	{
		return;
	}

	STATETREE_LOG(Verbose, TEXT("State Completed %s (%d)"), *UEnum::GetDisplayValueAsText(Exec.LastTickStatus).ToString(), Exec.StateChangeCount);

	// Call from child towards root to allow to pass results back.
	// Note: Completed is assumed to be called immediately after tick or enter state, so there's no property copying.

	for (int32 FrameIndex = Exec.ActiveFrames.Num() - 1; FrameIndex >= 0; FrameIndex--)
	{
		const FStateTreeExecutionFrame& CurrentFrame = Exec.ActiveFrames[FrameIndex];
		const UStateTree* CurrentStateTree = CurrentFrame.StateTree;

		FCurrentlyProcessedFrameScope FrameScope(*this, CurrentFrame, FrameIndex);

		if (FrameIndex <= Exec.EnterStateFailedFrameIndex.Get())
		{
			for (int32 Index = CurrentFrame.ActiveStates.Num() - 1; Index >= 0; Index--)
			{
				const FStateTreeStateHandle CurrentHandle = CurrentFrame.ActiveStates[Index];
				const FCompactStateTreeState& State = CurrentStateTree->States[CurrentHandle.Index];

				FCurrentlyProcessedStateScope StateScope(*this, CurrentHandle);
				
				STATETREE_LOG(Verbose, TEXT("%*sState '%s'"), Index*UE::StateTree::DebugIndentSize, TEXT(""), *DebugGetStatePath(Exec.ActiveFrames, &CurrentFrame, Index));
				STATETREE_TRACE_STATE_EVENT(CurrentHandle, EStateTreeTraceEventType::OnStateCompleted);

				// Notify Tasks
				for (int32 TaskIndex = (State.TasksBegin + State.TasksNum) - 1; TaskIndex >= State.TasksBegin; TaskIndex--)
				{
					// Call task completed only if EnterState() was called.
					// The task order in the tree (BF) allows us to use the comparison.
					// Relying here that invalid value of Exec.EnterStateFailedTaskIndex == MAX_uint16.
					if (TaskIndex <= Exec.EnterStateFailedTaskIndex.Get())
					{
						const FStateTreeTaskBase& Task = CurrentStateTree->Nodes[TaskIndex].Get<const FStateTreeTaskBase>();

						// Ignore disabled task
						if (Task.bTaskEnabled == false)
						{
							STATETREE_LOG(VeryVerbose, TEXT("%*sSkipped 'StateCompleted' for disabled Task: '%s'"), UE::StateTree::DebugIndentSize, TEXT(""), *Task.Name.ToString());
							continue;
						}
						
						STATETREE_LOG(Verbose, TEXT("%*s  Task '%s'"), Index*UE::StateTree::DebugIndentSize, TEXT(""), *Task.Name.ToString());
						Task.StateCompleted(*this, Exec.LastTickStatus, CurrentFrame.ActiveStates);
					}
				}
			}
		}
	}
}

EStateTreeRunStatus FStateTreeExecutionContext::TickEvaluatorsAndGlobalTasks(const float DeltaTime, const bool bTickGlobalTasks)
{
	CSV_SCOPED_TIMING_STAT_EXCLUSIVE(StateTree_TickEvaluators);
	STATETREE_TRACE_SCOPED_PHASE(EStateTreeUpdatePhase::TickingGlobalTasks);

	STATETREE_LOG(VeryVerbose, TEXT("Ticking Evaluators & Global Tasks"));

	FStateTreeExecutionState& Exec = GetExecState();

	EStateTreeRunStatus Result = EStateTreeRunStatus::Running;

	for (int32 FrameIndex = 0; FrameIndex < Exec.ActiveFrames.Num(); FrameIndex++)
	{
		FStateTreeExecutionFrame& CurrentFrame = Exec.ActiveFrames[FrameIndex];
		if (CurrentFrame.bIsGlobalFrame)
		{
			FCurrentlyProcessedFrameScope FrameScope(*this, CurrentFrame, FrameIndex);

			const UStateTree* CurrentStateTree = CurrentFrame.StateTree;

			// Tick evaluators
			for (int32 EvalIndex = CurrentStateTree->EvaluatorsBegin; EvalIndex < (CurrentStateTree->EvaluatorsBegin + CurrentStateTree->EvaluatorsNum); EvalIndex++)
			{
				const FStateTreeEvaluatorBase& Eval = CurrentStateTree->Nodes[EvalIndex].Get<const FStateTreeEvaluatorBase>();
				const FStateTreeDataView EvalInstanceView = GetDataView(CurrentFrame, Eval.InstanceDataHandle);

				// Copy bound properties.
				if (Eval.BindingsBatch.IsValid())
				{
					CopyBatch(CurrentFrame, EvalInstanceView, Eval.BindingsBatch);
				}
				STATETREE_LOG(VeryVerbose, TEXT("  Tick: '%s'"), *Eval.Name.ToString());
				{
					QUICK_SCOPE_CYCLE_COUNTER(StateTree_Eval_Tick);
					Eval.Tick(*this, DeltaTime);

					STATETREE_TRACE_EVALUATOR_EVENT(EvalIndex, EvalInstanceView, EStateTreeTraceEventType::OnTicked);
				}
			}

			if (bTickGlobalTasks)
			{
				// Used to stop ticking tasks after one fails, but we still want to keep updating the data views so that property binding works properly.
				bool bShouldTickTasks = true;
				const bool bHasEvents = !EventsToProcess.IsEmpty();

				for (int32 TaskIndex = CurrentStateTree->GlobalTasksBegin; TaskIndex < (CurrentStateTree->GlobalTasksBegin + CurrentStateTree->GlobalTasksNum); TaskIndex++)
				{
					const FStateTreeTaskBase& Task = CurrentStateTree->Nodes[TaskIndex].Get<const FStateTreeTaskBase>();
					const FStateTreeDataView TaskDataView = GetDataView(CurrentFrame, Task.InstanceDataHandle);

					// Ignore disabled task
					if (Task.bTaskEnabled == false)
					{
						STATETREE_LOG(VeryVerbose, TEXT("%*sSkipped 'Tick' for disabled Task: '%s'"), UE::StateTree::DebugIndentSize, TEXT(""), *Task.Name.ToString());
						continue;
					}

					const bool bNeedsTick = bShouldTickTasks && (Task.bShouldCallTick || (bHasEvents && Task.bShouldCallTickOnlyOnEvents));
					STATETREE_LOG(VeryVerbose, TEXT("  Tick: '%s' %s"), *Task.Name.ToString(), !bNeedsTick ? TEXT("[not ticked]") : TEXT(""));
					if (!bNeedsTick)
					{
						continue;
					}

					// Copy bound properties.
					// Only copy properties when the task is actually ticked, and copy properties at tick is requested.
					if (Task.BindingsBatch.IsValid() && Task.bShouldCopyBoundPropertiesOnTick)
					{
						CopyBatch(CurrentFrame, TaskDataView, Task.BindingsBatch);
					}

					//STATETREE_TRACE_TASK_EVENT(TaskIndex, TaskDataView, EStateTreeTraceEventType::OnTickingTask, EStateTreeRunStatus::Running);
					EStateTreeRunStatus TaskResult = EStateTreeRunStatus::Unset;
					{
						QUICK_SCOPE_CYCLE_COUNTER(StateTree_Task_Tick);
						CSV_SCOPED_TIMING_STAT_EXCLUSIVE(StateTree_Task_Tick);

						TaskResult = Task.Tick(*this, DeltaTime);
					}

					STATETREE_TRACE_TASK_EVENT(TaskIndex, TaskDataView,
						TaskResult != EStateTreeRunStatus::Running ? EStateTreeTraceEventType::OnTaskCompleted : EStateTreeTraceEventType::OnTicked,
						TaskResult);

					// If a global task succeeds or fails, it will stop the whole tree.
					if (TaskResult != EStateTreeRunStatus::Running)
					{
						Result = TaskResult;
					}
						
					if (TaskResult == EStateTreeRunStatus::Failed)
					{
						bShouldTickTasks = false;
					}
				}
			}
		}
	}

	return Result;
}


EStateTreeRunStatus FStateTreeExecutionContext::StartEvaluatorsAndGlobalTasks(FStateTreeIndex16& OutLastInitializedTaskIndex)
{
	CSV_SCOPED_TIMING_STAT_EXCLUSIVE(StateTree_StartEvaluators);
	STATETREE_TRACE_SCOPED_PHASE(EStateTreeUpdatePhase::StartGlobalTasks);

	STATETREE_LOG(Verbose, TEXT("Start Evaluators & Global tasks"));

	FStateTreeExecutionState& Exec = GetExecState();

	OutLastInitializedTaskIndex = FStateTreeIndex16();
	EStateTreeRunStatus Result = EStateTreeRunStatus::Running;

	for (int32 FrameIndex = 0; FrameIndex < Exec.ActiveFrames.Num(); FrameIndex++)
	{
		FStateTreeExecutionFrame& CurrentFrame = Exec.ActiveFrames[FrameIndex];
		if (CurrentFrame.bIsGlobalFrame)
		{
			FCurrentlyProcessedFrameScope FrameScope(*this, CurrentFrame, FrameIndex);
			
			const UStateTree* CurrentStateTree = CurrentFrame.StateTree;

			// Start evaluators
			for (int32 EvalIndex = CurrentStateTree->EvaluatorsBegin; EvalIndex < (CurrentStateTree->EvaluatorsBegin + CurrentStateTree->EvaluatorsNum); EvalIndex++)
			{
				const FStateTreeEvaluatorBase& Eval = CurrentStateTree->Nodes[EvalIndex].Get<const FStateTreeEvaluatorBase>();
				const FStateTreeDataView EvalInstanceView = GetDataView(CurrentFrame, Eval.InstanceDataHandle);

				// Copy bound properties.
				if (Eval.BindingsBatch.IsValid())
				{
					CopyBatch(CurrentFrame, EvalInstanceView, Eval.BindingsBatch);
				}
				STATETREE_LOG(Verbose, TEXT("  Start: '%s'"), *Eval.Name.ToString());
				{
					QUICK_SCOPE_CYCLE_COUNTER(StateTree_Eval_TreeStart);
					Eval.TreeStart(*this);

