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

#include <zenhttp/httpclient.h>
#include <zenhttp/httpserver.h>

#include <zencore/compactbinarybuilder.h>
#include <zencore/compactbinarypackage.h>
#include <zencore/compositebuffer.h>
#include <zencore/except.h>
#include <zencore/filesystem.h>
#include <zencore/iobuffer.h>
#include <zencore/logging.h>
#include <zencore/session.h>
#include <zencore/sharedbuffer.h>
#include <zencore/stream.h>
#include <zencore/testing.h>
#include <zencore/trace.h>
#include <zenhttp/formatters.h>
#include <zenhttp/httpshared.h>

ZEN_THIRD_PARTY_INCLUDES_START
#include <cpr/cpr.h>
ZEN_THIRD_PARTY_INCLUDES_END

static std::atomic<uint32_t> HttpClientRequestIdCounter{0};

namespace zen {

using namespace std::literals;

//////////////////////////////////////////////////////////////////////////
//
// CPR helpers

cpr::Body
AsCprBody(const CbObject& Obj)
{
	return cpr::Body((const char*)Obj.GetBuffer().GetData(), Obj.GetBuffer().GetSize());
}

cpr::Body
AsCprBody(const IoBuffer& Obj)
{
	return cpr::Body((const char*)Obj.GetData(), Obj.GetSize());
}

cpr::Body
AsCprBody(const CompositeBuffer& Buffers)
{
	SharedBuffer Buffer = Buffers.Flatten();

	// This is super inefficient, should be fixed
	std::string String{(const char*)Buffer.GetData(), Buffer.GetSize()};
	return cpr::Body{std::move(String)};
}

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

HttpClient::Response
ResponseWithPayload(cpr::Response& HttpResponse, const HttpResponseCode WorkResponseCode, IoBuffer&& Payload)
{
	// This ends up doing a memcpy, would be good to get rid of it by streaming results
	// into buffer directly
	IoBuffer ResponseBuffer = Payload ? std::move(Payload) : IoBuffer(IoBuffer::Clone, HttpResponse.text.data(), HttpResponse.text.size());

	if (auto It = HttpResponse.header.find("Content-Type"); It != HttpResponse.header.end())
	{
		const HttpContentType ContentType = ParseContentType(It->second);

		ResponseBuffer.SetContentType(ContentType);
	}

	if (!IsHttpSuccessCode(WorkResponseCode) && WorkResponseCode != HttpResponseCode::NotFound)
	{
		ZEN_WARN("HttpClient request failed: {}", HttpResponse);
	}

	return HttpClient::Response{.StatusCode		 = WorkResponseCode,
								.ResponsePayload = std::move(ResponseBuffer),
								.Header			 = HttpClient::KeyValueMap(HttpResponse.header.begin(), HttpResponse.header.end()),
								.UploadedBytes	 = gsl::narrow<int64_t>(HttpResponse.uploaded_bytes),
								.DownloadedBytes = gsl::narrow<int64_t>(HttpResponse.downloaded_bytes),
								.ElapsedSeconds	 = HttpResponse.elapsed};
}

HttpClient::Response
CommonResponse(cpr::Response&& HttpResponse, IoBuffer&& Payload = {})
{
	const HttpResponseCode WorkResponseCode = HttpResponseCode(HttpResponse.status_code);
	if (HttpResponse.error)
	{
		ZEN_WARN("HttpClient client error: {}", HttpResponse);

		// Client side failure code
		return HttpClient::Response{
			.StatusCode		 = WorkResponseCode,
			.ResponsePayload = IoBufferBuilder::MakeCloneFromMemory(HttpResponse.text.data(), HttpResponse.text.size()),
			.Header			 = HttpClient::KeyValueMap(HttpResponse.header.begin(), HttpResponse.header.end()),
			.UploadedBytes	 = gsl::narrow<int64_t>(HttpResponse.uploaded_bytes),
			.DownloadedBytes = gsl::narrow<int64_t>(HttpResponse.downloaded_bytes),
			.ElapsedSeconds	 = HttpResponse.elapsed,
			.Error			 = HttpClient::ErrorContext{.ErrorCode	  = gsl::narrow<int>(HttpResponse.error.code),
														.ErrorMessage = HttpResponse.error.message}};
	}

	if (WorkResponseCode == HttpResponseCode::NoContent || (HttpResponse.text.empty() && !Payload))
	{
		return HttpClient::Response{.StatusCode		 = WorkResponseCode,
									.Header			 = HttpClient::KeyValueMap(HttpResponse.header.begin(), HttpResponse.header.end()),
									.UploadedBytes	 = gsl::narrow<int64_t>(HttpResponse.uploaded_bytes),
									.DownloadedBytes = gsl::narrow<int64_t>(HttpResponse.downloaded_bytes),
									.ElapsedSeconds	 = HttpResponse.elapsed};
	}
	else
	{
		return ResponseWithPayload(HttpResponse, WorkResponseCode, std::move(Payload));
	}
}

