#include "./socket.hpp"

#include "./detail/net_common.hpp"
#include "../detect.hpp"
#include "../util/variant.hpp"

namespace mijin
{
namespace
{
inline constexpr int LISTEN_BACKLOG = 3;
StreamError translateErrno() noexcept
{
    switch (errno)
    {
    case EIO:
        return StreamError::IO_ERROR;
    default:
        return StreamError::UNKNOWN_ERROR;
    }
}

int readFlags(const ReadOptions& options)
{
    return (options.partial ? 0 : MSG_WAITALL)
         | (options.peek ? MSG_PEEK : 0);
}

#if MIJIN_TARGET_OS == MIJIN_OS_LINUX
const int SOCKOPT_ONE = 1;

bool appendSocketFlags(int handle, int flags) noexcept
{
    const int currentFlags = fcntl(handle, F_GETFL);
    if (currentFlags < 0)
    {
        return false;
    }
    return fcntl(handle, F_SETFL, currentFlags | flags) >= 0;
}

bool removeSocketFlags(int handle, int flags) noexcept
{
    const int currentFlags = fcntl(handle, F_GETFL);
    if (currentFlags < 0)
    {
        return false;
    }
    return fcntl(handle, F_SETFL, currentFlags & ~flags) >= 0;
}

long osRecv(int socket, std::span<std::uint8_t> buffer, int flags)
{
    return static_cast<long>(recv(socket, buffer.data(), buffer.size(), flags));
}

long osSend(int socket, std::span<const std::uint8_t> buffer, int flags)
{
    return static_cast<long>(send(socket, buffer.data(), buffer.size(), flags));
}

int osCreateSocket(int domain, int type, int protocol)
{
    return socket(domain, type, protocol);
}

int osCloseSocket(int socket)
{
    return ::close(socket);
}

bool osIsSocketValid(int socket)
{
    return socket >= 0;
}

bool osSetSocketNonBlocking(int socket, bool blocking)
{
    if (blocking)
    {
        return appendSocketFlags(socket, O_NONBLOCK);
    }
    else
    {
        return removeSocketFlags(socket, O_NONBLOCK);
    }
}
#elif MIJIN_TARGET_OS == MIJIN_OS_WINDOWS
using in_addr_t = ULONG;

const char SOCKOPT_ONE = 1;
thread_local bool gWsaInited = false;

class WSAGuard
{
public:
    ~WSAGuard() noexcept
    {
        if (gWsaInited)
        {
            WSACleanup();
        }
    }
} thread_local [[maybe_unused]] gWsaGuard;

long osRecv(SOCKET socket, std::span<std::uint8_t> buffer, int flags)
{
    return recv(socket, reinterpret_cast<char*>(buffer.data()), static_cast<int>(buffer.size()), flags);
}

long osSend(SOCKET socket, std::span<const std::uint8_t> buffer, int flags)
{
    return send(socket, reinterpret_cast<const char*>(buffer.data()), static_cast<int>(buffer.size()), flags);
}

SOCKET osCreateSocket(int addressFamily, int type, int protocol)
{
    if (!detail::initWSA())
    {
        return INVALID_SOCKET_HANDLE;
    }
    return socket(addressFamily, type, protocol);
}

int osCloseSocket(SOCKET socket)
{
    return closesocket(socket);
}

bool osIsSocketValid(SOCKET socket)
{
    return socket != INVALID_SOCKET;
}

bool osSetSocketNonBlocking(SOCKET socket, bool blocking)
{
    u_long value = blocking ? 0 : 1;
    return ioctlsocket(socket, FIONBIO, &value) == NO_ERROR;
}
#endif // MIJIN_TARGET_OS == MIJIN_OS_LINUX
}

namespace detail
{
#if MIJIN_TARGET_OS == MIJIN_OS_WINDOWS
bool initWSA() noexcept
{
    if (gWsaInited)
    {
        return true;
    }

    WSADATA wsaData;
    if (WSAStartup(MAKEWORD(2, 2), &wsaData) != 0)
    {
        return false;
    }
    gWsaInited = true;
    return true;
}

StreamError translateWSAError() noexcept
{
    // TODO
    return StreamError::UNKNOWN_ERROR;
}

