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

#include "CpuProfilerTraceAnalysis.h"

#include "AnalysisServicePrivate.h"
#include "CborReader.h"
#include "CborWriter.h"
#include "Common/Utils.h"
#include "HAL/LowLevelMemTracker.h"
#include "Model/ThreadsPrivate.h"
#include "Model/MonotonicTimeline.h"
#include "Serialization/MemoryReader.h"
#include "Serialization/MemoryWriter.h"
#include "TraceServices/Model/TimingProfiler.h"
#include "TraceServices/Utils.h"

#define CPUPROFILER_DEBUG_LOGF(Format, ...) //{ if (ThreadState.ThreadId == 2) FPlatformMisc::LowLevelOutputDebugStringf(Format, __VA_ARGS__); }
#define CPUPROFILER_DEBUG_BEGIN_EVENT(Time, Event) { ++TotalScopeCount; }
#define CPUPROFILER_DEBUG_END_EVENT(Time)

namespace TraceServices
{

////////////////////////////////////////////////////////////////////////////////////////////////////

FCpuProfilerAnalyzer::FCpuProfilerAnalyzer(IAnalysisSession& InSession, IEditableTimingProfilerProvider& InEditableTimingProfilerProvider, IEditableThreadProvider& InEditableThreadProvider)
	: Session(InSession)
	, EditableTimingProfilerProvider(InEditableTimingProfilerProvider)
	, EditableThreadProvider(InEditableThreadProvider)
{
}

////////////////////////////////////////////////////////////////////////////////////////////////////

FCpuProfilerAnalyzer::~FCpuProfilerAnalyzer()
{
	for (auto& KV : ThreadStatesMap)
	{
		FThreadState* ThreadState = KV.Value;
		delete ThreadState;
	}
}

////////////////////////////////////////////////////////////////////////////////////////////////////

void FCpuProfilerAnalyzer::OnAnalysisBegin(const FOnAnalysisContext& Context)
{
	auto& Builder = Context.InterfaceBuilder;

	Builder.RouteEvent(RouteId_EventSpec, "CpuProfiler", "EventSpec");
	Builder.RouteEvent(RouteId_EndThread, "CpuProfiler", "EndThread");
	Builder.RouteEvent(RouteId_EventBatchV3, "CpuProfiler", "EventBatchV3"); // added in UE 5.6
	Builder.RouteEvent(RouteId_EventBatchV2, "CpuProfiler", "EventBatchV2"); // backward compatibility, added in UE 5.1, removed in 5.6
	Builder.RouteEvent(RouteId_EventBatch, "CpuProfiler", "EventBatch"); // backward compatibility; removed in UE 5.1
	Builder.RouteEvent(RouteId_EndCapture, "CpuProfiler", "EndCapture"); // backward compatibility; removed in UE 5.1
	Builder.RouteEvent(RouteId_MetadataSpec, "CpuProfiler", "MetadataSpec");
	Builder.RouteEvent(RouteId_Metadata, "CpuProfiler", "Metadata");
	Builder.RouteLoggerEvents(RouteId_CpuScope, "Cpu", true);
}

////////////////////////////////////////////////////////////////////////////////////////////////////

void FCpuProfilerAnalyzer::OnAnalysisEnd()
{
	LLM_SCOPE_BYNAME(TEXT("Insights/FCpuProfilerAnalyzer"));

	for (auto& KV : ThreadStatesMap)
	{
		FThreadState& ThreadState = *KV.Value;

		if (ThreadState.LastCycle != ~0ull) // if EndThread is not received
		{
			DispatchRemainingPendingEvents(ThreadState);
			EndOpenEvents(ThreadState, std::numeric_limits<double>::infinity());
		}

		check(ThreadState.PendingEvents.Num() == 0); // no pending events
		check(ThreadState.ScopeStack.Num() == 0); // no open events
	}

	bool bPossibleOutputEventTypeIssue = false;
	ScopeNameToTimerIdMap.ValueSort([](const FTimerInfo& A, const FTimerInfo& B) { return A.Count > B.Count; });
	for (auto& KV : ScopeNameToTimerIdMap)
	{
		if (KV.Value.Count < 1000)
		{
			break;
		}
		UE_LOG(LogTraceServices, Warning, TEXT("[CpuProfiler] Timer defined %u times! (id=%d name=\"%s\")"), KV.Value.Count, KV.Value.Id, (const TCHAR*)KV.Key);
		bPossibleOutputEventTypeIssue = true;
	}
	if (bPossibleOutputEventTypeIssue)
	{
		UE_LOG(LogTraceServices, Warning, TEXT("[CpuProfiler] Possible incorrect use of FCpuProfilerTrace::OutputEventType()!"));
	}

	UE_LOG(LogTraceServices, Log, TEXT("[CpuProfiler] Analysis completed (%d threads, %d timers, %d spec ids, %llu scopes, %llu bytes, %.1f bytes/scope)."),
		ThreadStatesMap.Num(),
		ScopeNameToTimerIdMap.Num(),
		SpecIdToTimerIdMap.Num(),
		TotalScopeCount,
		TotalEventSize,
		(double)TotalEventSize / (double)TotalScopeCount);