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

struct HttpClient::Impl : public RefCounted
{
	Impl(spdlog::logger& Log);
	~Impl();

	// Session allocation

	struct Session
	{
		Session(Impl* InOuter, cpr::Session* InSession) : Outer(InOuter), CprSession(InSession) {}
		~Session() { Outer->ReleaseSession(CprSession); }

		inline cpr::Session* operator->() const { return CprSession; }
		inline cpr::Response Get()
		{
			cpr::Response Result = CprSession->Get();
			ZEN_TRACE("GET {}", Result);
			return Result;
		}
		inline cpr::Response Download(cpr::WriteCallback&& write)
		{
			cpr::Response Result = CprSession->Download(write);
			ZEN_TRACE("GET {}", Result);
			return Result;
		}
		inline cpr::Response Head()
		{
			cpr::Response Result = CprSession->Head();
			ZEN_TRACE("HEAD {}", Result);
			return Result;
		}
		inline cpr::Response Put()
		{
			cpr::Response Result = CprSession->Put();
			ZEN_TRACE("PUT {}", Result);
			return Result;
		}
		inline cpr::Response Post()
		{
			cpr::Response Result = CprSession->Post();
			ZEN_TRACE("POST {}", Result);
			return Result;
		}
		inline cpr::Response Delete()
		{
			cpr::Response Result = CprSession->Delete();
			ZEN_TRACE("DELETE {}", Result);
			return Result;
		}

		spdlog::logger& Logger() { return Outer->Logger(); }

	private:
		Impl*		  Outer;
		cpr::Session* CprSession;

		Session(Session&&) = delete;
		Session& operator=(Session&&) = delete;
	};

	Session AllocSession(const std::string_view	   BaseUrl,
						 const std::string_view	   Url,
						 const HttpClientSettings& ConnectionSettings,
						 const KeyValueMap&		   AdditionalHeader,
						 const KeyValueMap&		   Parameters);

	spdlog::logger& Logger() { return m_Log; }

private:
	spdlog::logger&			   m_Log;
	RwLock					   m_SessionLock;
	std::vector<cpr::Session*> m_Sessions;

	void ReleaseSession(cpr::Session*);
};

HttpClient::Impl::Impl(spdlog::logger& Log) : m_Log(Log)
{
}

HttpClient::Impl::~Impl()
{
	m_SessionLock.WithExclusiveLock([&] {
		for (auto CprSession : m_Sessions)
		{
			delete CprSession;
		}
		m_Sessions.clear();
	});
}

HttpClient::Impl::Session
HttpClient::Impl::AllocSession(const std::string_view	 BaseUrl,
							   const std::string_view	 ResourcePath,
							   const HttpClientSettings& ConnectionSettings,
							   const KeyValueMap&		 AdditionalHeader,
							   const KeyValueMap&		 Parameters)
{
	bool		  IsNew		 = false;
	cpr::Session* CprSession = nullptr;
	m_SessionLock.WithExclusiveLock([&] {
		if (m_Sessions.empty())
		{
			CprSession = new cpr::Session();
			IsNew	   = true;
		}
		else
		{
			CprSession = m_Sessions.back();
			m_Sessions.pop_back();
		}
	});

	if (IsNew)
	{
		CprSession->SetConnectTimeout(ConnectionSettings.ConnectTimeout);
		CprSession->SetTimeout(ConnectionSettings.Timeout);
		if (ConnectionSettings.AssumeHttp2)
		{
			CprSession->SetHttpVersion(cpr::HttpVersion{cpr::HttpVersionCode::VERSION_2_0_PRIOR_KNOWLEDGE});
		}
	}

	if (!AdditionalHeader->empty())
	{
		CprSession->SetHeader(cpr::Header(AdditionalHeader->begin(), AdditionalHeader->end()));
	}
	else
	{
		CprSession->SetHeader({});
	}
	if (!Parameters->empty())
	{
		cpr::Parameters Tmp;
		for (auto It = Parameters->begin(); It != Parameters->end(); It++)
		{
			Tmp.Add({It->first, It->second});
		}
		CprSession->SetParameters(Tmp);
	}
	else
	{
		CprSession->SetParameters({});
	}

