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

#include "wshttpsys.h"

#if ZEN_WITH_HTTPSYS

#	include "wsframecodec.h"

#	include <zencore/logging.h>

namespace zen {

static LoggerRef
WsHttpSysLog()
{
	static LoggerRef g_Logger = logging::Get("ws_httpsys");
	return g_Logger;
}

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

WsHttpSysConnection::WsHttpSysConnection(HANDLE RequestQueueHandle, HTTP_REQUEST_ID RequestId, IWebSocketHandler& Handler, PTP_IO Iocp)
: m_RequestQueueHandle(RequestQueueHandle)
, m_RequestId(RequestId)
, m_Handler(Handler)
, m_Iocp(Iocp)
, m_ReadBuffer(8192)
{
	m_ReadIoContext.ContextType	 = HttpSysIoContext::Type::kWebSocketRead;
	m_ReadIoContext.Owner		 = this;
	m_WriteIoContext.ContextType = HttpSysIoContext::Type::kWebSocketWrite;
	m_WriteIoContext.Owner		 = this;
}

WsHttpSysConnection::~WsHttpSysConnection()
{
	ZEN_ASSERT(m_OutstandingOps.load() == 0);

	if (m_IsOpen.exchange(false))
	{
		Disconnect();
	}
}

void
WsHttpSysConnection::Start()
{
	m_SelfRef = Ref<WsHttpSysConnection>(this);
	IssueAsyncRead();
}

void
WsHttpSysConnection::Shutdown()
{
	m_ShutdownRequested.store(true, std::memory_order_relaxed);

	if (!m_IsOpen.exchange(false))
	{
		return;
	}

	// Cancel pending I/O — completions will fire with ERROR_OPERATION_ABORTED
	HttpCancelHttpRequest(m_RequestQueueHandle, m_RequestId, nullptr);
}

bool
WsHttpSysConnection::IsOpen() const
{
	return m_IsOpen.load(std::memory_order_relaxed);
}

//////////////////////////////////////////////////////////////////////////
//
// Async read path
//

void
WsHttpSysConnection::IssueAsyncRead()
{
	if (!m_IsOpen.load(std::memory_order_relaxed) || m_ShutdownRequested.load(std::memory_order_relaxed))
	{
		MaybeReleaseSelfRef();
		return;
	}

	m_OutstandingOps.fetch_add(1, std::memory_order_relaxed);

	ZeroMemory(&m_ReadIoContext.Overlapped, sizeof(OVERLAPPED));

	StartThreadpoolIo(m_Iocp);

	ULONG Result = HttpReceiveRequestEntityBody(m_RequestQueueHandle,
												m_RequestId,
												0,	// Flags
												m_ReadBuffer.data(),
												(ULONG)m_ReadBuffer.size(),
												nullptr,  // BytesRead (ignored for async)
												&m_ReadIoContext.Overlapped);

	if (Result != NO_ERROR && Result != ERROR_IO_PENDING)
	{
		CancelThreadpoolIo(m_Iocp);
		m_OutstandingOps.fetch_sub(1, std::memory_order_relaxed);

		if (m_IsOpen.exchange(false))
		{
			m_Handler.OnWebSocketClose(*this, 1006, "read issue failed");
		}

		MaybeReleaseSelfRef();
	}
}

void
WsHttpSysConnection::OnReadCompletion(ULONG IoResult, ULONG_PTR NumberOfBytesTransferred)
{
	// Hold a transient ref to prevent mid-callback destruction after MaybeReleaseSelfRef
	Ref<WsHttpSysConnection> Guard(this);

	if (IoResult != NO_ERROR)
	{
		m_OutstandingOps.fetch_sub(1, std::memory_order_relaxed);

		if (m_IsOpen.exchange(false))
		{
			if (IoResult == ERROR_HANDLE_EOF)
			{
				m_Handler.OnWebSocketClose(*this, 1006, "connection closed");
			}
			else if (IoResult != ERROR_OPERATION_ABORTED)
			{
				m_Handler.OnWebSocketClose(*this, 1006, "connection lost");
			}
		}

		MaybeReleaseSelfRef();
		return;
	}

	if (NumberOfBytesTransferred > 0)
	{
		m_Accumulated.insert(m_Accumulated.end(), m_ReadBuffer.begin(), m_ReadBuffer.begin() + NumberOfBytesTransferred);
		ProcessReceivedData();
	}

	m_OutstandingOps.fetch_sub(1, std::memory_order_relaxed);

	if (m_IsOpen.load(std::memory_order_relaxed))
	{
		IssueAsyncRead();
	}
	else
	{
		MaybeReleaseSelfRef();
	}
}