	// Clean-up...
	for (auto& KV : ThreadStatesMap)
	{
		FThreadState* ThreadState = KV.Value;
		delete ThreadState;
	}
	ThreadStatesMap.Reset();
	ThreadStatesMap.Shrink();
	SpecIdToTimerIdMap.Reset();
	SpecIdToTimerIdMap.Shrink();
	ScopeNameToTimerIdMap.Reset();
	ScopeNameToTimerIdMap.Shrink();
}

////////////////////////////////////////////////////////////////////////////////////////////////////

bool FCpuProfilerAnalyzer::OnEvent(uint16 RouteId, EStyle Style, const FOnEventContext& Context)
{
	LLM_SCOPE_BYNAME(TEXT("Insights/FCpuProfilerAnalyzer"));

	FAnalysisSessionEditScope _(Session);

	const auto& EventData = Context.EventData;
	switch (RouteId)
	{
	case RouteId_EventSpec:
	{
		uint32 SpecId = EventData.GetValue<uint32>("Id");

		const TCHAR* TimerName = nullptr;
		FString Name;
		if (EventData.GetString("Name", Name))
		{
			TimerName = *Name;
		}
		else
		{
			uint8 CharSize = EventData.GetValue<uint8>("CharSize");
			if (CharSize == sizeof(ANSICHAR))
			{
				const ANSICHAR* AnsiName = reinterpret_cast<const ANSICHAR*>(EventData.GetAttachment());
				Name = StringCast<TCHAR>(AnsiName).Get();
				TimerName = *Name;
			}
			else if (CharSize == 0 || CharSize == sizeof(TCHAR)) // 0 for backwards compatibility
			{
				TimerName = reinterpret_cast<const TCHAR*>(EventData.GetAttachment());
			}
			else
			{
				Name = FString::Printf(TEXT("<invalid %u>"), SpecId);
				TimerName = *Name;
			}
		}

		if (TimerName[0] == 0)
		{
			Name = FString::Printf(TEXT("<noname %u>"), SpecId);
			TimerName = *Name;
		}

		const TCHAR* FileName = nullptr;
		FString File;
		uint32 Line = 0;
		if (EventData.GetString("File", File) && !File.IsEmpty())
		{
			FileName = *File;
			Line = EventData.GetValue<uint32>("Line");
		}

		DefineTimer(SpecId, Session.StoreString(TimerName), FileName, Line, true);
		break;
	}

	case RouteId_EndThread:
	{
		const uint32 ThreadId = FTraceAnalyzerUtils::GetThreadIdField(Context);
		FThreadState& ThreadState = GetThreadState(ThreadId);

		if (ThreadState.LastCycle == ~0ull)
		{
			// Ignore timing events received after EndThread.
			break;
		}

		DispatchRemainingPendingEvents(ThreadState);

		const uint64 Cycle = EventData.GetValue<uint64>("Cycle", ThreadState.LastCycle); // added in UE 5.4
		if (Cycle != 0)
		{
			ensure(Cycle >= ThreadState.LastCycle);
			double Timestamp = Context.EventTime.AsSeconds(Cycle);
			Session.UpdateDurationSeconds(Timestamp);
			EndOpenEvents(ThreadState, Timestamp);
		}

		check(ThreadState.PendingEvents.Num() == 0); // no pending events
		check(ThreadState.ScopeStack.Num() == 0); // no open events

		ThreadState.LastCycle = ~0ull;
		break;
	}

	case RouteId_EventBatchV3:
	case RouteId_EventBatchV2: // backward compatibility
	{
		const uint32 ThreadId = Context.ThreadInfo.GetId();
		FThreadState& ThreadState = GetThreadState(ThreadId);

		if (ThreadState.LastCycle == ~0ull)
		{
			// Ignore timing events received after EndThread.
			break;
		}

		TArrayView<const uint8> DataView = Context.EventData.GetArrayView<uint8>("Data");
		const uint32 BufferSize = DataView.Num();
		const uint8* BufferPtr = DataView.GetData();

		ProcessBufferV2(Context.EventTime, ThreadState, BufferPtr, BufferSize, RouteId == RouteId_EventBatchV3 ? 3 : 2);
		if (ThreadState.LastCycle != 0)
		{
			double Timestamp = Context.EventTime.AsSeconds(ThreadState.LastCycle);
			Session.UpdateDurationSeconds(Timestamp);
		}

		TotalEventSize += BufferSize;
		break;
	}

	case RouteId_EventBatch: // backward compatibility
	case RouteId_EndCapture: // backward compatibility
	{
		const uint32 ThreadId = FTraceAnalyzerUtils::GetThreadIdField(Context);
		FThreadState& ThreadState = GetThreadState(ThreadId);

		if (ThreadState.LastCycle == ~0ull)
		{
			// Ignore timing events received after EndThread.
			break;
		}

		TArrayView<const uint8> DataView = FTraceAnalyzerUtils::LegacyAttachmentArray("Data", Context);
		const uint32 BufferSize = DataView.Num();
		const uint8* BufferPtr = DataView.GetData();