	ExtendableStringBuilder<128> UrlBuffer;
	UrlBuffer << BaseUrl << ResourcePath;
	CprSession->SetUrl(UrlBuffer.c_str());

	return Session(this, CprSession);
}

void
HttpClient::Impl::ReleaseSession(cpr::Session* CprSession)
{
	CprSession->SetUrl({});
	CprSession->SetHeader({});
	CprSession->SetBody({});
	m_SessionLock.WithExclusiveLock([&] { m_Sessions.push_back(CprSession); });
}

namespace detail {

	static std::atomic_uint32_t TempFileBaseIndex;

}  // namespace detail

class TempPayloadFile
{
public:
	TempPayloadFile() : m_FileHandle(nullptr), m_WriteOffset(0) {}
	~TempPayloadFile()
	{
		try
		{
			if (m_FileHandle)
			{
#if ZEN_PLATFORM_WINDOWS
				// Mark file for deletion when final handle is closed
				FILE_DISPOSITION_INFO Fdi{.DeleteFile = TRUE};

				SetFileInformationByHandle(m_FileHandle, FileDispositionInfo, &Fdi, sizeof Fdi);
				BOOL Success = CloseHandle(m_FileHandle);
#else
				std::filesystem::path FilePath = zen::PathFromHandle(m_FileHandle);
				unlink(FilePath.c_str());
				int	 Fd		 = int(uintptr_t(m_FileHandle));
				bool Success = (close(Fd) == 0);
#endif
				if (!Success)
				{
					ZEN_WARN("Error reported on file handle close, reason '{}'", GetLastErrorAsString());
				}

				m_FileHandle = nullptr;
			}
		}
		catch (std::exception& Ex)
		{
			ZEN_ERROR("Failed deleting temp file {}. Reason '{}'", m_FileHandle, Ex.what());
		}
	}

	std::error_code Open(const std::filesystem::path& TempFolderPath)
	{
		ZEN_ASSERT(m_FileHandle == nullptr);

		std::uint64_t TmpIndex = ((std::chrono::system_clock::to_time_t(std::chrono::system_clock::now()) & 0xffffffffu) << 32) |
								 detail::TempFileBaseIndex.fetch_add(1);

		std::filesystem::path FileName = TempFolderPath / fmt::to_string(TmpIndex);
#if ZEN_PLATFORM_WINDOWS
		LPCWSTR				  lpFileName			= FileName.c_str();
		const DWORD			  dwDesiredAccess		= (GENERIC_READ | GENERIC_WRITE | DELETE);
		const DWORD			  dwShareMode			= FILE_SHARE_READ | FILE_SHARE_WRITE | FILE_SHARE_DELETE;
		LPSECURITY_ATTRIBUTES lpSecurityAttributes	= nullptr;
		const DWORD			  dwCreationDisposition = CREATE_ALWAYS;
		const DWORD			  dwFlagsAndAttributes	= FILE_ATTRIBUTE_NORMAL;
		const HANDLE		  hTemplateFile			= nullptr;
		const HANDLE		  FileHandle			= CreateFile(lpFileName,
											 dwDesiredAccess,
											 dwShareMode,
											 lpSecurityAttributes,
											 dwCreationDisposition,
											 dwFlagsAndAttributes,
											 hTemplateFile);

		if (FileHandle == INVALID_HANDLE_VALUE)
		{
			return MakeErrorCodeFromLastError();
		}
#else	// ZEN_PLATFORM_WINDOWS
		int OpenFlags = O_RDWR | O_CREAT | O_TRUNC | O_CLOEXEC;
		int Fd = open(FileName.c_str(), OpenFlags, 0666);
		if (Fd < 0)
		{
			return MakeErrorCodeFromLastError();
		}
		fchmod(Fd, 0666);

		void* FileHandle = (void*)(uintptr_t(Fd));
#endif	// ZEN_PLATFORM_WINDOWS
		m_FileHandle = FileHandle;

		return {};
	}

	std::error_code Write(std::string_view DataString)
	{
		ZEN_ASSERT(m_FileHandle != nullptr);
		const uint64_t MaxChunkSize = 2u * 1024 * 1024 * 1024;
		const void*	   Data			= DataString.data();
		std::size_t	   Size			= DataString.size();

		while (Size)
		{
			const uint64_t NumberOfBytesToWrite = Min(Size, MaxChunkSize);
			uint64_t	   NumberOfBytesWritten = 0;
#if ZEN_PLATFORM_WINDOWS
			OVERLAPPED Ovl{};

