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

#include <zenstore/vfsimpl.h>

#include <zencore/fmtutils.h>
#include <zencore/logging.h>
#include <zenstore/cache/structuredcachestore.h>
#include <zenstore/projectstore.h>
#include <zenvfs/projfs.h>
#include <zenvfs/vfs.h>

#include <memory>
#include <unordered_map>

#if ZEN_WITH_VFS

namespace zen {

using namespace std::literals;

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

VfsOplogDataSource::VfsOplogDataSource(std::string_view ProjectId, std::string_view OplogId, Ref<ProjectStore> InProjectStore)
: m_ProjectId(ProjectId)
, m_OplogId(OplogId)
, m_ProjectStore(std::move(InProjectStore))
{
}

void
VfsOplogDataSource::ReadNamedData(std::string_view Path, void* Buffer, uint64_t ByteOffset, uint64_t ByteCount)
{
	ZEN_UNUSED(Path, Buffer, ByteOffset, ByteCount);
}

void
VfsOplogDataSource::ReadChunkData(const Oid& ChunkId, void* Buffer, uint64_t ByteOffset, uint64_t ByteCount)
{
	IoBuffer ChunkBuffer = m_ProjectStore->GetChunk(m_ProjectId, m_OplogId, ChunkId);
	if (ChunkBuffer)
	{
		ZEN_ASSERT(ChunkBuffer.GetSize() >= ByteOffset);
		ZEN_ASSERT(ChunkBuffer.GetSize() - ByteOffset >= ByteCount);
		MutableMemoryView Target(Buffer, ByteCount);
		Target.CopyFrom(ChunkBuffer.GetView().Mid(ByteOffset, ByteCount));
	}
}

void
VfsOplogDataSource::PopulateDirectory(std::string NodePath, VfsTreeNode& DirNode)
{
	// This should never be called
	ZEN_UNUSED(NodePath, DirNode);
}

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

VfsCacheDataSource::VfsCacheDataSource(std::string_view NamespaceId, std::string_view BucketId, Ref<ZenCacheStore> InCacheStore)
: m_NamespaceId(NamespaceId)
, m_BucketId(BucketId)
, m_CacheStore(std::move(InCacheStore))
{
}

VfsCacheDataSource::~VfsCacheDataSource()
{
}

void
VfsCacheDataSource::ReadNamedData(std::string_view Name, void* Buffer, uint64_t ByteOffset, uint64_t ByteCount)
{
	if (auto DotIndex = Name.find_first_of('.'); DotIndex != std::string_view::npos)
	{
		Name = Name.substr(0, DotIndex);
	}

	IoHash HashKey = IoHash::FromHexString(Name);

	CacheRequestContext CacheContext{};

	ZenCacheValue Value;
	if (m_CacheStore->Get(CacheContext, m_NamespaceId, m_BucketId, HashKey, /* out */ Value))
	{
		// TODO bounds check!
		auto DataPtr = reinterpret_cast<const uint8_t*>(Value.Value.GetData()) + ByteOffset;

		memcpy(Buffer, DataPtr, ByteCount);

		return;
	}
}

void
VfsCacheDataSource::ReadChunkData(const Oid& ChunkId, void* Buffer, uint64_t ByteOffset, uint64_t ByteCount)
{
	ZEN_UNUSED(ChunkId, Buffer, ByteOffset, ByteCount);
}

void
VfsCacheDataSource::PopulateDirectory(std::string NodePath, VfsTreeNode& DirNode)
{
	ZEN_UNUSED(NodePath, DirNode);
}

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

VfsServiceImpl::VfsServiceImpl()
{
}

VfsServiceImpl::~VfsServiceImpl()
{
	Unmount();
}

void
VfsServiceImpl::Mount(std::string_view MountPoint)
{
	ZEN_INFO("VFS mount requested at '{}'", MountPoint);

#	if ZEN_PLATFORM_WINDOWS
	if (!IsProjFsAvailable())
	{
		throw std::runtime_error("Projected File System component not available");
	}
#	endif

	if (!m_MountpointPath.empty())
	{
		throw std::runtime_error("VFS already mounted");
	}

	m_MountpointPath = MountPoint;

	RefreshVfs();
}

void
VfsServiceImpl::Unmount()
{
	if (m_MountpointPath.empty())
	{
		return;
	}

	ZEN_INFO("unmounting VFS from '{}'", m_MountpointPath);

	m_MountpointPath.clear();

	RefreshVfs();
}

void
VfsServiceImpl::AddService(Ref<ProjectStore>&& Ps)
{
	m_ProjectStore = std::move(Ps);

	RefreshVfs();
}

void
VfsServiceImpl::AddService(Ref<ZenCacheStore>&& Z$)
{
	m_ZenCacheStore = std::move(Z$);