		ProcessBuffer(Context.EventTime, ThreadState, BufferPtr, BufferSize);

		if (RouteId == RouteId_EndCapture)
		{
			DispatchRemainingPendingEvents(ThreadState);
			if (ThreadState.LastCycle != 0)
			{
				double Timestamp = Context.EventTime.AsSeconds(ThreadState.LastCycle);
				Session.UpdateDurationSeconds(Timestamp);
				EndOpenEvents(ThreadState, Timestamp);
			}
			ThreadState.LastCycle = ~0ull;
		}
		else
		{
			if (ThreadState.LastCycle != 0)
			{
				double Timestamp = Context.EventTime.AsSeconds(ThreadState.LastCycle);
				Session.UpdateDurationSeconds(Timestamp);
			}
		}

		TotalEventSize += BufferSize;
		break;
	}

	case RouteId_CpuScope:
		if (Style == EStyle::EnterScope)
		{
			OnCpuScopeEnter(Context);
		}
		else
		{
			OnCpuScopeLeave(Context);
		}
		break;

	case RouteId_MetadataSpec:
	{
		uint32 SpecId = Context.EventData.GetValue<uint32>("Id");

		FString Name, NameFormat;
		Context.EventData.GetString("Name", Name);
		Context.EventData.GetString("NameFormat", NameFormat);
		TArrayView<const uint8> FieldNames = EventData.GetArrayView<uint8>("FieldNames");

		if (Name.Compare(NameFormat) == 0)
		{
			Name.Empty();
		}

		int Index = 0;
		while (Index < NameFormat.Len() && Index < Name.Len())
		{
			if (Name[Index] != NameFormat[Index])
			{
				break;
			}

			++Index;
		}

		if (Index > 1)
		{
			NameFormat.MidInline(Index);
		}

		if (Name.IsEmpty())
		{
			const FString Separators = TEXT("% (=");
			Index = 0;
			bool bIsInFormatSpecifier = false;
			while (Index < NameFormat.Len())
			{
				int32 SpecIndex = -1;
				if (Separators.FindChar(NameFormat[Index], SpecIndex))
				{
					Name = NameFormat.Left(Index);
					NameFormat.MidInline(Index);
					break;
				}

				++Index;
			}

			if (Name.IsEmpty())
			{
				if (!NameFormat.IsEmpty())
				{
					Name = NameFormat;
					NameFormat.Empty();
				}
				else
				{
					Name = Session.StoreString(TEXT("Unknown"));
				}
			}
		}

		FMetadataSpec Spec;
		if (!NameFormat.IsEmpty())
		{
			Spec.Format = Session.StoreString(NameFormat);
		}

		if (FieldNames.Num() > 0)
		{
			FMemoryReaderView MemoryReader(FieldNames);
			FCborReader CborReader(&MemoryReader, ECborEndianness::StandardCompliant);
			FCborContext CborContext;

			while (CborReader.ReadNext(CborContext))
			{
				if (CborContext.MajorType() == ECborCode::TextString)
				{
					FString Field = CborContext.AsString();
					Spec.FieldNames.Add(Session.StoreString(Field));
				}
			}
		}

		uint32 TimerId = 0;
		uint32* FoundTimerIdPtr = SpecIdToTimerIdMap.Find(SpecId);
		if (FoundTimerIdPtr == nullptr)
		{
			TimerId = DefineTimer(SpecId, Session.StoreString(*Name), nullptr, 0, false);
		}
		else
		{
			TimerId = *FoundTimerIdPtr;
			EditableTimingProfilerProvider.SetTimerName(TimerId, Name);
		}

		if (Spec.FieldNames.Num() > 0 || Spec.Format != nullptr)
		{
			uint32 MetadataSpecId = EditableTimingProfilerProvider.AddMetadataSpec(MoveTemp(Spec));
			EditableTimingProfilerProvider.SetMetadataSpec(TimerId, MetadataSpecId);
		}

		break;
	}
	case RouteId_Metadata:
	{
		uint32 MetadataId = Context.EventData.GetValue<uint32>("Id");
		uint32 SpecId = Context.EventData.GetValue<uint32>("SpecId");
		TArray<uint8> Metadata(EventData.GetArrayView<uint8>("Metadata"));

		// We don't know if the Metadata or the BeginMetadataEvent events arrive first so handle both cases.
		uint32* TimerIdPtr = MetadataIdToTimerIdMap.Find(MetadataId);
		if (TimerIdPtr == nullptr)
		{
			uint32 TimerId = GetTimerId(SpecId);
			TimerId = EditableTimingProfilerProvider.AddMetadata(TimerId, MoveTemp(Metadata));
			MetadataIdToTimerIdMap.Add(MetadataId, TimerId);
		}
		else
		{
			uint32 MetadataTimerId = *TimerIdPtr;
			uint32 TimerId = GetTimerId(SpecId);
			// Replace the placeholder metadata added if we received an event with this metadata first.
			EditableTimingProfilerProvider.SetMetadata(MetadataTimerId, MoveTemp(Metadata), TimerId);
		}

		break;
	}
	}

	return true;
}

////////////////////////////////////////////////////////////////////////////////////////////////////

void FCpuProfilerAnalyzer::ProcessBuffer(const FEventTime& EventTime, FThreadState& ThreadState, const uint8* BufferPtr, uint32 BufferSize)
{
	uint64 LastCycle = ThreadState.LastCycle;