					STATETREE_TRACE_EVALUATOR_EVENT(EvalIndex, EvalInstanceView, EStateTreeTraceEventType::OnTreeStarted);
				}
			}

			// Start Global tasks
			// Even if we call Enter/ExitState() on global tasks, they do not enter any specific state.
			const FStateTreeTransitionResult Transition = {}; // Empty transition
		
			for (int32 TaskIndex = CurrentStateTree->GlobalTasksBegin; TaskIndex < (CurrentStateTree->GlobalTasksBegin + CurrentStateTree->GlobalTasksNum); TaskIndex++)
			{
				const FStateTreeTaskBase& Task =  CurrentStateTree->Nodes[TaskIndex].Get<const FStateTreeTaskBase>();
				const FStateTreeDataView TaskDataView = GetDataView(CurrentFrame, Task.InstanceDataHandle);

				// Copy bound properties.
				if (Task.BindingsBatch.IsValid())
				{
					CopyBatch(CurrentFrame, TaskDataView, Task.BindingsBatch);
				}

				// Ignore disabled task
				if (Task.bTaskEnabled == false)
				{
					STATETREE_LOG(VeryVerbose, TEXT("%*sSkipped 'EnterState' for disabled Task: '%s'"), UE::StateTree::DebugIndentSize, TEXT(""), *Task.Name.ToString());
					continue;
				}

				STATETREE_LOG(Verbose, TEXT("  Start: '%s'"), *Task.Name.ToString());
				{
					QUICK_SCOPE_CYCLE_COUNTER(StateTree_Task_TreeStart);
					const EStateTreeRunStatus TaskStatus = Task.EnterState(*this, Transition); 

					STATETREE_TRACE_TASK_EVENT(TaskIndex, TaskDataView, EStateTreeTraceEventType::OnEntered, TaskStatus);

					if (TaskStatus != EStateTreeRunStatus::Running)
					{
						OutLastInitializedTaskIndex = FStateTreeIndex16(TaskIndex);
						Result = TaskStatus;
						break;
					}
				}
			}
		}
	}

	return Result;
}

void FStateTreeExecutionContext::StopEvaluatorsAndGlobalTasks(const EStateTreeRunStatus CompletionStatus, const FStateTreeIndex16 LastInitializedTaskIndex)
{
	CSV_SCOPED_TIMING_STAT_EXCLUSIVE(StateTree_StopEvaluators);
	STATETREE_TRACE_SCOPED_PHASE(EStateTreeUpdatePhase::StopGlobalTasks);

	STATETREE_LOG(Verbose, TEXT("Stop Evaluators & Global Tasks"));

	FStateTreeExecutionState& Exec = GetExecState();

	// Update bindings
	for (int32 FrameIndex = 0; FrameIndex < Exec.ActiveFrames.Num(); FrameIndex++)
	{
		FStateTreeExecutionFrame& CurrentFrame = Exec.ActiveFrames[FrameIndex];
		if (CurrentFrame.bIsGlobalFrame)
		{
			FCurrentlyProcessedFrameScope FrameScope(*this, CurrentFrame, FrameIndex);
			
			const UStateTree* CurrentStateTree = CurrentFrame.StateTree;

			for (int32 EvalIndex = CurrentStateTree->EvaluatorsBegin; EvalIndex < (CurrentStateTree->EvaluatorsBegin + CurrentStateTree->EvaluatorsNum); EvalIndex++)
			{
				const FStateTreeEvaluatorBase& Eval = CurrentStateTree->Nodes[EvalIndex].Get<const FStateTreeEvaluatorBase>();
				const FStateTreeDataView EvalInstanceView = GetDataView(CurrentFrame, Eval.InstanceDataHandle);

				// Copy bound properties.
				if (Eval.BindingsBatch.IsValid())
				{
					CopyBatch(CurrentFrame, EvalInstanceView, Eval.BindingsBatch);
				}
			}

			for (int32 TaskIndex = CurrentStateTree->GlobalTasksBegin; TaskIndex < (CurrentStateTree->GlobalTasksBegin + CurrentStateTree->GlobalTasksNum); TaskIndex++)
			{
				const FStateTreeTaskBase& Task = CurrentStateTree->Nodes[TaskIndex].Get<const FStateTreeTaskBase>();
				const FStateTreeDataView TaskDataView = GetDataView(CurrentFrame, Task.InstanceDataHandle);

				// Copy bound properties.
				if (Task.BindingsBatch.IsValid() && Task.bShouldCopyBoundPropertiesOnExitState)
				{
					CopyBatch(CurrentFrame, TaskDataView, Task.BindingsBatch);
				}
			}
		}
	}

	// Call in reverse order.
	FStateTreeTransitionResult Transition;
	Transition.TargetState = FStateTreeStateHandle::FromCompletionStatus(CompletionStatus);
	Transition.CurrentRunStatus = CompletionStatus;

	for (int32 FrameIndex = Exec.ActiveFrames.Num() - 1; FrameIndex >= 0; FrameIndex--)
	{
		const FStateTreeExecutionFrame& CurrentFrame = Exec.ActiveFrames[FrameIndex];
		if (CurrentFrame.bIsGlobalFrame)
		{
			FCurrentlyProcessedFrameScope FrameScope(*this, CurrentFrame, FrameIndex);

			const UStateTree* CurrentStateTree = CurrentFrame.StateTree;

			for (int32 TaskIndex = (CurrentStateTree->GlobalTasksBegin + CurrentStateTree->GlobalTasksNum) - 1;  TaskIndex >= CurrentStateTree->GlobalTasksBegin; TaskIndex--)
			{
				const FStateTreeTaskBase& Task =  CurrentStateTree->Nodes[TaskIndex].Get<const FStateTreeTaskBase>();
				const FStateTreeDataView TaskDataView = GetDataView(CurrentFrame, Task.InstanceDataHandle);

				// Ignore disabled task
				if (Task.bTaskEnabled == false)
				{
					STATETREE_LOG(VeryVerbose, TEXT("%*sSkipped 'ExitState' for disabled Task: '%s'"), UE::StateTree::DebugIndentSize, TEXT(""), *Task.Name.ToString());
					continue;
				}

				// Relying here that invalid value of LastInitializedTaskIndex == MAX_uint16.
				if (TaskIndex <= LastInitializedTaskIndex.Get())
				{
					STATETREE_LOG(Verbose, TEXT("  Stop: '%s'"), *Task.Name.ToString());
					{
						QUICK_SCOPE_CYCLE_COUNTER(StateTree_Task_TreeStop);
						Task.ExitState(*this, Transition);
					}
					STATETREE_TRACE_TASK_EVENT(TaskIndex, TaskDataView, EStateTreeTraceEventType::OnExited, Transition.CurrentRunStatus);
				}
			}

			for (int32 EvalIndex = (CurrentStateTree->EvaluatorsBegin + CurrentStateTree->EvaluatorsNum) - 1; EvalIndex >= CurrentStateTree->EvaluatorsBegin; EvalIndex--)
			{
				const FStateTreeEvaluatorBase& Eval = CurrentStateTree->Nodes[EvalIndex].Get<const FStateTreeEvaluatorBase>();
				const FStateTreeDataView EvalInstanceView = GetDataView(CurrentFrame, Eval.InstanceDataHandle);
				
				STATETREE_LOG(Verbose, TEXT("  Stop: '%s'"), *Eval.Name.ToString());
				{
					QUICK_SCOPE_CYCLE_COUNTER(StateTree_Eval_TreeStop);
					Eval.TreeStop(*this);

					STATETREE_TRACE_EVALUATOR_EVENT(EvalIndex, EvalInstanceView, EStateTreeTraceEventType::OnTreeStopped);
				}
			}
		}
	}
}

EStateTreeRunStatus FStateTreeExecutionContext::TickTasks(const float DeltaTime)
{
	CSV_SCOPED_TIMING_STAT_EXCLUSIVE(StateTree_TickTasks);
	STATETREE_TRACE_SCOPED_PHASE(EStateTreeUpdatePhase::TickingTasks);

	FStateTreeExecutionState& Exec = GetExecState();

	if (Exec.ActiveFrames.IsEmpty())
	{
		return EStateTreeRunStatus::Failed;
	}

	EStateTreeRunStatus Result = EStateTreeRunStatus::Running;
	int32 NumTotalTasks = 0;

	const bool bHasEvents = !EventsToProcess.IsEmpty();

	Exec.CompletedFrameIndex = FStateTreeIndex16::Invalid;
	Exec.CompletedStateHandle = FStateTreeStateHandle::Invalid;
	
	// Used to stop ticking tasks after one fails, but we still want to keep updating the data views so that property binding works properly.
	bool bShouldTickTasks = true;

	STATETREE_CLOG(Exec.ActiveFrames.Num() > 0, VeryVerbose, TEXT("Ticking Tasks"));

	for (int32 FrameIndex = 0; FrameIndex < Exec.ActiveFrames.Num(); FrameIndex++)
	{
		const FStateTreeExecutionFrame& CurrentFrame = Exec.ActiveFrames[FrameIndex];
		const UStateTree* CurrentStateTree = CurrentFrame.StateTree;

		FCurrentlyProcessedFrameScope FrameScope(*this, CurrentFrame, FrameIndex);

		for (int32 Index = 0; Index < CurrentFrame.ActiveStates.Num(); Index++)
		{
			const FStateTreeStateHandle CurrentHandle = CurrentFrame.ActiveStates[Index];
			const FCompactStateTreeState& State = CurrentStateTree->States[CurrentHandle.Index];

			FCurrentlyProcessedStateScope StateScope(*this, CurrentHandle);
			STATETREE_TRACE_SCOPED_STATE(CurrentHandle);

			STATETREE_CLOG(State.TasksNum > 0, VeryVerbose, TEXT("%*sState '%s'"), Index*UE::StateTree::DebugIndentSize, TEXT(""), *DebugGetStatePath(Exec.ActiveFrames, &CurrentFrame, Index));

			if (State.Type == EStateTreeStateType::Linked)
			{
				if (State.ParameterDataHandle.IsValid()
					&& State.ParameterBindingsBatch.IsValid())
				{
					const FStateTreeDataView StateParamsDataView = GetDataView(CurrentFrame, State.ParameterDataHandle);
					CopyBatch(CurrentFrame, StateParamsDataView, State.ParameterBindingsBatch);
				}
			}