			Ovl.Offset	   = DWORD(m_WriteOffset & 0xffff'ffffu);
			Ovl.OffsetHigh = DWORD(m_WriteOffset >> 32);

			DWORD dwNumberOfBytesWritten = 0;

			BOOL Success = ::WriteFile(m_FileHandle, Data, DWORD(NumberOfBytesToWrite), &dwNumberOfBytesWritten, &Ovl);
			if (Success)
			{
				NumberOfBytesWritten = static_cast<uint64_t>(dwNumberOfBytesWritten);
			}
#else
			static_assert(sizeof(off_t) >= sizeof(uint64_t), "sizeof(off_t) does not support large files");
			int Fd = int(uintptr_t(m_FileHandle));
			int BytesWritten = pwrite(Fd, Data, NumberOfBytesToWrite, m_WriteOffset);
			bool Success = (BytesWritten > 0);
			if (Success)
			{
				NumberOfBytesWritten = static_cast<uint64_t>(BytesWritten);
			}
#endif

			if (!Success)
			{
				return MakeErrorCodeFromLastError();
			}

			Size -= NumberOfBytesWritten;
			m_WriteOffset += NumberOfBytesWritten;
			Data = reinterpret_cast<const uint8_t*>(Data) + NumberOfBytesWritten;
		}
		return {};
	}

	IoBuffer DetachToIoBuffer()
	{
		ZEN_ASSERT(m_FileHandle != nullptr);
		void*	 FileHandle = m_FileHandle;
		IoBuffer Buffer(IoBuffer::File, FileHandle, 0, m_WriteOffset, /*IsWholeFile*/ true);
		Buffer.SetDeleteOnClose(true);
		m_FileHandle  = 0;
		m_WriteOffset = 0;
		return Buffer;
	}

private:
	void*		  m_FileHandle;
	std::uint64_t m_WriteOffset;
};

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

HttpClient::HttpClient(std::string_view BaseUri, const HttpClientSettings& Connectionsettings)
: m_Log(zen::logging::Get(Connectionsettings.LogCategory))
, m_BaseUri(BaseUri)
, m_ConnectionSettings(Connectionsettings)
, m_Impl(new Impl(m_Log))
{
	StringBuilder<32> SessionId;
	GetSessionId().ToString(SessionId);
	m_SessionId = SessionId;
}

HttpClient::~HttpClient()
{
}

HttpClient::Response
HttpClient::TransactPackage(std::string_view Url, CbPackage Package, const KeyValueMap& AdditionalHeader)
{
	ZEN_TRACE_CPU("HttpClient::TransactPackage");

	Impl::Session Sess = m_Impl->AllocSession(m_BaseUri, Url, m_ConnectionSettings, AdditionalHeader, {});

	// First, list of offered chunks for filtering on the server end

	std::vector<IoHash>			  AttachmentsToSend;
	std::span<const CbAttachment> Attachments = Package.GetAttachments();

	const uint32_t RequestId	   = ++HttpClientRequestIdCounter;
	auto		   RequestIdString = fmt::to_string(RequestId);

	if (Attachments.empty() == false)
	{
		CbObjectWriter Writer;
		Writer.BeginArray("offer");

		for (const CbAttachment& Attachment : Attachments)
		{
			Writer.AddHash(Attachment.GetHash());
		}

		Writer.EndArray();

		BinaryWriter MemWriter;
		Writer.Save(MemWriter);