	CPUPROFILER_DEBUG_LOGF(TEXT("[%u] ProcessBuffer %llu (%.9f)\n"), ThreadState.ThreadId, LastCycle, EventTime.AsSeconds(LastCycle));

	check(EventTime.GetTimestamp() == 0);
	const uint64 BaseCycle = EventTime.AsCycle64();

	int32 RemainingPending = ThreadState.PendingEvents.Num();
	const FPendingEvent* PendingCursor = ThreadState.PendingEvents.GetData();

	const uint8* BufferEnd = BufferPtr + BufferSize;
	while (BufferPtr < BufferEnd)
	{
		uint64 DecodedCycle = FTraceAnalyzerUtils::Decode7bit(BufferPtr);
		uint64 ActualCycle = (DecodedCycle >> 1);

		// ActualCycle larger or equal to LastCycle means we have a new
		// base value.
		if (ActualCycle < LastCycle)
		{
			ActualCycle += LastCycle;
		}

		// If we late connect we will be joining the cycle stream mid-flow and
		// will have missed out on it's base timestamp. Reconstruct it here.
		if (ActualCycle < BaseCycle)
		{
			ActualCycle += BaseCycle;
		}

		// Dispatch pending events that are younger than the one we've just decoded.
		DispatchPendingEvents(LastCycle, ActualCycle, ThreadState, PendingCursor, RemainingPending, (DecodedCycle & 1ull) != 0);

		double ActualTime = EventTime.AsSeconds(ActualCycle);

		if (DecodedCycle & 1ull)
		{
			uint32 SpecId = IntCastChecked<uint32>(FTraceAnalyzerUtils::Decode7bit(BufferPtr));
			uint32 TimerId = GetTimerId(SpecId);

			FEventScopeState& ScopeState = ThreadState.ScopeStack.AddDefaulted_GetRef();
			ScopeState.StartCycle = ActualCycle;
			ScopeState.EventTypeId = TimerId;

			CPUPROFILER_DEBUG_LOGF(TEXT("[%u]  B=%llu (%.9f)\n"), ThreadState.ThreadId, ActualCycle, ActualTime);
			FTimingProfilerEvent Event;
			Event.TimerIndex = TimerId;
			ThreadState.Timeline->AppendBeginEvent(ActualTime, Event);
			CPUPROFILER_DEBUG_BEGIN_EVENT(ActualTime, Event);
		}
		else
		{
			// If we receive mismatched end events ignore them for now.
			// This can happen for example because tracing connects to the store after events were traced. Those events can be lost.
			if (ThreadState.ScopeStack.Num() > 0)
			{
				ThreadState.ScopeStack.Pop();
				CPUPROFILER_DEBUG_LOGF(TEXT("[%u]  E=%llu (%.9f)\n"), ThreadState.ThreadId, ActualCycle, ActualTime);
				ThreadState.Timeline->AppendEndEvent(ActualTime);
				CPUPROFILER_DEBUG_END_EVENT(ActualTime);
			}
		}

		check(ActualCycle > 0);
		LastCycle = ActualCycle;
	}
	check(BufferPtr == BufferEnd);

	if (RemainingPending == 0)
	{
		//CPUPROFILER_DEBUG_LOGF(TEXT("[%u] MetaEvents: %d added\n"), ThreadState.ThreadId, ThreadState.PendingEvents.Num());
		ThreadState.PendingEvents.Reset();
	}
	else
	{
		const int32 NumEventsToRemove = ThreadState.PendingEvents.Num() - RemainingPending;
		CPUPROFILER_DEBUG_LOGF(TEXT("[%u] MetaEvents: %d added, %d still pending\n"), ThreadState.ThreadId, NumEventsToRemove, RemainingPending);
		ThreadState.PendingEvents.RemoveAt(0, NumEventsToRemove);
	}

	ThreadState.LastCycle = LastCycle;
}

////////////////////////////////////////////////////////////////////////////////////////////////////

void FCpuProfilerAnalyzer::ProcessBufferV2(const FEventTime& EventTime, FThreadState& ThreadState, const uint8* BufferPtr, uint32 BufferSize, int32 Version)
{
	uint64 LastCycle = ThreadState.LastCycle;

	CPUPROFILER_DEBUG_LOGF(TEXT("[%u] ProcessBuffer %llu (%.9f)\n"), ThreadState.ThreadId, LastCycle, EventTime.AsSeconds(LastCycle));

	check(EventTime.GetTimestamp() == 0);
	const uint64 BaseCycle = EventTime.AsCycle64();

	int32 RemainingPending = ThreadState.PendingEvents.Num();
	const FPendingEvent* PendingCursor = ThreadState.PendingEvents.GetData();

	const uint8* BufferEnd = BufferPtr + BufferSize;
	while (BufferPtr < BufferEnd)
	{
		uint64 DecodedCycle = FTraceAnalyzerUtils::Decode7bit(BufferPtr);
		uint64 ActualCycle = (DecodedCycle >> 2);

		// ActualCycle larger or equal to LastCycle means we have a new
		// base value.
		if (ActualCycle < LastCycle)
		{
			ActualCycle += LastCycle;
		}

		// If we late connect we will be joining the cycle stream mid-flow and
		// will have missed out on it's base timestamp. Reconstruct it here.
		if (ActualCycle < BaseCycle)
		{
			ActualCycle += BaseCycle;
		}