			// Update Tasks data and tick if possible (ie. if no task has yet failed and so bShouldTickTasks is true)
			for (int32 TaskIndex = State.TasksBegin; TaskIndex < (State.TasksBegin + State.TasksNum); TaskIndex++)
			{
				const FStateTreeTaskBase& Task = CurrentStateTree->Nodes[TaskIndex].Get<const FStateTreeTaskBase>();
				const FStateTreeDataView TaskDataView = GetDataView(CurrentFrame, Task.InstanceDataHandle);

				// Ignore disabled task
				if (Task.bTaskEnabled == false)
				{
					STATETREE_LOG(VeryVerbose, TEXT("%*sSkipped 'Tick' for disabled Task: '%s'"), UE::StateTree::DebugIndentSize, TEXT(""), *Task.Name.ToString());
					continue;
				}

				const bool bNeedsTick = bShouldTickTasks && (Task.bShouldCallTick || (bHasEvents && Task.bShouldCallTickOnlyOnEvents));
				STATETREE_LOG(VeryVerbose, TEXT("%*s  Tick: '%s' %s"), Index*UE::StateTree::DebugIndentSize, TEXT(""), *Task.Name.ToString(), !bNeedsTick ? TEXT("[not ticked]") : TEXT(""));
				if (!bNeedsTick)
				{
					continue;
				}
				
				// Copy bound properties.
				// Only copy properties when the task is actually ticked, and copy properties at tick is requested.
				if (Task.BindingsBatch.IsValid() && Task.bShouldCopyBoundPropertiesOnTick)
				{
					CopyBatch(CurrentFrame, TaskDataView, Task.BindingsBatch);
				}

				//STATETREE_TRACE_TASK_EVENT(TaskIndex, TaskDataView, EStateTreeTraceEventType::OnTickingTask, EStateTreeRunStatus::Running);
				EStateTreeRunStatus TaskResult = EStateTreeRunStatus::Unset;
				{
					QUICK_SCOPE_CYCLE_COUNTER(StateTree_Task_Tick);
					CSV_SCOPED_TIMING_STAT_EXCLUSIVE(StateTree_Task_Tick);

					TaskResult = Task.Tick(*this, DeltaTime);
				}

				STATETREE_TRACE_TASK_EVENT(TaskIndex, TaskDataView,
					TaskResult != EStateTreeRunStatus::Running ? EStateTreeTraceEventType::OnTaskCompleted : EStateTreeTraceEventType::OnTicked,
					TaskResult);
				
				// TODO: Add more control over which states can control the failed/succeeded result.
				if (TaskResult != EStateTreeRunStatus::Running)
				{
					// Store the first state that completed, will be used to decide where to trigger transitions.
					if (!Exec.CompletedStateHandle.IsValid())
					{
						Exec.CompletedFrameIndex = FStateTreeIndex16(FrameIndex);
						Exec.CompletedStateHandle = CurrentHandle;
					}
					Result = TaskResult;
				}
				
				if (TaskResult == EStateTreeRunStatus::Failed)
				{
					bShouldTickTasks = false;
				}
			}
			NumTotalTasks += State.TasksNum;
		}
	}

	if (NumTotalTasks == 0)
	{
		// No tasks, done ticking.
		Result = EStateTreeRunStatus::Succeeded;
		Exec.CompletedFrameIndex = FStateTreeIndex16(0);
		Exec.CompletedStateHandle = Exec.ActiveFrames[0].ActiveStates.GetStateSafe(0);
	}

	return Result;
}

bool FStateTreeExecutionContext::TestAllConditions(const FStateTreeExecutionFrame& CurrentFrame, const int32 ConditionsOffset, const int32 ConditionsNum)
{
	CSV_SCOPED_TIMING_STAT_EXCLUSIVE(StateTree_TestConditions);

	if (ConditionsNum == 0)
	{
		return true;
	}

	TStaticArray<EStateTreeConditionOperand, UE::StateTree::MaxConditionIndent + 1> Operands(InPlace, EStateTreeConditionOperand::Copy);
	TStaticArray<bool, UE::StateTree::MaxConditionIndent + 1> Values(InPlace, false);

	int32 Level = 0;
	
	for (int32 Index = 0; Index < ConditionsNum; Index++)
	{
		const int32 ConditionIndex = ConditionsOffset + Index;
		const FStateTreeConditionBase& Cond = CurrentFrame.StateTree->Nodes[ConditionIndex].Get<const FStateTreeConditionBase>();
		const FStateTreeDataView ConditionDataView = GetDataView(CurrentFrame, Cond.InstanceDataHandle);
		
		bool bValue = false;
		if (Cond.EvaluationMode == EStateTreeConditionEvaluationMode::Evaluated)
		{
			// Copy bound properties.
			if (Cond.BindingsBatch.IsValid())
			{
				// Use validated copy, since we test in situations where the sources are not always valid (e.g. enter conditions may try to access inactive parent state). 
				if (!CopyBatchWithValidation(CurrentFrame, ConditionDataView, Cond.BindingsBatch))
				{
					// If the source data cannot be accessed, the whole expression evaluates to false.
					Values[0] = false;
					break;
				}
			}
			
			bValue = Cond.TestCondition(*this);
			STATETREE_TRACE_CONDITION_EVENT(ConditionIndex, ConditionDataView, bValue ? EStateTreeTraceEventType::Passed : EStateTreeTraceEventType::Failed);
			
			// Reset copied properties that might contain object references.
			if (Cond.BindingsBatch.IsValid())
			{
				CurrentFrame.StateTree->PropertyBindings.ResetObjects(Cond.BindingsBatch, ConditionDataView);
			}
		}
		else
		{
			bValue = Cond.EvaluationMode == EStateTreeConditionEvaluationMode::ForcedTrue ? true : /* EStateTreeConditionEvaluationMode::AlwaysFalse */ false;
			STATETREE_TRACE_CONDITION_EVENT(ConditionIndex, FStateTreeDataView{}, bValue ? EStateTreeTraceEventType::Passed : EStateTreeTraceEventType::Failed);
		}

		const int32 DeltaIndent = Cond.DeltaIndent;
		const int32 OpenParens = FMath::Max(0, DeltaIndent) + 1;	// +1 for the current value that is stored at the empty slot at the top of the value stack.
		const int32 ClosedParens = FMath::Max(0, -DeltaIndent) + 1;

		// Store the operand to apply when merging higher level down when returning to this level.
		// @todo: remove this conditions in 5.1, needs resaving existing StateTrees.
		const EStateTreeConditionOperand Operand = Index == 0 ? EStateTreeConditionOperand::Copy : Cond.Operand;
		Operands[Level] = Operand;

		// Store current value at the top of the stack.
		Level += OpenParens;
		Values[Level] = bValue;

		// Evaluate and merge down values based on closed braces.
		// The current value is placed in parens (see +1 above), which makes merging down and applying the new value consistent.
		// The default operand is copy, so if the value is needed immediately, it is just copied down, or if we're on the same level,
		// the operand storing above gives handles with the right logic.
		for (int32 Paren = 0; Paren < ClosedParens; Paren++)
		{
			Level--;
			switch (Operands[Level])
			{
			case EStateTreeConditionOperand::Copy:
				Values[Level] = Values[Level + 1];
				break;
			case EStateTreeConditionOperand::And:
				Values[Level] &= Values[Level + 1];
				break;
			case EStateTreeConditionOperand::Or:
				Values[Level] |= Values[Level + 1];
				break;
			}
			Operands[Level] = EStateTreeConditionOperand::Copy;
		}
	}
	
	return Values[0];
}

FString FStateTreeExecutionContext::DebugGetEventsAsString() const
{
	FString Result;
	for (const FStateTreeEvent& Event : EventsToProcess)
	{
		if (!Result.IsEmpty())
		{
			Result += TEXT(", ");
		}
		Result += Event.Tag.ToString();
	}
	return Result;
}

bool FStateTreeExecutionContext::RequestTransition(const FStateTreeExecutionFrame& CurrentFrame, const FStateTreeStateHandle NextState, const EStateTreeTransitionPriority Priority, const EStateTreeSelectionFallback Fallback)
{
	// Skip lower priority transitions.
	if (NextTransition.Priority >= Priority)
	{
		return false;
	}

	if (NextState.IsCompletionState())
	{
		SetupNextTransition(CurrentFrame, NextState, Priority);
		STATETREE_LOG(Verbose, TEXT("Transition on state '%s' -> state '%s'"),
			*GetSafeStateName(CurrentFrame, CurrentFrame.ActiveStates.Last()), *NextState.Describe());
		return true;
	}
	if (!NextState.IsValid())
	{
		// NotSet is no-operation, but can be used to mask a transition at parent state. Returning unset keeps updating current state.
		SetupNextTransition(CurrentFrame, FStateTreeStateHandle::Invalid, Priority);
		return true;
	}

	TArray<FStateTreeExecutionFrame, TFixedAllocator<MaxExecutionFrames>> NewNextActiveFrames;
	if (SelectState(CurrentFrame, NextState, NewNextActiveFrames, Fallback))
	{
		SetupNextTransition(CurrentFrame, NextState, Priority);
		NextTransition.NextActiveFrames = NewNextActiveFrames;

		STATETREE_LOG(Verbose, TEXT("Transition on state '%s' -[%s]-> state '%s'"),
			*GetSafeStateName(CurrentFrame, CurrentFrame.ActiveStates.Last()),
			*GetSafeStateName(CurrentFrame, NextState),
			*GetSafeStateName(NextTransition.NextActiveFrames.Last(), NextTransition.NextActiveFrames.Last().ActiveStates.Last()));
		
		return true;
	}
		
	return false;
}

void FStateTreeExecutionContext::SetupNextTransition(const FStateTreeExecutionFrame& CurrentFrame, const FStateTreeStateHandle NextState, const EStateTreeTransitionPriority Priority)
{
	const FStateTreeExecutionState& Exec = GetExecState();

