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

#include "structuredcachestore.h"

#include <zencore/except.h>

#include <zencore/compactbinarybuilder.h>
#include <zencore/compactbinarypackage.h>
#include <zencore/compactbinaryvalidation.h>
#include <zencore/compress.h>
#include <zencore/except.h>
#include <zencore/filesystem.h>
#include <zencore/fmtutils.h>
#include <zencore/logging.h>
#include <zencore/scopeguard.h>
#include <zencore/string.h>
#include <zencore/thread.h>
#include <zencore/timer.h>
#include <zencore/trace.h>
#include <zenstore/cidstore.h>

#include <xxhash.h>

#if ZEN_PLATFORM_WINDOWS
#	include <zencore/windows.h>
#endif

ZEN_THIRD_PARTY_INCLUDES_START
#include <fmt/core.h>
#include <gsl/gsl-lite.hpp>
ZEN_THIRD_PARTY_INCLUDES_END

#if ZEN_WITH_TESTS
#	include <zencore/testing.h>
#	include <zencore/testutils.h>
#	include <zencore/workthreadpool.h>
#	include <random>
#endif

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

namespace zen {

namespace {

#pragma pack(push)
#pragma pack(1)

	struct CacheBucketIndexHeader
	{
		static constexpr uint32_t ExpectedMagic	 = 0x75696478;	// 'uidx';
		static constexpr uint32_t CurrentVersion = 1;

		uint32_t Magic			  = ExpectedMagic;
		uint32_t Version		  = CurrentVersion;
		uint64_t EntryCount		  = 0;
		uint64_t LogPosition	  = 0;
		uint32_t PayloadAlignment = 0;
		uint32_t Checksum		  = 0;

		static uint32_t ComputeChecksum(const CacheBucketIndexHeader& Header)
		{
			return XXH32(&Header.Magic, sizeof(CacheBucketIndexHeader) - sizeof(uint32_t), 0xC0C0'BABA);
		}
	};

	static_assert(sizeof(CacheBucketIndexHeader) == 32);

	struct LegacyDiskLocation
	{
		inline LegacyDiskLocation() = default;

		inline LegacyDiskLocation(uint64_t Offset, uint64_t ValueSize, uint32_t IndexSize, uint64_t Flags)
		: OffsetAndFlags(CombineOffsetAndFlags(Offset, Flags))
		, LowerSize(ValueSize & 0xFFFFffff)
		, IndexDataSize(IndexSize)
		{
		}

		static const uint64_t kOffsetMask = 0x0000'ffFF'ffFF'ffFFull;
		static const uint64_t kSizeMask	  = 0x00FF'0000'0000'0000ull;  // Most significant bits of value size (lower 32 bits in LowerSize)
		static const uint64_t kFlagsMask  = 0xff00'0000'0000'0000ull;
		static const uint64_t kStandaloneFile = 0x8000'0000'0000'0000ull;  // Stored as a separate file
		static const uint64_t kStructured	  = 0x4000'0000'0000'0000ull;  // Serialized as compact binary
		static const uint64_t kTombStone	  = 0x2000'0000'0000'0000ull;  // Represents a deleted key/value
		static const uint64_t kCompressed	  = 0x1000'0000'0000'0000ull;  // Stored in compressed buffer format

		static uint64_t CombineOffsetAndFlags(uint64_t Offset, uint64_t Flags) { return Offset | Flags; }

		inline uint64_t		  Offset() const { return OffsetAndFlags & kOffsetMask; }
		inline uint64_t		  Size() const { return LowerSize; }
		inline uint64_t		  IsFlagSet(uint64_t Flag) const { return OffsetAndFlags & Flag; }
		inline ZenContentType GetContentType() const
		{
			ZenContentType ContentType = ZenContentType::kBinary;

			if (IsFlagSet(LegacyDiskLocation::kStructured))
			{
				ContentType = ZenContentType::kCbObject;
			}

			if (IsFlagSet(LegacyDiskLocation::kCompressed))
			{
				ContentType = ZenContentType::kCompressedBinary;
			}

			return ContentType;
		}
		inline uint64_t Flags() const { return OffsetAndFlags & kFlagsMask; }

	private:
		uint64_t OffsetAndFlags = 0;
		uint32_t LowerSize		= 0;
		uint32_t IndexDataSize	= 0;
	};

	struct LegacyDiskIndexEntry
	{
		IoHash			   Key;
		LegacyDiskLocation Location;
	};

#pragma pack(pop)

	static_assert(sizeof(LegacyDiskIndexEntry) == 36);

	const char* IndexExtension		= ".uidx";
	const char* LogExtension		= ".slog";
	const char* LegacyDataExtension = ".sobs";

	std::filesystem::path GetIndexPath(const std::filesystem::path& BucketDir, const std::string& BucketName)
	{
		return BucketDir / (BucketName + IndexExtension);
	}

	std::filesystem::path GetTempIndexPath(const std::filesystem::path& BucketDir, const std::string& BucketName)
	{
		return BucketDir / (BucketName + ".tmp" + IndexExtension);
	}

	std::filesystem::path GetLogPath(const std::filesystem::path& BucketDir, const std::string& BucketName)
	{
		return BucketDir / (BucketName + LogExtension);
	}

	std::filesystem::path GetLegacyLogPath(const std::filesystem::path& BucketDir)
	{
		return BucketDir / (std::string("zen") + LogExtension);
	}

	std::filesystem::path GetLegacyDataPath(const std::filesystem::path& BucketDir)
	{
		return BucketDir / (std::string("zen") + LegacyDataExtension);
	}

	bool ValidateLegacyEntry(const LegacyDiskIndexEntry& Entry, std::string& OutReason)
	{
		if (Entry.Key == IoHash::Zero)
		{
			OutReason = fmt::format("Invalid hash key {}", Entry.Key.ToHexString());
			return false;
		}
		if (Entry.Location.Flags() & ~(LegacyDiskLocation::kStandaloneFile | LegacyDiskLocation::kStructured |
									   LegacyDiskLocation::kTombStone | LegacyDiskLocation::kCompressed))
		{
			OutReason = fmt::format("Invalid flags {} for entry {}", Entry.Location.Flags(), Entry.Key.ToHexString());
			return false;
		}
		if (!Entry.Location.IsFlagSet(LegacyDiskLocation::kTombStone))
		{
			return true;
		}
		uint64_t Size = Entry.Location.Size();
		if (Size == 0)
		{
			OutReason = fmt::format("Invalid size {} for entry {}", Size, Entry.Key.ToHexString());
			return false;
		}
		return true;
	}

	bool ValidateEntry(const DiskIndexEntry& Entry, std::string& OutReason)
	{
		if (Entry.Key == IoHash::Zero)
		{
			OutReason = fmt::format("Invalid hash key {}", Entry.Key.ToHexString());
			return false;
		}
		if (Entry.Location.GetFlags() &
			~(DiskLocation::kStandaloneFile | DiskLocation::kStructured | DiskLocation::kTombStone | DiskLocation::kCompressed))
		{
			OutReason = fmt::format("Invalid flags {} for entry {}", Entry.Location.GetFlags(), Entry.Key.ToHexString());
			return false;
		}
		if (Entry.Location.IsFlagSet(DiskLocation::kTombStone))
		{
			return true;
		}
		uint64_t Size = Entry.Location.Size();
		if (Size == 0)
		{
			OutReason = fmt::format("Invalid size {} for entry {}", Size, Entry.Key.ToHexString());
			return false;
		}
		return true;
	}

}  // namespace

namespace fs = std::filesystem;

static CbObject
LoadCompactBinaryObject(const fs::path& Path)
{
	FileContents Result = ReadFile(Path);

	if (!Result.ErrorCode)
	{
		IoBuffer Buffer = Result.Flatten();
		if (CbValidateError Error = ValidateCompactBinary(Buffer, CbValidateMode::All); Error == CbValidateError::None)
		{
			return LoadCompactBinaryObject(Buffer);
		}
	}

	return CbObject();
}

static void
SaveCompactBinaryObject(const fs::path& Path, const CbObject& Object)
{
	WriteFile(Path, Object.GetBuffer().AsIoBuffer());
}

ZenCacheNamespace::ZenCacheNamespace(CasGc& Gc, const std::filesystem::path& RootDir)
: GcStorage(Gc)
, GcContributor(Gc)
, m_RootDir(RootDir)
, m_DiskLayer(RootDir)
{
	ZEN_INFO("initializing structured cache at '{}'", RootDir);
	CreateDirectories(RootDir);

	m_DiskLayer.DiscoverBuckets();

#if ZEN_USE_CACHE_TRACKER
	m_AccessTracker.reset(new ZenCacheTracker(RootDir));
#endif
}

ZenCacheNamespace::~ZenCacheNamespace()
{
}

bool
ZenCacheNamespace::Get(std::string_view InBucket, const IoHash& HashKey, ZenCacheValue& OutValue)
{
	ZEN_TRACE_CPU("Z$::Get");

	bool Ok = m_MemLayer.Get(InBucket, HashKey, OutValue);

#if ZEN_USE_CACHE_TRACKER
	auto _ = MakeGuard([&] {
		if (!Ok)
			return;

		m_AccessTracker->TrackAccess(InBucket, HashKey);
	});
#endif

	if (Ok)
	{
		ZEN_ASSERT(OutValue.Value.Size());

		return true;
	}

	Ok = m_DiskLayer.Get(InBucket, HashKey, OutValue);

	if (Ok)
	{
		ZEN_ASSERT(OutValue.Value.Size());

		if (OutValue.Value.Size() <= m_DiskLayerSizeThreshold)
		{
			m_MemLayer.Put(InBucket, HashKey, OutValue);
		}
	}

	return Ok;
}

void
ZenCacheNamespace::Put(std::string_view InBucket, const IoHash& HashKey, const ZenCacheValue& Value)
{
	ZEN_TRACE_CPU("Z$::Put");

	// Store value and index

	ZEN_ASSERT(Value.Value.Size());

	m_DiskLayer.Put(InBucket, HashKey, Value);

#if ZEN_USE_REF_TRACKING
	if (Value.Value.GetContentType() == ZenContentType::kCbObject)
	{
		if (ValidateCompactBinary(Value.Value, CbValidateMode::All) == CbValidateError::None)
		{
			CbObject Object{SharedBuffer(Value.Value)};

			uint8_t								TempBuffer[8 * sizeof(IoHash)];
			std::pmr::monotonic_buffer_resource Linear{TempBuffer, sizeof TempBuffer};
			std::pmr::polymorphic_allocator		Allocator{&Linear};
			std::pmr::vector<IoHash>			CidReferences{Allocator};

			Object.IterateAttachments([&](CbFieldView Field) { CidReferences.push_back(Field.AsAttachment()); });

			m_Gc.OnNewCidReferences(CidReferences);
		}
	}
#endif

	if (Value.Value.Size() <= m_DiskLayerSizeThreshold)
	{
		m_MemLayer.Put(InBucket, HashKey, Value);
	}
}

bool
ZenCacheNamespace::DropBucket(std::string_view Bucket)
{
	ZEN_INFO("dropping bucket '{}'", Bucket);

	// TODO: should ensure this is done atomically across all layers

	const bool MemDropped  = m_MemLayer.DropBucket(Bucket);
	const bool DiskDropped = m_DiskLayer.DropBucket(Bucket);
	const bool AnyDropped  = MemDropped || DiskDropped;

	ZEN_INFO("bucket '{}' was {}", Bucket, AnyDropped ? "dropped" : "not found");

	return AnyDropped;
}

void
ZenCacheNamespace::Flush()
{
	m_DiskLayer.Flush();
}

void
ZenCacheNamespace::Scrub(ScrubContext& Ctx)
{
	if (m_LastScrubTime == Ctx.ScrubTimestamp())
	{
		return;
	}

	m_LastScrubTime = Ctx.ScrubTimestamp();

	m_DiskLayer.Scrub(Ctx);
	m_MemLayer.Scrub(Ctx);
}

void
ZenCacheNamespace::GatherReferences(GcContext& GcCtx)
{
	Stopwatch  Timer;
	const auto Guard =
		MakeGuard([&] { ZEN_INFO("cache gathered all references from '{}' in {}", m_RootDir, NiceTimeSpanMs(Timer.GetElapsedTimeMs())); });

	access_tracking::AccessTimes AccessTimes;
	m_MemLayer.GatherAccessTimes(AccessTimes);

	m_DiskLayer.UpdateAccessTimes(AccessTimes);
	m_DiskLayer.GatherReferences(GcCtx);
}

void
ZenCacheNamespace::CollectGarbage(GcContext& GcCtx)
{
	m_MemLayer.Reset();
	m_DiskLayer.CollectGarbage(GcCtx);
}

GcStorageSize
ZenCacheNamespace::StorageSize() const
{
	return {.DiskSize = m_DiskLayer.TotalSize(), .MemorySize = m_MemLayer.TotalSize()};
}

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

ZenCacheMemoryLayer::ZenCacheMemoryLayer()
{
}

ZenCacheMemoryLayer::~ZenCacheMemoryLayer()
{
}

bool
ZenCacheMemoryLayer::Get(std::string_view InBucket, const IoHash& HashKey, ZenCacheValue& OutValue)
{
	RwLock::SharedLockScope _(m_Lock);

	auto it = m_Buckets.find(std::string(InBucket));

	if (it == m_Buckets.end())
	{
		return false;
	}

	CacheBucket* Bucket = &it->second;

	_.ReleaseNow();

	// There's a race here. Since the lock is released early to allow
	// inserts, the bucket delete path could end up deleting the
	// underlying data structure

	return Bucket->Get(HashKey, OutValue);
}

void
ZenCacheMemoryLayer::Put(std::string_view InBucket, const IoHash& HashKey, const ZenCacheValue& Value)
{
	CacheBucket* Bucket = nullptr;