		// Dispatch pending events that are younger than the one we've just decoded.
		DispatchPendingEvents(LastCycle, ActualCycle, ThreadState, PendingCursor, RemainingPending, (DecodedCycle & 1ull) != 0);

		double ActualTime = EventTime.AsSeconds(ActualCycle);

		if (DecodedCycle & 2ull)
		{
			constexpr uint32 CoroutineSpecId        = (1u << 31u) - 1u;
			constexpr uint32 CoroutineUnknownSpecId = (1u << 31u) - 2u;

			if (DecodedCycle & 1ull)
			{
				uint64 CoroutineId = FTraceAnalyzerUtils::Decode7bit(BufferPtr);
				uint32 TimerScopeDepth = IntCastChecked<uint32>(FTraceAnalyzerUtils::Decode7bit(BufferPtr));

				// Begins a "CoroTask" scoped timer.
				{
					if (CoroutineTimerId == ~0u)
					{
						CoroutineTimerId = DefineNewTimerChecked(CoroutineSpecId, TEXT("Coroutine"));
					}

					TArray<uint8> CborData;
					{
						CborData.Reserve(256);
						FMemoryWriter MemoryWriter(CborData, false, true);
						FCborWriter CborWriter(&MemoryWriter, ECborEndianness::StandardCompliant);
						CborWriter.WriteContainerStart(ECborCode::Map, 2); // 2 is the FieldCount
						CborWriter.WriteValue("Id", 2);
						CborWriter.WriteValue(CoroutineId);
						CborWriter.WriteValue("C", 1); // continuation?
						CborWriter.WriteValue(false);
					}
					uint32 MetadataTimerId = EditableTimingProfilerProvider.AddMetadata(CoroutineTimerId, MoveTemp(CborData));

					FEventScopeState& ScopeState = ThreadState.ScopeStack.AddDefaulted_GetRef();
					ScopeState.StartCycle = ActualCycle;
					ScopeState.EventTypeId = MetadataTimerId;

					CPUPROFILER_DEBUG_LOGF(TEXT("[%u] *B=%llu (%.9f)\n"), ThreadState.ThreadId, ActualCycle, ActualTime);
					FTimingProfilerEvent Event;
					Event.TimerIndex = MetadataTimerId;
					ThreadState.Timeline->AppendBeginEvent(ActualTime, Event);
					CPUPROFILER_DEBUG_BEGIN_EVENT(ActualTime, Event);
				}

				// Begins the CPU scoped timers (suspended in previous coroutine execution).
				{
					if (CoroutineUnknownTimerId == ~0u)
					{
						CoroutineUnknownTimerId = DefineNewTimerChecked(CoroutineUnknownSpecId, TEXT("<unknown>"));
					}

					//TODO: Restore the saved stack of CPU scoped timers for this CoroutineId.
					for (uint32 i = 0; i < TimerScopeDepth; ++i)
					{
						FEventScopeState& ScopeState = ThreadState.ScopeStack.AddDefaulted_GetRef();
						ScopeState.StartCycle = ActualCycle;
						ScopeState.EventTypeId = CoroutineUnknownTimerId;

						CPUPROFILER_DEBUG_LOGF(TEXT("[%u] +B=%llu (%.9f)\n"), ThreadState.ThreadId, ActualCycle, ActualTime);
						FTimingProfilerEvent Event;
						Event.TimerIndex = CoroutineUnknownTimerId;
						ThreadState.Timeline->AppendBeginEvent(ActualTime, Event);
						CPUPROFILER_DEBUG_BEGIN_EVENT(ActualTime, Event);
					}
				}
			}
			else
			{
				uint32 TimerScopeDepth = IntCastChecked<uint32>(FTraceAnalyzerUtils::Decode7bit(BufferPtr));

				if (TimerScopeDepth != 0)
				{
					//TODO: Save current stack of CPU scoped timers (using id from metadata of CoroTask timer?)

					// Ends (suspends) the CPU scoped timers.
					for (uint32 i = 0; i < TimerScopeDepth; ++i)
					{
						// If we receive mismatched end events ignore them for now.
						// This can happen for example because tracing connects to the store after events were traced. Those events can be lost.
						if (ThreadState.ScopeStack.Num() > 0)
						{
							ThreadState.ScopeStack.Pop();
							CPUPROFILER_DEBUG_LOGF(TEXT("[%u] +E=%llu (%.9f)\n"), ThreadState.ThreadId, ActualCycle, ActualTime);
							ThreadState.Timeline->AppendEndEvent(ActualTime);
							CPUPROFILER_DEBUG_END_EVENT(ActualTime);
						}
					}

					// Update the "continuation" (suspended or destroyed) metadata flag.
					if (ThreadState.ScopeStack.Num() > 0)
					{
						uint32 MetadataTimerId = ThreadState.ScopeStack.Top().EventTypeId;
						TArrayView<uint8> Metadata = EditableTimingProfilerProvider.GetEditableMetadata(MetadataTimerId);
						if (ensure(Metadata.Num() > 0))
						{
							// Change the last byte in metadata to "true".
							Metadata.GetData()[Metadata.Num() - 1] = (uint8)(ECborCode::Prim | ECborCode::True);
						}
					}
				}