	NextTransition.CurrentRunStatus = Exec.LastTickStatus;
	NextTransition.SourceState = CurrentlyProcessedState;
	NextTransition.SourceStateTree = CurrentFrame.StateTree;
	NextTransition.SourceRootState = CurrentFrame.ActiveStates.GetStateSafe(0);
	NextTransition.TargetState = NextState;
	NextTransition.Priority = Priority;

	FStateTreeExecutionFrame& NewFrame = NextTransition.NextActiveFrames.AddDefaulted_GetRef();
	NewFrame.StateTree = CurrentFrame.StateTree;
	NewFrame.RootState = CurrentFrame.RootState;

	if (NextState == FStateTreeStateHandle::Invalid)
	{
		NewFrame.ActiveStates = {};
	}
	else
	{
		NewFrame.ActiveStates = FStateTreeActiveStates(NextState);
	}
}

bool FStateTreeExecutionContext::TriggerTransitions()
{
	CSV_SCOPED_TIMING_STAT_EXCLUSIVE(StateTree_TriggerTransition);
	STATETREE_TRACE_SCOPED_PHASE(EStateTreeUpdatePhase::TriggerTransitions);

	FAllowDirectTransitionsScope AllowDirectTransitionsScope(*this); // Set flag for the scope of this function to allow direct transitions without buffering.
	FStateTreeExecutionState& Exec = GetExecState();

	if (EventsToProcess.Num() > 0)
	{
		STATETREE_LOG_AND_TRACE(Verbose, TEXT("Trigger transitions with events [%s]"), *DebugGetEventsAsString());
	}

	NextTransition.Reset();

	//
	// Process transition requests
	//
	for (const FStateTreeTransitionRequest& Request : InstanceData.GetTransitionRequests())
	{
		// Find frame associated with the request.
		const int32 FrameIndex = Exec.ActiveFrames.IndexOfByPredicate([&Request](const FStateTreeExecutionFrame& Frame)
		{
			return Frame.StateTree == Request.SourceStateTree && Frame.RootState == Request.SourceRootState;
		});

		if (FrameIndex != INDEX_NONE)
		{
			const FStateTreeExecutionFrame& CurrentFrame = Exec.ActiveFrames[FrameIndex];
			if (RequestTransition(CurrentFrame, Request.TargetState, Request.Priority))
			{
				NextTransitionSource = FStateTreeTransitionSource(EStateTreeTransitionSourceType::ExternalRequest, Request.TargetState, Request.Priority);
			}
		}
	}
	InstanceData.ResetTransitionRequests();

	//
	// Check tick, event, and task based transitions first.
	//
	if (Exec.ActiveFrames.Num() > 0)
	{
		for (int32 FrameIndex = 0; FrameIndex < Exec.ActiveFrames.Num(); FrameIndex++)
		{
			FStateTreeExecutionFrame& CurrentFrame = Exec.ActiveFrames[FrameIndex];
			const UStateTree* CurrentStateTree = CurrentFrame.StateTree;

			FCurrentlyProcessedFrameScope FrameScope(*this, CurrentFrame, FrameIndex);

			for (int32 StateIndex = CurrentFrame.ActiveStates.Num() - 1; StateIndex >= 0; StateIndex--)
			{
				const FStateTreeStateHandle StateHandle = CurrentFrame.ActiveStates[StateIndex];
				const FCompactStateTreeState& State = CurrentStateTree->States[StateHandle.Index];

				// Do not process any transitions from a disabled state
				if (!State.bEnabled)
				{
					continue;
				}
				
				FCurrentlyProcessedStateScope StateScope(*this, StateHandle);
				STATETREE_TRACE_SCOPED_STATE(StateHandle);

				if (State.bHasTransitionTasks)
				{
					STATETREE_CLOG(State.TasksNum > 0, VeryVerbose, TEXT("%*sTrigger task transitions in state '%s'"), StateIndex*UE::StateTree::DebugIndentSize, TEXT(""), *DebugGetStatePath(Exec.ActiveFrames, &CurrentFrame, StateIndex));

					for (int32 TaskIndex = (State.TasksBegin + State.TasksNum) - 1; TaskIndex >= State.TasksBegin; TaskIndex--)
					{
						const FStateTreeTaskBase& Task = CurrentStateTree->Nodes[TaskIndex].Get<const FStateTreeTaskBase>();
						const FStateTreeDataView TaskDataView = GetDataView(CurrentFrame, Task.InstanceDataHandle);

						// Ignore disabled task
						if (Task.bTaskEnabled == false)
						{
							STATETREE_LOG(VeryVerbose, TEXT("%*sSkipped 'TriggerTransitions' for disabled Task: '%s'"), UE::StateTree::DebugIndentSize, TEXT(""), *Task.Name.ToString());
							continue;
						}

						if (Task.bShouldAffectTransitions)
						{
							STATETREE_LOG(VeryVerbose, TEXT("%*sTriggerTransitions: '%s'"), UE::StateTree::DebugIndentSize, TEXT(""), *Task.Name.ToString());
							STATETREE_TRACE_TASK_EVENT(TaskIndex, TaskDataView, EStateTreeTraceEventType::OnEvaluating, EStateTreeRunStatus::Running);
							check(TaskDataView.IsValid());
							Task.TriggerTransitions(*this);
						}
					}
				}
				
				for (uint8 i = 0; i < State.TransitionsNum; i++)
				{
					// All transition conditions must pass
					const int16 TransitionIndex = State.TransitionsBegin + i;
					const FCompactStateTransition& Transition = CurrentStateTree->Transitions[TransitionIndex];

					// Skip disabled transitions
					if (Transition.bTransitionEnabled == false)
					{
						continue;
					}
					
					// No need to test the transition if same or higher priority transition has already been processed.
					if (Transition.Priority <= NextTransition.Priority)
					{
						continue;
					}

					// Skip completion transitions
					if (EnumHasAnyFlags(Transition.Trigger, EStateTreeTransitionTrigger::OnStateCompleted))
					{
						continue;
					}

					// If a delayed transition has passed the delay, and remove it from the queue, and try trigger it.
					FStateTreeTransitionDelayedState* DelayedState = nullptr;
					if (Transition.HasDelay())
					{
						DelayedState = Exec.FindDelayedTransition(CurrentFrame.StateTree, FStateTreeIndex16(TransitionIndex));
						if (DelayedState != nullptr && DelayedState->TimeLeft <= 0.0f)
						{
							STATETREE_LOG(Verbose, TEXT("Passed delayed transition from '%s' (%s) -> '%s'"),
								*GetSafeStateName(CurrentFrame, CurrentFrame.ActiveStates.Last()), *State.Name.ToString(), *GetSafeStateName(CurrentFrame, Transition.State));

							Exec.DelayedTransitions.RemoveAllSwap([StateTree = CurrentFrame.StateTree, TransitionIndex](const FStateTreeTransitionDelayedState& DelayedState)
								{
									return DelayedState.StateTree == StateTree && DelayedState.TransitionIndex.Get() == TransitionIndex;
								});

							// Trigger Delayed Transition when the delay has passed.
							if (RequestTransition(CurrentFrame, Transition.State, Transition.Priority, Transition.Fallback))
							{
								NextTransitionSource = FStateTreeTransitionSource(FStateTreeIndex16(TransitionIndex), Transition.State, Transition.Priority);
							}
							continue;
						}
					}

					const bool bShouldTrigger = Transition.Trigger == EStateTreeTransitionTrigger::OnTick
												|| (Transition.Trigger == EStateTreeTransitionTrigger::OnEvent
													&& HasEventToProcess(Transition.EventTag));

					bool bPassed = false; 
					if (bShouldTrigger)
					{
						STATETREE_TRACE_TRANSITION_EVENT(FStateTreeTransitionSource(FStateTreeIndex16(TransitionIndex), Transition.State, Transition.Priority), EStateTreeTraceEventType::OnEvaluating);
						STATETREE_TRACE_SCOPED_PHASE(EStateTreeUpdatePhase::TransitionConditions);
						bPassed = TestAllConditions(CurrentFrame, Transition.ConditionsBegin, Transition.ConditionsNum);
					}

					if (bPassed)
					{
						// If the transitions is delayed, set up the delay. 
						if (Transition.HasDelay())
						{
							if (DelayedState == nullptr)
							{
								// Initialize new delayed transition.
								const float DelayDuration = Transition.Delay.GetRandomDuration();
								if (DelayDuration > 0.0f)
								{
									DelayedState = &Exec.DelayedTransitions.AddDefaulted_GetRef();
									DelayedState->StateTree = CurrentFrame.StateTree;
									DelayedState->TransitionIndex = FStateTreeIndex16(TransitionIndex);
									DelayedState->TimeLeft = DelayDuration;
									BeginDelayedTransition(*DelayedState);
									STATETREE_LOG(Verbose, TEXT("Delayed transition triggered from '%s' (%s) -> '%s' %.1fs"),
										*GetSafeStateName(CurrentFrame, CurrentFrame.ActiveStates.Last()), *State.Name.ToString(), *GetSafeStateName(CurrentFrame, Transition.State), DelayedState->TimeLeft);
									
									// Delay state added, skip requesting the transition.
									continue;
								}
								// Fallthrough to request transition if duration was zero. 
							}
							else
							{
								// We get here if the transitions re-triggers during the delay, on which case we'll just ignore it.
								continue;
							}
						}

						if (RequestTransition(CurrentFrame, Transition.State, Transition.Priority, Transition.Fallback))
						{
							NextTransitionSource = FStateTreeTransitionSource(FStateTreeIndex16(TransitionIndex), Transition.State, Transition.Priority);
						}
					}
				}
			}

			if (CurrentFrame.bIsGlobalFrame)
			{
				// Global frame
				if (CurrentFrame.StateTree->bHasGlobalTransitionTasks)
				{
					STATETREE_LOG(VeryVerbose, TEXT("Trigger global task transitions"));
					for (int32 TaskIndex = (CurrentStateTree->GlobalTasksBegin + CurrentStateTree->GlobalTasksNum) - 1; TaskIndex >= CurrentFrame.StateTree->GlobalTasksBegin; TaskIndex--)
					{
						const FStateTreeTaskBase& Task =  CurrentStateTree->Nodes[TaskIndex].Get<const FStateTreeTaskBase>();
						const FStateTreeDataView TaskDataView = GetDataView(CurrentFrame, Task.InstanceDataHandle);