	{
		RwLock::SharedLockScope _(m_Lock);

		if (auto It = m_Buckets.find(std::string(InBucket)); It != m_Buckets.end())
		{
			Bucket = &It->second;
		}
	}

	if (Bucket == nullptr)
	{
		// New bucket

		RwLock::ExclusiveLockScope _(m_Lock);

		if (auto It = m_Buckets.find(std::string(InBucket)); It != m_Buckets.end())
		{
			Bucket = &It->second;
		}
		else
		{
			Bucket = &m_Buckets[std::string(InBucket)];
		}
	}

	// Note that since the underlying IoBuffer is retained, the content type is also

	Bucket->Put(HashKey, Value);
}

bool
ZenCacheMemoryLayer::DropBucket(std::string_view Bucket)
{
	RwLock::ExclusiveLockScope _(m_Lock);

	return !!m_Buckets.erase(std::string(Bucket));
}

void
ZenCacheMemoryLayer::Scrub(ScrubContext& Ctx)
{
	RwLock::SharedLockScope _(m_Lock);

	for (auto& Kv : m_Buckets)
	{
		Kv.second.Scrub(Ctx);
	}
}

void
ZenCacheMemoryLayer::GatherAccessTimes(zen::access_tracking::AccessTimes& AccessTimes)
{
	using namespace zen::access_tracking;

	RwLock::SharedLockScope _(m_Lock);

	for (auto& Kv : m_Buckets)
	{
		std::vector<KeyAccessTime>& Bucket = AccessTimes.Buckets[Kv.first];
		Kv.second.GatherAccessTimes(Bucket);
	}
}

void
ZenCacheMemoryLayer::Reset()
{
	RwLock::ExclusiveLockScope _(m_Lock);
	m_Buckets.clear();
}

uint64_t
ZenCacheMemoryLayer::TotalSize() const
{
	uint64_t				TotalSize{};
	RwLock::SharedLockScope _(m_Lock);

	for (auto& Kv : m_Buckets)
	{
		TotalSize += Kv.second.TotalSize();
	}

	return TotalSize;
}

void
ZenCacheMemoryLayer::CacheBucket::Scrub(ScrubContext& Ctx)
{
	RwLock::SharedLockScope _(m_BucketLock);

	std::vector<IoHash> BadHashes;

	for (auto& Kv : m_CacheMap)
	{
		if (Kv.first != IoHash::HashBuffer(Kv.second.Payload))
		{
			BadHashes.push_back(Kv.first);
		}
	}

	if (!BadHashes.empty())
	{
		Ctx.ReportBadCasChunks(BadHashes);
	}
}

void
ZenCacheMemoryLayer::CacheBucket::GatherAccessTimes(std::vector<zen::access_tracking::KeyAccessTime>& AccessTimes)
{
	RwLock::SharedLockScope _(m_BucketLock);
	std::transform(m_CacheMap.begin(), m_CacheMap.end(), std::back_inserter(AccessTimes), [](const auto& Kv) {
		return access_tracking::KeyAccessTime{.Key = Kv.first, .LastAccess = Kv.second.LastAccess};
	});
}

bool
ZenCacheMemoryLayer::CacheBucket::Get(const IoHash& HashKey, ZenCacheValue& OutValue)
{
	RwLock::SharedLockScope _(m_BucketLock);

	if (auto It = m_CacheMap.find(HashKey); It != m_CacheMap.end())
	{
		BucketValue& Value = It.value();
		OutValue.Value	   = Value.Payload;

		Value.LastAccess.store(GcClock::TickCount(), std::memory_order_relaxed);

		return true;
	}

	return false;
}

void
ZenCacheMemoryLayer::CacheBucket::Put(const IoHash& HashKey, const ZenCacheValue& Value)
{
	{
		RwLock::ExclusiveLockScope _(m_BucketLock);
		m_CacheMap.insert_or_assign(HashKey, BucketValue(Value.Value, GcClock::TickCount()));
	}

	m_TotalSize.fetch_add(Value.Value.GetSize(), std::memory_order::relaxed);
}

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

ZenCacheDiskLayer::CacheBucket::CacheBucket(std::string BucketName) : m_BucketName(std::move(BucketName))
{
}

ZenCacheDiskLayer::CacheBucket::~CacheBucket()
{
}

bool
ZenCacheDiskLayer::CacheBucket::Delete(std::filesystem::path BucketDir)
{
	if (std::filesystem::exists(BucketDir))
	{
		DeleteDirectories(BucketDir);

		return true;
	}

	return false;
}

void
ZenCacheDiskLayer::CacheBucket::OpenOrCreate(std::filesystem::path BucketDir, bool AllowCreate)
{
	using namespace std::literals;

	m_BlocksBasePath = BucketDir / "blocks";

	CreateDirectories(BucketDir);

	std::filesystem::path ManifestPath{BucketDir / "zen_manifest"};

	bool IsNew = false;

	CbObject Manifest = LoadCompactBinaryObject(ManifestPath);

	if (Manifest)
	{
		m_BucketId = Manifest["BucketId"].AsObjectId();
		m_IsOk	   = m_BucketId != Oid::Zero;
	}
	else if (AllowCreate)
	{
		m_BucketId.Generate();

		CbObjectWriter Writer;
		Writer << "BucketId"sv << m_BucketId;
		Manifest = Writer.Save();
		SaveCompactBinaryObject(ManifestPath, Manifest);
		IsNew = true;
	}
	else
	{
		return;
	}

	OpenLog(BucketDir, IsNew);

	for (CbFieldView Entry : Manifest["Timestamps"])
	{
		const CbObjectView Obj = Entry.AsObjectView();
		const IoHash	   Key = Obj["Key"sv].AsHash();

		if (auto It = m_Index.find(Key); It != m_Index.end())
		{
			It.value().LastAccess.store(Obj["LastAccess"sv].AsInt64(), std::memory_order_relaxed);
		}
	}

	m_IsOk = true;
}

void
ZenCacheDiskLayer::CacheBucket::MakeIndexSnapshot()
{
	ZEN_INFO("write store snapshot for '{}'", m_BucketDir / m_BucketName);
	uint64_t   EntryCount = 0;
	Stopwatch  Timer;
	const auto _ = MakeGuard([&] {
		ZEN_INFO("wrote store snapshot for '{}' containing #{} entries in {}",
				 m_BucketDir / m_BucketName,
				 EntryCount,
				 NiceTimeSpanMs(Timer.GetElapsedTimeMs()));
	});

	namespace fs = std::filesystem;

	fs::path IndexPath	   = GetIndexPath(m_BucketDir, m_BucketName);
	fs::path STmpIndexPath = GetTempIndexPath(m_BucketDir, m_BucketName);

	// Move index away, we keep it if something goes wrong
	if (fs::is_regular_file(STmpIndexPath))
	{
		fs::remove(STmpIndexPath);
	}
	if (fs::is_regular_file(IndexPath))
	{
		fs::rename(IndexPath, STmpIndexPath);
	}

	try
	{
		m_SlogFile.Flush();

		// Write the current state of the location map to a new index state
		uint64_t					LogCount = 0;
		std::vector<DiskIndexEntry> Entries;

		{
			Entries.resize(m_Index.size());

			uint64_t EntryIndex = 0;
			for (auto& Entry : m_Index)
			{
				DiskIndexEntry& IndexEntry = Entries[EntryIndex++];
				IndexEntry.Key			   = Entry.first;
				IndexEntry.Location		   = Entry.second.Location;
			}

			LogCount = m_SlogFile.GetLogCount();
		}

		BasicFile ObjectIndexFile;
		ObjectIndexFile.Open(IndexPath, BasicFile::Mode::kTruncate);
		CacheBucketIndexHeader Header = {.EntryCount	   = Entries.size(),
										 .LogPosition	   = LogCount,
										 .PayloadAlignment = gsl::narrow<uint32_t>(m_PayloadAlignment)};

		Header.Checksum = CacheBucketIndexHeader::ComputeChecksum(Header);

		ObjectIndexFile.Write(&Header, sizeof(CacheBucketIndexHeader), 0);
		ObjectIndexFile.Write(Entries.data(), Entries.size() * sizeof(DiskIndexEntry), sizeof(CacheBucketIndexHeader));
		ObjectIndexFile.Flush();
		ObjectIndexFile.Close();
		EntryCount = Entries.size();
	}
	catch (std::exception& Err)
	{
		ZEN_ERROR("snapshot FAILED, reason: '{}'", Err.what());

		// Restore any previous snapshot

		if (fs::is_regular_file(STmpIndexPath))
		{
			fs::remove(IndexPath);
			fs::rename(STmpIndexPath, IndexPath);
		}
	}
	if (fs::is_regular_file(STmpIndexPath))
	{
		fs::remove(STmpIndexPath);
	}
}

uint64_t
ZenCacheDiskLayer::CacheBucket::ReadIndexFile()
{
	std::vector<DiskIndexEntry> Entries;
	std::filesystem::path		IndexPath = GetIndexPath(m_BucketDir, m_BucketName);
	if (std::filesystem::is_regular_file(IndexPath))
	{
		Stopwatch  Timer;
		const auto _ = MakeGuard([&] {
			ZEN_INFO("read store '{}' index containing #{} entries in {}",
					 m_BucketDir / m_BucketName,
					 Entries.size(),
					 NiceTimeSpanMs(Timer.GetElapsedTimeMs()));
		});

		BasicFile ObjectIndexFile;
		ObjectIndexFile.Open(IndexPath, BasicFile::Mode::kRead);
		uint64_t Size = ObjectIndexFile.FileSize();
		if (Size >= sizeof(CacheBucketIndexHeader))
		{
			uint64_t			   ExpectedEntryCount = (Size - sizeof(sizeof(CacheBucketIndexHeader))) / sizeof(DiskIndexEntry);
			CacheBucketIndexHeader Header;
			ObjectIndexFile.Read(&Header, sizeof(Header), 0);
			if ((Header.Magic == CacheBucketIndexHeader::ExpectedMagic) && (Header.Version == CacheBucketIndexHeader::CurrentVersion) &&
				(Header.Checksum == CacheBucketIndexHeader::ComputeChecksum(Header)) && (Header.PayloadAlignment > 0) &&
				(Header.EntryCount <= ExpectedEntryCount))
			{
				Entries.resize(Header.EntryCount);
				ObjectIndexFile.Read(Entries.data(), Header.EntryCount * sizeof(DiskIndexEntry), sizeof(CacheBucketIndexHeader));
				m_PayloadAlignment = Header.PayloadAlignment;

				std::string InvalidEntryReason;
				for (const DiskIndexEntry& Entry : Entries)
				{
					if (!ValidateEntry(Entry, InvalidEntryReason))
					{
						ZEN_WARN("skipping invalid entry in '{}', reason: '{}'", IndexPath, InvalidEntryReason);
						continue;
					}
					m_Index.insert_or_assign(Entry.Key, IndexEntry(Entry.Location, GcClock::TickCount()));
				}

				return Header.LogPosition;
			}
			else
			{
				ZEN_WARN("skipping invalid index file '{}'", IndexPath);
			}
		}
	}
	return 0;
}

uint64_t
ZenCacheDiskLayer::CacheBucket::ReadLog(uint64_t SkipEntryCount)
{
	std::vector<DiskIndexEntry> Entries;
	std::filesystem::path		LogPath = GetLogPath(m_BucketDir, m_BucketName);
	if (std::filesystem::is_regular_file(LogPath))
	{
		Stopwatch					Timer;
		const auto					_ = MakeGuard([&] {
			 ZEN_INFO("read store '{}' log containing #{} entries in {}", LogPath, Entries.size(), NiceTimeSpanMs(Timer.GetElapsedTimeMs()));
		 });
		TCasLogFile<DiskIndexEntry> CasLog;
		CasLog.Open(LogPath, CasLogFile::Mode::kRead);
		if (CasLog.Initialize())
		{
			uint64_t EntryCount = CasLog.GetLogCount();
			if (EntryCount < SkipEntryCount)
			{
				ZEN_WARN("reading full log at '{}', reason: Log position from index snapshot is out of range", LogPath);
				SkipEntryCount = 0;
			}
			uint64_t ReadCount = EntryCount - SkipEntryCount;
			m_Index.reserve(ReadCount);
			uint64_t InvalidEntryCount = 0;
			CasLog.Replay(
				[&](const DiskIndexEntry& Record) {
					std::string InvalidEntryReason;
					if (Record.Location.Flags & DiskLocation::kTombStone)
					{
						m_Index.erase(Record.Key);
						return;
					}
					if (!ValidateEntry(Record, InvalidEntryReason))
					{
						ZEN_WARN("skipping invalid entry in '{}', reason: '{}'", LogPath, InvalidEntryReason);
						++InvalidEntryCount;
						return;
					}
					m_Index.insert_or_assign(Record.Key, IndexEntry(Record.Location, GcClock::TickCount()));
				},
				SkipEntryCount);
			if (InvalidEntryCount)
			{
				ZEN_WARN("found #{} invalid entries in '{}'", InvalidEntryCount, m_BucketDir / m_BucketName);
			}
		}
	}
	return 0;
};

uint64_t
ZenCacheDiskLayer::CacheBucket::MigrateLegacyData(bool CleanSource)
{
	std::filesystem::path LegacyLogPath = GetLegacyLogPath(m_BucketDir);

	if (!std::filesystem::is_regular_file(LegacyLogPath) || std::filesystem::file_size(LegacyLogPath) == 0)
	{
		return 0;
	}