				// Ends the "CoroTask" scoped timer.
				{
					// If we receive mismatched end events ignore them for now.
					// This can happen for example because tracing connects to the store after events were traced. Those events can be lost.
					if (ThreadState.ScopeStack.Num() > 0)
					{
						ThreadState.ScopeStack.Pop();
						CPUPROFILER_DEBUG_LOGF(TEXT("[%u] *E=%llu (%.9f)\n"), ThreadState.ThreadId, ActualCycle, ActualTime);
						ThreadState.Timeline->AppendEndEvent(ActualTime);
						CPUPROFILER_DEBUG_END_EVENT(ActualTime);
					}
				}
			}
		}
		else
		{
			if (DecodedCycle & 1ull)
			{
				uint32 SpecId = IntCastChecked<uint32>(FTraceAnalyzerUtils::Decode7bit(BufferPtr));

				uint32 TimerId = 0;
				if (Version == 3)
				{
					if (SpecId & 1u) // The last bit is set if this is a metadata id.
					{
						// Get the actual Metadata Id.
						uint32 MetadataId = SpecId >> 1;
						uint32* TimerIdPtr = MetadataIdToTimerIdMap.Find(MetadataId);
						if (TimerIdPtr == nullptr)
						{
							constexpr uint32 MetadataUnknownSpecId = (1u << 31u) - 3u;
							if (MetadataUnknownTimerId == ~0u)
							{
								MetadataUnknownTimerId = DefineNewTimerChecked(MetadataUnknownSpecId, TEXT("<unknown>"));
							}

							// Add an empty placeholder metadata so we obtain a MetadataId to use as the TimerId. Will be replaced with the actual metadata if the metadata event arrives later.
							TimerId = EditableTimingProfilerProvider.AddMetadata(MetadataUnknownTimerId, TArray<uint8>());
							MetadataIdToTimerIdMap.Add(MetadataId, TimerId);
						}
						else
						{
							TimerId = *TimerIdPtr;
						}
					}
					else
					{
						// Get the actual Spec Id.
						SpecId = SpecId >> 1;
						TimerId = GetTimerId(SpecId);
					}
				}
				else
				{
					TimerId = GetTimerId(SpecId);
				}

				FEventScopeState& ScopeState = ThreadState.ScopeStack.AddDefaulted_GetRef();
				ScopeState.StartCycle = ActualCycle;
				ScopeState.EventTypeId = TimerId;

				CPUPROFILER_DEBUG_LOGF(TEXT("[%u]  B=%llu (%.9f)\n"), ThreadState.ThreadId, ActualCycle, ActualTime);
				FTimingProfilerEvent Event;
				Event.TimerIndex = TimerId;
				ThreadState.Timeline->AppendBeginEvent(ActualTime, Event);
				CPUPROFILER_DEBUG_BEGIN_EVENT(ActualTime, Event);
			}
			else
			{
				// If we receive mismatched end events ignore them for now.
				// This can happen for example because tracing connects to the store after events were traced. Those events can be lost.
				if (ThreadState.ScopeStack.Num() > 0)
				{
					ThreadState.ScopeStack.Pop();
					CPUPROFILER_DEBUG_LOGF(TEXT("[%u]  E=%llu (%.9f)\n"), ThreadState.ThreadId, ActualCycle, ActualTime);
					ThreadState.Timeline->AppendEndEvent(ActualTime);
					CPUPROFILER_DEBUG_END_EVENT(ActualTime);
				}
			}
		}

		check(ActualCycle > 0);
		LastCycle = ActualCycle;
	}
	check(BufferPtr == BufferEnd);

	if (RemainingPending == 0)
	{
		//CPUPROFILER_DEBUG_LOGF(TEXT("[%u] MetaEvents: %d added\n"), ThreadState.ThreadId, ThreadState.PendingEvents.Num());
		ThreadState.PendingEvents.Reset();
	}
	else
	{
		const int32 NumEventsToRemove = ThreadState.PendingEvents.Num() - RemainingPending;
		CPUPROFILER_DEBUG_LOGF(TEXT("[%u] MetaEvents: %d added, %d still pending\n"), ThreadState.ThreadId, NumEventsToRemove, RemainingPending);
		ThreadState.PendingEvents.RemoveAt(0, NumEventsToRemove);
	}

	ThreadState.LastCycle = LastCycle;
}

////////////////////////////////////////////////////////////////////////////////////////////////////

void FCpuProfilerAnalyzer::DispatchPendingEvents(
	uint64& LastCycle,
	uint64 CurrentCycle,
	FThreadState& ThreadState,
	const FPendingEvent*& PendingCursor,
	int32& RemainingPending,
	bool bIsBeginEvent)
{
	if (ThreadState.bShouldIgnorePendingEvents)
	{
		PendingCursor += RemainingPending;
		RemainingPending = 0;
		return;
	}

	for (; RemainingPending > 0; RemainingPending--, PendingCursor++)
	{
		bool bEnter = true;
		uint64 PendingCycle = PendingCursor->Cycle;
		if (int64(PendingCycle) < 0)
		{
			PendingCycle = ~PendingCycle;
			bEnter = false;
		}

		if ((PendingCycle > CurrentCycle) ||
			(PendingCycle == CurrentCycle && !bIsBeginEvent))
		{
			break;
		}

		if (PendingCycle < LastCycle)
		{
			// Time needs to increase monotonically.
			// We are not allowing pending events (with metadata) older than regular CPU timing events.
			// When this happens we further ignore all pending events on this thread.
			// The issue can occur in late connect trace sessions with trace protocol <= 6 (i.e. the scoped events have relative timestamps).
			ThreadState.bShouldIgnorePendingEvents = true;
			PendingCursor += RemainingPending;
			RemainingPending = 0;
			UE_LOG(LogTraceServices, Error, TEXT("[CpuProfiler] Detected non-monotonically increasing timestamp. Further CPU timing events with metadata are ignored on thread %u."), ThreadState.ThreadId);
			break;
		}