						// Ignore disabled task
						if (Task.bTaskEnabled == false)
						{
							STATETREE_LOG(VeryVerbose, TEXT("%*sSkipped 'TriggerTransitions' for disabled Task: '%s'"), UE::StateTree::DebugIndentSize, TEXT(""), *Task.Name.ToString());
							continue;
						}

						if (Task.bShouldAffectTransitions)
						{
							STATETREE_LOG(VeryVerbose, TEXT("%*sTriggerTransitions: '%s'"), UE::StateTree::DebugIndentSize, TEXT(""), *Task.Name.ToString());
							STATETREE_TRACE_TASK_EVENT(TaskIndex, TaskDataView, EStateTreeTraceEventType::OnEvaluating, EStateTreeRunStatus::Running);
							check(TaskDataView.IsValid());
							Task.TriggerTransitions(*this);
						}
					}
				}
				
			}
		}
	}


	//
	// Check state completion transitions.
	//
	bool bProcessSubTreeCompletion = true;

	if (NextTransition.Priority == EStateTreeTransitionPriority::None
		&& Exec.LastTickStatus != EStateTreeRunStatus::Running)
	{
		// Start from the last completed state if specified.
		const int32 FrameStartIndex = Exec.CompletedFrameIndex.IsValid() ? Exec.CompletedFrameIndex.AsInt32() : (Exec.ActiveFrames.Num() - 1);
		check(FrameStartIndex >= 0 && FrameStartIndex < Exec.ActiveFrames.Num());
		
		for (int32 FrameIndex = FrameStartIndex; FrameIndex >= 0; FrameIndex--)
		{
			FStateTreeExecutionFrame& CurrentFrame = Exec.ActiveFrames[FrameIndex];
			const UStateTree* CurrentStateTree = CurrentFrame.StateTree;

			FCurrentlyProcessedFrameScope FrameScope(*this, CurrentFrame, FrameIndex);

			int32 StateStartIndex = CurrentFrame.ActiveStates.Num() - 1; // This is ok, even if the ActiveStates is 0, -1 will skip the whole state loop below.
			if (FrameIndex == FrameStartIndex
				&& Exec.CompletedStateHandle.IsValid())
			{
				StateStartIndex = CurrentFrame.ActiveStates.IndexOfReverse(Exec.CompletedStateHandle);
				// INDEX_NONE (-1) will skip the whole state loop below. We still want to warn.
				ensureMsgf(StateStartIndex != INDEX_NONE, TEXT("If CompletedFrameIndex and CompletedStateHandle are specified, we expect that the state is found"));
			}
			
			const EStateTreeTransitionTrigger CompletionTrigger = Exec.LastTickStatus == EStateTreeRunStatus::Succeeded ? EStateTreeTransitionTrigger::OnStateSucceeded : EStateTreeTransitionTrigger::OnStateFailed;
		
			// Check completion transitions
			for (int32 StateIndex = StateStartIndex; StateIndex >= 0; StateIndex--)
			{
				const FStateTreeStateHandle StateHandle = CurrentFrame.ActiveStates[StateIndex];
				const FCompactStateTreeState& State = CurrentStateTree->States[StateHandle.Index];

				FCurrentlyProcessedStateScope StateScope(*this, StateHandle);
				STATETREE_TRACE_SCOPED_STATE_PHASE(StateHandle, EStateTreeUpdatePhase::TriggerTransitions);

				for (uint8 i = 0; i < State.TransitionsNum; i++)
				{
					// All transition conditions must pass
					const int16 TransitionIndex = State.TransitionsBegin + i;
					const FCompactStateTransition& Transition = CurrentStateTree->Transitions[TransitionIndex];

					// Skip disabled transitions
					if (Transition.bTransitionEnabled == false)
					{
						continue;
					}

					if (EnumHasAnyFlags(Transition.Trigger, CompletionTrigger))
					{
						bool bPassed = false;
						{
							STATETREE_TRACE_TRANSITION_EVENT(FStateTreeTransitionSource(FStateTreeIndex16(TransitionIndex), Transition.State, Transition.Priority), EStateTreeTraceEventType::OnEvaluating);
							STATETREE_TRACE_SCOPED_PHASE(EStateTreeUpdatePhase::TransitionConditions);
							bPassed = TestAllConditions(CurrentFrame, Transition.ConditionsBegin, Transition.ConditionsNum);
						}

						if (bPassed)
						{
							// No delay allowed on completion conditions.
							// No priority on completion transitions, use the priority to signal that state is selected.
							if (RequestTransition(CurrentFrame, Transition.State, EStateTreeTransitionPriority::Normal, Transition.Fallback))
							{
								NextTransitionSource = FStateTreeTransitionSource(FStateTreeIndex16(TransitionIndex), Transition.State, Transition.Priority);
								break;
							}
						}
					}
				}

				if (NextTransition.Priority != EStateTreeTransitionPriority::None)
				{
					break;
				}
			}

			if (NextTransition.Priority == EStateTreeTransitionPriority::None)
			{
				STATETREE_LOG_AND_TRACE(Verbose, TEXT("Could not trigger completion transition, jump back to root state."));
				FCurrentlyProcessedStateScope StateScope(*this, FStateTreeStateHandle::Root);
				if (RequestTransition(CurrentFrame, FStateTreeStateHandle::Root, EStateTreeTransitionPriority::Normal))
				{
					NextTransitionSource = FStateTreeTransitionSource(EStateTreeTransitionSourceType::Internal, FStateTreeStateHandle::Root, EStateTreeTransitionPriority::Normal);
				}
				else
				{
					STATETREE_LOG_AND_TRACE(Warning, TEXT("Failed to select root state. Stopping the tree with failure."));

					SetupNextTransition(CurrentFrame, FStateTreeStateHandle::Failed, EStateTreeTransitionPriority::Critical);

					// In this case we don't want to complete subtrees, we want to force the whole tree to stop.
					bProcessSubTreeCompletion = false;
				}
			}
		}
	}

	// Check if the transition was succeed/failed, if we're on a sub-tree, complete the subtree instead of transition.
	if (NextTransition.TargetState.IsCompletionState() && bProcessSubTreeCompletion)
	{
		const int32 SourceFrameIndex = Exec.ActiveFrames.IndexOfByPredicate([&NextTransition = NextTransition](const FStateTreeExecutionFrame& Frame)
		{
			return Frame.StateTree == NextTransition.SourceStateTree && Frame.RootState == NextTransition.SourceRootState;
		});
		// Check that the transition source frame is a sub-tree, the first frame (0 index) is not a subtree. 
		if (SourceFrameIndex > 0)
		{
			const FStateTreeExecutionFrame& SourceFrame = Exec.ActiveFrames[SourceFrameIndex];
			const int32 ParentFrameIndex = SourceFrameIndex - 1;
			const FStateTreeExecutionFrame& ParentFrame = Exec.ActiveFrames[ParentFrameIndex];
			const FStateTreeStateHandle ParentLinkedState = ParentFrame.ActiveStates.Last();

			if (ParentLinkedState.IsValid())
			{
				const EStateTreeRunStatus RunStatus = NextTransition.TargetState.ToCompletionStatus(); 
				STATETREE_LOG(Verbose, TEXT("Completed subtree '%s' from state '%s': %s"),
					*GetSafeStateName(ParentFrame, ParentLinkedState), *GetSafeStateName(SourceFrame, NextTransition.SourceState), *UEnum::GetDisplayValueAsText(RunStatus).ToString());

				// Set the parent linked state as last completed state, and update tick status to the status from the transition.
				Exec.CompletedFrameIndex = FStateTreeIndex16(ParentFrameIndex);
				Exec.CompletedStateHandle = ParentLinkedState;
				Exec.LastTickStatus = RunStatus;

				// Clear the transition and return that no transition took place.
				// Since the LastTickStatus != running, the transition loop will try another transition
				// now starting from the linked parent state. If we run out of retires in the selection loop (e.g. very deep hierarchy)
				// we will continue on next tick.
				NextTransition.Reset();
				return false;
			}
		}
	}

	return NextTransition.TargetState.IsValid();
}

bool FStateTreeExecutionContext::SelectState(const FStateTreeExecutionFrame& CurrentFrame,
											const FStateTreeStateHandle NextState,
											TArray<FStateTreeExecutionFrame, TFixedAllocator<MaxExecutionFrames>>& OutNextActiveFrames,
											const EStateTreeSelectionFallback Fallback)
{
	const FStateTreeExecutionState& Exec = GetExecState();

	if (Exec.ActiveFrames.IsEmpty())
	{
		STATETREE_LOG(Error, TEXT("%hs: SelectState can only be called on initialized tree.  '%s' using StateTree '%s'."),
			__FUNCTION__, *GetNameSafe(&Owner), *GetFullNameSafe(&RootStateTree));
		return false;
	}
	
	if (!NextState.IsValid())
	{
		return false;
	}

	// Walk towards the root from current state.
	TStaticArray<FStateTreeStateHandle, FStateTreeActiveStates::MaxStates> ParentStates;
	int32 NumParentStates = 0;
	FStateTreeStateHandle CurrState = NextState;
	while (CurrState.IsValid())
	{
		if (NumParentStates == FStateTreeActiveStates::MaxStates)
		{
			STATETREE_LOG(Error, TEXT("%hs: Reached max execution depth when trying to select state %s from '%s'.  '%s' using StateTree '%s'."),
				__FUNCTION__, *GetSafeStateName(CurrentFrame, NextState), *GetStateStatusString(Exec), *GetNameSafe(&Owner), *GetFullNameSafe(&RootStateTree));
			return false;
		}
		// Store the states that are in between the 'NextState' and common ancestor. 
		ParentStates[NumParentStates++] = CurrState;
		CurrState = CurrentFrame.StateTree->States[CurrState.Index].Parent;
	}

	const UStateTree* NextStateTree = CurrentFrame.StateTree;
	const FStateTreeStateHandle NextRootState = ParentStates[NumParentStates - 1]; 