		Sess->UpdateHeader({{"Content-Type", "application/x-ue-offer"}, {"UE-Session", m_SessionId}, {"UE-Request", RequestIdString}});
		Sess->SetBody(cpr::Body{(const char*)MemWriter.Data(), MemWriter.Size()});

		cpr::Response FilterResponse = Sess.Post();

		if (FilterResponse.status_code == 200)
		{
			IoBuffer ResponseBuffer(IoBuffer::Wrap, FilterResponse.text.data(), FilterResponse.text.size());
			CbObject ResponseObject = LoadCompactBinaryObject(ResponseBuffer);

			for (CbFieldView& Entry : ResponseObject["need"])
			{
				ZEN_ASSERT(Entry.IsHash());
				AttachmentsToSend.push_back(Entry.AsHash());
			}
		}
	}

	// Prepare package for send

	CbPackage SendPackage;
	SendPackage.SetObject(Package.GetObject(), Package.GetObjectHash());

	for (const IoHash& AttachmentCid : AttachmentsToSend)
	{
		const CbAttachment* Attachment = Package.FindAttachment(AttachmentCid);

		if (Attachment)
		{
			SendPackage.AddAttachment(*Attachment);
		}
		else
		{
			// This should be an error -- server asked to have something we can't find
		}
	}

	// Transmit package payload

	CompositeBuffer Message		= FormatPackageMessageBuffer(SendPackage);
	SharedBuffer	FlatMessage = Message.Flatten();

	Sess->UpdateHeader({{"Content-Type", "application/x-ue-cbpkg"}, {"UE-Session", m_SessionId}, {"UE-Request", RequestIdString}});
	Sess->SetBody(cpr::Body{(const char*)FlatMessage.GetData(), FlatMessage.GetSize()});

	cpr::Response FilterResponse = Sess.Post();

	if (!IsHttpSuccessCode(FilterResponse.status_code))
	{
		return {.StatusCode = HttpResponseCode(FilterResponse.status_code)};
	}

	IoBuffer ResponseBuffer(IoBuffer::Clone, FilterResponse.text.data(), FilterResponse.text.size());

	if (auto It = FilterResponse.header.find("Content-Type"); It != FilterResponse.header.end())
	{
		HttpContentType ContentType = ParseContentType(It->second);

		ResponseBuffer.SetContentType(ContentType);
	}

	return {.StatusCode = HttpResponseCode(FilterResponse.status_code), .ResponsePayload = ResponseBuffer};
}

//////////////////////////////////////////////////////////////////////////
//
// Standard HTTP verbs
//

HttpClient::Response
HttpClient::Put(std::string_view Url, const IoBuffer& Payload, const KeyValueMap& AdditionalHeader)
{
	ZEN_TRACE_CPU("HttpClient::Put");

	Impl::Session Sess = m_Impl->AllocSession(m_BaseUri, Url, m_ConnectionSettings, AdditionalHeader, {});
	Sess->SetBody(AsCprBody(Payload));
	Sess->UpdateHeader(cpr::Header{{"Content-Type", std::string(MapContentTypeToString(Payload.GetContentType()))}});

	return CommonResponse(Sess.Put());
}

HttpClient::Response
HttpClient::Get(std::string_view Url, const KeyValueMap& AdditionalHeader, const KeyValueMap& Parameters)
{
	ZEN_TRACE_CPU("HttpClient::Get");
	Impl::Session Sess = m_Impl->AllocSession(m_BaseUri, Url, m_ConnectionSettings, AdditionalHeader, Parameters);

	return CommonResponse(Sess.Get());
}

HttpClient::Response
HttpClient::Head(std::string_view Url, const KeyValueMap& AdditionalHeader)
{
	ZEN_TRACE_CPU("HttpClient::Head");

	Impl::Session Sess = m_Impl->AllocSession(m_BaseUri, Url, m_ConnectionSettings, AdditionalHeader, {});

	return CommonResponse(Sess.Head());
}

HttpClient::Response
HttpClient::Delete(std::string_view Url, const KeyValueMap& AdditionalHeader)
{
	ZEN_TRACE_CPU("HttpClient::Delete");

	Impl::Session Sess = m_Impl->AllocSession(m_BaseUri, Url, m_ConnectionSettings, AdditionalHeader, {});

	return CommonResponse(Sess.Delete());
}

HttpClient::Response
HttpClient::Post(std::string_view Url, const KeyValueMap& AdditionalHeader, const KeyValueMap& Parameters)
{
	ZEN_TRACE_CPU("HttpClient::PostNoPayload");

