/// @file dpf/net/link_log.hpp
/// @brief Run-log records for listeners and established party links.
/// @details `log_link_up` is called once per socket after the handshake and
///          after the stream array has adopted and tuned it, so the socket
///          options it reads back are the ones the kernel applied (Linux
///          doubles `SO_SNDBUF`/`SO_RCVBUF` and clamps them to `wmem_max` and
///          `rmem_max`). `TCP_INFO` at that point carries the kernel's RTT
///          estimate from the connection setup and the handshake exchange.
///          Encrypted links record the TLS version and cipher, how this side
///          authenticated the peer (`auth=key` or `none`), the peer's key, and
///          whether the peer authenticated this side. With encryption off the
///          record says `auth=none encryption=none`, and the first plaintext
///          link to an address off this host also raises one warning.
#ifndef LIBDPF_INCLUDE_DPF_NET_LINK_LOG_HPP__
#define LIBDPF_INCLUDE_DPF_NET_LINK_LOG_HPP__

#include <cstddef>
#include <cstdint>
#include <cstring>
#include <string>

#include <arpa/inet.h>
#include <netinet/in.h>
#include <netinet/tcp.h>
#include <sys/socket.h>
#include <sys/un.h>

#include "dpf/log.hpp"
#include "dpf/net/policy.hpp"
#include "dpf/net/security.hpp"

namespace dpf
{
namespace net
{
namespace detail
{

inline std::string sockaddr_text(const sockaddr_storage & ss)
{
    char host[INET6_ADDRSTRLEN] = {};
    if (ss.ss_family == AF_INET)
    {
        const auto & a = reinterpret_cast<const sockaddr_in &>(ss);
        if (::inet_ntop(AF_INET, &a.sin_addr, host, sizeof(host)) == nullptr)
            return "unknown";
        return std::string(host) + ":" + std::to_string(ntohs(a.sin_port));
    }
    if (ss.ss_family == AF_INET6)
    {
        const auto & a = reinterpret_cast<const sockaddr_in6 &>(ss);
        if (::inet_ntop(AF_INET6, &a.sin6_addr, host, sizeof(host)) == nullptr)
            return "unknown";
        return "[" + std::string(host) + "]:" + std::to_string(ntohs(a.sin6_port));
    }
    if (ss.ss_family == AF_UNIX)
    {
        const auto & a = reinterpret_cast<const sockaddr_un &>(ss);
        return std::string("unix:") + (a.sun_path[0] != '\0' ? a.sun_path : "(unnamed)");
    }
    return "unknown";
}

inline bool loopback(const sockaddr_storage & ss)
{
    if (ss.ss_family == AF_INET)
        return (ntohl(reinterpret_cast<const sockaddr_in &>(ss).sin_addr.s_addr) >> 24)
            == 127u;
    if (ss.ss_family == AF_INET6)
    {
        const auto & a = reinterpret_cast<const sockaddr_in6 &>(ss).sin6_addr;
        if (IN6_IS_ADDR_LOOPBACK(&a))
            return true;
        return IN6_IS_ADDR_V4MAPPED(&a) && a.s6_addr[12] == 127;
    }
    return ss.ss_family == AF_UNIX;
}

inline int int_opt(int fd, int level, int name)
{
    int v = -1;
    socklen_t len = sizeof(v);
    if (::getsockopt(fd, level, name, &v, &len) != 0)
        return -1;
    return v;
}

}  // namespace detail

/// @brief Record a listener: this process accepts any address on `port`.
/// @param encrypted whether connections on it must complete TLS 1.3 first
inline void log_listen(unsigned short port, bool sctp, bool encrypted = false)
{
    DPF_LOG(info, "listen").kv("addr", "0.0.0.0").kv("port", port)
        .kv("tcp", true).kv("sctp", sctp)
        .kv("encryption", encrypted ? "tls1.3" : "none");
}

/// @brief Record one established socket of a party link.
/// @param how `accept` or `connect`
/// @param peer the other end's role (`p1`, `dealer`, ...)
/// @param lane which socket of a `parallel` link (0 otherwise)
/// @param sec how the link was secured (null or unencrypted: plaintext)
inline void log_link_up(const char * how, const std::string & peer, transport kind,
    std::size_t lanes, std::uint32_t lane, std::uint32_t epoch, int fd,
    const socket_options & requested, const link_security * sec = nullptr)
{
    const bool encrypted = sec != nullptr && sec->encrypted;
    if (!log::enabled(log::level::info) || fd < 0)
        return;
    sockaddr_storage local{};
    sockaddr_storage remote{};
    socklen_t local_len = sizeof(local);
    socklen_t remote_len = sizeof(remote);
    const bool have_local =
        ::getsockname(fd, reinterpret_cast<sockaddr *>(&local), &local_len) == 0;
    const bool have_remote =
        ::getpeername(fd, reinterpret_cast<sockaddr *>(&remote), &remote_len) == 0;
    {
        log::record rec(log::level::info, "link.up");
        rec.kv("how", how).kv("peer", peer).kv("transport", transport_name(kind))
            .kv("lanes", lanes).kv("lane", lane).kv("epoch", epoch)
            .kv("local", have_local ? detail::sockaddr_text(local) : std::string("unknown"))
            .kv("remote", have_remote ? detail::sockaddr_text(remote) : std::string("unknown"))
            .kv("auth", encrypted ? sec->peer_auth : std::string("none"))
            .kv("encryption",
                encrypted ? sec->protocol + "/" + sec->cipher : std::string("none"));
        if (encrypted)
            rec.kv("peer_key", sec->peer_key ? sec->peer_key->base64() : std::string("none"))
                .kv("peer_verified_us", sec->peer_verified_us);
        if (kind != transport::sctp)
        {
            rec.kv("nodelay", detail::int_opt(fd, IPPROTO_TCP, TCP_NODELAY))
                .kv("quickack_req", requested.quickack)
                .kv("keepalive", detail::int_opt(fd, SOL_SOCKET, SO_KEEPALIVE))
                .kv("sndbuf_req", requested.send_buffer)
                .kv("sndbuf", detail::int_opt(fd, SOL_SOCKET, SO_SNDBUF))
                .kv("rcvbuf_req", requested.recv_buffer)
                .kv("rcvbuf", detail::int_opt(fd, SOL_SOCKET, SO_RCVBUF));
#if defined(TCP_INFO)
            tcp_info ti{};
            socklen_t ti_len = sizeof(ti);
            if (::getsockopt(fd, IPPROTO_TCP, TCP_INFO, &ti, &ti_len) == 0)
                rec.kv("rtt_us", ti.tcpi_rtt).kv("rttvar_us", ti.tcpi_rttvar)
                    .kv("pmtu", ti.tcpi_pmtu).kv("snd_mss", ti.tcpi_snd_mss)
                    .kv("snd_cwnd", ti.tcpi_snd_cwnd)
                    .kv("retrans", ti.tcpi_total_retrans);
#endif
        }
    }
    if (!encrypted && have_remote && !detail::loopback(remote)
        && log::first_time("net.plaintext_remote"))
        DPF_LOG(warning, "link.plaintext").kv("remote", detail::sockaddr_text(remote))
            .kv("detail", "encryption is off: this party link is unauthenticated "
                "and unencrypted, and the handshake's party id is not verified");
}

}  // namespace net
}  // namespace dpf

#endif  // LIBDPF_INCLUDE_DPF_NET_LINK_LOG_HPP__