	ZEN_INFO("migrating store {}", m_BucketDir / m_BucketName);

	std::filesystem::path LegacyDataPath = GetLegacyDataPath(m_BucketDir);

	uint64_t   MigratedChunkCount = 0;
	uint32_t   MigratedBlockCount = 0;
	Stopwatch  MigrationTimer;
	uint64_t   TotalSize = 0;
	const auto _		 = MakeGuard([&] {
		ZEN_INFO("migrated store '{}' to #{} chunks in #{} blocks in {} ({})",
				 m_BucketDir / m_BucketName,
				 MigratedChunkCount,
				 MigratedBlockCount,
				 NiceTimeSpanMs(MigrationTimer.GetElapsedTimeMs()),
				 NiceBytes(TotalSize));
	});

	uint64_t BlockFileSize = 0;
	{
		BasicFile BlockFile;
		BlockFile.Open(LegacyDataPath, CleanSource ? BasicFile::Mode::kWrite : BasicFile::Mode::kRead);
		BlockFileSize = BlockFile.FileSize();
	}

	std::unordered_map<IoHash, LegacyDiskIndexEntry, IoHash::Hasher> LegacyDiskIndex;
	uint64_t														 InvalidEntryCount = 0;

	size_t							  BlockChunkCount = 0;
	TCasLogFile<LegacyDiskIndexEntry> LegacyCasLog;
	LegacyCasLog.Open(LegacyLogPath, CleanSource ? CasLogFile::Mode::kWrite : CasLogFile::Mode::kRead);
	{
		Stopwatch  Timer;
		const auto __ = MakeGuard([&] {
			ZEN_INFO("read store '{}' legacy log containing #{} entries in {}",
					 LegacyLogPath,
					 LegacyDiskIndex.size(),
					 NiceTimeSpanMs(Timer.GetElapsedTimeMs()));
		});
		if (LegacyCasLog.Initialize())
		{
			LegacyDiskIndex.reserve(LegacyCasLog.GetLogCount());
			LegacyCasLog.Replay(
				[&](const LegacyDiskIndexEntry& Record) {
					if (Record.Location.IsFlagSet(LegacyDiskLocation::kTombStone))
					{
						LegacyDiskIndex.erase(Record.Key);
						return;
					}
					std::string InvalidEntryReason;
					if (!ValidateLegacyEntry(Record, InvalidEntryReason))
					{
						ZEN_WARN("skipping invalid entry in '{}', reason: '{}'", LegacyLogPath, InvalidEntryReason);
						++InvalidEntryCount;
						return;
					}
					if (m_Index.contains(Record.Key))
					{
						return;
					}
					LegacyDiskIndex[Record.Key] = Record;
				},
				0);

			std::vector<IoHash> BadEntries;
			for (const auto& Entry : LegacyDiskIndex)
			{
				const LegacyDiskIndexEntry& Record(Entry.second);
				if (Record.Location.IsFlagSet(LegacyDiskLocation::kStandaloneFile))
				{
					continue;
				}
				if (Record.Location.Offset() + Record.Location.Size() <= BlockFileSize)
				{
					BlockChunkCount++;
					continue;
				}
				ZEN_WARN("skipping invalid entry in '{}', reason: location is outside of file", LegacyLogPath);
				BadEntries.push_back(Entry.first);
			}
			for (const IoHash& BadHash : BadEntries)
			{
				LegacyDiskIndex.erase(BadHash);
			}
			InvalidEntryCount += BadEntries.size();
		}
	}
	if (InvalidEntryCount)
	{
		ZEN_WARN("found #{} invalid entries in '{}'", InvalidEntryCount, m_BucketDir / m_BucketName);
	}

	if (LegacyDiskIndex.empty())
	{
		LegacyCasLog.Close();
		if (CleanSource)
		{
			// Older versions of ZenCacheDiskLayer expects the legacy files to exist if it can find
			// a manifest and crashes on startup if they don't.
			// In order to not break startup when switching back an older version, lets just reset
			// the legacy data files to zero length.

			BasicFile LegacyLog;
			LegacyLog.Open(LegacyLogPath, BasicFile::Mode::kTruncate);
			BasicFile LegacySobs;
			LegacySobs.Open(LegacyDataPath, BasicFile::Mode::kTruncate);
		}
		return 0;
	}

	std::filesystem::path LogPath = GetLogPath(m_BucketDir, m_BucketName);
	CreateDirectories(LogPath.parent_path());
	TCasLogFile<DiskIndexEntry> CasLog;
	CasLog.Open(LogPath, CasLogFile::Mode::kWrite);

	std::unordered_map<size_t, IoHash> ChunkIndexToChunkHash;
	std::vector<BlockStoreLocation>	   ChunkLocations;
	ChunkIndexToChunkHash.reserve(BlockChunkCount);
	ChunkLocations.reserve(BlockChunkCount);

	std::vector<DiskIndexEntry> LogEntries;
	LogEntries.reserve(LegacyDiskIndex.size() - BlockChunkCount);

	for (const auto& Entry : LegacyDiskIndex)
	{
		const IoHash&			  ChunkHash = Entry.first;
		const LegacyDiskLocation& Location	= Entry.second.Location;
		if (Location.IsFlagSet(LegacyDiskLocation::kStandaloneFile))
		{
			uint8_t		 Flags		 = 0xff & (Location.Flags() >> 56);
			DiskLocation NewLocation = DiskLocation(Location.Size(), Flags);
			LogEntries.push_back({.Key = Entry.second.Key, .Location = NewLocation});
			continue;
		}
		size_t ChunkIndex = ChunkLocations.size();
		ChunkLocations.push_back({.BlockIndex = 0, .Offset = Location.Offset(), .Size = Location.Size()});
		ChunkIndexToChunkHash[ChunkIndex] = ChunkHash;
		TotalSize += Location.Size();
	}
	for (const DiskIndexEntry& Entry : LogEntries)
	{
		m_Index.insert_or_assign(Entry.Key, IndexEntry(Entry.Location, GcClock::TickCount()));
	}
	CasLog.Append(LogEntries);

	m_BlockStore.Split(
		ChunkLocations,
		LegacyDataPath,
		m_BlocksBasePath,
		MaxBlockSize,
		BlockStoreDiskLocation::MaxBlockIndex + 1,
		m_PayloadAlignment,
		CleanSource,
		[this, &LegacyDiskIndex, &ChunkIndexToChunkHash, &LegacyCasLog, &CasLog, CleanSource, &MigratedBlockCount, &MigratedChunkCount](
			const BlockStore::MovedChunksArray& MovedChunks) {
			std::vector<DiskIndexEntry> LogEntries;
			LogEntries.reserve(MovedChunks.size());
			for (const auto& Entry : MovedChunks)
			{
				size_t						ChunkIndex	= Entry.first;
				const BlockStoreLocation&	NewLocation = Entry.second;
				const IoHash&				ChunkHash	= ChunkIndexToChunkHash[ChunkIndex];
				const LegacyDiskIndexEntry& OldEntry	= LegacyDiskIndex[ChunkHash];
				const LegacyDiskLocation&	OldLocation = OldEntry.Location;
				uint8_t						Flags		= 0xff & (OldLocation.Flags() >> 56);
				LogEntries.push_back({.Key = ChunkHash, .Location = DiskLocation(NewLocation, m_PayloadAlignment, Flags)});
			}
			for (const DiskIndexEntry& Entry : LogEntries)
			{
				m_Index.insert_or_assign(Entry.Key, IndexEntry(Entry.Location, GcClock::TickCount()));
			}
			CasLog.Append(LogEntries);
			CasLog.Flush();
			if (CleanSource)
			{
				std::vector<LegacyDiskIndexEntry> LegacyLogEntries;
				LegacyLogEntries.reserve(MovedChunks.size());
				for (const auto& Entry : MovedChunks)
				{
					size_t						ChunkIndex	= Entry.first;
					const IoHash&				ChunkHash	= ChunkIndexToChunkHash[ChunkIndex];
					const LegacyDiskIndexEntry& OldEntry	= LegacyDiskIndex[ChunkHash];
					const LegacyDiskLocation&	OldLocation = OldEntry.Location;
					LegacyDiskLocation			NewLocation(OldLocation.Offset(),
													OldLocation.Size(),
													0,
													OldLocation.Flags() | LegacyDiskLocation::kTombStone);
					LegacyLogEntries.push_back(LegacyDiskIndexEntry{.Key = ChunkHash, .Location = NewLocation});
				}
				LegacyCasLog.Append(LegacyLogEntries);
				LegacyCasLog.Flush();
			}
			MigratedBlockCount++;
			MigratedChunkCount += MovedChunks.size();
		});

	LegacyCasLog.Close();
	CasLog.Close();

	if (CleanSource)
	{
		// Older versions of ZenCacheDiskLayer expects the legacy files to exist if it can find
		// a manifest and crashes on startup if they don't.
		// In order to not break startup when switching back an older version, lets just reset
		// the legacy data files to zero length.

		BasicFile LegacyLog;
		LegacyLog.Open(LegacyLogPath, BasicFile::Mode::kTruncate);
		BasicFile LegacySobs;
		LegacySobs.Open(LegacyDataPath, BasicFile::Mode::kTruncate);
	}
	return MigratedChunkCount;
}

void
ZenCacheDiskLayer::CacheBucket::OpenLog(const fs::path& BucketDir, const bool IsNew)
{
	m_BucketDir = BucketDir;

	m_TotalSize = 0;

	m_Index.clear();

	std::filesystem::path LegacyLogPath = GetLegacyLogPath(m_BucketDir);
	std::filesystem::path LogPath		= GetLogPath(m_BucketDir, m_BucketName);
	std::filesystem::path IndexPath		= GetIndexPath(m_BucketDir, m_BucketName);

	if (IsNew)
	{
		std::filesystem::path LegacyDataPath = GetLegacyDataPath(m_BucketDir);
		fs::remove(LegacyLogPath);
		fs::remove(LegacyDataPath);
		fs::remove(LogPath);
		fs::remove(IndexPath);
		fs::remove_all(m_BlocksBasePath);
	}

	uint64_t LogPosition		 = ReadIndexFile();
	uint64_t LogEntryCount		 = ReadLog(LogPosition);
	uint64_t LegacyLogEntryCount = MigrateLegacyData(true);

	CreateDirectories(m_BucketDir);

	m_SlogFile.Open(LogPath, CasLogFile::Mode::kWrite);

	std::vector<BlockStoreLocation> KnownLocations;
	KnownLocations.reserve(m_Index.size());
	for (const auto& Entry : m_Index)
	{
		const DiskLocation& Location = Entry.second.Location;
		m_TotalSize.fetch_add(Location.Size(), std::memory_order::relaxed);
		if (Location.IsFlagSet(DiskLocation::kStandaloneFile))
		{
			continue;
		}
		const BlockStoreLocation& BlockLocation = Location.GetBlockLocation(m_PayloadAlignment);
		KnownLocations.push_back(BlockLocation);
	}

	m_BlockStore.Initialize(m_BlocksBasePath, MaxBlockSize, BlockStoreDiskLocation::MaxBlockIndex + 1, KnownLocations);

	if (IsNew || ((LogEntryCount + LegacyLogEntryCount) > 0))
	{
		MakeIndexSnapshot();
	}
	// TODO: should validate integrity of container files here
}

void
ZenCacheDiskLayer::CacheBucket::BuildPath(PathBuilderBase& Path, const IoHash& HashKey)
{
	char HexString[sizeof(HashKey.Hash) * 2];
	ToHexBytes(HashKey.Hash, sizeof HashKey.Hash, HexString);

	Path.Append(m_BucketDir);
	Path.Append(L"/blob/");
	Path.AppendAsciiRange(HexString, HexString + 3);
	Path.AppendSeparator();
	Path.AppendAsciiRange(HexString + 3, HexString + 5);
	Path.AppendSeparator();
	Path.AppendAsciiRange(HexString + 5, HexString + sizeof(HexString));
}

bool
ZenCacheDiskLayer::CacheBucket::GetInlineCacheValue(const DiskLocation& Loc, ZenCacheValue& OutValue)
{
	BlockStoreLocation Location = Loc.GetBlockLocation(m_PayloadAlignment);

	OutValue.Value = m_BlockStore.TryGetChunk(Location);
	if (!OutValue.Value)
	{
		return false;
	}
	OutValue.Value.SetContentType(Loc.GetContentType());

	return true;
}

bool
ZenCacheDiskLayer::CacheBucket::GetStandaloneCacheValue(const DiskLocation& Loc, const IoHash& HashKey, ZenCacheValue& OutValue)
{
	ExtendablePathBuilder<256> DataFilePath;
	BuildPath(DataFilePath, HashKey);

	RwLock::SharedLockScope ValueLock(LockForHash(HashKey));

	if (IoBuffer Data = IoBufferBuilder::MakeFromFile(DataFilePath.ToPath()))
	{
		OutValue.Value = Data;
		OutValue.Value.SetContentType(Loc.GetContentType());

		return true;
	}

	return false;
}

bool
ZenCacheDiskLayer::CacheBucket::Get(const IoHash& HashKey, ZenCacheValue& OutValue)
{
	if (!m_IsOk)
	{
		return false;
	}

