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

#include "storageserverinstance.h"

#include "hydration.h"

#include <zencore/assertfmt.h>
#include <zencore/filesystem.h>
#include <zencore/fmtutils.h>
#include <zencore/logging.h>

namespace zen {

StorageServerInstance::StorageServerInstance(ZenServerEnvironment& RunEnvironment, const Configuration& Config, std::string_view ModuleId)
: m_Config(Config)
, m_ModuleId(ModuleId)
, m_ServerInstance(RunEnvironment, ZenServerInstance::ServerMode::kStorageServer)
{
	m_BaseDir = RunEnvironment.CreateChildDir(ModuleId);
	m_TempDir = Config.HydrationTempPath / ModuleId;
}

StorageServerInstance::~StorageServerInstance()
{
}

void
StorageServerInstance::SpawnServerProcess()
{
	ZEN_ASSERT_FORMAT(!m_ServerInstance.IsRunning(), "Storage server instance for module '{}' is already running", m_ModuleId);
	m_ServerInstance.ResetDeadProcess();

	m_ServerInstance.SetServerExecutablePath(GetRunningExecutablePath());
	m_ServerInstance.SetDataDir(m_BaseDir);
#if ZEN_PLATFORM_WINDOWS
	m_ServerInstance.SetJobObject(m_JobObject);
#endif

	ExtendableStringBuilder<256> AdditionalOptions;
	AdditionalOptions << "--allow-port-probing=false";
	if (m_Config.HttpThreadCount != 0)
	{
		AdditionalOptions << " --http-threads=" << m_Config.HttpThreadCount;
	}
	if (m_Config.CoreLimit != 0)
	{
		AdditionalOptions << " --corelimit=" << m_Config.CoreLimit;
	}
	if (!m_Config.ConfigPath.empty())
	{
		AdditionalOptions << " --config=\"" << MakeSafeAbsolutePath(m_Config.ConfigPath).string() << "\"";
	}

	m_ServerInstance.SpawnServerAndWaitUntilReady(m_Config.BasePort, AdditionalOptions.ToView());
	ZEN_DEBUG("Storage server instance for module '{}' started, listening on port {}", m_ModuleId, m_Config.BasePort);

	m_ServerInstance.EnableShutdownOnDestroy();
}

void
StorageServerInstance::GetProcessMetrics(ProcessMetrics& OutMetrics) const
{
	OutMetrics.MemoryBytes		  = m_MemoryBytes.load();
	OutMetrics.KernelTimeMs		  = m_KernelTimeMs.load();
	OutMetrics.UserTimeMs		  = m_UserTimeMs.load();
	OutMetrics.WorkingSetSize	  = m_WorkingSetSize.load();
	OutMetrics.PeakWorkingSetSize = m_PeakWorkingSetSize.load();
	OutMetrics.PagefileUsage	  = m_PagefileUsage.load();
	OutMetrics.PeakPagefileUsage  = m_PeakPagefileUsage.load();
}

void
StorageServerInstance::ProvisionLocked()
{
	if (m_ServerInstance.IsRunning())
	{
		ZEN_WARN("Storage server instance for module '{}' is already provisioned", m_ModuleId);
		return;
	}

	ZEN_INFO("Provisioning storage server instance for module '{}', at '{}'", m_ModuleId, m_BaseDir);
	try
	{
		Hydrate();
		SpawnServerProcess();
	}
	catch (const std::exception& Ex)
	{
		ZEN_WARN("Failed spawning server instance for module '{}', at '{}' during provisioning. Reason: {}",
				 m_ModuleId,
				 m_BaseDir,
				 Ex.what());
		throw;
	}
}

void
StorageServerInstance::DeprovisionLocked()
{
	if (m_ServerInstance.IsRunning())
	{
		// m_ServerInstance.Shutdown() never throws.
		m_ServerInstance.Shutdown();
	}