//////////////////////////////////////////////////////////////////////////
//
// Frame parsing
//

void
WsHttpSysConnection::ProcessReceivedData()
{
	while (!m_Accumulated.empty())
	{
		WsFrameParseResult Frame = WsFrameCodec::TryParseFrame(m_Accumulated.data(), m_Accumulated.size());
		if (!Frame.IsValid)
		{
			break;	// not enough data yet
		}

		// Remove consumed bytes
		m_Accumulated.erase(m_Accumulated.begin(), m_Accumulated.begin() + Frame.BytesConsumed);

		switch (Frame.Opcode)
		{
			case WebSocketOpcode::kText:
			case WebSocketOpcode::kBinary:
				{
					WebSocketMessage Msg;
					Msg.Opcode	= Frame.Opcode;
					Msg.Payload = IoBuffer(IoBuffer::Clone, Frame.Payload.data(), Frame.Payload.size());
					m_Handler.OnWebSocketMessage(*this, Msg);
					break;
				}

			case WebSocketOpcode::kPing:
				{
					// Auto-respond with pong carrying the same payload
					std::vector<uint8_t> PongFrame = WsFrameCodec::BuildFrame(WebSocketOpcode::kPong, Frame.Payload);
					EnqueueWrite(std::move(PongFrame));
					break;
				}

			case WebSocketOpcode::kPong:
				// Unsolicited pong — ignore per RFC 6455
				break;

			case WebSocketOpcode::kClose:
				{
					uint16_t		 Code = 1000;
					std::string_view Reason;

					if (Frame.Payload.size() >= 2)
					{
						Code = (uint16_t(Frame.Payload[0]) << 8) | uint16_t(Frame.Payload[1]);
						if (Frame.Payload.size() > 2)
						{
							Reason = std::string_view(reinterpret_cast<const char*>(Frame.Payload.data() + 2), Frame.Payload.size() - 2);
						}
					}

					// Echo close frame back if we haven't sent one yet
					{
						bool ShouldSendClose = false;
						{
							RwLock::ExclusiveLockScope _(m_WriteLock);
							if (!m_CloseSent)
							{
								m_CloseSent		= true;
								ShouldSendClose = true;
							}
						}
						if (ShouldSendClose)
						{
							std::vector<uint8_t> CloseFrame = WsFrameCodec::BuildCloseFrame(Code);
							EnqueueWrite(std::move(CloseFrame));
						}
					}

					m_IsOpen.store(false);
					m_Handler.OnWebSocketClose(*this, Code, Reason);
					Disconnect();
					return;
				}

			default:
				ZEN_LOG_WARN(WsHttpSysLog(), "Unknown WebSocket opcode: {:#x}", static_cast<uint8_t>(Frame.Opcode));
				break;
		}
	}
}

//////////////////////////////////////////////////////////////////////////
//
// Async write path
//

void
WsHttpSysConnection::EnqueueWrite(std::vector<uint8_t> Frame)
{
	bool ShouldFlush = false;

	{
		RwLock::ExclusiveLockScope _(m_WriteLock);
		m_WriteQueue.push_back(std::move(Frame));

		if (!m_IsWriting)
		{
			m_IsWriting = true;
			ShouldFlush = true;
		}
	}

	if (ShouldFlush)
	{
		FlushWriteQueue();
	}
}

void
WsHttpSysConnection::FlushWriteQueue()
{
	{
		RwLock::ExclusiveLockScope _(m_WriteLock);

		if (m_WriteQueue.empty())
		{
			m_IsWriting = false;
			return;
		}

		m_CurrentWriteBuffer = std::move(m_WriteQueue.front());
		m_WriteQueue.pop_front();
	}

	m_OutstandingOps.fetch_add(1, std::memory_order_relaxed);

	ZeroMemory(&m_WriteChunk, sizeof(m_WriteChunk));
	m_WriteChunk.DataChunkType			 = HttpDataChunkFromMemory;
	m_WriteChunk.FromMemory.pBuffer		 = m_CurrentWriteBuffer.data();
	m_WriteChunk.FromMemory.BufferLength = (ULONG)m_CurrentWriteBuffer.size();

	ZeroMemory(&m_WriteIoContext.Overlapped, sizeof(OVERLAPPED));

	StartThreadpoolIo(m_Iocp);