	RwLock::SharedLockScope _(m_IndexLock);
	auto					It = m_Index.find(HashKey);
	if (It == m_Index.end())
	{
		return false;
	}
	IndexEntry& Entry = It.value();
	Entry.LastAccess.store(GcClock::TickCount(), std::memory_order_relaxed);
	DiskLocation Location = Entry.Location;
	if (Location.IsFlagSet(DiskLocation::kStandaloneFile))
	{
		// We don't need to hold the index lock when we read a standalone file
		_.ReleaseNow();
		return GetStandaloneCacheValue(Location, HashKey, OutValue);
	}
	return GetInlineCacheValue(Location, OutValue);
}

void
ZenCacheDiskLayer::CacheBucket::Put(const IoHash& HashKey, const ZenCacheValue& Value)
{
	if (!m_IsOk)
	{
		return;
	}

	if (Value.Value.Size() >= m_LargeObjectThreshold)
	{
		return PutStandaloneCacheValue(HashKey, Value);
	}
	PutInlineCacheValue(HashKey, Value);
}

void
ZenCacheDiskLayer::CacheBucket::Drop()
{
	m_BlockStore.Close();
	m_SlogFile.Close();
	DeleteDirectories(m_BucketDir);
}

void
ZenCacheDiskLayer::CacheBucket::Flush()
{
	m_BlockStore.Flush();

	RwLock::SharedLockScope _(m_IndexLock);
	MakeIndexSnapshot();
	SaveManifest();
}

void
ZenCacheDiskLayer::CacheBucket::SaveManifest()
{
	using namespace std::literals;

	CbObjectWriter Writer;
	Writer << "BucketId"sv << m_BucketId;

	if (!m_Index.empty())
	{
		Writer.BeginArray("Timestamps"sv);
		for (auto& Kv : m_Index)
		{
			const IoHash&	  Key	= Kv.first;
			const IndexEntry& Entry = Kv.second;

			Writer.BeginObject();
			Writer << "Key"sv << Key;
			Writer << "LastAccess"sv << Entry.LastAccess;
			Writer.EndObject();
		}
		Writer.EndArray();
	}

	SaveCompactBinaryObject(m_BucketDir / "zen_manifest", Writer.Save());
}

void
ZenCacheDiskLayer::CacheBucket::Scrub(ScrubContext& Ctx)
{
	std::vector<IoHash> BadKeys;

	{
		RwLock::SharedLockScope _(m_IndexLock);

		for (auto& Kv : m_Index)
		{
			const IoHash&		HashKey = Kv.first;
			const DiskLocation& Loc		= Kv.second.Location;

			ZenCacheValue Value;

			if (Loc.IsFlagSet(DiskLocation::kStandaloneFile))
			{
				if (GetStandaloneCacheValue(Loc, HashKey, Value))
				{
					// Note: we cannot currently validate contents since we don't
					// have a content hash!
					continue;
				}
			}
			else if (GetInlineCacheValue(Loc, Value))
			{
				// Validate contents
				continue;
			}
			// Value not found
			BadKeys.push_back(HashKey);
		}
	}

	if (BadKeys.empty())
	{
		return;
	}

	if (Ctx.RunRecovery())
	{
		RwLock::ExclusiveLockScope _(m_IndexLock);

		for (const IoHash& BadKey : BadKeys)
		{
			// Log a tombstone and delete the in-memory index for the bad entry

			const auto	 It		  = m_Index.find(BadKey);
			DiskLocation Location = It->second.Location;
			Location.Flags |= DiskLocation::kTombStone;
			m_SlogFile.Append(DiskIndexEntry{.Key = BadKey, .Location = Location});
			m_Index.erase(BadKey);
		}
	}

	// Let whomever it concerns know about the bad chunks. This could
	// be used to invalidate higher level data structures more efficiently
	// than a full validation pass might be able to do
	Ctx.ReportBadCasChunks(BadKeys);
}

void
ZenCacheDiskLayer::CacheBucket::GatherReferences(GcContext& GcCtx)
{
	ZEN_TRACE_CPU("Z$::DiskLayer::CacheBucket::GatherReferences");

	uint64_t WriteBlockTimeUs		 = 0;
	uint64_t WriteBlockLongestTimeUs = 0;
	uint64_t ReadBlockTimeUs		 = 0;
	uint64_t ReadBlockLongestTimeUs	 = 0;

	Stopwatch  TotalTimer;
	const auto _ = MakeGuard([&] {
		ZEN_INFO("gathered references from '{}' in {} write lock: {} ({}), read lock: {} ({})",
				 m_BucketDir / m_BucketName,
				 NiceTimeSpanMs(TotalTimer.GetElapsedTimeMs()),
				 NiceLatencyNs(WriteBlockTimeUs),
				 NiceLatencyNs(WriteBlockLongestTimeUs),
				 NiceLatencyNs(ReadBlockTimeUs),
				 NiceLatencyNs(ReadBlockLongestTimeUs));
	});

	const GcClock::TimePoint ExpireTime =
		GcCtx.MaxCacheDuration() == GcClock::Duration::max() ? GcClock::TimePoint::min() : GcCtx.Time() - GcCtx.MaxCacheDuration();

	const GcClock::Tick ExpireTicks = ExpireTime.time_since_epoch().count();

	IndexMap Index;
	{
		RwLock::SharedLockScope __(m_IndexLock);
		Stopwatch				Timer;
		const auto				___ = MakeGuard([&] {
			 uint64_t ElapsedUs = Timer.GetElapsedTimeUs();
			 WriteBlockTimeUs += ElapsedUs;
			 WriteBlockLongestTimeUs = std::max(ElapsedUs, WriteBlockLongestTimeUs);
		 });
		Index						= m_Index;
	}

	std::vector<IoHash> ExpiredKeys;
	ExpiredKeys.reserve(1024);

	std::vector<IoHash> Cids;
	Cids.reserve(1024);

	for (const auto& Entry : Index)
	{
		const IoHash& Key = Entry.first;
		if (Entry.second.LastAccess < ExpireTicks)
		{
			ExpiredKeys.push_back(Key);
			continue;
		}

		const DiskLocation& Loc = Entry.second.Location;

		if (Loc.IsFlagSet(DiskLocation::kStructured))
		{
			if (Cids.size() > 1024)
			{
				GcCtx.ContributeCids(Cids);
				Cids.clear();
			}

			ZenCacheValue CacheValue;
			{
				RwLock::SharedLockScope __(m_IndexLock);
				Stopwatch				Timer;
				const auto				___ = MakeGuard([&] {
					 uint64_t ElapsedUs = Timer.GetElapsedTimeUs();
					 WriteBlockTimeUs += ElapsedUs;
					 WriteBlockLongestTimeUs = std::max(ElapsedUs, WriteBlockLongestTimeUs);
				 });
				if (Loc.IsFlagSet(DiskLocation::kStandaloneFile))
				{
					if (!GetStandaloneCacheValue(Loc, Key, CacheValue))
					{
						continue;
					}
				}
				else if (!GetInlineCacheValue(Loc, CacheValue))
				{
					continue;
				}
			}

			ZEN_ASSERT(CacheValue.Value);
			ZEN_ASSERT(CacheValue.Value.GetContentType() == ZenContentType::kCbObject);
			CbObject Obj(SharedBuffer{CacheValue.Value});
			Obj.IterateAttachments([&Cids](CbFieldView Field) { Cids.push_back(Field.AsAttachment()); });
		}
	}

	GcCtx.ContributeCids(Cids);
	GcCtx.ContributeCacheKeys(m_BucketName, std::move(ExpiredKeys));
}

void
ZenCacheDiskLayer::CacheBucket::CollectGarbage(GcContext& GcCtx)
{
	ZEN_TRACE_CPU("Z$::DiskLayer::CacheBucket::CollectGarbage");

	ZEN_INFO("collecting garbage from '{}'", m_BucketDir / m_BucketName);

	Stopwatch TotalTimer;
	uint64_t  WriteBlockTimeUs		  = 0;
	uint64_t  WriteBlockLongestTimeUs = 0;
	uint64_t  ReadBlockTimeUs		  = 0;
	uint64_t  ReadBlockLongestTimeUs  = 0;
	uint64_t  TotalChunkCount		  = 0;
	uint64_t  DeletedSize			  = 0;
	uint64_t  OldTotalSize			  = m_TotalSize.load(std::memory_order::relaxed);

	uint64_t DeletedCount = 0;
	uint64_t MovedCount	  = 0;

	const auto _ = MakeGuard([&] {
		ZEN_INFO(
			"garbage collect from '{}' DONE after {}, write lock: {} ({}), read lock: {} ({}), collected {} bytes, deleted #{} and moved "
			"#{} "
			"of #{} "
			"entires ({}).",
			m_BucketDir / m_BucketName,
			NiceTimeSpanMs(TotalTimer.GetElapsedTimeMs()),
			NiceLatencyNs(WriteBlockTimeUs),
			NiceLatencyNs(WriteBlockLongestTimeUs),
			NiceLatencyNs(ReadBlockTimeUs),
			NiceLatencyNs(ReadBlockLongestTimeUs),
			NiceBytes(DeletedSize),
			DeletedCount,
			MovedCount,
			TotalChunkCount,
			NiceBytes(OldTotalSize));
		RwLock::SharedLockScope _(m_IndexLock);
		SaveManifest();
	});

	m_SlogFile.Flush();

	std::span<const IoHash> ExpiredCacheKeys = GcCtx.ExpiredCacheKeys(m_BucketName);
	std::vector<IoHash>		DeleteCacheKeys;
	DeleteCacheKeys.reserve(ExpiredCacheKeys.size());
	GcCtx.FilterCas(ExpiredCacheKeys, [&](const IoHash& ChunkHash, bool Keep) {
		if (Keep)
		{
			return;
		}
		DeleteCacheKeys.push_back(ChunkHash);
	});
	if (DeleteCacheKeys.empty())
	{
		ZEN_INFO("garbage collect SKIPPED, for '{}', no expired cache keys found", m_BucketDir / m_BucketName);
		return;
	}

	std::vector<DiskIndexEntry>		 ExpiredStandaloneEntries;
	IndexMap						 Index;
	BlockStore::ReclaimSnapshotState BlockStoreState;
	{
		RwLock::SharedLockScope __(m_IndexLock);
		Stopwatch				Timer;
		const auto				____ = MakeGuard([&] {
			 uint64_t ElapsedUs = Timer.GetElapsedTimeUs();
			 WriteBlockTimeUs += ElapsedUs;
			 WriteBlockLongestTimeUs = std::max(ElapsedUs, WriteBlockLongestTimeUs);
		 });
		if (m_Index.empty())
		{
			ZEN_INFO("garbage collect SKIPPED, for '{}', container is empty", m_BucketDir / m_BucketName);
			return;
		}
		BlockStoreState = m_BlockStore.GetReclaimSnapshotState();

		SaveManifest();
		Index = m_Index;

		for (const IoHash& Key : DeleteCacheKeys)
		{
			if (auto It = Index.find(Key); It != Index.end())
			{
				DiskIndexEntry Entry = {.Key = It->first, .Location = It->second.Location};
				if (Entry.Location.Flags & DiskLocation::kStandaloneFile)
				{
					Entry.Location.Flags |= DiskLocation::kTombStone;
					ExpiredStandaloneEntries.push_back(Entry);
				}
			}
		}
		if (GcCtx.IsDeletionMode())
		{
			for (const auto& Entry : ExpiredStandaloneEntries)
			{
				m_Index.erase(Entry.Key);
			}
			m_SlogFile.Append(ExpiredStandaloneEntries);
		}
	}

	if (GcCtx.IsDeletionMode())
	{
		std::error_code			   Ec;
		ExtendablePathBuilder<256> Path;

		for (const auto& Entry : ExpiredStandaloneEntries)
		{
			const IoHash&		Key = Entry.Key;
			const DiskLocation& Loc = Entry.Location;

			Path.Reset();
			BuildPath(Path, Key);
			fs::path FilePath = Path.ToPath();

			{
				RwLock::SharedLockScope __(m_IndexLock);
				Stopwatch				Timer;
				const auto				____ = MakeGuard([&] {
					 uint64_t ElapsedUs = Timer.GetElapsedTimeUs();
					 WriteBlockTimeUs += ElapsedUs;
					 WriteBlockLongestTimeUs = std::max(ElapsedUs, WriteBlockLongestTimeUs);
				 });
				if (m_Index.contains(Key))
				{
					// Someone added it back, let the file on disk be
					ZEN_DEBUG("skipping z$ delete standalone of file '{}' FAILED, it has been added back", Path.ToUtf8());
					continue;
				}
				__.ReleaseNow();

				RwLock::ExclusiveLockScope ValueLock(LockForHash(Key));
				if (fs::is_regular_file(FilePath))
				{
					ZEN_DEBUG("deleting standalone cache file '{}'", Path.ToUtf8());
					fs::remove(FilePath, Ec);
				}
			}

			if (Ec)
			{
				ZEN_WARN("delete expired z$ standalone file '{}' FAILED, reason: '{}'", Path.ToUtf8(), Ec.message());
				Ec.clear();
				DiskLocation RestoreLocation = Loc;
				RestoreLocation.Flags &= ~DiskLocation::kTombStone;

				RwLock::ExclusiveLockScope __(m_IndexLock);
				Stopwatch				   Timer;
				const auto				   ___ = MakeGuard([&] {
					uint64_t ElapsedUs = Timer.GetElapsedTimeUs();
					ReadBlockTimeUs += ElapsedUs;
					ReadBlockLongestTimeUs = std::max(ElapsedUs, ReadBlockLongestTimeUs);
				});
				if (m_Index.contains(Key))
				{
					continue;
				}
				m_SlogFile.Append(DiskIndexEntry{.Key = Key, .Location = RestoreLocation});
				m_Index.insert({Key, {Loc, GcClock::TickCount()}});
				m_TotalSize.fetch_add(Entry.Location.Size(), std::memory_order::relaxed);
				continue;
			}
			m_TotalSize.fetch_sub(Entry.Location.Size(), std::memory_order::relaxed);
			DeletedSize += Entry.Location.Size();
			DeletedCount++;
		}
	}