	// Crashed or Hibernated: process already dead; skip Shutdown.
	// Dehydrate preserves instance state for future re-provisioning. Failure means saved state
	// may be stale or absent, but the process is already dead so the slot can still be released.
	// Swallow the exception and proceed with cleanup rather than leaving the module stuck.
	try
	{
		Dehydrate();
	}
	catch (const std::exception& Ex)
	{
		ZEN_WARN("Dehydration of module {} failed during deprovisioning, current state not saved. Reason: {}", m_ModuleId, Ex.what());
	}
}

void
StorageServerInstance::HibernateLocked()
{
	// Signal server to shut down, but keep data around for later wake

	if (!m_ServerInstance.IsRunning())
	{
		return;
	}

	// m_ServerInstance.Shutdown() never throws.
	m_ServerInstance.Shutdown();
}

void
StorageServerInstance::WakeLocked()
{
	// Start server in-place using existing data

	if (m_ServerInstance.IsRunning())
	{
		return;
	}

	try
	{
		SpawnServerProcess();
	}
	catch (const std::exception& Ex)
	{
		ZEN_WARN("Failed spawning server instance for module '{}', at '{}' during waking. Reason: {}", m_ModuleId, m_BaseDir, Ex.what());
		throw;
	}
}

void
StorageServerInstance::Hydrate()
{
	HydrationConfig Config{.ServerStateDir		= m_BaseDir,
						   .TempDir				= m_TempDir,
						   .ModuleId			= m_ModuleId,
						   .TargetSpecification = m_Config.HydrationTargetSpecification};

	std::unique_ptr<HydrationStrategyBase> Hydrator = CreateHydrator(Config);

	Hydrator->Hydrate();
}

void
StorageServerInstance::Dehydrate()
{
	HydrationConfig Config{.ServerStateDir		= m_BaseDir,
						   .TempDir				= m_TempDir,
						   .ModuleId			= m_ModuleId,
						   .TargetSpecification = m_Config.HydrationTargetSpecification};

	std::unique_ptr<HydrationStrategyBase> Hydrator = CreateHydrator(Config);

	Hydrator->Dehydrate();
}

StorageServerInstance::SharedLockedPtr::SharedLockedPtr() : m_Lock(nullptr), m_Instance(nullptr)
{
}

StorageServerInstance::SharedLockedPtr::SharedLockedPtr(RwLock& Lock, StorageServerInstance* Instance, bool Wait)
: m_Lock(nullptr)
, m_Instance(nullptr)
{
	ZEN_ASSERT(Instance != nullptr);
	if (Wait)
	{
		Lock.AcquireShared();
		m_Lock	   = &Lock;
		m_Instance = Instance;
	}
	else
	{
		if (Lock.TryAcquireShared())
		{
			m_Lock	   = &Lock;
			m_Instance = Instance;
		}
	}
}

StorageServerInstance::SharedLockedPtr::SharedLockedPtr(SharedLockedPtr&& Rhs) : m_Lock(Rhs.m_Lock), m_Instance(Rhs.m_Instance)
{
	Rhs.m_Lock	   = nullptr;
	Rhs.m_Instance = nullptr;
}

StorageServerInstance::SharedLockedPtr::~SharedLockedPtr()
{
	if (m_Lock != nullptr)
	{
		m_Lock->ReleaseShared();
		m_Lock = nullptr;
	}
	m_Instance = nullptr;
}

StorageServerInstance::SharedLockedPtr&
StorageServerInstance::SharedLockedPtr::operator=(SharedLockedPtr&& Rhs)
{
	if (m_Lock)
	{
		m_Lock->ReleaseShared();
		m_Lock	   = nullptr;
		m_Instance = nullptr;
	}
	m_Lock		   = Rhs.m_Lock;
	m_Instance	   = Rhs.m_Instance;
	Rhs.m_Lock	   = nullptr;
	Rhs.m_Instance = nullptr;
	return *this;
}

std::string_view
StorageServerInstance::SharedLockedPtr::GetModuleId() const
{
	ZEN_ASSERT(m_Instance != nullptr);
	return m_Instance->m_ModuleId;
}

bool
StorageServerInstance::SharedLockedPtr::IsRunning() const
{
	ZEN_ASSERT(m_Instance != nullptr);
	return m_Instance->m_ServerInstance.IsRunning();
}