	Impl::Session Sess = m_Impl->AllocSession(m_BaseUri, Url, m_ConnectionSettings, AdditionalHeader, Parameters);

	return CommonResponse(Sess.Post());
}

HttpClient::Response
HttpClient::Post(std::string_view Url, const IoBuffer& Payload, const KeyValueMap& AdditionalHeader)
{
	ZEN_TRACE_CPU("HttpClient::PostWithPayload");

	Impl::Session Sess = m_Impl->AllocSession(m_BaseUri, Url, m_ConnectionSettings, AdditionalHeader, {});

	Sess->SetBody(AsCprBody(Payload));
	Sess->UpdateHeader(cpr::Header{{"Content-Type", std::string(MapContentTypeToString(Payload.GetContentType()))}});

	return CommonResponse(Sess.Post());
}

HttpClient::Response
HttpClient::Post(std::string_view Url, CbObject Payload, const KeyValueMap& AdditionalHeader)
{
	ZEN_TRACE_CPU("HttpClient::PostObjectPayload");

	Impl::Session Sess = m_Impl->AllocSession(m_BaseUri, Url, m_ConnectionSettings, AdditionalHeader, {});

	Sess->SetBody(AsCprBody(Payload));
	Sess->UpdateHeader(cpr::Header{{"Content-Type", std::string(MapContentTypeToString(ZenContentType::kCbObject))}});

	return CommonResponse(Sess.Post());
}

HttpClient::Response
HttpClient::Post(std::string_view Url, CbPackage Pkg, const KeyValueMap& AdditionalHeader)
{
	ZEN_TRACE_CPU("HttpClient::PostPackage");

	CompositeBuffer Message = zen::FormatPackageMessageBuffer(Pkg);

	Impl::Session Sess = m_Impl->AllocSession(m_BaseUri, Url, m_ConnectionSettings, AdditionalHeader, {});
	Sess->SetBody(AsCprBody(Message));
	Sess->UpdateHeader(cpr::Header{{"Content-Type", std::string(MapContentTypeToString(ZenContentType::kCbPackage))}});

	return CommonResponse(Sess.Post());
}

HttpClient::Response
HttpClient::Upload(std::string_view Url, const IoBuffer& Payload, const KeyValueMap& AdditionalHeader)
{
	ZEN_TRACE_CPU("HttpClient::Upload");

	Impl::Session Sess = m_Impl->AllocSession(m_BaseUri, Url, m_ConnectionSettings, AdditionalHeader, {});
	Sess->UpdateHeader(cpr::Header{{"Content-Type", std::string(MapContentTypeToString(Payload.GetContentType()))}});

	uint64_t Offset = 0;
	if (Payload.IsWholeFile())
	{
		auto ReadCallback = [&Payload, &Offset](char* buffer, size_t& size, intptr_t) {
			size						   = Min<size_t>(size, Payload.GetSize() - Offset);
			IoBuffer		  PayloadRange = IoBuffer(Payload, Offset, size);
			MutableMemoryView Data(buffer, size);
			Data.CopyFrom(PayloadRange.GetView());
			Offset += size;
			return true;
		};
		Sess->SetReadCallback(cpr::ReadCallback(gsl::narrow<cpr::cpr_off_t>(Payload.GetSize()), ReadCallback));
	}
	else
	{
		Sess->SetBody(AsCprBody(Payload));
	}
	return CommonResponse(Sess.Put());
}

HttpClient::Response
HttpClient::Upload(std::string_view Url, const CompositeBuffer& Payload, ZenContentType ContentType, const KeyValueMap& AdditionalHeader)
{
	ZEN_TRACE_CPU("HttpClient::Upload");

	Impl::Session Sess = m_Impl->AllocSession(m_BaseUri, Url, m_ConnectionSettings, AdditionalHeader, {});
	Sess->UpdateHeader(cpr::Header{{"Content-Type", std::string(MapContentTypeToString(ContentType))}});

	uint64_t				  SizeLeft	   = Payload.GetSize();
	CompositeBuffer::Iterator BufferIt	   = Payload.GetIterator(0);
	auto					  ReadCallback = [&Payload, &BufferIt, &SizeLeft](char* buffer, size_t& size, intptr_t) {
		 size = Min<size_t>(size, SizeLeft);
		 MutableMemoryView Data(buffer, size);
		 Payload.CopyTo(Data, BufferIt);
		 SizeLeft -= size;
		 return true;
	};
	Sess->SetReadCallback(cpr::ReadCallback(gsl::narrow<cpr::cpr_off_t>(Payload.GetSize()), ReadCallback));

	return CommonResponse(Sess.Put());
}

HttpClient::Response
HttpClient::Download(std::string_view Url, const std::filesystem::path& TempFolderPath, const KeyValueMap& AdditionalHeader)
{
	ZEN_TRACE_CPU("HttpClient::Download");