StreamError translateWinError(DWORD error) noexcept
{
    // TODO
    (void) error;
    return StreamError::UNKNOWN_ERROR;
}

StreamError translateWinError() noexcept
{
    return translateWinError(GetLastError());
}
#endif // MIJIN_TARGET_OS == MIJIN_OS_WINDOWS
}// namespace impl

StreamError TCPStream::readRaw(std::span<std::uint8_t> buffer, const ReadOptions& options, std::size_t* outBytesRead)
{
    MIJIN_ASSERT(isOpen(), "Socket is not open.");
    setAsync(false);

    const long bytesRead = osRecv(handle_, buffer, readFlags(options));
    if (bytesRead < 0)
    {
        return translateErrno();
    }
    *outBytesRead = static_cast<std::size_t>(bytesRead);

    return StreamError::SUCCESS;
}

StreamError TCPStream::writeRaw(std::span<const std::uint8_t> buffer)
{
    MIJIN_ASSERT(isOpen(), "Socket is not open.");
    setAsync(false);

    if (osSend(handle_, buffer, 0) < 0)
    {
        return translateErrno();
    }

    return StreamError::SUCCESS;
}

mijin::Task<StreamError> TCPStream::c_readRaw(std::span<std::uint8_t> buffer, const ReadOptions& options, std::size_t* outBytesRead)
{
    MIJIN_ASSERT(isOpen(), "Socket is not open.");
    setAsync(true);

    if (buffer.empty())
    {
        co_return StreamError::SUCCESS;
    }

    while(true)
    {
        const long bytesRead = osRecv(handle_, buffer, readFlags(options));
        if (bytesRead > 0)
        {
            if (outBytesRead != nullptr) {
                *outBytesRead = static_cast<std::size_t>(bytesRead);
            }
            co_return StreamError::SUCCESS;
        }
        if (bytesRead == 0)
        {
            co_return StreamError::CONNECTION_CLOSED;
        }
        if (errno != EAGAIN)
        {
            co_return translateErrno();
        }
        co_await mijin::c_suspend();
    }
}

Task<StreamError> TCPStream::c_writeRaw(std::span<const std::uint8_t> buffer)
{
    MIJIN_ASSERT(isOpen(), "Socket is not open.");

    if (buffer.empty())
    {
        co_return StreamError::SUCCESS;
    }

    setAsync(true);

    while (true)
    {
        const long bytesSent = osSend(handle_, buffer, 0);
        if (bytesSent == static_cast<long>(buffer.size()))
        {
            co_return StreamError::SUCCESS;
        }
        else if (bytesSent == 0)
        {
            co_return StreamError::CONNECTION_CLOSED;
        }
        else if (errno != EAGAIN)
        {
            co_return translateErrno();
        }
        co_await c_suspend();
    }
}

void TCPStream::setAsync(bool async)
{
    if (async == async_)
    {
        return;
    }
    async_ = async;

    osSetSocketNonBlocking(handle_, async);
}

std::size_t TCPStream::tell()
{
    return 0;
}

StreamError TCPStream::seek(std::intptr_t /* pos */, SeekMode /* seekMode */)
{
    return StreamError::NOT_SUPPORTED;
}

void TCPStream::flush()
{

}

bool TCPStream::isAtEnd()
{
    return !isOpen();
}

StreamFeatures TCPStream::getFeatures()
{
    return {
        .read = true,
        .write = true,
        .tell = false,
        .seek = false,
        .async = true,
        .readOptions = {
            .partial = true,
            .peek = true
        }
    };
}