		// Update LastCycle in order to verify time (of following pending events) increases monotonically.
		LastCycle = PendingCycle;

		double PendingTime = PendingCursor->Time;

		if (bEnter)
		{
			CPUPROFILER_DEBUG_LOGF(TEXT("[%u] >B=%llu (%.9f)\n"), ThreadState.ThreadId, PendingCycle, PendingTime);
			FTimingProfilerEvent Event;
			Event.TimerIndex = PendingCursor->TimerId;
			ThreadState.Timeline->AppendBeginEvent(PendingTime, Event);
			CPUPROFILER_DEBUG_BEGIN_EVENT(PendingTime, Event);
		}
		else
		{
			CPUPROFILER_DEBUG_LOGF(TEXT("[%u] >E=%llu (%.9f)\n"), ThreadState.ThreadId, PendingCycle, PendingTime);
			ThreadState.Timeline->AppendEndEvent(PendingTime);
			CPUPROFILER_DEBUG_END_EVENT(PendingTime);
		}
	}

	ThreadState.LastCycle = LastCycle;
}

////////////////////////////////////////////////////////////////////////////////////////////////////

void FCpuProfilerAnalyzer::DispatchRemainingPendingEvents(FThreadState& ThreadState)
{
	int32 RemainingPending = ThreadState.PendingEvents.Num();
	if (RemainingPending > 0)
	{
		uint64 LastCycle = ThreadState.LastCycle;
		const FPendingEvent* PendingCursor = ThreadState.PendingEvents.GetData();
		DispatchPendingEvents(LastCycle, ~0ull, ThreadState, PendingCursor, RemainingPending, true);
		check(RemainingPending == 0);
		ThreadState.PendingEvents.Reset();
	}
}

////////////////////////////////////////////////////////////////////////////////////////////////////

void FCpuProfilerAnalyzer::EndOpenEvents(FThreadState& ThreadState, double Timestamp)
{
	while (ThreadState.ScopeStack.Num())
	{
		ThreadState.ScopeStack.Pop();
		CPUPROFILER_DEBUG_LOGF(TEXT("[%u] ~E=%llu (%.9f)\n"), ThreadState.ThreadId, ThreadState.LastCycle, Timestamp);
		ThreadState.Timeline->AppendEndEvent(Timestamp);
		CPUPROFILER_DEBUG_END_EVENT(Timestamp);
	}
}

////////////////////////////////////////////////////////////////////////////////////////////////////

void FCpuProfilerAnalyzer::OnCpuScopeEnter(const FOnEventContext& Context)
{
	if (Context.EventTime.GetTimestamp() == 0)
	{
		return;
	}

	uint32 ThreadId = Context.ThreadInfo.GetId();
	FThreadState& ThreadState = GetThreadState(ThreadId);

	if (ThreadState.bShouldIgnorePendingEvents)
	{
		return;
	}

	uint32 SpecId = Context.EventData.GetTypeInfo().GetId();
	SpecId = ~SpecId; // to keep out of the way of normal spec IDs.

	uint32 TimerId;
	uint32* TimerIdIter = SpecIdToTimerIdMap.Find(SpecId);
	if (TimerIdIter)
	{
		TimerId = *TimerIdIter;
	}
	else
	{
		FString ScopeName;
		ScopeName += Context.EventData.GetTypeInfo().GetName();
		TimerId = DefineTimer(SpecId, Session.StoreString(*ScopeName), nullptr, 0, false);
	}

	TArray<uint8> CborData;
	Context.EventData.SerializeToCbor(CborData);
	TimerId = EditableTimingProfilerProvider.AddMetadata(TimerId, MoveTemp(CborData));

	uint64 Cycle = Context.EventTime.AsCycle64();
	double Time = Context.EventTime.AsSeconds();

	check(ThreadState.LastCycle <= Cycle);
	check(ThreadState.LastPendingEventTime <= Time);
	ThreadState.LastPendingEventTime = Time;

	ThreadState.PendingEvents.Add({ Cycle, Time, TimerId });
}

////////////////////////////////////////////////////////////////////////////////////////////////////

void FCpuProfilerAnalyzer::OnCpuScopeLeave(const FOnEventContext& Context)
{
	if (Context.EventTime.GetTimestamp() == 0)
	{
		return;
	}

	uint32 ThreadId = Context.ThreadInfo.GetId();
	FThreadState& ThreadState = GetThreadState(ThreadId);

	if (ThreadState.bShouldIgnorePendingEvents)
	{
		return;
	}

	uint64 Cycle = Context.EventTime.AsCycle64();
	double Time = Context.EventTime.AsSeconds();

	check(ThreadState.LastCycle <= Cycle);
	check(ThreadState.LastPendingEventTime <= Time);
	ThreadState.LastPendingEventTime = Time;

	ThreadState.PendingEvents.Add({ ~Cycle, Time, 0 });
}

////////////////////////////////////////////////////////////////////////////////////////////////////

uint32 FCpuProfilerAnalyzer::DefineTimer(uint32 SpecId, const TCHAR* Name, const TCHAR* File, uint32 Line, bool bMergeByName)
{
	// Expected: Name is already a pointer in a string store.