	// Find the frame that the next state belongs to.
	int32 CurrentFrameIndex = INDEX_NONE;
	int32 CurrentStateTreeIndex = INDEX_NONE;

	for (int32 FrameIndex = Exec.ActiveFrames.Num() - 1; FrameIndex >= 0; FrameIndex--)
	{
		const FStateTreeExecutionFrame& Frame = Exec.ActiveFrames[FrameIndex]; 
		if (Frame.StateTree == NextStateTree)
		{
			CurrentStateTreeIndex = FrameIndex;
			if (Frame.RootState == NextRootState)
			{
				CurrentFrameIndex = FrameIndex;
				break;
			}
		}
	}

	// Copy common frames over.
	if (CurrentFrameIndex != INDEX_NONE)
	{
		const int32 NumCommonFrames = CurrentFrameIndex + 1;
		OutNextActiveFrames = MakeArrayView(Exec.ActiveFrames.GetData(), NumCommonFrames);
	}
	else if (CurrentStateTreeIndex != INDEX_NONE)
	{
		// If we could not find a common frame, we assume that we jumped to different subtree in same asset.
		const int32 NumCommonFrames = CurrentStateTreeIndex + 1;
		OutNextActiveFrames = MakeArrayView(Exec.ActiveFrames.GetData(), NumCommonFrames);
	}
	else
	{
		STATETREE_LOG(Error, TEXT("%hs: Encountered unrecognized state %s during state selection from '%s'.  '%s' using StateTree '%s'."),
			__FUNCTION__, *GetNameSafe(NextStateTree), *GetStateStatusString(Exec), *GetNameSafe(&Owner), *GetFullNameSafe(&RootStateTree));
		return false;
	}
	
	// Append in between state in reverse order, they were collected from leaf towards the root.
	// Note: NextState will be added by SelectStateInternal() if conditions pass.
	const int32 LastFrameIndex = OutNextActiveFrames.Num() - 1;
	FStateTreeExecutionFrame& LastFrame = OutNextActiveFrames[LastFrameIndex];

	LastFrame.ActiveStates.Reset();
	for (int32 Index = NumParentStates - 1; Index > 0; Index--)
	{
		LastFrame.ActiveStates.Push(ParentStates[Index]);
	}

	TArray<FStateTreeExecutionFrame, TFixedAllocator<MaxExecutionFrames>> InitialNextActiveFrames;
	
	if (Fallback == EStateTreeSelectionFallback::NextSelectableSibling)
	{
		InitialNextActiveFrames = OutNextActiveFrames;
	}
	
	// We take copy of the last frame and assign it later, as SelectStateInternal() might change the array and invalidate the pointer.
	if (SelectStateInternal(OutNextActiveFrames[LastFrameIndex], NextState, OutNextActiveFrames))
	{
		return true;
	}

	// Failed to Select Next State, handle fallback here
	// Return true on the first next sibling that gets selected successfully
	if (Fallback == EStateTreeSelectionFallback::NextSelectableSibling && NumParentStates >= 2)
	{
		// InBetweenStates is in reversed order (i.e. from leaf to root)
		const FStateTreeStateHandle Parent = ParentStates[1];
		if (Parent.IsValid())
		{
			const FCompactStateTreeState& ParentState = CurrentFrame.StateTree->States[Parent.Index];

			uint16 ChildState = CurrentFrame.StateTree->States[NextState.Index].GetNextSibling();
			for (; ChildState < ParentState.ChildrenEnd; ChildState = CurrentFrame.StateTree->States[ChildState].GetNextSibling())
			{
				FStateTreeStateHandle ChildStateHandle = FStateTreeStateHandle(ChildState);

				// Start selection from blank slate.
				OutNextActiveFrames = InitialNextActiveFrames;
	
				// We take copy of the last frame and assign it later, as SelectStateInternal() might change the array and invalidate the pointer.
				if (SelectStateInternal(OutNextActiveFrames[LastFrameIndex], ChildStateHandle, OutNextActiveFrames))
				{
					return true;
				}
			}
		}
	}
	
	return false;
}

bool FStateTreeExecutionContext::SelectStateInternal(FStateTreeExecutionFrame& CurrentFrame, const FStateTreeStateHandle NextState,
														TArray<FStateTreeExecutionFrame, TFixedAllocator<MaxExecutionFrames>>& OutNextActiveFrames)
{
	CSV_SCOPED_TIMING_STAT_EXCLUSIVE(StateTree_SelectState);

	const FStateTreeExecutionState& Exec = GetExecState();

	if (!NextState.IsValid())
	{
		// Trying to select non-existing state.
		STATETREE_LOG(Error, TEXT("%hs: Trying to select invalid state from '%s'.  '%s' using StateTree '%s'."),
            __FUNCTION__, *GetStateStatusString(Exec), *GetNameSafe(&Owner), *GetFullNameSafe(CurrentFrame.StateTree));
		return false;
	}

	FCurrentlyProcessedFrameScope FrameScope(*this, CurrentFrame, INDEX_NONE);

	const UStateTree* CurrentStateTree = CurrentFrame.StateTree;
	const FCompactStateTreeState& CurrentState = CurrentStateTree->States[NextState.Index];

	if (CurrentState.bEnabled == false)
	{
		// Do not select disabled state
		STATETREE_LOG(VeryVerbose, TEXT("%hs: Ignoring disabled state '%s'.  '%s' using StateTree '%s'."),
			__FUNCTION__, *GetSafeStateName(CurrentFrame, NextState), *GetNameSafe(&Owner), *GetFullNameSafe(CurrentFrame.StateTree));
		return false;
	}

	STATETREE_TRACE_SCOPED_STATE_PHASE(NextState, EStateTreeUpdatePhase::StateSelection);

	// The state cannot be directly selected.
	if (CurrentState.SelectionBehavior == EStateTreeStateSelectionBehavior::None)
	{
		return false;
	}

	// Check that the state can be entered
	STATETREE_TRACE_SCOPED_PHASE(EStateTreeUpdatePhase::EnterConditions);
	const bool bEnterConditionsPassed = TestAllConditions(CurrentFrame, CurrentState.EnterConditionsBegin, CurrentState.EnterConditionsNum);

	if (bEnterConditionsPassed)
	{
		if (!CurrentFrame.ActiveStates.Push(NextState))
		{
			STATETREE_LOG(Error, TEXT("%hs: Reached max execution depth when trying to select state %s from '%s'.  '%s' using StateTree '%s'."),
				__FUNCTION__, *GetSafeStateName(CurrentFrame, NextState), *GetStateStatusString(Exec), *GetNameSafe(&Owner), *GetFullNameSafe(CurrentFrame.StateTree));
			return false;
		}
		
		if (CurrentState.Type == EStateTreeStateType::Linked && CurrentState.LinkedState.IsValid())
		{
			if (OutNextActiveFrames.Num() == MaxExecutionFrames)
			{
				STATETREE_LOG(Error, TEXT("%hs: Reached max execution depth when trying to select state %s from '%s'.  '%s' using StateTree '%s'."),
					__FUNCTION__, *GetSafeStateName(CurrentFrame, NextState), *GetStateStatusString(Exec), *GetNameSafe(&Owner), *GetFullNameSafe(CurrentFrame.StateTree));
				return false;
			}

			FStateTreeExecutionFrame NewFrame;
			NewFrame.StateTree = CurrentFrame.StateTree;
			NewFrame.RootState = CurrentState.LinkedState;
			NewFrame.GlobalInstanceIndexBase = CurrentFrame.GlobalInstanceIndexBase;

			// If the Frame already exists, copy instance indices so that conditions that rely on active states work correctly.
			const FStateTreeExecutionFrame* ExistingFrame = Exec.ActiveFrames.FindByPredicate(
				[StateTree = CurrentFrame.StateTree, RootState = CurrentState.LinkedState](const FStateTreeExecutionFrame& Frame)
				{
					return Frame.StateTree == StateTree && Frame.RootState == RootState;
				});
			if (ExistingFrame)
			{
				NewFrame.ActiveInstanceIndexBase = ExistingFrame->ActiveInstanceIndexBase;
				NewFrame.StateParameterDataIndex = ExistingFrame->StateParameterDataIndex;
				// No need to update the global instance index base since we're on the same asset.
			}

			// Check and prevent recursion.
			const bool bNewFrameAlreadySelected = OutNextActiveFrames.ContainsByPredicate([&NewFrame](const FStateTreeExecutionFrame& Frame) {
				return Frame.IsSameFrame(NewFrame);
			});
			
			if (bNewFrameAlreadySelected)
			{
				STATETREE_LOG(Error, TEXT("%hs: Trying to recursively enter subtree '%s' from '%s'.  '%s' using StateTree '%s'."),
					__FUNCTION__, *GetSafeStateName(NewFrame, NewFrame.RootState), *GetStateStatusString(Exec), *GetNameSafe(&Owner), *GetFullNameSafe(CurrentFrame.StateTree));
				return false;
			}
			
			OutNextActiveFrames.Push(NewFrame);

			// If State is linked, proceed to the linked state.
			if (SelectStateInternal(OutNextActiveFrames.Last(), CurrentState.LinkedState, OutNextActiveFrames))
			{
				return true;
			}
			
			OutNextActiveFrames.Pop();
		}
		else if (CurrentState.SelectionBehavior == EStateTreeStateSelectionBehavior::TryEnterState)
		{
			// Select this state.
			STATETREE_TRACE_STATE_EVENT(NextState, EStateTreeTraceEventType::OnStateSelected);
			return true;
		}
		else if (CurrentState.SelectionBehavior == EStateTreeStateSelectionBehavior::TryFollowTransitions)
		{
			EStateTreeTransitionPriority CurrentPriority = EStateTreeTransitionPriority::None;

			for (uint8 i = 0; i < CurrentState.TransitionsNum; i++)
			{
				const int16 TransitionIndex = CurrentState.TransitionsBegin + i;
				const FCompactStateTransition& Transition = RootStateTree.Transitions[TransitionIndex];