StreamError TCPStream::open(ip_address_t address, std::uint16_t port) noexcept
{
    MIJIN_ASSERT(!isOpen(), "Socket is already open.");

    handle_ = osCreateSocket(AF_INET, SOCK_STREAM, 0);
    if (!osIsSocketValid(handle_))
    {
        return translateErrno();
    }

    const bool connected = std::visit(Visitor{
        [&](const IPv4Address& address4)
        {
#if __BYTE_ORDER__ != __ORDER_LITTLE_ENDIAN__
#error "TODO: swap byte order of the address"
#endif
            sockaddr_in connectAddress =
            {
                .sin_family = AF_INET,
                .sin_port = htons(port),
                .sin_addr = std::bit_cast<in_addr>(address4.octets)
            };
            return connect(handle_, reinterpret_cast<sockaddr*>(&connectAddress), sizeof(sockaddr_in)) == 0;
        },
        [&](IPv6Address address6)
        {
            for (std::uint16_t& hextet : address6.hextets) {
                hextet = htons(hextet);
            }
            sockaddr_in6 connectAddress =
            {
                .sin6_family = AF_INET6,
                .sin6_port = htons(port),
                .sin6_addr = std::bit_cast<in6_addr>(address6)
            };
            return connect(handle_, reinterpret_cast<sockaddr*>(&connectAddress), sizeof(sockaddr_in6)) == 0;
        }
    }, address);
    if (!connected)
    {
        osCloseSocket(handle_);
        handle_ = INVALID_SOCKET_HANDLE;
        return translateErrno();
    }

    return StreamError::SUCCESS;
}

void TCPStream::close() noexcept
{
    MIJIN_ASSERT(isOpen(), "Socket is not open.");
    osCloseSocket(handle_);
    handle_ = INVALID_SOCKET_HANDLE;
}

TCPStream& TCPSocket::getStream() noexcept
{
    return stream_;
}

StreamError TCPServerSocket::setup(ip_address_t address, std::uint16_t port) noexcept
{
    MIJIN_ASSERT(!isListening(), "Socket is already listening.");

    handle_ = osCreateSocket(AF_INET, SOCK_STREAM, 0);
    if (!osIsSocketValid(handle_))
    {
        return translateErrno();
    }
    if (setsockopt(handle_, SOL_SOCKET, SO_REUSEADDR, &SOCKOPT_ONE, sizeof(int)) != 0)
    {
        close();
        return translateErrno();
    }

    const bool bound = std::visit(Visitor{
        [&](const IPv4Address& address4)
        {
#if __BYTE_ORDER__ != __ORDER_LITTLE_ENDIAN__
#error "TODO: swap byte order of the address"
#endif
            sockaddr_in bindAddress =
            {
                .sin_family = AF_INET,
                .sin_port = htons(port),
                .sin_addr = std::bit_cast<in_addr>(address4.octets)
            };
            return bind(handle_, reinterpret_cast<sockaddr*>(&bindAddress), sizeof(sockaddr_in)) == 0;
        },
        [&](IPv6Address address6)
        {
            for (std::uint16_t& hextet : address6.hextets) {
                hextet = htons(hextet);
            }
            sockaddr_in6 bindAddress =
            {
                .sin6_family = AF_INET6,
                .sin6_port = htons(port),
                .sin6_addr = std::bit_cast<in6_addr>(address6)
            };
            return bind(handle_, reinterpret_cast<sockaddr*>(&bindAddress), sizeof(sockaddr_in6)) == 0;
        }
    }, address);
    if (!bound
        || (listen(handle_, LISTEN_BACKLOG) < 0)
        || !osSetSocketNonBlocking(handle_, true))
    {
        close();
        return translateErrno();
    }
    return StreamError::SUCCESS;
}

void TCPServerSocket::close() noexcept
{
    MIJIN_ASSERT(isListening(), "Socket is not listening.");

    osCloseSocket(handle_);
    handle_ = INVALID_SOCKET_HANDLE;
}

Task<StreamResult<std::unique_ptr<Socket>>> TCPServerSocket::c_waitForConnection() noexcept
{
    while (isListening())
    {
        sockaddr_in client = {};
        socklen_t LENGTH = sizeof(sockaddr_in);
        const socket_handle_t newSocket = accept(handle_, reinterpret_cast<sockaddr*>(&client), &LENGTH);
        if (!osIsSocketValid(newSocket))
        {
            if (errno != EAGAIN)
            {
                co_return translateErrno();
            }
            co_await c_suspend();
            continue;
        }
        std::unique_ptr<TCPSocket> socket = std::make_unique<TCPSocket>();
        socket->stream_.handle_ = newSocket;
        co_return socket;
    }
    co_return StreamError::CONNECTION_CLOSED;
}
}