	// The CPU scoped events (timers) can be merged by name.
	// Ex.: If bMergeByName == true and there are multiple timers defined in code with same name,
	//      those will appear in Insights as a single timer.

	// Check if a timer with same name was already defined.
	FTimerInfo* FindTimerIdByName = ScopeNameToTimerIdMap.Find((uint64)Name);
	if (FindTimerIdByName)
	{
		// Yes, a timer with same name was already defined.

		++(FindTimerIdByName->Count);

		uint32 TimerId;

		// Check if SpecId is already mapped to timer.
		const uint32* FindTimerId = SpecIdToTimerIdMap.Find(SpecId);
		if (FindTimerId && bMergeByName)
		{
			// Yes, SpecId was already mapped to a timer (ex. as an <unknown> timer).
			TimerId = *FindTimerId;

			// Update name for mapped timer.
			EditableTimingProfilerProvider.SetTimerNameAndLocation(TimerId, Name, File, Line);

			// In this case, we do not remap the SpecId to the previously defined timer with same name.
			// This is because the two timers are already used in timelines.
			// So we will continue to use separate timers, even if those have same name.
		}
		else
		{
			if (bMergeByName)
			{
				// Use the previously defined timer with same name.
				TimerId = FindTimerIdByName->Id;
			}
			else
			{
				// Define a new CPU timer.
				TimerId = EditableTimingProfilerProvider.AddCpuTimer(Name, File, Line);
			}

			// Map this SpecId to the previously defined timer with same name.
			SpecIdToTimerIdMap.Add(SpecId, TimerId);
		}

		return TimerId;
	}
	else
	{
		// No, a timer with same name was not defined (or we do not want to merge by name).

		uint32 TimerId;

		// Check if SpecId is already mapped to timer.
		const uint32* FindTimerId = SpecIdToTimerIdMap.Find(SpecId);
		if (FindTimerId)
		{
			// Yes, SpecId was already mapped to a timer (ex. as an <unknown> timer).
			TimerId = *FindTimerId;

			// Update name for mapped timer.
			EditableTimingProfilerProvider.SetTimerNameAndLocation(TimerId, Name, File, Line);
		}
		else
		{
			// Define a new CPU timer.
			TimerId = EditableTimingProfilerProvider.AddCpuTimer(Name, File, Line);

			// Map the SpecId to the timer.
			SpecIdToTimerIdMap.Add(SpecId, TimerId);
		}

		// Map the name to the timer.
		ScopeNameToTimerIdMap.Add((uint64)Name, { TimerId, 1 });
		return TimerId;
	}
}

////////////////////////////////////////////////////////////////////////////////////////////////////

uint32 FCpuProfilerAnalyzer::DefineNewTimerChecked(uint32 SpecId, const TCHAR* TimerName, const TCHAR* File, uint32 Line)
{
	TimerName = Session.StoreString(TimerName);
	uint32 NewTimerId = EditableTimingProfilerProvider.AddCpuTimer(TimerName, File, Line);
	SpecIdToTimerIdMap.Add(SpecId, NewTimerId);
	return NewTimerId;
}

////////////////////////////////////////////////////////////////////////////////////////////////////

uint32 FCpuProfilerAnalyzer::GetTimerId(uint32 SpecId)
{
	if (uint32* FindIt = SpecIdToTimerIdMap.Find(SpecId))
	{
		return *FindIt;
	}
	else
	{
		// Adds a timer with an "unknown" name.
		// The "unknown" timers are not merged by name, because the actual name
		// might be updated when an EventSpec event is received (for this SpecId).
		return DefineNewTimerChecked(SpecId, *FString::Printf(TEXT("<unknown %u>"), SpecId));
	}
}

////////////////////////////////////////////////////////////////////////////////////////////////////

FCpuProfilerAnalyzer::FThreadState& FCpuProfilerAnalyzer::GetThreadState(uint32 ThreadId)
{
	FThreadState* ThreadState = ThreadStatesMap.FindRef(ThreadId);
	if (!ThreadState)
	{
		ThreadState = new FThreadState();
		ThreadState->ThreadId = ThreadId;
		ThreadState->Timeline = &EditableTimingProfilerProvider.GetCpuThreadEditableTimeline(ThreadId);
		ThreadStatesMap.Add(ThreadId, ThreadState);

		// Just in case the rest of Insight's reporting/analysis doesn't know about
		// this thread, we'll explicitly add it. For fault tolerance.
		EditableThreadProvider.AddThread(ThreadId, nullptr, TPri_Normal);
	}
	return *ThreadState;
}

////////////////////////////////////////////////////////////////////////////////////////////////////

} // namespace TraceServices

#undef CPUPROFILER_DEBUG_LOGF
#undef CPUPROFILER_DEBUG_BEGIN_EVENT
#undef CPUPROFILER_DEBUG_END_EVENT