	TotalChunkCount = Index.size();

	std::vector<IoHash> TotalChunkHashes;
	TotalChunkHashes.reserve(TotalChunkCount);
	for (const auto& Entry : Index)
	{
		const DiskLocation& Location = Entry.second.Location;

		if (Location.Flags & DiskLocation::kStandaloneFile)
		{
			continue;
		}
		TotalChunkHashes.push_back(Entry.first);
	}

	if (TotalChunkHashes.empty())
	{
		return;
	}
	TotalChunkCount = TotalChunkHashes.size();

	std::vector<BlockStoreLocation> ChunkLocations;
	BlockStore::ChunkIndexArray		KeepChunkIndexes;
	std::vector<IoHash>				ChunkIndexToChunkHash;
	ChunkLocations.reserve(TotalChunkCount);
	ChunkLocations.reserve(TotalChunkCount);
	ChunkIndexToChunkHash.reserve(TotalChunkCount);

	GcCtx.FilterCas(TotalChunkHashes, [&](const IoHash& ChunkHash, bool Keep) {
		auto				KeyIt		 = Index.find(ChunkHash);
		const DiskLocation& DiskLocation = KeyIt->second.Location;
		BlockStoreLocation	Location	 = DiskLocation.GetBlockLocation(m_PayloadAlignment);
		size_t				ChunkIndex	 = ChunkLocations.size();
		ChunkLocations.push_back(Location);
		ChunkIndexToChunkHash[ChunkIndex] = ChunkHash;
		if (Keep)
		{
			KeepChunkIndexes.push_back(ChunkIndex);
		}
	});

	size_t DeleteCount = TotalChunkCount - KeepChunkIndexes.size();

	const bool PerformDelete = GcCtx.IsDeletionMode() && GcCtx.CollectSmallObjects();
	if (!PerformDelete)
	{
		m_BlockStore.ReclaimSpace(BlockStoreState, ChunkLocations, KeepChunkIndexes, m_PayloadAlignment, true);
		uint64_t TotalSize = m_TotalSize.load(std::memory_order_relaxed);
		ZEN_INFO("garbage collect from '{}' DISABLED, found #{} {} chunks of total #{} {}",
				 m_BucketDir / m_BucketName,
				 DeleteCount,
				 0,	 // NiceBytes(TotalSize - NewTotalSize),
				 TotalChunkCount,
				 NiceBytes(TotalSize));
		return;
	}

	std::vector<IoHash> DeletedChunks;
	m_BlockStore.ReclaimSpace(
		BlockStoreState,
		ChunkLocations,
		KeepChunkIndexes,
		m_PayloadAlignment,
		false,
		[&](const BlockStore::MovedChunksArray& MovedChunks, const BlockStore::ChunkIndexArray& RemovedChunks) {
			std::vector<DiskIndexEntry> LogEntries;
			LogEntries.reserve(MovedChunks.size() + RemovedChunks.size());
			for (const auto& Entry : MovedChunks)
			{
				size_t					  ChunkIndex	  = Entry.first;
				const BlockStoreLocation& NewLocation	  = Entry.second;
				const IoHash&			  ChunkHash		  = ChunkIndexToChunkHash[ChunkIndex];
				const DiskLocation&		  OldDiskLocation = Index[ChunkHash].Location;
				LogEntries.push_back(
					{.Key = ChunkHash, .Location = DiskLocation(NewLocation, m_PayloadAlignment, OldDiskLocation.GetFlags())});
			}
			for (const size_t ChunkIndex : RemovedChunks)
			{
				const IoHash&		ChunkHash		= ChunkIndexToChunkHash[ChunkIndex];
				const DiskLocation& OldDiskLocation = Index[ChunkHash].Location;
				LogEntries.push_back({.Key		= ChunkHash,
									  .Location = DiskLocation(OldDiskLocation.GetBlockLocation(m_PayloadAlignment),
															   m_PayloadAlignment,
															   OldDiskLocation.GetFlags() | DiskLocation::kTombStone)});
				DeletedChunks.push_back(ChunkHash);
			}

			m_SlogFile.Append(LogEntries);
			m_SlogFile.Flush();
			{
				RwLock::ExclusiveLockScope __(m_IndexLock);
				Stopwatch				   Timer;
				const auto				   ____ = MakeGuard([&] {
					uint64_t ElapsedUs = Timer.GetElapsedTimeUs();
					ReadBlockTimeUs += ElapsedUs;
					ReadBlockLongestTimeUs = std::max(ElapsedUs, ReadBlockLongestTimeUs);
				});
				for (const DiskIndexEntry& Entry : LogEntries)
				{
					if (Entry.Location.GetFlags() & DiskLocation::kTombStone)
					{
						m_Index.erase(Entry.Key);
						uint64_t ChunkSize = Entry.Location.GetBlockLocation(m_PayloadAlignment).Size;
						m_TotalSize.fetch_sub(ChunkSize);
						continue;
					}
					m_Index[Entry.Key].Location = Entry.Location;
				}
			}
		},
		[&]() { return GcCtx.CollectSmallObjects(); });

	GcCtx.DeletedCas(DeletedChunks);
}

void
ZenCacheDiskLayer::CacheBucket::UpdateAccessTimes(const std::vector<zen::access_tracking::KeyAccessTime>& AccessTimes)
{
	using namespace access_tracking;

	for (const KeyAccessTime& KeyTime : AccessTimes)
	{
		if (auto It = m_Index.find(KeyTime.Key); It != m_Index.end())
		{
			IndexEntry& Entry = It.value();
			Entry.LastAccess.store(KeyTime.LastAccess, std::memory_order_relaxed);
		}
	}
}

void
ZenCacheDiskLayer::CollectGarbage(GcContext& GcCtx)
{
	RwLock::SharedLockScope _(m_Lock);

	for (auto& Kv : m_Buckets)
	{
		Kv.second.CollectGarbage(GcCtx);
	}
}

void
ZenCacheDiskLayer::UpdateAccessTimes(const zen::access_tracking::AccessTimes& AccessTimes)
{
	RwLock::SharedLockScope _(m_Lock);

	for (const auto& Kv : AccessTimes.Buckets)
	{
		if (auto It = m_Buckets.find(Kv.first); It != m_Buckets.end())
		{
			CacheBucket& Bucket = It->second;
			Bucket.UpdateAccessTimes(Kv.second);
		}
	}
}

void
ZenCacheDiskLayer::CacheBucket::PutStandaloneCacheValue(const IoHash& HashKey, const ZenCacheValue& Value)
{
	uint64_t NewFileSize = Value.Value.Size();

	TemporaryFile DataFile;

	std::error_code Ec;
	DataFile.CreateTemporary(m_BucketDir.c_str(), Ec);
	if (Ec)
	{
		throw std::system_error(Ec, fmt::format("Failed to open temporary file for put in '{}'", m_BucketDir));
	}

	bool CleanUpTempFile = false;
	auto __				 = MakeGuard([&] {
		 if (CleanUpTempFile)
		 {
			 std::error_code Ec;
			 std::filesystem::remove(DataFile.GetPath(), Ec);
			 if (Ec)
			 {
				 ZEN_WARN("Failed to clean up temporary file '{}' for put in '{}', reason '{}'",
						  DataFile.GetPath(),
						  m_BucketDir,
						  Ec.message());
			 }
		 }
	 });

	DataFile.WriteAll(Value.Value, Ec);
	if (Ec)
	{
		throw std::system_error(Ec,
								fmt::format("Failed to write payload ({} bytes) to temporary file '{}' for put in '{}'",
											NiceBytes(NewFileSize),
											DataFile.GetPath().string(),
											m_BucketDir));
	}

	ExtendablePathBuilder<256> DataFilePath;
	BuildPath(DataFilePath, HashKey);
	std::filesystem::path FsPath{DataFilePath.ToPath()};

	// We retry to move the file since it can be held open for read.
	// This happens if the server processes a Get request for the file or
	// if we are busy sending the file upstream
	int RetryCount = 3;
	do
	{
		Ec.clear();
		{
			RwLock::ExclusiveLockScope ValueLock(LockForHash(HashKey));

			DataFile.MoveTemporaryIntoPlace(FsPath, Ec);

			// Once we have called MoveTemporaryIntoPlace automatic clean up the temp file
			// will be disabled as the file handle has already been closed
			CleanUpTempFile = Ec ? true : false;

			if (Ec)
			{
				std::error_code ExistingEc;
				uint64_t		OldFileSize = std::filesystem::file_size(FsPath, ExistingEc);
				if (!ExistingEc && (OldFileSize == NewFileSize))
				{
					ZEN_INFO(
						"Failed to move temporary file '{}' to '{}'. Target file has same size, assuming concurrent write of same value, "
						"move "
						"failed with reason '{}'",
						DataFile.GetPath(),
						FsPath.string(),
						m_BucketDir,
						Ec.message());
					return;
				}
			}
		}

		if (!Ec)
		{
			uint8_t EntryFlags = DiskLocation::kStandaloneFile;

			if (Value.Value.GetContentType() == ZenContentType::kCbObject)
			{
				EntryFlags |= DiskLocation::kStructured;
			}
			else if (Value.Value.GetContentType() == ZenContentType::kCompressedBinary)
			{
				EntryFlags |= DiskLocation::kCompressed;
			}

			DiskLocation Loc(NewFileSize, EntryFlags);
			IndexEntry	 Entry = IndexEntry(Loc, GcClock::TickCount());

			uint64_t				   OldFileSize = 0;
			RwLock::ExclusiveLockScope _(m_IndexLock);
			if (auto It = m_Index.find(HashKey); It == m_Index.end())
			{
				// Previously unknown object
				m_Index.insert({HashKey, Entry});
			}
			else
			{
				// TODO: should check if write is idempotent and bail out if it is?
				OldFileSize = It.value().Location.Size();
				It.value()	= Entry;
			}

			m_SlogFile.Append({.Key = HashKey, .Location = Loc});
			if (OldFileSize <= NewFileSize)
			{
				m_TotalSize.fetch_add(NewFileSize - OldFileSize, std::memory_order::relaxed);
			}
			else
			{
				m_TotalSize.fetch_sub(OldFileSize - NewFileSize, std::memory_order::relaxed);
			}
			return;
		}

		std::filesystem::path ParentPath = FsPath.parent_path();
		if (!std::filesystem::is_directory(ParentPath))
		{
			Ec.clear();
			std::filesystem::create_directories(ParentPath, Ec);
			if (!Ec)
			{
				// Retry without sleep
				continue;
			}
			throw std::system_error(
				Ec,
				fmt::format("Failed to create parent directory '{}' for file '{}' for put in '{}'", ParentPath, FsPath, m_BucketDir));
		}

		ZEN_INFO("Failed renaming temporary file '{}' to '{}' for put in '{}', pausing and retrying, reason '{}'",
				 DataFile.GetPath().string(),
				 FsPath.string(),
				 m_BucketDir,
				 Ec.message());

		// Semi arbitrary back-off
		zen::Sleep(200 * (4 - RetryCount));	 // Sleep at most for a total of 2 seconds
		RetryCount--;
	} while (RetryCount > 0);

	throw std::system_error(Ec, fmt::format("Failed to finalize file '{}' for put in '{}'", DataFilePath.ToUtf8(), m_BucketDir));
}

void
ZenCacheDiskLayer::CacheBucket::PutInlineCacheValue(const IoHash& HashKey, const ZenCacheValue& Value)
{
	uint8_t EntryFlags = 0;

	if (Value.Value.GetContentType() == ZenContentType::kCbObject)
	{
		EntryFlags |= DiskLocation::kStructured;
	}
	else if (Value.Value.GetContentType() == ZenContentType::kCompressedBinary)
	{
		EntryFlags |= DiskLocation::kCompressed;
	}

	m_BlockStore.WriteChunk(Value.Value.Data(), Value.Value.Size(), m_PayloadAlignment, [&](const BlockStoreLocation& BlockStoreLocation) {
		DiskLocation		 Location(BlockStoreLocation, m_PayloadAlignment, EntryFlags);
		const DiskIndexEntry DiskIndexEntry{.Key = HashKey, .Location = Location};
		m_SlogFile.Append(DiskIndexEntry);
		RwLock::ExclusiveLockScope _(m_IndexLock);
		if (auto It = m_Index.find(HashKey); It != m_Index.end())
		{
			// TODO: should check if write is idempotent and bail out if it is?
			// this would requiring comparing contents on disk unless we add a
			// content hash to the index entry
			IndexEntry& Entry = It.value();
			Entry.Location	  = Location;
			Entry.LastAccess.store(GcClock::TickCount(), std::memory_order_relaxed);
		}
		else
		{
			m_Index.insert({HashKey, {Location, GcClock::TickCount()}});
		}
	});
	m_TotalSize.fetch_add(Value.Value.Size(), std::memory_order::relaxed);
}

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

ZenCacheDiskLayer::ZenCacheDiskLayer(const std::filesystem::path& RootDir) : m_RootDir(RootDir)
{
}

ZenCacheDiskLayer::~ZenCacheDiskLayer() = default;

bool
ZenCacheDiskLayer::Get(std::string_view InBucket, const IoHash& HashKey, ZenCacheValue& OutValue)
{
	const auto	 BucketName = std::string(InBucket);
	CacheBucket* Bucket		= nullptr;

	{
		RwLock::SharedLockScope _(m_Lock);

		auto it = m_Buckets.find(BucketName);

		if (it != m_Buckets.end())
		{
			Bucket = &it->second;
		}
	}

	if (Bucket == nullptr)
	{
		// Bucket needs to be opened/created

		RwLock::ExclusiveLockScope _(m_Lock);

		if (auto it = m_Buckets.find(BucketName); it != m_Buckets.end())
		{
			Bucket = &it->second;
		}
		else
		{
			auto It = m_Buckets.try_emplace(BucketName, BucketName);
			Bucket	= &It.first->second;

			std::filesystem::path BucketPath = m_RootDir;
			BucketPath /= BucketName;

