/// @file dpf/net/socket_tune.hpp
/// @brief Apply `socket_options` to TCP and unix-domain sockets.
#ifndef LIBDPF_INCLUDE_DPF_NET_SOCKET_TUNE_HPP__
#define LIBDPF_INCLUDE_DPF_NET_SOCKET_TUNE_HPP__

#include <system_error>
#include <type_traits>

#include "dpf/net/asio_ns.hpp"

#if defined(__linux__)
#include <netinet/in.h>
#include <netinet/tcp.h>
#include <sys/socket.h>
#endif

#include "dpf/net/policy.hpp"

namespace dpf
{
namespace net
{

/// @brief Linux clears `TCP_QUICKACK` after one ACK. Call again after I/O.
inline void rearm_quickack(asio::ip::tcp::socket & sock)
{
#if defined(TCP_QUICKACK)
    std::error_code ec;
    using quickack =
        asio::detail::socket_option::boolean<IPPROTO_TCP, TCP_QUICKACK>;
    sock.set_option(quickack(true), ec);
#else
    (void)sock;
#endif
}

namespace detail
{

template <typename Socket>
inline void apply_buffers(Socket & sock, const socket_options & o)
{
    std::error_code ec;
    if (o.send_buffer > 0)
        sock.set_option(asio::socket_base::send_buffer_size(o.send_buffer), ec);
    if (o.recv_buffer > 0)
        sock.set_option(asio::socket_base::receive_buffer_size(o.recv_buffer),
            ec);
}

}  // namespace detail

inline void tune_tcp(asio::ip::tcp::socket & sock, const socket_options & o = {})
{
    std::error_code ec;
    sock.set_option(asio::ip::tcp::no_delay(o.no_delay), ec);
    sock.set_option(asio::socket_base::keep_alive(o.keepalive), ec);
#if defined(__linux__)
    const int fd = sock.native_handle();
    if (o.keepalive && o.keepalive_idle_s > 0)
        (void)::setsockopt(fd, IPPROTO_TCP, TCP_KEEPIDLE, &o.keepalive_idle_s,
            sizeof(o.keepalive_idle_s));
    if (o.keepalive && o.keepalive_interval_s > 0)
        (void)::setsockopt(fd, IPPROTO_TCP, TCP_KEEPINTVL,
            &o.keepalive_interval_s, sizeof(o.keepalive_interval_s));
    if (o.keepalive && o.keepalive_count > 0)
        (void)::setsockopt(fd, IPPROTO_TCP, TCP_KEEPCNT, &o.keepalive_count,
            sizeof(o.keepalive_count));
#endif
    detail::apply_buffers(sock, o);
    if (o.quickack)
        rearm_quickack(sock);
}

namespace detail
{

template <typename S, typename = void>
struct is_layered_stream : std::false_type
{
};

template <typename S>
struct is_layered_stream<S, std::void_t<typename S::next_layer_type>> : std::true_type
{
};

}  // namespace detail

/// @brief The socket under `s`: itself, or the TCP socket under a TLS stream.
template <typename S>
inline auto & base_socket(S & s)
{
    if constexpr (detail::is_layered_stream<S>::value)
        return base_socket(s.next_layer());
    else
        return s;
}

inline void tune_stream(asio::ip::tcp::socket & sock, const socket_options & o = {})
{
    tune_tcp(sock, o);
}

template <typename Socket>
inline void tune_stream(Socket & sock, const socket_options & o = {})
{
    if constexpr (detail::is_layered_stream<Socket>::value)
        tune_stream(base_socket(sock), o);
    else
        detail::apply_buffers(sock, o);
}

inline void rearm_stream(asio::ip::tcp::socket & sock, const socket_options & o)
{
    if (o.quickack)
        rearm_quickack(sock);
}

template <typename Socket>
inline void rearm_stream(Socket & sock, const socket_options & o)
{
    if constexpr (detail::is_layered_stream<Socket>::value)
        rearm_stream(base_socket(sock), o);
    else
    {
        (void)sock;
        (void)o;
    }
}

}  // namespace net
}  // namespace dpf

#endif