				// Skip disabled transitions
				if (Transition.bTransitionEnabled == false)
				{
					continue;
				}

				// No need to test the transition if same or higher priority transition has already been processed.
				if (Transition.Priority <= CurrentPriority)
				{
					continue;
				}

				// Skip completion transitions
				if (EnumHasAnyFlags(Transition.Trigger, EStateTreeTransitionTrigger::OnStateCompleted))
				{
					continue;
				}

				// Cannot follow transitions with delay.
				if (Transition.HasDelay())
				{
					continue;
				}

				// Try to prevent (infinite) loops in the selection.
				if (CurrentFrame.ActiveStates.Contains(Transition.State))
				{
					STATETREE_LOG(Error, TEXT("%hs: Loop detected when trying to select state %s from '%s'. Prior states: %s.  '%s' using StateTree '%s'."),
						__FUNCTION__, *GetSafeStateName(CurrentFrame, NextState), *GetStateStatusString(Exec), *DebugGetStatePath(OutNextActiveFrames, &CurrentFrame), *GetNameSafe(&Owner), *GetFullNameSafe(CurrentFrame.StateTree));
					continue;
				}

				const bool bShouldTrigger = Transition.Trigger == EStateTreeTransitionTrigger::OnTick
											|| (Transition.Trigger == EStateTreeTransitionTrigger::OnEvent
												&& HasEventToProcess(Transition.EventTag));

				bool bTransitionConditionsPassed = false;
				if (bShouldTrigger)
				{
					STATETREE_TRACE_TRANSITION_EVENT(FStateTreeTransitionSource(FStateTreeIndex16(TransitionIndex), Transition.State, Transition.Priority), EStateTreeTraceEventType::OnEvaluating);
					STATETREE_TRACE_SCOPED_PHASE(EStateTreeUpdatePhase::TransitionConditions);
					bTransitionConditionsPassed = bShouldTrigger && TestAllConditions(CurrentFrame, Transition.ConditionsBegin, Transition.ConditionsNum);
				}

				if (bTransitionConditionsPassed)
				{
					// Using SelectState() instead of SelectStateInternal to treat the transitions the same way as regular transitions,
					// e.g. it may jump to a completely different branch.
					TArray<FStateTreeExecutionFrame, TFixedAllocator<MaxExecutionFrames>> NewActiveFrames;
					if (SelectState(CurrentFrame, Transition.State, NewActiveFrames, Transition.Fallback))
					{
						// Selection succeeded.
						// Cannot break yet because higher priority transitions may override the selection. 
						OutNextActiveFrames = NewActiveFrames;
						CurrentPriority = Transition.Priority;
					}
				}
			}

			if (CurrentPriority != EStateTreeTransitionPriority::None)
			{
				return true;
			}
		}
		else if (CurrentState.SelectionBehavior == EStateTreeStateSelectionBehavior::TrySelectChildrenInOrder)
		{
			if (CurrentState.HasChildren())
			{
				// If the state has children, proceed to select children.
				for (uint16 ChildState = CurrentState.ChildrenBegin; ChildState < CurrentState.ChildrenEnd; ChildState = CurrentStateTree->States[ChildState].GetNextSibling())
				{
					if (SelectStateInternal(CurrentFrame, FStateTreeStateHandle(ChildState), OutNextActiveFrames))
					{
						// Selection succeeded
						return true;
					}
				}
			}
			else
			{
				// Select this state (For backwards compatibility)
				STATETREE_TRACE_STATE_EVENT(NextState, EStateTreeTraceEventType::OnStateSelected);
				return true;
			}
		}
		
		CurrentFrame.ActiveStates.Pop();
	}

	// Nothing got selected.
	return false;
}

FString FStateTreeExecutionContext::GetSafeStateName(const FStateTreeExecutionFrame& CurrentFrame, const FStateTreeStateHandle State) const
{
	if (State == FStateTreeStateHandle::Invalid)
	{
		return TEXT("(State Invalid)");
	}
	else if (State == FStateTreeStateHandle::Succeeded)
	{
		return TEXT("(State Succeeded)");
	}
	else if (State == FStateTreeStateHandle::Failed)
	{
		return TEXT("(State Failed)");
	}
	else if (CurrentFrame.StateTree && CurrentFrame.StateTree->States.IsValidIndex(State.Index))
	{
		return *CurrentFrame.StateTree->States[State.Index].Name.ToString();
	}
	return TEXT("(Unknown)");
}

FString FStateTreeExecutionContext::DebugGetStatePath(TConstArrayView<FStateTreeExecutionFrame> ActiveFrames, const FStateTreeExecutionFrame* CurrentFrame, const int32 ActiveStateIndex) const
{
	FString StatePath;
	const UStateTree* LastStateTree = &RootStateTree;
		
	for (const FStateTreeExecutionFrame& Frame : ActiveFrames)
	{
		if (!ensure(Frame.StateTree))
		{
			return StatePath;
		}

		// If requested up the active state, clamp count.
		int32 Num = Frame.ActiveStates.Num();
		if (CurrentFrame == &Frame && Frame.ActiveStates.IsValidIndex(ActiveStateIndex))
		{
			Num = ActiveStateIndex + 1;
		}

		if (Frame.StateTree != LastStateTree)
		{
			StatePath.Appendf(TEXT("[%s]"), *GetNameSafe(Frame.StateTree));
			LastStateTree = Frame.StateTree;
		}
		
		for (int32 i = 0; i < Num; i++)
		{
			const FCompactStateTreeState& State = Frame.StateTree->States[Frame.ActiveStates[i].Index];
			StatePath.Appendf(TEXT("%s%s"), i == 0 ? TEXT("") : TEXT("."), *State.Name.ToString());
		}
	}
		
	return StatePath;
}

FString FStateTreeExecutionContext::GetStateStatusString(const FStateTreeExecutionState& ExecState) const
{
	if (ExecState.TreeRunStatus != EStateTreeRunStatus::Running)
	{
		return TEXT("--:") + UEnum::GetDisplayValueAsText(ExecState.LastTickStatus).ToString();
	}
	return GetSafeStateName(ExecState.ActiveFrames.Last(), ExecState.ActiveFrames.Last().ActiveStates.Last()) + TEXT(":") + UEnum::GetDisplayValueAsText(ExecState.LastTickStatus).ToString();
}

EStateTreeRunStatus FStateTreeExecutionContext::GetLastTickStatus() const
{
	const FStateTreeExecutionState& Exec = GetExecState();
	return Exec.LastTickStatus;
}

FString FStateTreeExecutionContext::GetInstanceDescription() const
{
	return FString::Printf(TEXT("%s"), *GetNameSafe(&Owner));
}

TConstArrayView<FStateTreeExecutionFrame> FStateTreeExecutionContext::GetActiveFrames() const
{
	const FStateTreeExecutionState& Exec = GetExecState();
	return Exec.ActiveFrames;
}


#if WITH_GAMEPLAY_DEBUGGER

FString FStateTreeExecutionContext::GetDebugInfoString() const
{
	const FStateTreeExecutionState& Exec = GetExecState();

	FString DebugString = FString::Printf(TEXT("StateTree (asset: '%s')\n"), *GetFullNameSafe(&RootStateTree));

	DebugString += TEXT("Status: ");
	switch (Exec.TreeRunStatus)
	{
	case EStateTreeRunStatus::Failed:
		DebugString += TEXT("Failed\n");
		break;
	case EStateTreeRunStatus::Succeeded:
		DebugString += TEXT("Succeeded\n");
		break;
	case EStateTreeRunStatus::Running:
		DebugString += TEXT("Running\n");
		break;
	default:
		DebugString += TEXT("--\n");
	}

	// Active States
	DebugString += TEXT("Current State:\n");
	for (const FStateTreeExecutionFrame& CurrentFrame : Exec.ActiveFrames)
	{
		const UStateTree* CurrentStateTree = CurrentFrame.StateTree;

		if (CurrentFrame.bIsGlobalFrame)
		{
			DebugString += FString::Printf(TEXT("\nEvaluators\n  [ %-30s | %8s | %15s ]\n"),
				TEXT("Name"), TEXT("Bindings"), TEXT("Data Handle"));
			for (int32 EvalIndex = CurrentStateTree->EvaluatorsBegin; EvalIndex < (CurrentStateTree->EvaluatorsBegin + CurrentStateTree->EvaluatorsNum); EvalIndex++)
			{
				const FStateTreeEvaluatorBase& Eval = CurrentStateTree->Nodes[EvalIndex].Get<const FStateTreeEvaluatorBase>();
				DebugString += FString::Printf(TEXT("| %-30s | %8d | %15s |\n"),
					*Eval.Name.ToString(), Eval.BindingsBatch.Get(), *Eval.InstanceDataHandle.Describe());
			}
			
			DebugString += FString::Printf(TEXT("\nGlobal Tasks\n"));
			for (int32 TaskIndex = CurrentStateTree->GlobalTasksBegin; TaskIndex < (CurrentStateTree->GlobalTasksBegin + CurrentStateTree->GlobalTasksNum); TaskIndex++)
			{
				const FStateTreeTaskBase& Task = CurrentStateTree->Nodes[TaskIndex].Get<const FStateTreeTaskBase>();
				if (Task.bTaskEnabled)
				{
					Task.AppendDebugInfoString(DebugString, *this);
				}
			}
		}
		
		for (int32 Index = 0; Index < CurrentFrame.ActiveStates.Num(); Index++)
		{
			FStateTreeStateHandle Handle = CurrentFrame.ActiveStates[Index];
			if (Handle.IsValid())
			{
				const FCompactStateTreeState& State = RootStateTree.States[Handle.Index];
				DebugString += FString::Printf(TEXT("[%s]\n"), *State.Name.ToString());

				if (State.TasksNum > 0)
				{
					DebugString += TEXT("\nTasks:\n");
					for (int32 TaskIndex = State.TasksBegin; TaskIndex < (State.TasksBegin + State.TasksNum); TaskIndex++)
					{
						const FStateTreeTaskBase& Task = RootStateTree.Nodes[TaskIndex].Get<const FStateTreeTaskBase>();
						if (Task.bTaskEnabled)
						{
							Task.AppendDebugInfoString(DebugString, *this);
						}
					}
				}
			}
		}
	}

	return DebugString;
}
#endif // WITH_GAMEPLAY_DEBUGGER

#if WITH_STATETREE_DEBUG
void FStateTreeExecutionContext::DebugPrintInternalLayout()
{
	LOG_SCOPE_VERBOSITY_OVERRIDE(LogStateTree, ELogVerbosity::Log);

	// @todo: this looks like more a UStateTree thing...
	