			Bucket->OpenOrCreate(BucketPath);
		}
	}

	ZEN_ASSERT(Bucket != nullptr);

	return Bucket->Get(HashKey, OutValue);
}

void
ZenCacheDiskLayer::Put(std::string_view InBucket, const IoHash& HashKey, const ZenCacheValue& Value)
{
	const auto	 BucketName = std::string(InBucket);
	CacheBucket* Bucket		= nullptr;

	{
		RwLock::SharedLockScope _(m_Lock);

		auto it = m_Buckets.find(BucketName);

		if (it != m_Buckets.end())
		{
			Bucket = &it->second;
		}
	}

	if (Bucket == nullptr)
	{
		// New bucket needs to be created

		RwLock::ExclusiveLockScope _(m_Lock);

		if (auto it = m_Buckets.find(BucketName); it != m_Buckets.end())
		{
			Bucket = &it->second;
		}
		else
		{
			auto It = m_Buckets.try_emplace(BucketName, BucketName);
			Bucket	= &It.first->second;

			std::filesystem::path BucketPath = m_RootDir;
			BucketPath /= BucketName;

			Bucket->OpenOrCreate(BucketPath);
		}
	}

	ZEN_ASSERT(Bucket != nullptr);

	if (Bucket->IsOk())
	{
		Bucket->Put(HashKey, Value);
	}
}

void
ZenCacheDiskLayer::DiscoverBuckets()
{
	DirectoryContent DirContent;
	GetDirectoryContent(m_RootDir, DirectoryContent::IncludeDirsFlag, DirContent);

	// Initialize buckets

	RwLock::ExclusiveLockScope _(m_Lock);

	for (const std::filesystem::path& BucketPath : DirContent.Directories)
	{
		std::string BucketName = PathToUtf8(BucketPath.stem());
		// New bucket needs to be created
		if (auto It = m_Buckets.find(BucketName); It != m_Buckets.end())
		{
		}
		else
		{
			auto InsertResult = m_Buckets.try_emplace(BucketName, BucketName);

			CacheBucket& Bucket = InsertResult.first->second;

			Bucket.OpenOrCreate(BucketPath, /* AllowCreate */ false);

			if (Bucket.IsOk())
			{
				ZEN_INFO("Discovered bucket '{}'", BucketName);
			}
			else
			{
				ZEN_WARN("Found directory '{}' in our base directory '{}' but it is not a valid bucket", BucketName, m_RootDir);

				m_Buckets.erase(InsertResult.first);
			}
		}
	}
}

bool
ZenCacheDiskLayer::DropBucket(std::string_view InBucket)
{
	RwLock::ExclusiveLockScope _(m_Lock);

	auto it = m_Buckets.find(std::string(InBucket));

	if (it != m_Buckets.end())
	{
		CacheBucket* Bucket = &it->second;

		Bucket->Drop();

		m_Buckets.erase(it);

		return true;
	}

	std::filesystem::path BucketPath = m_RootDir;
	BucketPath /= std::string(InBucket);

	return CacheBucket::Delete(BucketPath);
}

void
ZenCacheDiskLayer::Flush()
{
	std::vector<CacheBucket*> Buckets;

	{
		RwLock::SharedLockScope _(m_Lock);
		Buckets.reserve(m_Buckets.size());
		for (auto& Kv : m_Buckets)
		{
			Buckets.push_back(&Kv.second);
		}
	}

	for (auto& Bucket : Buckets)
	{
		Bucket->Flush();
	}
}

void
ZenCacheDiskLayer::Scrub(ScrubContext& Ctx)
{
	RwLock::SharedLockScope _(m_Lock);

	for (auto& Kv : m_Buckets)
	{
		Kv.second.Scrub(Ctx);
	}
}

void
ZenCacheDiskLayer::GatherReferences(GcContext& GcCtx)
{
	RwLock::SharedLockScope _(m_Lock);

	for (auto& Kv : m_Buckets)
	{
		Kv.second.GatherReferences(GcCtx);
	}
}

uint64_t
ZenCacheDiskLayer::TotalSize() const
{
	uint64_t				TotalSize{};
	RwLock::SharedLockScope _(m_Lock);

	for (auto& Kv : m_Buckets)
	{
		TotalSize += Kv.second.TotalSize();
	}

	return TotalSize;
}

//////////////////////////// ZenCacheStore

static constexpr std::string_view ZenCacheNamespaceDirPrefix = "ns_";

ZenCacheStore::ZenCacheStore(CasGc& Gc, std::filesystem::path BasePath) : GcStorage(Gc), GcContributor(Gc)
{
	CreateDirectories(BasePath);

	DirectoryContent DirContent;
	GetDirectoryContent(BasePath, DirectoryContent::IncludeDirsFlag, DirContent);

	std::vector<std::string> LegacyBuckets;
	std::vector<std::string> Namespaces;
	for (const std::filesystem::path& DirPath : DirContent.Directories)
	{
		std::string DirName = PathToUtf8(DirPath.stem());
		if (DirName.starts_with(ZenCacheNamespaceDirPrefix))
		{
			Namespaces.push_back(DirName.substr(3));
			continue;
		}
		LegacyBuckets.push_back(DirName);
	}

	ZEN_INFO("Found #{} namespaces in '{}' and #{} legacy buckets", Namespaces.size(), BasePath, LegacyBuckets.size());

	if (std::find(Namespaces.begin(), Namespaces.end(), DefaultNamespace) == Namespaces.end())
	{
		ZEN_INFO("Moving #{} legacy buckets to anonymous namespace", LegacyBuckets.size());
		std::filesystem::path DefaultNamespaceFolder = BasePath / fmt::format("{}{}", ZenCacheNamespaceDirPrefix, DefaultNamespace);
		CreateDirectories(DefaultNamespaceFolder);

		// Move any non-namespace folders into the default namespace folder
		for (const std::string& DirName : LegacyBuckets)
		{
			std::filesystem::path LegacyFolder = BasePath / DirName;
			std::filesystem::path NewPath	   = DefaultNamespaceFolder / DirName;
			std::error_code		  Ec;
			std::filesystem::rename(LegacyFolder, NewPath, Ec);
			if (Ec)
			{
				ZEN_ERROR("Unable to move '{}' to '{}', reason '{}'", LegacyFolder, NewPath, Ec.message());
			}
		}
		Namespaces.push_back(std::string(DefaultNamespace));
	}

	for (const std::string& NamespaceName : Namespaces)
	{
		m_Namespaces[NamespaceName] =
			std::make_unique<ZenCacheNamespace>(Gc, BasePath / fmt::format("{}{}", ZenCacheNamespaceDirPrefix, NamespaceName));
	}
}

ZenCacheStore::~ZenCacheStore()
{
	m_Namespaces.clear();
}

bool
ZenCacheStore::Get(std::string_view Namespace, std::string_view Bucket, const IoHash& HashKey, ZenCacheValue& OutValue)
{
	if (ZenCacheNamespace* Store = GetNamespace(Namespace); Store)
	{
		return Store->Get(Bucket, HashKey, OutValue);
	}
	ZEN_WARN("request for unknown namespace '{}' in ZenCacheStore::Get, bucket '{}', key '{}'", Namespace, Bucket, HashKey.ToHexString());
	return false;
}

void
ZenCacheStore::Put(std::string_view Namespace, std::string_view Bucket, const IoHash& HashKey, const ZenCacheValue& Value)
{
	if (ZenCacheNamespace* Store = GetNamespace(Namespace); Store)
	{
		return Store->Put(Bucket, HashKey, Value);
	}
	ZEN_WARN("request for unknown namespace '{}' in ZenCacheStore::Put, bucket '{}', key '{}'", Namespace, Bucket, HashKey.ToHexString());
}

bool
ZenCacheStore::DropBucket(std::string_view Namespace, std::string_view Bucket)
{
	if (ZenCacheNamespace* Store = GetNamespace(Namespace); Store)
	{
		return Store->DropBucket(Bucket);
	}
	ZEN_WARN("request for unknown namespace '{}' in ZenCacheStore::Put, bucket '{}'", Namespace, Bucket);
	return false;
}

void
ZenCacheStore::Flush()
{
	IterateNamespaces([&](std::string_view, ZenCacheNamespace& Store) { Store.Flush(); });
}

void
ZenCacheStore::Scrub(ScrubContext& Ctx)
{
	IterateNamespaces([&](std::string_view, ZenCacheNamespace& Store) { Store.Scrub(Ctx); });
}

ZenCacheNamespace*
ZenCacheStore::GetNamespace(std::string_view Namespace)
{
	RwLock::SharedLockScope _(m_NamespacesLock);
	if (auto It = m_Namespaces.find(std::string(Namespace)); It != m_Namespaces.end())
	{
		return It->second.get();
	}
	return nullptr;
}

void
ZenCacheStore::IterateNamespaces(const std::function<void(std::string_view Namespace, ZenCacheNamespace& Store)>& Callback) const
{
	std::vector<std::pair<std::string, ZenCacheNamespace&> > Namespaces;
	{
		RwLock::SharedLockScope _(m_NamespacesLock);
		Namespaces.reserve(m_Namespaces.size());
		for (const auto& Entry : m_Namespaces)
		{
			Namespaces.push_back({Entry.first, *Entry.second});
		}
	}
	for (auto& Entry : Namespaces)
	{
		Callback(Entry.first, Entry.second);
	}
}

void
ZenCacheStore::GatherReferences(GcContext& GcCtx)
{
	IterateNamespaces([&](std::string_view, ZenCacheNamespace& Store) { Store.GatherReferences(GcCtx); });
}

void
ZenCacheStore::CollectGarbage(GcContext& GcCtx)
{
	IterateNamespaces([&](std::string_view, ZenCacheNamespace& Store) { Store.CollectGarbage(GcCtx); });
}

GcStorageSize
ZenCacheStore::StorageSize() const
{
	GcStorageSize Size;
	IterateNamespaces([&](std::string_view, ZenCacheNamespace& Store) {
		GcStorageSize StoreSize = Store.StorageSize();
		Size.MemorySize += StoreSize.MemorySize;
		Size.DiskSize += StoreSize.DiskSize;
	});
	return Size;
}

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

#if ZEN_WITH_TESTS
}

namespace zen {

using namespace std::literals;

namespace testutils {
	IoHash CreateKey(size_t KeyValue) { return IoHash::HashBuffer(&KeyValue, sizeof(size_t)); }

	IoBuffer CreateBinaryCacheValue(uint64_t Size)
	{
		static std::random_device rd;
		static std::mt19937		  g(rd());

		std::vector<uint8_t> Values;
		Values.resize(Size);
		for (size_t Idx = 0; Idx < Size; ++Idx)
		{
			Values[Idx] = static_cast<uint8_t>(Idx);
		}
		std::shuffle(Values.begin(), Values.end(), g);

		IoBuffer Buf(IoBuffer::Clone, Values.data(), Values.size());
		Buf.SetContentType(ZenContentType::kBinary);
		return Buf;
	};

}  // namespace testutils

TEST_CASE("z$.store")
{
	ScopedTemporaryDirectory TempDir;

	CasGc Gc;

	ZenCacheNamespace Zcs(Gc, TempDir.Path() / "cache");

	const int kIterationCount = 100;

	for (int i = 0; i < kIterationCount; ++i)
	{
		const IoHash Key = IoHash::HashBuffer(&i, sizeof i);

		CbObjectWriter Cbo;
		Cbo << "hey" << i;
		CbObject Obj = Cbo.Save();

		ZenCacheValue Value;
		Value.Value = Obj.GetBuffer().AsIoBuffer();
		Value.Value.SetContentType(ZenContentType::kCbObject);

		Zcs.Put("test_bucket"sv, Key, Value);
	}

	for (int i = 0; i < kIterationCount; ++i)
	{
		const IoHash Key = IoHash::HashBuffer(&i, sizeof i);

		ZenCacheValue Value;
		Zcs.Get("test_bucket"sv, Key, /* out */ Value);

		REQUIRE(Value.Value);
		CHECK(Value.Value.GetContentType() == ZenContentType::kCbObject);
		CHECK_EQ(ValidateCompactBinary(Value.Value, CbValidateMode::All), CbValidateError::None);
		CbObject Obj = LoadCompactBinaryObject(Value.Value);
		CHECK_EQ(Obj["hey"].AsInt32(), i);
	}
}

TEST_CASE("z$.size")
{
	const auto CreateCacheValue = [](size_t Size) -> CbObject {
		std::vector<uint8_t> Buf;
		Buf.resize(Size);

		CbObjectWriter Writer;
		Writer.AddBinary("Binary"sv, Buf.data(), Buf.size());
		return Writer.Save();
	};

	SUBCASE("mem/disklayer")
	{
		const size_t			 Count = 16;
		ScopedTemporaryDirectory TempDir;

		GcStorageSize CacheSize;

		{
			CasGc			  Gc;
			ZenCacheNamespace Zcs(Gc, TempDir.Path() / "cache");

			CbObject CacheValue = CreateCacheValue(Zcs.DiskLayerThreshold() - 256);

			IoBuffer Buffer = CacheValue.GetBuffer().AsIoBuffer();
			Buffer.SetContentType(ZenContentType::kCbObject);

			for (size_t Key = 0; Key < Count; ++Key)
			{
				const size_t Bucket = Key % 4;
				Zcs.Put(fmt::format("test_bucket-{}", Bucket), IoHash::HashBuffer(&Key, sizeof(uint32_t)), {.Value = Buffer});
			}