	RefreshVfs();
}

void
VfsServiceImpl::RefreshVfs()
{
	if (m_VfsHost && m_MountpointPath.empty())
	{
		m_VfsHost->RequestStop();
		m_VfsThread.join();
		m_VfsHost.reset();
		m_VfsThreadRunning.Reset();
		m_VfsDataSource = nullptr;

		return;
	}

	if (!m_VfsHost && !m_MountpointPath.empty())
	{
		m_VfsThread = std::thread(&VfsServiceImpl::VfsThread, this);
		m_VfsThreadRunning.Wait();

		// At this stage, m_VfsHost should be initialized

		ZEN_ASSERT(m_VfsHost);
	}

	if (m_ProjectStore && m_VfsHost)
	{
		if (!m_VfsDataSource)
		{
			m_VfsDataSource = new VfsServiceDataSource(this);
		}

		m_VfsHost->AddMount("projects"sv, m_VfsDataSource);
	}

	if (m_ZenCacheStore && m_VfsHost)
	{
		if (!m_VfsDataSource)
		{
			m_VfsDataSource = new VfsServiceDataSource(this);
		}

		m_VfsHost->AddMount("ddc_cache"sv, m_VfsDataSource);
	}
}

void
VfsServiceImpl::VfsThread()
{
	SetCurrentThreadName("VFS");

	ZEN_INFO("VFS service thread now RUNNING");

	try
	{
		m_VfsHost = std::make_unique<VfsHost>(m_MountpointPath);
		m_VfsHost->Initialize();

		m_VfsThreadRunning.Set();
		m_VfsHost->Run();
	}
	catch (const std::exception& Ex)
	{
		ZEN_WARN("exception caught in VFS thread: {}", Ex.what());

		m_VfsThreadException = std::current_exception();
	}

	if (m_VfsHost)
	{
		m_VfsHost->Cleanup();
	}

	ZEN_INFO("VFS service thread now EXITING");
}

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

Ref<VfsOplogDataSource>
VfsServiceDataSource::GetOplogDataSource(std::string_view ProjectId, std::string_view OplogId)
{
	ExtendableStringBuilder<256> Key;
	Key << ProjectId << "." << OplogId;
	std::string StdKey{Key};

	RwLock::ExclusiveLockScope _(m_Lock);

	if (auto It = m_OplogSourceMap.find(StdKey); It == m_OplogSourceMap.end())
	{
		Ref<VfsOplogDataSource> NewSource{new VfsOplogDataSource(ProjectId, OplogId, m_VfsImpl->m_ProjectStore)};
		m_OplogSourceMap[StdKey] = NewSource;
		return NewSource;
	}
	else
	{
		return It->second;
	}
}

Ref<VfsCacheDataSource>
VfsServiceDataSource::GetCacheDataSource(std::string_view NamespaceId, std::string_view BucketId)
{
	ExtendableStringBuilder<256> Key;
	Key << NamespaceId << "." << BucketId;
	std::string StdKey{Key};

	RwLock::ExclusiveLockScope _(m_Lock);

	if (auto It = m_CacheSourceMap.find(StdKey); It == m_CacheSourceMap.end())
	{
		Ref<VfsCacheDataSource> NewSource{new VfsCacheDataSource(NamespaceId, BucketId, m_VfsImpl->m_ZenCacheStore)};
		m_CacheSourceMap[StdKey] = NewSource;
		return NewSource;
	}
	else
	{
		return It->second;
	}
}

void
VfsServiceDataSource::ReadNamedData(std::string_view Path, void* Buffer, uint64_t ByteOffset, uint64_t ByteCount)
{
	ZEN_UNUSED(Path, Buffer, ByteOffset, ByteCount);
}

void
VfsServiceDataSource::ReadChunkData(const Oid& ChunkId, void* Buffer, uint64_t ByteOffset, uint64_t ByteCount)
{
	ZEN_UNUSED(ChunkId, Buffer, ByteOffset, ByteCount);
}

void
VfsServiceDataSource::PopulateDirectory(std::string NodePath, VfsTreeNode& DirNode)
{
	if (NodePath == "projects"sv)
	{
		// Project enumeration

		m_VfsImpl->m_ProjectStore->DiscoverProjects();

		m_VfsImpl->m_ProjectStore->IterateProjects(
			[&](ProjectStore::Project& Project) { DirNode.AddVirtualNode(Project.Identifier, m_VfsImpl->m_VfsDataSource); });
	}
	else if (NodePath.starts_with("projects\\"sv))
	{
		std::string_view ProjectId{NodePath};
		ProjectId = ProjectId.substr(9);  // Skip "projects\"

		if (std::string_view::size_type SlashOffset = ProjectId.find_first_of('\\'); SlashOffset == std::string_view::npos)
		{
			Ref<ProjectStore::Project> Project = m_VfsImpl->m_ProjectStore->OpenProject(ProjectId);

			if (!Project)
			{
				// No such project found?

