#include "./socket.hpp"

#include "../detect.hpp"

#if MIJIN_TARGET_OS == MIJIN_OS_LINUX
#include <fcntl.h>
#include <unistd.h>
#include <arpa/inet.h>
#include <sys/socket.h>
#endif

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

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;
}

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

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 ::ssize_t bytesRead = recv(handle_, buffer.data(), buffer.size(), 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 (send(handle_, buffer.data(), buffer.size(), 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);

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

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

    while (true)
    {
        if (send(handle_, buffer.data(), buffer.size(), 0) >= 0)
        {
            co_return StreamError::SUCCESS;
        }
        else if (errno != EAGAIN)
        {
            co_return translateErrno();
        }
        co_await mijin::c_suspend();
    }
}

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

    if (async)
    {
        appendSocketFlags(handle_, O_NONBLOCK);
    }
    else
    {
        removeSocketFlags(handle_, O_NONBLOCK);
    }
}

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

StreamError TCPStream::seek(std::intptr_t /* pos */, mijin::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(const char* address, std::uint16_t port) noexcept
{
    MIJIN_ASSERT(!isOpen(), "Socket is already open.");

    handle_ = socket(AF_INET, SOCK_STREAM, 0);
    if (handle_ < 0)
    {
        return translateErrno();
    }
    sockaddr_in connectAddress =
    {
        .sin_family = AF_INET,
        .sin_port = htons(port),
        .sin_addr = {inet_addr(address)}
    };
    if (connect(handle_, reinterpret_cast<sockaddr*>(&connectAddress), sizeof(sockaddr_in)) < 0)
    {
        ::close(handle_);
        handle_ = -1;
        return translateErrno();
    }

    return StreamError::SUCCESS;
}

void TCPStream::close() noexcept
{
    MIJIN_ASSERT(isOpen(), "Socket is not open.");
    ::close(handle_);
    handle_ = -1;
}

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

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

    handle_ = socket(AF_INET, SOCK_STREAM, 0);
    if (handle_ < 0)
    {
        return translateErrno();
    }
    sockaddr_in bindAddress =
    {
        .sin_family = AF_INET,
        .sin_port = htons(port),
        .sin_addr = {inet_addr(address)}
    };
    static const int ONE = 1;
    if ((setsockopt(handle_, SOL_SOCKET, SO_REUSEADDR, &ONE, sizeof(int)))
        || (bind(handle_, reinterpret_cast<sockaddr*>(&bindAddress), sizeof(sockaddr_in)) < 0)
        || (listen(handle_, LISTEN_BACKLOG) < 0)
        || !appendSocketFlags(handle_, O_NONBLOCK))
    {
        close();
        return translateErrno();
    }
    return StreamError::SUCCESS;
}

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

    ::close(handle_);
    handle_ = -1;
}

Task<StreamResult<std::unique_ptr<Socket>>> TCPServerSocket::c_waitForConnection() noexcept
{
    while (isListening())
    {
        sockaddr_in client = {};
        socklen_t LENGTH = sizeof(sockaddr_in);
        const int newSocket = accept(handle_, reinterpret_cast<sockaddr*>(&client), &LENGTH);
        if (newSocket < 0)
        {
            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;
}
}