			CacheSize = Zcs.StorageSize();
			CHECK_EQ(CacheValue.GetSize() * Count, CacheSize.DiskSize);
			CHECK_EQ(CacheValue.GetSize() * Count, CacheSize.MemorySize);
		}

		{
			CasGc			  Gc;
			ZenCacheNamespace Zcs(Gc, TempDir.Path() / "cache");

			const GcStorageSize SerializedSize = Zcs.StorageSize();
			CHECK_EQ(SerializedSize.MemorySize, 0);
			CHECK_EQ(SerializedSize.DiskSize, CacheSize.DiskSize);

			for (size_t Bucket = 0; Bucket < 4; ++Bucket)
			{
				Zcs.DropBucket(fmt::format("test_bucket-{}", Bucket));
			}
			CHECK_EQ(0, Zcs.StorageSize().DiskSize);
		}
	}

	SUBCASE("disklayer")
	{
		const size_t			 Count = 16;
		ScopedTemporaryDirectory TempDir;

		GcStorageSize CacheSize;

		{
			CasGc			  Gc;
			ZenCacheNamespace Zcs(Gc, TempDir.Path() / "cache");

			CbObject CacheValue = CreateCacheValue(Zcs.DiskLayerThreshold() + 64);

			IoBuffer Buffer = CacheValue.GetBuffer().AsIoBuffer();
			Buffer.SetContentType(ZenContentType::kCbObject);

			for (size_t Key = 0; Key < Count; ++Key)
			{
				const size_t Bucket = Key % 4;
				Zcs.Put(fmt::format("test_bucket-{}", Bucket), IoHash::HashBuffer(&Key, sizeof(uint32_t)), {.Value = Buffer});
			}

			CacheSize = Zcs.StorageSize();
			CHECK_EQ(CacheValue.GetSize() * Count, CacheSize.DiskSize);
			CHECK_EQ(0, CacheSize.MemorySize);
		}

		{
			CasGc			  Gc;
			ZenCacheNamespace Zcs(Gc, TempDir.Path() / "cache");

			const GcStorageSize SerializedSize = Zcs.StorageSize();
			CHECK_EQ(SerializedSize.MemorySize, 0);
			CHECK_EQ(SerializedSize.DiskSize, CacheSize.DiskSize);

			for (size_t Bucket = 0; Bucket < 4; ++Bucket)
			{
				Zcs.DropBucket(fmt::format("test_bucket-{}", Bucket));
			}
			CHECK_EQ(0, Zcs.StorageSize().DiskSize);
		}
	}
}

TEST_CASE("z$.gc")
{
	using namespace testutils;

	SUBCASE("gather references does NOT add references for expired cache entries")
	{
		ScopedTemporaryDirectory TempDir;
		std::vector<IoHash>		 Cids{CreateKey(1), CreateKey(2), CreateKey(3)};

		const auto CollectAndFilter = [](CasGc&					 Gc,
										 GcClock::TimePoint		 Time,
										 GcClock::Duration		 MaxDuration,
										 std::span<const IoHash> Cids,
										 std::vector<IoHash>&	 OutKeep) {
			GcContext GcCtx(Time);
			GcCtx.MaxCacheDuration(MaxDuration);
			Gc.CollectGarbage(GcCtx);
			OutKeep.clear();
			GcCtx.FilterCids(Cids, [&OutKeep](const IoHash& Hash) { OutKeep.push_back(Hash); });
		};

		{
			CasGc			  Gc;
			ZenCacheNamespace Zcs(Gc, TempDir.Path() / "cache");
			const auto		  Bucket = "teardrinker"sv;

			// Create a cache record
			const IoHash   Key = CreateKey(42);
			CbObjectWriter Record;
			Record << "Key"sv
				   << "SomeRecord"sv;

			for (size_t Idx = 0; auto& Cid : Cids)
			{
				Record.AddBinaryAttachment(fmt::format("attachment-{}", Idx++), Cid);
			}

			IoBuffer Buffer = Record.Save().GetBuffer().AsIoBuffer();
			Buffer.SetContentType(ZenContentType::kCbObject);

			Zcs.Put(Bucket, Key, {.Value = Buffer});

			std::vector<IoHash> Keep;

			// Collect garbage with 1 hour max cache duration
			{
				CollectAndFilter(Gc, GcClock::Now(), std::chrono::hours(1), Cids, Keep);
				CHECK_EQ(Cids.size(), Keep.size());
			}

			// Move forward in time
			{
				CollectAndFilter(Gc, GcClock::Now() + std::chrono::hours(2), std::chrono::hours(1), Cids, Keep);
				CHECK_EQ(0, Keep.size());
			}
		}

		// Expect timestamps to be serialized
		{
			CasGc				Gc;
			ZenCacheNamespace	Zcs(Gc, TempDir.Path() / "cache");
			std::vector<IoHash> Keep;

			// Collect garbage with 1 hour max cache duration
			{
				CollectAndFilter(Gc, GcClock::Now(), std::chrono::hours(1), Cids, Keep);
				CHECK_EQ(3, Keep.size());
			}

			// Move forward in time
			{
				CollectAndFilter(Gc, GcClock::Now() + std::chrono::hours(2), std::chrono::hours(1), Cids, Keep);
				CHECK_EQ(0, Keep.size());
			}
		}
	}

	SUBCASE("gc removes standalone values")
	{
		ScopedTemporaryDirectory TempDir;
		CasGc					 Gc;
		ZenCacheNamespace		 Zcs(Gc, TempDir.Path() / "cache");
		const auto				 Bucket		 = "fortysixandtwo"sv;
		const GcClock::TimePoint CurrentTime = GcClock::Now();

		std::vector<IoHash> Keys{CreateKey(1), CreateKey(2), CreateKey(3)};

		for (const auto& Key : Keys)
		{
			IoBuffer Value = testutils::CreateBinaryCacheValue(128 << 10);
			Zcs.Put(Bucket, Key, {.Value = Value});
		}

		{
			GcContext GcCtx;
			GcCtx.MaxCacheDuration(std::chrono::hours(46));

			Gc.CollectGarbage(GcCtx);

			for (const auto& Key : Keys)
			{
				ZenCacheValue CacheValue;
				const bool	  Exists = Zcs.Get(Bucket, Key, CacheValue);
				CHECK(Exists);
			}
		}

		// Move forward in time and collect again
		{
			GcContext GcCtx(CurrentTime + std::chrono::hours(46));
			GcCtx.MaxCacheDuration(std::chrono::minutes(2));

			Gc.CollectGarbage(GcCtx);

			for (const auto& Key : Keys)
			{
				ZenCacheValue CacheValue;
				const bool	  Exists = Zcs.Get(Bucket, Key, CacheValue);
				CHECK(!Exists);
			}

			CHECK_EQ(0, Zcs.StorageSize().DiskSize);
		}
	}

	SUBCASE("gc removes small objects")
	{
		ScopedTemporaryDirectory TempDir;
		CasGc					 Gc;
		ZenCacheNamespace		 Zcs(Gc, TempDir.Path() / "cache");
		const auto				 Bucket		 = "rightintwo"sv;
		const GcClock::TimePoint CurrentTime = GcClock::Now();

		std::vector<IoHash> Keys{CreateKey(1), CreateKey(2), CreateKey(3)};

		for (const auto& Key : Keys)
		{
			IoBuffer Value = testutils::CreateBinaryCacheValue(128);
			Zcs.Put(Bucket, Key, {.Value = Value});
		}

		{
			GcContext GcCtx;
			GcCtx.MaxCacheDuration(std::chrono::hours(2));
			GcCtx.CollectSmallObjects(true);

			Gc.CollectGarbage(GcCtx);

			for (const auto& Key : Keys)
			{
				ZenCacheValue CacheValue;
				const bool	  Exists = Zcs.Get(Bucket, Key, CacheValue);
				CHECK(Exists);
			}
		}

		// Move forward in time and collect again
		{
			GcContext GcCtx(CurrentTime + std::chrono::hours(2));
			GcCtx.MaxCacheDuration(std::chrono::minutes(2));
			GcCtx.CollectSmallObjects(true);

			Zcs.Flush();
			Gc.CollectGarbage(GcCtx);

			for (const auto& Key : Keys)
			{
				ZenCacheValue CacheValue;
				const bool	  Exists = Zcs.Get(Bucket, Key, CacheValue);
				CHECK(!Exists);
			}

			CHECK_EQ(0, Zcs.StorageSize().DiskSize);
		}
	}
}

TEST_CASE("z$.legacyconversion")
{
	ScopedTemporaryDirectory TempDir;

	uint64_t			  ChunkSizes[]	  = {2041,
							 1123,
							 1223,
							 1239,
							 341,
							 1412,
							 912,
							 774,
							 341,
							 431,
							 554,
							 1098,
							 2048,
							 339 + 64 * 1024,
							 561 + 64 * 1024,
							 16 + 64 * 1024,
							 16 + 64 * 1024,
							 2048,
							 2048};
	size_t				  ChunkCount	  = sizeof(ChunkSizes) / sizeof(uint64_t);
	size_t				  SingleBlockSize = 0;
	std::vector<IoBuffer> Chunks;
	Chunks.reserve(ChunkCount);
	for (uint64_t Size : ChunkSizes)
	{
		Chunks.push_back(testutils::CreateBinaryCacheValue(Size));
		SingleBlockSize += Size;
	}

	std::vector<IoHash> ChunkHashes;
	ChunkHashes.reserve(ChunkCount);
	for (const IoBuffer& Chunk : Chunks)
	{
		ChunkHashes.push_back(IoHash::HashBuffer(Chunk.Data(), Chunk.Size()));
	}

	CreateDirectories(TempDir.Path());

	const std::string Bucket = "rightintwo";
	{
		CasGc					 Gc;
		ZenCacheNamespace		 Zcs(Gc, TempDir.Path());
		const GcClock::TimePoint CurrentTime = GcClock::Now();

		for (size_t i = 0; i < ChunkCount; i++)
		{
			Zcs.Put(Bucket, ChunkHashes[i], {.Value = Chunks[i]});
		}

		std::vector<IoHash> KeepChunks;
		for (size_t i = 0; i < ChunkCount; i += 2)
		{
			KeepChunks.push_back(ChunkHashes[i]);
		}
		GcContext GcCtx(CurrentTime + std::chrono::hours(2));
		GcCtx.MaxCacheDuration(std::chrono::minutes(2));
		GcCtx.CollectSmallObjects(true);
		GcCtx.ContributeCas(KeepChunks);
		Zcs.Flush();
		Gc.CollectGarbage(GcCtx);
	}
	std::filesystem::path BucketDir		= TempDir.Path() / Bucket;
	std::filesystem::path BlocksBaseDir = BucketDir / "blocks";

	std::filesystem::path CasPath		 = BlockStore ::GetBlockPath(BlocksBaseDir, 1);
	std::filesystem::path LegacyDataPath = GetLegacyDataPath(BucketDir);
	std::filesystem::remove(LegacyDataPath);
	std::filesystem::rename(CasPath, LegacyDataPath);

	std::vector<DiskIndexEntry> LogEntries;
	std::filesystem::path		IndexPath = GetIndexPath(BucketDir, Bucket);
	if (std::filesystem::is_regular_file(IndexPath))
	{
		BasicFile ObjectIndexFile;
		ObjectIndexFile.Open(IndexPath, BasicFile::Mode::kRead);
		uint64_t Size = ObjectIndexFile.FileSize();
		if (Size >= sizeof(CacheBucketIndexHeader))
		{
			uint64_t			   ExpectedEntryCount = (Size - sizeof(sizeof(CacheBucketIndexHeader))) / sizeof(DiskIndexEntry);
			CacheBucketIndexHeader Header;
			ObjectIndexFile.Read(&Header, sizeof(Header), 0);
			if (Header.Magic == CacheBucketIndexHeader::ExpectedMagic && Header.Version == CacheBucketIndexHeader::CurrentVersion &&
				Header.PayloadAlignment > 0 && Header.EntryCount == ExpectedEntryCount)
			{
				LogEntries.resize(Header.EntryCount);
				ObjectIndexFile.Read(LogEntries.data(), Header.EntryCount * sizeof(DiskIndexEntry), sizeof(CacheBucketIndexHeader));
			}
		}
		ObjectIndexFile.Close();
		std::filesystem::remove(IndexPath);
	}

	std::filesystem::path LogPath = GetLogPath(BucketDir, Bucket);
	{
		TCasLogFile<DiskIndexEntry> CasLog;
		CasLog.Open(LogPath, CasLogFile::Mode::kRead);
		LogEntries.reserve(CasLog.GetLogCount());
		CasLog.Replay([&](const DiskIndexEntry& Record) { LogEntries.push_back(Record); }, 0);
	}
	TCasLogFile<LegacyDiskIndexEntry> LegacyLog;
	std::filesystem::path			  LegacylogPath = GetLegacyLogPath(BucketDir);
	LegacyLog.Open(LegacylogPath, CasLogFile::Mode::kTruncate);

	for (const DiskIndexEntry& Entry : LogEntries)
	{
		uint64_t Size;
		uint64_t Offset;
		if (Entry.Location.IsFlagSet(DiskLocation::kStandaloneFile))
		{
			Size   = Entry.Location.Location.StandaloneSize;
			Offset = 0;
		}
		else
		{
			BlockStoreLocation Location = Entry.Location.GetBlockLocation(16);
			Size						= Location.Size;
			Offset						= Location.Offset;
		}
		LegacyDiskLocation	 LegacyLocation(Offset, Size, 0, static_cast<uint64_t>(Entry.Location.Flags) << 56);
		LegacyDiskIndexEntry LegacyEntry = {.Key = Entry.Key, .Location = LegacyLocation};
		LegacyLog.Append(LegacyEntry);
	}
	LegacyLog.Close();

	std::filesystem::remove_all(BlocksBaseDir);
	std::filesystem::remove(LogPath);
	std::filesystem::remove(IndexPath);