				return;
			}

			// Oplog enumeration

			std::vector<std::string> Oplogs = Project->ScanForOplogs();

			for (auto& Oplog : Oplogs)
			{
				DirNode.AddVirtualNode(Oplog, m_VfsImpl->m_VfsDataSource);
			}
		}
		else
		{
			std::string_view OplogId = ProjectId.substr(SlashOffset + 1);
			ProjectId				 = ProjectId.substr(0, SlashOffset);

			Ref<ProjectStore::Project> Project = m_VfsImpl->m_ProjectStore->OpenProject(ProjectId);

			if (!Project)
			{
				// No such project found?

				return;
			}

			// Oplog contents enumeration

			if (Ref<ProjectStore::Oplog> Oplog = Project->OpenOplog(OplogId, /*AllowCompact*/ false, /*VerifyPathOnDisk*/ true))
			{
				Ref<VfsOplogDataSource> DataSource = GetOplogDataSource(ProjectId, OplogId);

				// Get metadata for all chunks
				std::vector<ProjectStore::Oplog::ChunkInfo> ChunkInfos = Oplog->GetAllChunksInfo(Project->RootDir);

				std::unordered_map<zen::Oid, uint64_t> ChunkSizes;

				for (const auto& Ci : ChunkInfos)
				{
					ChunkSizes[Ci.ChunkId] = Ci.ChunkSize;
				}

				auto EmitFilesForDataArray = [&](zen::CbArrayView DataArray) {
					for (auto DataIter : DataArray)
					{
						if (zen::CbObjectView Data = DataIter.AsObjectView())
						{
							std::filesystem::path FileName(Data["filename"sv].AsU8String());
							zen::Oid			  ChunkId = Data["id"sv].AsObjectId();

							if (auto FindIt = ChunkSizes.find(ChunkId); FindIt != ChunkSizes.end())
							{
								DirNode.AddFileNode(FileName.string(), FindIt->second /* file size */, ChunkId, DataSource);
							}
							else
							{
								ZEN_WARN("no chunk metadata found for chunk {} (file: '{}')", ChunkId, FileName);
							}
						}
					}
				};

				Oplog->IterateOplog(
					[&](CbObjectView Op) {
						EmitFilesForDataArray(Op["packagedata"sv].AsArrayView());
						EmitFilesForDataArray(Op["bulkdata"sv].AsArrayView());
					},
					ProjectStore::Oplog::Paging{});

				DirNode.AddFileNode("stats.json", 42, Oid::Zero);
			}
		}
	}
	else if (NodePath == "ddc_cache"sv)
	{
		// Namespace enumeration

		std::vector<std::string> Namespaces = m_VfsImpl->m_ZenCacheStore->GetNamespaces();

		for (auto& Namespace : Namespaces)
		{
			DirNode.AddVirtualNode(Namespace, m_VfsImpl->m_VfsDataSource);
		}
	}
	else if (NodePath.starts_with("ddc_cache\\"sv))
	{
		std::string_view NamespaceId{NodePath};
		NamespaceId = NamespaceId.substr(10);  // Skip "ddc_cache\"

		auto& Cache = m_VfsImpl->m_ZenCacheStore;

		if (std::string_view::size_type SlashOffset = NamespaceId.find_first_of('\\'); SlashOffset == std::string_view::npos)
		{
			// Bucket enumeration

			if (auto NsInfo = Cache->GetNamespaceInfo(NamespaceId))
			{
				for (auto& BucketName : NsInfo->BucketNames)
				{
					DirNode.AddVirtualNode(BucketName, m_VfsImpl->m_VfsDataSource);
				}
			}
		}
		else
		{
			// Bucket contents enumeration

			std::string_view BucketId = NamespaceId.substr(SlashOffset + 1);
			NamespaceId				  = NamespaceId.substr(0, SlashOffset);

			Ref<VfsCacheDataSource> DataSource = GetCacheDataSource(NamespaceId, BucketId);

			auto Enumerator = [&](const IoHash& Key, const CacheValueDetails::ValueDetails& Details) {
				ExtendableStringBuilder<64> KeyString;
				Key.ToHexString(KeyString);
				KeyString.Append(".udd");
				DirNode.AddFileNode(KeyString, Details.Size, Oid::Zero, DataSource);
			};

			Cache->EnumerateBucketContents(NamespaceId, BucketId, Enumerator);
		}
	}
}

}  // namespace zen
#endif