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

#include "VirtualizationSourceControlUtilities.h"

#include "Async/TaskGraphInterfaces.h"
#include "ISourceControlModule.h"
#include "ISourceControlProvider.h"
#include "ISourceControlRevision.h"
#include "Misc/PackagePath.h"
#include "Misc/PackageSegment.h"
#include "SourceControlOperations.h"

// When enabled we push the source control work to the main thread via the task graph system.
// Note that when enabled this can potentially cause thread locks so is no a production ready 
// fix. Realistically we need to fix the SourceControl API to accept requests from any thread 
// which is currently under discussion.
#define UE_FORCE_SOURCECONTROL_TO_MAIN_THREAD 1

// This code relies on changes to the SourceControl API which need to be discussed, enabling this
// will allow the code to compile so it can be submitted without causing problems to others.
// The feature is entirely opt in so it shouldn't affect anyone else.
#define UE_FIX_COMPILE_ISSUES 1

namespace UE::Virtualization::Experimental
{

bool FVirtualizationSourceControlUtilities::SyncPayloadSidecarFile(const FPackagePath& PackagePath)
{
	TRACE_CPUPROFILER_EVENT_SCOPE(FPayloadSideCarFunctionality::SyncPayloadSidecarFile);

	if (!ISourceControlModule::Get().IsEnabled())
	{
		UE_LOG(LogVirtualization, Error, TEXT("Attempting to sync a .upayload for '%s' but source control is disabled!"), *PackagePath.GetDebugName());
		return false;
	}

	// We only allow the perforce source control system as we have not adequately tested the others!
	const FName SourceControlName = ISourceControlModule::Get().GetProvider().GetName();
	if (SourceControlName != TEXT("Perforce"))
	{
		UE_LOG(LogVirtualization, Error, TEXT("Attempting to sync a .upayload for '%s' but source control is '%s' and only Perforce is currently supported!"), *PackagePath.GetDebugName(), *SourceControlName.ToString());
		return false;
	}

#if UE_FORCE_SOURCECONTROL_TO_MAIN_THREAD
	// ISourceControlOperation commands must be invoked from the game thread so we need to push the work there
	// and then wait on the results.
	bool bResult = false;
	FGraphEventRef EventRef = FFunctionGraphTask::CreateAndDispatchWhenReady([this, &bResult, PackagePath]()
		{
			bResult = SyncPayloadSidecarFileInternal(PackagePath);
		}, TStatId(), nullptr, ENamedThreads::GameThread);

	FTaskGraphInterface::Get().WaitUntilTaskCompletes(EventRef);
	return bResult;
#else
	return SyncPayloadSidecarFileInternal(PackagePath);
#endif //UE_FORCE_SOURCECONTROL_TO_MAIN_THREAD
}

bool FVirtualizationSourceControlUtilities::SyncPayloadSidecarFileInternal(const FPackagePath& PackagePath)
{
	TRACE_CPUPROFILER_EVENT_SCOPE(FPayloadSideCarFunctionality::SyncPayloadSidecarFileInternal);

	ISourceControlProvider& SCCProvider = ISourceControlModule::Get().GetProvider();

	const FString AssetFilePath = PackagePath.GetLocalFullPath(EPackageSegment::Header);
	const FString SidecarFilePath = PackagePath.GetLocalFullPath(EPackageSegment::PayloadSidecar);

	// Update the state of the .uasset file in the cache and store the history of the file
	{
		TRACE_CPUPROFILER_EVENT_SCOPE(FPayloadSideCarFunctionality::SyncPayloadSidecarGameThread::UpdateStatus);

		TSharedRef<FUpdateStatus, ESPMode::ThreadSafe> UpdateStatusOperation = ISourceControlOperation::Create<FUpdateStatus>();
		UpdateStatusOperation->SetUpdateHistory(true);
		if (SCCProvider.Execute(UpdateStatusOperation, AssetFilePath) != ECommandResult::Succeeded)
		{
			UE_LOG(LogVirtualization, Error, TEXT("Failed to update source control state for '%s'"), *PackagePath.GetDebugName());
			return false;
		}
	}

	// Get the state of the .uasset from the cache
	FSourceControlStatePtr State;
	{ 
		TRACE_CPUPROFILER_EVENT_SCOPE(FPayloadSideCarFunctionality::SyncPayloadSidecarGameThread::GetState);
		State = SCCProvider.GetState(AssetFilePath, EStateCacheUsage::Use);
		if (!State)
		{
			UE_LOG(LogVirtualization, Error, TEXT("Failed to find source control state for '%s'"), *PackagePath.GetDebugName());
			return false;
		}
	}

	// Make sure we have access to a valid revision
#if UE_FIX_COMPILE_ISSUES
	checkf(false, TEXT("Attempting to call SyncPayloadSidecarFile before UE_FIX_COMPILE_ISSUES was fixed!"));
	const int32 LocalRevision = INDEX_NONE;
#else
	const int32 LocalRevision = State->GetLocalRevision();
#endif //UE_FIX_COMPILE_ISSUES

	if (LocalRevision == INDEX_NONE)
	{
		UE_LOG(LogVirtualization, Error, TEXT("Failed to find source control revision for '%s'"), *PackagePath.GetDebugName());
		return false;
	}

	// Now we can access the history for the revision that the .uasset is currently synced to
	TSharedPtr<ISourceControlRevision, ESPMode::ThreadSafe> Revision = State->FindHistoryRevision(LocalRevision);
	if (!Revision)
	{
		UE_LOG(LogVirtualization, Error, TEXT("Failed to find the revision (%d) history for '%s'"), LocalRevision, *PackagePath.GetDebugName());
		return false;
	}

	// For P4 the CheckInIdentifier is actually the changelist that the revision was submitted under
	const int32 ChangelistNumber = Revision->GetCheckInIdentifier();
	if (ChangelistNumber == INDEX_NONE)
	{
		UE_LOG(LogVirtualization, Error, TEXT("Revision (%d) history was invalid for '%s'"), LocalRevision, *PackagePath.GetDebugName());
		return false;
	}

	// The revision number passed to FSync should be the changelist number, not the file revision
	// NOTE: This will not force sync, if the file is the correct version in the workspace but has 
	// been deleted, this will not fix it!
	{
		TRACE_CPUPROFILER_EVENT_SCOPE(FPayloadSideCarFunctionality::SyncPayloadSidecarGameThread::Sync);
	
		TSharedRef<FSync, ESPMode::ThreadSafe> SyncCommand = ISourceControlOperation::Create<FSync>();
		SyncCommand->SetRevision(FString::Printf(TEXT("%d"), ChangelistNumber));

		if (SCCProvider.Execute(SyncCommand, SidecarFilePath, EConcurrency::Asynchronous) == ECommandResult::Succeeded)
		{
			UE_LOG(LogVirtualization, Verbose, TEXT("Successfully synced .upayload file for '%s'"), *PackagePath.GetDebugName());
			return true;
		}
		else
		{
			UE_LOG(LogVirtualization, Error, TEXT("Failed to sync .upayload file for '%s'"), *PackagePath.GetDebugName());
			return false;
		}
	}

	return true;
}

} // namespace UE::Virtualization::Experimental