	{
		CasGc			  Gc;
		ZenCacheNamespace Zcs(Gc, TempDir.Path());

		for (size_t i = 0; i < ChunkCount; i += 2)
		{
			ZenCacheValue Value;
			CHECK(Zcs.Get(Bucket, ChunkHashes[i], Value));
			CHECK(ChunkHashes[i] == IoHash::HashBuffer(Value.Value));
			CHECK(!Zcs.Get(Bucket, ChunkHashes[i + 1], Value));
		}
	}
}

TEST_CASE("z$.threadedinsert")	// * doctest::skip(true))
{
	//	for (uint32_t i = 0; i < 100; ++i)
	{
		ScopedTemporaryDirectory TempDir;

		const uint64_t kChunkSize  = 1048;
		const int32_t  kChunkCount = 8192;

		struct Chunk
		{
			std::string Bucket;
			IoBuffer	Buffer;
		};
		std::unordered_map<IoHash, Chunk, IoHash::Hasher> Chunks;
		Chunks.reserve(kChunkCount);

		const std::string Bucket1 = "rightinone";
		const std::string Bucket2 = "rightintwo";

		for (int32_t Idx = 0; Idx < kChunkCount; ++Idx)
		{
			while (true)
			{
				IoBuffer Chunk = testutils::CreateBinaryCacheValue(kChunkSize);
				IoHash	 Hash  = HashBuffer(Chunk);
				if (Chunks.contains(Hash))
				{
					continue;
				}
				Chunks[Hash] = {.Bucket = Bucket1, .Buffer = Chunk};
				break;
			}
			while (true)
			{
				IoBuffer Chunk = testutils::CreateBinaryCacheValue(kChunkSize);
				IoHash	 Hash  = HashBuffer(Chunk);
				if (Chunks.contains(Hash))
				{
					continue;
				}
				Chunks[Hash] = {.Bucket = Bucket2, .Buffer = Chunk};
				break;
			}
		}

		CreateDirectories(TempDir.Path());

		WorkerThreadPool  ThreadPool(4);
		CasGc			  Gc;
		ZenCacheNamespace Zcs(Gc, TempDir.Path());

		{
			std::atomic<size_t> WorkCompleted = 0;
			for (const auto& Chunk : Chunks)
			{
				ThreadPool.ScheduleWork([&Zcs, &WorkCompleted, &Chunk]() {
					Zcs.Put(Chunk.second.Bucket, Chunk.first, {.Value = Chunk.second.Buffer});
					WorkCompleted.fetch_add(1);
				});
			}
			while (WorkCompleted < Chunks.size())
			{
				Sleep(1);
			}
		}

		const uint64_t TotalSize = Zcs.StorageSize().DiskSize;
		CHECK_EQ(kChunkSize * Chunks.size(), TotalSize);

		{
			std::atomic<size_t> WorkCompleted = 0;
			for (const auto& Chunk : Chunks)
			{
				ThreadPool.ScheduleWork([&Zcs, &WorkCompleted, &Chunk]() {
					std::string	  Bucket	= Chunk.second.Bucket;
					IoHash		  ChunkHash = Chunk.first;
					ZenCacheValue CacheValue;

					CHECK(Zcs.Get(Bucket, ChunkHash, CacheValue));
					IoHash Hash = IoHash::HashBuffer(CacheValue.Value);
					CHECK(ChunkHash == Hash);
					WorkCompleted.fetch_add(1);
				});
			}
			while (WorkCompleted < Chunks.size())
			{
				Sleep(1);
			}
		}
		std::unordered_map<IoHash, std::string, IoHash::Hasher> GcChunkHashes;
		GcChunkHashes.reserve(Chunks.size());
		for (const auto& Chunk : Chunks)
		{
			GcChunkHashes[Chunk.first] = Chunk.second.Bucket;
		}
		{
			std::unordered_map<IoHash, Chunk, IoHash::Hasher> NewChunks;

			for (int32_t Idx = 0; Idx < kChunkCount; ++Idx)
			{
				{
					IoBuffer Chunk	= testutils::CreateBinaryCacheValue(kChunkSize);
					IoHash	 Hash	= HashBuffer(Chunk);
					NewChunks[Hash] = {.Bucket = Bucket1, .Buffer = Chunk};
				}
				{
					IoBuffer Chunk	= testutils::CreateBinaryCacheValue(kChunkSize);
					IoHash	 Hash	= HashBuffer(Chunk);
					NewChunks[Hash] = {.Bucket = Bucket2, .Buffer = Chunk};
				}
			}

			std::atomic<size_t>	 WorkCompleted	 = 0;
			std::atomic_uint32_t AddedChunkCount = 0;
			for (const auto& Chunk : NewChunks)
			{
				ThreadPool.ScheduleWork([&Zcs, &WorkCompleted, Chunk, &AddedChunkCount]() {
					Zcs.Put(Chunk.second.Bucket, Chunk.first, {.Value = Chunk.second.Buffer});
					AddedChunkCount.fetch_add(1);
					WorkCompleted.fetch_add(1);
				});
			}

			for (const auto& Chunk : Chunks)
			{
				ThreadPool.ScheduleWork([&Zcs, &WorkCompleted, Chunk]() {
					ZenCacheValue CacheValue;
					if (Zcs.Get(Chunk.second.Bucket, Chunk.first, CacheValue))
					{
						CHECK(Chunk.first == IoHash::HashBuffer(CacheValue.Value));
					}
					WorkCompleted.fetch_add(1);
				});
			}
			while (AddedChunkCount.load() < NewChunks.size())
			{
				// Need to be careful since we might GC blocks we don't know outside of RwLock::ExclusiveLockScope
				for (const auto& Chunk : NewChunks)
				{
					ZenCacheValue CacheValue;
					if (Zcs.Get(Chunk.second.Bucket, Chunk.first, CacheValue))
					{
						GcChunkHashes[Chunk.first] = Chunk.second.Bucket;
					}
				}
				std::vector<IoHash> KeepHashes;
				KeepHashes.reserve(GcChunkHashes.size());
				for (const auto& Entry : GcChunkHashes)
				{
					KeepHashes.push_back(Entry.first);
				}
				size_t C = 0;
				while (C < KeepHashes.size())
				{
					if (C % 155 == 0)
					{
						if (C < KeepHashes.size() - 1)
						{
							KeepHashes[C] = KeepHashes[KeepHashes.size() - 1];
							KeepHashes.pop_back();
						}
						if (C + 3 < KeepHashes.size() - 1)
						{
							KeepHashes[C + 3] = KeepHashes[KeepHashes.size() - 1];
							KeepHashes.pop_back();
						}
					}
					C++;
				}

				GcContext GcCtx;
				GcCtx.CollectSmallObjects(true);
				GcCtx.ContributeCas(KeepHashes);
				Zcs.CollectGarbage(GcCtx);
				CasChunkSet& Deleted = GcCtx.DeletedCas();
				Deleted.IterateChunks([&GcChunkHashes](const IoHash& ChunkHash) { GcChunkHashes.erase(ChunkHash); });
			}

			while (WorkCompleted < NewChunks.size() + Chunks.size())
			{
				Sleep(1);
			}

			{
				// Need to be careful since we might GC blocks we don't know outside of RwLock::ExclusiveLockScope
				for (const auto& Chunk : NewChunks)
				{
					ZenCacheValue CacheValue;
					if (Zcs.Get(Chunk.second.Bucket, Chunk.first, CacheValue))
					{
						GcChunkHashes[Chunk.first] = Chunk.second.Bucket;
					}
				}
				std::vector<IoHash> KeepHashes;
				KeepHashes.reserve(GcChunkHashes.size());
				for (const auto& Entry : GcChunkHashes)
				{
					KeepHashes.push_back(Entry.first);
				}
				size_t C = 0;
				while (C < KeepHashes.size())
				{
					if (C % 155 == 0)
					{
						if (C < KeepHashes.size() - 1)
						{
							KeepHashes[C] = KeepHashes[KeepHashes.size() - 1];
							KeepHashes.pop_back();
						}
						if (C + 3 < KeepHashes.size() - 1)
						{
							KeepHashes[C + 3] = KeepHashes[KeepHashes.size() - 1];
							KeepHashes.pop_back();
						}
					}
					C++;
				}

				GcContext GcCtx;
				GcCtx.CollectSmallObjects(true);
				GcCtx.ContributeCas(KeepHashes);
				Zcs.CollectGarbage(GcCtx);
				CasChunkSet& Deleted = GcCtx.DeletedCas();
				Deleted.IterateChunks([&GcChunkHashes](const IoHash& ChunkHash) { GcChunkHashes.erase(ChunkHash); });
			}
		}
		{
			std::atomic<size_t> WorkCompleted = 0;
			for (const auto& Chunk : GcChunkHashes)
			{
				ThreadPool.ScheduleWork([&Zcs, &WorkCompleted, Chunk]() {
					ZenCacheValue CacheValue;
					CHECK(Zcs.Get(Chunk.second, Chunk.first, CacheValue));
					CHECK(Chunk.first == IoHash::HashBuffer(CacheValue.Value));
					WorkCompleted.fetch_add(1);
				});
			}
			while (WorkCompleted < GcChunkHashes.size())
			{
				Sleep(1);
			}
		}
	}
}

TEST_CASE("z$.namespaces")
{
	using namespace testutils;

	const auto CreateCacheValue = [](size_t Size) -> CbObject {
		std::vector<uint8_t> Buf;
		Buf.resize(Size);

		CbObjectWriter Writer;
		Writer.AddBinary("Binary"sv, Buf.data(), Buf.size());
		return Writer.Save();
	};

	ScopedTemporaryDirectory TempDir;
	CreateDirectories(TempDir.Path());

	{
		CasGc		  Gc;
		ZenCacheStore Zcs(Gc, TempDir.Path() / "cache");
		const auto	  Bucket		  = "teardrinker"sv;
		const auto	  CustomNamespace = "mynamespace"sv;

		// Create a cache record
		const IoHash Key		= CreateKey(42);
		CbObject	 CacheValue = CreateCacheValue(4096);

		IoBuffer Buffer = CacheValue.GetBuffer().AsIoBuffer();
		Buffer.SetContentType(ZenContentType::kCbObject);

		ZenCacheValue PutValue = {.Value = Buffer};
		Zcs.Put(ZenCacheStore::DefaultNamespace, Bucket, Key, PutValue);

		ZenCacheValue GetValue;
		CHECK(Zcs.Get(ZenCacheStore::DefaultNamespace, Bucket, Key, GetValue));

		CHECK(!Zcs.Get(CustomNamespace, Bucket, Key, GetValue));

		// This should just be dropped for now until we decide how we add namespaces
		Zcs.Put(CustomNamespace, Bucket, Key, PutValue);
		CHECK(!Zcs.Get(CustomNamespace, Bucket, Key, GetValue));

		const IoHash Key2		 = CreateKey(43);
		CbObject	 CacheValue2 = CreateCacheValue(4096);

		IoBuffer Buffer2 = CacheValue2.GetBuffer().AsIoBuffer();
		Buffer2.SetContentType(ZenContentType::kCbObject);
		ZenCacheValue PutValue2 = {.Value = Buffer2};
		Zcs.Put(CustomNamespace, Bucket, Key2, PutValue2);

		CHECK(!Zcs.Get(ZenCacheStore::DefaultNamespace, Bucket, Key2, GetValue));
	}
}

TEST_CASE("z$.blocked.disklayer.put")
{
	ScopedTemporaryDirectory TempDir;

	GcStorageSize CacheSize;

	const auto CreateCacheValue = [](size_t Size) -> CbObject {
		std::vector<uint8_t> Buf;
		Buf.resize(Size);

		CbObjectWriter Writer;
		Writer.AddBinary("Binary"sv, Buf.data(), Buf.size());
		return Writer.Save();
	};

	CasGc			  Gc;
	ZenCacheNamespace Zcs(Gc, TempDir.Path() / "cache");

	CbObject CacheValue = CreateCacheValue(64 * 1024 + 64);

	IoBuffer Buffer = CacheValue.GetBuffer().AsIoBuffer();
	Buffer.SetContentType(ZenContentType::kCbObject);

	size_t Key	   = Buffer.Size();
	IoHash HashKey = IoHash::HashBuffer(&Key, sizeof(uint32_t));
	Zcs.Put("test_bucket", HashKey, {.Value = Buffer});

	ZenCacheValue BufferGet;
	CHECK(Zcs.Get("test_bucket", HashKey, BufferGet));

	// Overwriting with a value of same size should go fine
	Zcs.Put("test_bucket", HashKey, {.Value = Buffer});

	CbObject CacheValue2 = CreateCacheValue(64 * 1024 + 64 + 1);
	IoBuffer Buffer2	 = CacheValue2.GetBuffer().AsIoBuffer();
	Buffer2.SetContentType(ZenContentType::kCbObject);
#	if ZEN_PLATFORM_WINDOWS
	// On Windows platform, overwriting with different size while we have
	// it open for read should throw exception if file is held open
	CHECK_THROWS(Zcs.Put("test_bucket", HashKey, {.Value = Buffer2}));
#	else
	// Other platforms should handle overwrite just fine
	Zcs.Put("test_bucket", HashKey, {.Value = Buffer2});
#	endif

	BufferGet = ZenCacheValue{};

	// Read access has been removed, we should now be able to overwrite it
	Zcs.Put("test_bucket", HashKey, {.Value = Buffer2});
}

#endif

void
z$_forcelink()
{
}

}  // namespace zen