void
StorageServerInstance::UpdateMetricsLocked()
{
	if (m_ServerInstance.IsRunning())
	{
		ProcessMetrics Metrics;
		zen::GetProcessMetrics(m_ServerInstance.GetProcessHandle(), Metrics);

		m_MemoryBytes.store(Metrics.MemoryBytes);
		m_KernelTimeMs.store(Metrics.KernelTimeMs);
		m_UserTimeMs.store(Metrics.UserTimeMs);
		m_WorkingSetSize.store(Metrics.WorkingSetSize);
		m_PeakWorkingSetSize.store(Metrics.PeakWorkingSetSize);
		m_PagefileUsage.store(Metrics.PagefileUsage);
		m_PeakPagefileUsage.store(Metrics.PeakPagefileUsage);
	}
	// TODO: Resource metrics...
}

#if ZEN_WITH_TESTS
void
StorageServerInstance::SharedLockedPtr::TerminateForTesting() const
{
	ZEN_ASSERT(m_Instance != nullptr);
	m_Instance->m_ServerInstance.Terminate();
}
#endif

StorageServerInstance::ExclusiveLockedPtr::ExclusiveLockedPtr() : m_Lock(nullptr), m_Instance(nullptr)
{
}

StorageServerInstance::ExclusiveLockedPtr::ExclusiveLockedPtr(RwLock& Lock, StorageServerInstance* Instance, bool Wait)
: m_Lock(nullptr)
, m_Instance(nullptr)
{
	ZEN_ASSERT(Instance != nullptr);
	if (Wait)
	{
		Lock.AcquireExclusive();
		m_Lock	   = &Lock;
		m_Instance = Instance;
	}
	else
	{
		if (Lock.TryAcquireExclusive())
		{
			m_Lock	   = &Lock;
			m_Instance = Instance;
		}
	}
}

StorageServerInstance::ExclusiveLockedPtr::ExclusiveLockedPtr(ExclusiveLockedPtr&& Rhs) : m_Lock(Rhs.m_Lock), m_Instance(Rhs.m_Instance)
{
	Rhs.m_Lock	   = nullptr;
	Rhs.m_Instance = nullptr;
}

StorageServerInstance::ExclusiveLockedPtr::~ExclusiveLockedPtr()
{
	if (m_Lock != nullptr)
	{
		m_Lock->ReleaseExclusive();
		m_Lock = nullptr;
	}
	m_Instance = nullptr;
}

StorageServerInstance::ExclusiveLockedPtr&
StorageServerInstance::ExclusiveLockedPtr::operator=(ExclusiveLockedPtr&& Rhs)
{
	if (m_Lock)
	{
		m_Lock->ReleaseExclusive();
		m_Lock	   = nullptr;
		m_Instance = nullptr;
	}
	m_Lock		   = Rhs.m_Lock;
	m_Instance	   = Rhs.m_Instance;
	Rhs.m_Lock	   = nullptr;
	Rhs.m_Instance = nullptr;
	return *this;
}

std::string_view
StorageServerInstance::ExclusiveLockedPtr::GetModuleId() const
{
	ZEN_ASSERT(m_Instance != nullptr);
	return m_Instance->m_ModuleId;
}

bool
StorageServerInstance::ExclusiveLockedPtr::IsRunning() const
{
	ZEN_ASSERT(m_Instance != nullptr);
	return m_Instance->m_ServerInstance.IsRunning();
}

void
StorageServerInstance::ExclusiveLockedPtr::Provision()
{
	ZEN_ASSERT(m_Instance != nullptr);
	m_Instance->ProvisionLocked();
}

void
StorageServerInstance::ExclusiveLockedPtr::Deprovision()
{
	ZEN_ASSERT(m_Instance != nullptr);
	m_Instance->DeprovisionLocked();
}

void
StorageServerInstance::ExclusiveLockedPtr::Hibernate()
{
	ZEN_ASSERT(m_Instance != nullptr);
	m_Instance->HibernateLocked();
}

void
StorageServerInstance::ExclusiveLockedPtr::Wake()
{
	ZEN_ASSERT(m_Instance != nullptr);
	m_Instance->WakeLocked();
}

}  // namespace zen