	ULONG Result = HttpSendResponseEntityBody(m_RequestQueueHandle,
											  m_RequestId,
											  HTTP_SEND_RESPONSE_FLAG_MORE_DATA,
											  1,
											  &m_WriteChunk,
											  nullptr,
											  nullptr,
											  0,
											  &m_WriteIoContext.Overlapped,
											  nullptr);

	if (Result != NO_ERROR && Result != ERROR_IO_PENDING)
	{
		CancelThreadpoolIo(m_Iocp);
		m_OutstandingOps.fetch_sub(1, std::memory_order_relaxed);

		ZEN_LOG_DEBUG(WsHttpSysLog(), "WebSocket async write failed: {}", Result);

		{
			RwLock::ExclusiveLockScope _(m_WriteLock);
			m_WriteQueue.clear();
			m_IsWriting = false;
		}
		m_CurrentWriteBuffer.clear();

		if (m_IsOpen.exchange(false))
		{
			m_Handler.OnWebSocketClose(*this, 1006, "write error");
		}

		MaybeReleaseSelfRef();
	}
}

void
WsHttpSysConnection::OnWriteCompletion(ULONG IoResult, ULONG_PTR NumberOfBytesTransferred)
{
	ZEN_UNUSED(NumberOfBytesTransferred);

	// Hold a transient ref to prevent mid-callback destruction
	Ref<WsHttpSysConnection> Guard(this);

	m_OutstandingOps.fetch_sub(1, std::memory_order_relaxed);
	m_CurrentWriteBuffer.clear();

	if (IoResult != NO_ERROR)
	{
		ZEN_LOG_DEBUG(WsHttpSysLog(), "WebSocket write completion error: {}", IoResult);

		{
			RwLock::ExclusiveLockScope _(m_WriteLock);
			m_WriteQueue.clear();
			m_IsWriting = false;
		}

		if (m_IsOpen.exchange(false))
		{
			m_Handler.OnWebSocketClose(*this, 1006, "write error");
		}

		MaybeReleaseSelfRef();
		return;
	}

	FlushWriteQueue();
}

//////////////////////////////////////////////////////////////////////////
//
// Send interface
//

void
WsHttpSysConnection::SendText(std::string_view Text)
{
	if (!m_IsOpen.load(std::memory_order_relaxed))
	{
		return;
	}

	std::span<const uint8_t> Payload(reinterpret_cast<const uint8_t*>(Text.data()), Text.size());
	std::vector<uint8_t>	 Frame = WsFrameCodec::BuildFrame(WebSocketOpcode::kText, Payload);
	EnqueueWrite(std::move(Frame));
}

void
WsHttpSysConnection::SendBinary(std::span<const uint8_t> Data)
{
	if (!m_IsOpen.load(std::memory_order_relaxed))
	{
		return;
	}

	std::vector<uint8_t> Frame = WsFrameCodec::BuildFrame(WebSocketOpcode::kBinary, Data);
	EnqueueWrite(std::move(Frame));
}

void
WsHttpSysConnection::Close(uint16_t Code, std::string_view Reason)
{
	DoClose(Code, Reason);
}

void
WsHttpSysConnection::DoClose(uint16_t Code, std::string_view Reason)
{
	if (!m_IsOpen.exchange(false))
	{
		return;
	}

	{
		bool ShouldSendClose = false;
		{
			RwLock::ExclusiveLockScope _(m_WriteLock);
			if (!m_CloseSent)
			{
				m_CloseSent		= true;
				ShouldSendClose = true;
			}
		}
		if (ShouldSendClose)
		{
			std::vector<uint8_t> CloseFrame = WsFrameCodec::BuildCloseFrame(Code, Reason);
			EnqueueWrite(std::move(CloseFrame));
		}
	}

	m_Handler.OnWebSocketClose(*this, Code, Reason);

	// Cancel pending read I/O — completions drain via ERROR_OPERATION_ABORTED
	HttpCancelHttpRequest(m_RequestQueueHandle, m_RequestId, nullptr);
}

//////////////////////////////////////////////////////////////////////////
//
// Lifetime management
//

void
WsHttpSysConnection::MaybeReleaseSelfRef()
{
	if (m_OutstandingOps.load(std::memory_order_relaxed) == 0 && !m_IsOpen.load(std::memory_order_relaxed))
	{
		m_SelfRef = nullptr;
	}
}

void
WsHttpSysConnection::Disconnect()
{
	// Send final empty body with DISCONNECT to tell http.sys the connection is done
	HttpSendResponseEntityBody(m_RequestQueueHandle,
							   m_RequestId,
							   HTTP_SEND_RESPONSE_FLAG_DISCONNECT,
							   0,
							   nullptr,
							   nullptr,
							   nullptr,
							   0,
							   nullptr,
							   nullptr);
}

}  // namespace zen

#endif	// ZEN_WITH_HTTPSYS