	FString DebugString = FString::Printf(TEXT("StateTree (asset: '%s')\n"), *GetFullNameSafe(&RootStateTree));

	// Tree items (e.g. tasks, evaluators, conditions)
	DebugString += FString::Printf(TEXT("\nItems(%d)\n"), RootStateTree.Nodes.Num());
	for (int32 Index = 0; Index < RootStateTree.Nodes.Num(); Index++)
	{
		const FConstStructView Node = RootStateTree.Nodes[Index];
		DebugString += FString::Printf(TEXT("  %s\n"), Node.IsValid() ? *Node.GetScriptStruct()->GetName() : TEXT("null"));
	}

	// Instance InstanceData data (e.g. tasks)
	DebugString += FString::Printf(TEXT("\nInstance Data(%d)\n"), RootStateTree.DefaultInstanceData.Num());
	for (int32 Index = 0; Index < RootStateTree.DefaultInstanceData.Num(); Index++)
	{
		if (RootStateTree.DefaultInstanceData.IsObject(Index))
		{
			const UObject* Data = RootStateTree.DefaultInstanceData.GetObject(Index);
			DebugString += FString::Printf(TEXT("  %s\n"), *GetNameSafe(Data));
		}
		else
		{
			const FConstStructView Data = RootStateTree.DefaultInstanceData.GetStruct(Index);
			DebugString += FString::Printf(TEXT("  %s\n"), Data.IsValid() ? *Data.GetScriptStruct()->GetName() : TEXT("null"));
		}
	}

	// External data (e.g. fragments, subsystems)
	DebugString += FString::Printf(TEXT("\nExternal Data(%d)\n  [ %-40s | %-8s | %15s ]\n"), RootStateTree.ExternalDataDescs.Num(), TEXT("Name"), TEXT("Optional"), TEXT("Handle"));
	for (const FStateTreeExternalDataDesc& Desc : RootStateTree.ExternalDataDescs)
	{
		DebugString += FString::Printf(TEXT("  | %-40s | %8s | %15s |\n"), Desc.Struct ? *Desc.Struct->GetName() : TEXT("null"), *UEnum::GetDisplayValueAsText(Desc.Requirement).ToString(), *Desc.Handle.DataHandle.Describe());
	}

	// Bindings
	RootStateTree.PropertyBindings.DebugPrintInternalLayout(DebugString);

	// Transitions
	DebugString += FString::Printf(TEXT("\nTransitions(%d)\n  [ %-3s | %15s | %-20s | %-40s | %-8s ]\n"), RootStateTree.Transitions.Num()
		, TEXT("Idx"), TEXT("State"), TEXT("Transition Trigger"), TEXT("Transition Event Tag"), TEXT("Num Cond"));
	for (const FCompactStateTransition& Transition : RootStateTree.Transitions)
	{
		DebugString += FString::Printf(TEXT("  | %3d | %15s | %-20s | %-40s | %8d |\n"),
									Transition.ConditionsBegin, *Transition.State.Describe(),
									*UEnum::GetDisplayValueAsText(Transition.Trigger).ToString(),
									*Transition.EventTag.ToString(),
									Transition.ConditionsNum);
	}

	// States
	DebugString += FString::Printf(TEXT("\nStates(%d)\n"
		"  [ %-30s | %15s | %5s [%3s:%-3s[ | Begin Idx : %4s %4s %4s %4s | Num : %4s %4s %4s %4s | Transitions : %-16s %-40s %-16s %-40s ]\n"),
		RootStateTree.States.Num(),
		TEXT("Name"), TEXT("Parent"), TEXT("Child"), TEXT("Beg"), TEXT("End"),
		TEXT("Cond"), TEXT("Tr"), TEXT("Tsk"), TEXT("Evt"), TEXT("Cond"), TEXT("Tr"), TEXT("Tsk"), TEXT("Evt"),
		TEXT("Done State"), TEXT("Done Type"), TEXT("Failed State"), TEXT("Failed Type")
		);
	for (const FCompactStateTreeState& State : RootStateTree.States)
	{
		DebugString += FString::Printf(TEXT("  | %-30s | %15s | %5s [%3d:%-3d[ | %9s   %4d %4d %4d | %3s   %4d %4d %4d\n"),
									*State.Name.ToString(), *State.Parent.Describe(),
									TEXT(""), State.ChildrenBegin, State.ChildrenEnd,
									TEXT(""), State.EnterConditionsBegin, State.TransitionsBegin, State.TasksBegin,
									TEXT(""), State.EnterConditionsNum, State.TransitionsNum, State.TasksNum);
	}

	// Evaluators
	if (RootStateTree.EvaluatorsNum)
	{
		DebugString += FString::Printf(TEXT("\nEvaluators\n  [ %-30s | %8s | %10s ]\n"),
			TEXT("Name"), TEXT("Bindings"), TEXT("Struct Idx"));
		for (int32 EvalIndex = RootStateTree.EvaluatorsBegin; EvalIndex < (RootStateTree.EvaluatorsBegin + RootStateTree.EvaluatorsNum); EvalIndex++)
		{
			const FStateTreeEvaluatorBase& Eval = RootStateTree.Nodes[EvalIndex].Get<const FStateTreeEvaluatorBase>();
			DebugString += FString::Printf(TEXT("| %-30s | %8d | %10s |\n"),
				*Eval.Name.ToString(), Eval.BindingsBatch.Get(), *Eval.InstanceDataHandle.Describe());
		}
	}


	DebugString += FString::Printf(TEXT("\nTasks\n  [ %-30s | %-30s | %8s | %10s ]\n"),
		TEXT("State"), TEXT("Name"), TEXT("Bindings"), TEXT("Struct Idx"));
	for (const FCompactStateTreeState& State : RootStateTree.States)
	{
		// Tasks
		if (State.TasksNum)
		{
			for (int32 TaskIndex = State.TasksBegin; TaskIndex < (State.TasksBegin + State.TasksNum); TaskIndex++)
			{
				const FStateTreeTaskBase& Task = RootStateTree.Nodes[TaskIndex].Get<const FStateTreeTaskBase>();
				DebugString += FString::Printf(TEXT("  | %-30s | %-30s | %8d | %10s |\n"), *State.Name.ToString(),
					*Task.Name.ToString(), Task.BindingsBatch.Get(), *Task.InstanceDataHandle.Describe());
			}
		}
	}

	UE_LOG(LogStateTree, Log, TEXT("%s"), *DebugString);
}

int32 FStateTreeExecutionContext::GetStateChangeCount() const
{
	if (!InstanceData.IsValid())
	{
		return 0;
	}
	const FStateTreeExecutionState& Exec = GetExecState();
	return Exec.StateChangeCount;
}

#endif // WITH_STATETREE_DEBUG

FString FStateTreeExecutionContext::GetActiveStateName() const
{
	if (!InstanceData.IsValid())
	{
		return FString(TEXT("<None>"));
	}
	
	const FStateTreeExecutionState& Exec = GetExecState();

	FString FullStateName;
	
	const UStateTree* LastStateTree = &RootStateTree;
	int32 Indent = 0;

	for (int32 FrameIndex = 0; FrameIndex < Exec.ActiveFrames.Num(); FrameIndex++)
	{
		const FStateTreeExecutionFrame& CurrentFrame = Exec.ActiveFrames[FrameIndex];
		const UStateTree* CurrentStateTree = CurrentFrame.StateTree;

		// Append linked state marker at the end of the previous line.
		if (Indent > 0)
		{
			FullStateName += TEXT(" >");
		}
		// If tree has changed, append that too.
		if (CurrentFrame.StateTree != LastStateTree)
		{
			FullStateName.Appendf(TEXT(" [%s]"), *GetNameSafe(CurrentFrame.StateTree));
			LastStateTree = CurrentFrame.StateTree;
		}

		for (int32 Index = 0; Index < CurrentFrame.ActiveStates.Num(); Index++)
		{
			const FStateTreeStateHandle Handle = CurrentFrame.ActiveStates[Index];
			if (Handle.IsValid())
			{
				const FCompactStateTreeState& State = CurrentStateTree->States[Handle.Index];
				if (Indent > 0)
				{
					FullStateName += TEXT("\n");
				}
				FullStateName += FString::Printf(TEXT("%*s-"), Indent * 3, TEXT("")); // Indent
				FullStateName += *State.Name.ToString();
				Indent++;
			}
		}
	}

	switch (Exec.TreeRunStatus)
	{
	case EStateTreeRunStatus::Failed:
		FullStateName += TEXT(" FAILED\n");
		break;
	case EStateTreeRunStatus::Succeeded:
		FullStateName += TEXT(" SUCCEEDED\n");
		break;
	case EStateTreeRunStatus::Running:
		// Empty
		break;
	default:
		FullStateName += TEXT("--\n");
	}

	return FullStateName;
}

TArray<FName> FStateTreeExecutionContext::GetActiveStateNames() const
{
	TArray<FName> Result;

	if (!InstanceData.IsValid())
	{
		return Result;
	}
	
	const FStateTreeExecutionState& Exec = GetExecState();

	// Active States
	for (const FStateTreeExecutionFrame& CurrentFrame : Exec.ActiveFrames)
	{
		const UStateTree* CurrentStateTree = CurrentFrame.StateTree;
		for (int32 Index = 0; Index < CurrentFrame.ActiveStates.Num(); Index++)
		{
			const FStateTreeStateHandle Handle = CurrentFrame.ActiveStates[Index];
			if (Handle.IsValid())
			{
				const FCompactStateTreeState& State = CurrentStateTree->States[Handle.Index];
				Result.Add(State.Name);
			}
		}
	}

	return Result;
}

#undef STATETREE_LOG
#undef STATETREE_CLOG