	Impl::Session Sess = m_Impl->AllocSession(m_BaseUri, Url, m_ConnectionSettings, AdditionalHeader, {});

	std::string						 PayloadString;
	std::unique_ptr<TempPayloadFile> PayloadFile;

	cpr::Response Response = Sess.Download(cpr::WriteCallback{[&](std::string data, intptr_t) {
		if (!PayloadFile && (PayloadString.length() + data.length()) > (1024 * 1024))
		{
			PayloadFile		   = std::make_unique<TempPayloadFile>();
			std::error_code Ec = PayloadFile->Open(TempFolderPath);
			if (Ec)
			{
				ZEN_WARN("Failed to create temp file in '{}' for HttpClient::Download. Reason: {}", TempFolderPath.string(), Ec.message());
				return false;
			}
			PayloadFile->Write(PayloadString);
			PayloadString.clear();
		}
		if (PayloadFile)
		{
			std::error_code Ec = PayloadFile->Write(data);
			if (Ec)
			{
				ZEN_WARN("Failed to write to temp file in '{}' for HttpClient::Download. Reason: {}",
						 TempFolderPath.string(),
						 Ec.message());
				return false;
			}
		}
		else
		{
			PayloadString.append(data);
		}
		return true;
	}});

	if (!PayloadString.empty())
	{
		Response.text = std::move(PayloadString);
	}

	return CommonResponse(std::move(Response), PayloadFile ? PayloadFile->DetachToIoBuffer() : IoBuffer{});
}

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

CbObject
HttpClient::Response::AsObject() const
{
	// TODO: sanity check the payload format etc

	if (ResponsePayload)
	{
		return LoadCompactBinaryObject(ResponsePayload);
	}

	return {};
}

CbPackage
HttpClient::Response::AsPackage() const
{
	// TODO: sanity checks and error handling
	if (ResponsePayload)
	{
		return ParsePackageMessage(ResponsePayload);
	}

	return {};
}

std::string_view
HttpClient::Response::AsText() const
{
	if (ResponsePayload)
	{
		return std::string_view(reinterpret_cast<const char*>(ResponsePayload.GetData()), ResponsePayload.GetSize());
	}

	return {};
}

std::string
HttpClient::Response::ToText() const
{
	if (!ResponsePayload)
		return {};

	switch (ResponsePayload.GetContentType())
	{
		case ZenContentType::kCbObject:
			{
				zen::ExtendableStringBuilder<1024> ObjStr;
				zen::CbObject					   Object{SharedBuffer(ResponsePayload)};
				zen::CompactBinaryToJson(Object, ObjStr);
				return ObjStr.ToString();
			}
			break;

		case ZenContentType::kCSS:
		case ZenContentType::kHTML:
		case ZenContentType::kJavaScript:
		case ZenContentType::kJSON:
		case ZenContentType::kText:
		case ZenContentType::kYAML:
			return std::string{AsText()};

		default:
			return "<unhandled content format>";
	}
}

bool
HttpClient::Response::IsSuccess() const noexcept
{
	return !Error && IsHttpSuccessCode(StatusCode);
}

std::string
HttpClient::Response::ErrorMessage(std::string_view Prefix) const
{
	if (Error.has_value())
	{
		return fmt::format("{}: {}", Prefix, Error->ErrorMessage);
	}
	else if (StatusCode != HttpResponseCode::ImATeapot && (int)StatusCode)
	{
		return fmt::format("{}: HTTP error {} {} ({})", Prefix, (int)StatusCode, zen::ToString(StatusCode), AsText());
	}
	else
	{
		return fmt::format("{}: {}", Prefix, "unknown error");
	}
}

void
HttpClient::Response::ThrowError(std::string_view ErrorPrefix)
{
	if (!IsSuccess())
	{
		throw std::runtime_error(ErrorMessage(ErrorPrefix));
	}
}

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

#if ZEN_WITH_TESTS

TEST_CASE("httpclient")
{
	using namespace std::literals;

	SUBCASE("client") {}
}

void
httpclient_forcelink()
{
}

#endif

}  // namespace zen