/* -*- Mode:C++; c-file-style:"gnu"; indent-tabs-mode:nil; -*- */
/*
 * Copyright (c) 2014-2022,  Regents of the University of California,
 *                           Arizona Board of Regents,
 *                           Colorado State University,
 *                           University Pierre & Marie Curie, Sorbonne University,
 *                           Washington University in St. Louis,
 *                           Beijing Institute of Technology,
 *                           The University of Memphis.
 *
 * This file is part of NFD (Named Data Networking Forwarding Daemon).
 * See AUTHORS.md for complete list of NFD authors and contributors.
 *
 * NFD is free software: you can redistribute it and/or modify it under the terms
 * of the GNU General Public License as published by the Free Software Foundation,
 * either version 3 of the License, or (at your option) any later version.
 *
 * NFD is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY;
 * without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR
 * PURPOSE.  See the GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License along with
 * NFD, e.g., in COPYING.md file.  If not, see <http://www.gnu.org/licenses/>.
 */

#include "ethernet-transport.hpp"
#include "ethernet-protocol.hpp"
#include "common/global.hpp"

#include <pcap/pcap.h>

#include <cstring> // for memcpy()

#include <boost/endian/conversion.hpp>

namespace nfd::face {

NFD_LOG_INIT(EthernetTransport);

EthernetTransport::EthernetTransport(const ndn::net::NetworkInterface& localEndpoint,
                                     const ethernet::Address& remoteEndpoint)
  : m_socket(getGlobalIoService())
  , m_pcap(localEndpoint.getName())
  , m_srcAddress(localEndpoint.getEthernetAddress())
  , m_destAddress(remoteEndpoint)
  , m_interfaceName(localEndpoint.getName())
  , m_hasRecentlyReceived(false)
#ifdef _DEBUG
  , m_nDropped(0)
#endif
{
  try {
    m_pcap.activate(DLT_EN10MB);
    m_socket.assign(m_pcap.getFd());
  }
  catch (const PcapHelper::Error& e) {
    NDN_THROW_NESTED(Error(e.what()));
  }

  // Set initial transport state based upon the state of the underlying NetworkInterface
  handleNetifStateChange(localEndpoint.getState());

  m_netifStateChangedConn = localEndpoint.onStateChanged.connect(
    [this] (ndn::net::InterfaceState, ndn::net::InterfaceState newState) {
      handleNetifStateChange(newState);
    });

  m_netifMtuChangedConn = localEndpoint.onMtuChanged.connect(
    [this] (uint32_t, uint32_t mtu) {
      setMtu(mtu);
    });

  asyncRead();
}

void
EthernetTransport::doClose()
{
  NFD_LOG_FACE_TRACE(__func__);

  if (m_socket.is_open()) {
    // Cancel all outstanding operations and close the socket.
    // Use the non-throwing variants and ignore errors, if any.
    boost::system::error_code error;
    m_socket.cancel(error);
    m_socket.close(error);
  }
  m_pcap.close();

  // Ensure that the Transport stays alive at least
  // until all pending handlers are dispatched
  getGlobalIoService().post([this] {
    this->setState(TransportState::CLOSED);
  });
}

void
EthernetTransport::handleNetifStateChange(ndn::net::InterfaceState netifState)
{
  NFD_LOG_FACE_TRACE("netif is " << netifState);
  if (netifState == ndn::net::InterfaceState::RUNNING) {
    if (getState() == TransportState::DOWN) {
      this->setState(TransportState::UP);
    }
  }
  else if (getState() == TransportState::UP) {
    this->setState(TransportState::DOWN);
  }
}

void
EthernetTransport::doSend(const Block& packet)
{
  NFD_LOG_FACE_TRACE(__func__);

  sendPacket(packet);
}

void
EthernetTransport::sendPacket(const ndn::Block& block)
{
  ndn::EncodingBuffer buffer(block);

  // pad with zeroes if the payload is too short
  if (block.size() < ethernet::MIN_DATA_LEN) {
    static const uint8_t padding[ethernet::MIN_DATA_LEN] = {};
    buffer.appendBytes(ndn::make_span(padding).subspan(block.size()));
  }

  // construct and prepend the ethernet header
  uint16_t ethertype = boost::endian::native_to_big(ethernet::ETHERTYPE_NDN);
  buffer.prependBytes({reinterpret_cast<const uint8_t*>(&ethertype), ethernet::TYPE_LEN});
  buffer.prependBytes(m_srcAddress);
  buffer.prependBytes(m_destAddress);

  // send the frame
  int sent = pcap_inject(m_pcap, buffer.data(), buffer.size());
  if (sent < 0)
    handleError("Send operation failed: " + m_pcap.getLastError());
  else if (static_cast<size_t>(sent) < buffer.size())
    handleError("Failed to send the full frame: size=" + to_string(buffer.size()) +
                " sent=" + to_string(sent));
  else
    // print block size because we don't want to count the padding in buffer
    NFD_LOG_FACE_TRACE("Successfully sent: " << block.size() << " bytes");
}

void
EthernetTransport::asyncRead()
{
  m_socket.async_read_some(boost::asio::null_buffers(),
                           [this] (const auto& e, auto) { this->handleRead(e); });
}

void
EthernetTransport::handleRead(const boost::system::error_code& error)
{
  if (error) {
    // boost::asio::error::operation_aborted must be checked first: in that case, the Transport
    // may already have been destructed, therefore it's unsafe to call getState() or do logging.
    if (error != boost::asio::error::operation_aborted &&
        getState() != TransportState::CLOSING &&
        getState() != TransportState::FAILED &&
        getState() != TransportState::CLOSED) {
      handleError("Receive operation failed: " + error.message());
    }
    return;
  }

  auto [pkt, readErr] = m_pcap.readNextPacket();
  if (pkt.empty()) {
    NFD_LOG_FACE_WARN("Read error: " << readErr);
  }
  else {
    auto [eh, frameErr] = ethernet::checkFrameHeader(pkt, m_srcAddress,
                                                     m_destAddress.isMulticast() ? m_destAddress : m_srcAddress);
    if (eh == nullptr) {
      NFD_LOG_FACE_WARN(frameErr);
    }
    else {
      ethernet::Address sender(eh->ether_shost);
      pkt = pkt.subspan(ethernet::HDR_LEN);
      receivePayload(pkt, sender);
    }
  }

#ifdef _DEBUG
  size_t nDropped = m_pcap.getNDropped();
  if (nDropped - m_nDropped > 0)
    NFD_LOG_FACE_DEBUG("Detected " << nDropped - m_nDropped << " dropped frame(s)");
  m_nDropped = nDropped;
#endif

  asyncRead();
}

void
EthernetTransport::receivePayload(span<const uint8_t> payload, const ethernet::Address& sender)
{
  NFD_LOG_FACE_TRACE("Received: " << payload.size() << " bytes from " << sender);

  auto [isOk, element] = Block::fromBuffer(payload);
  if (!isOk) {
    NFD_LOG_FACE_WARN("Failed to parse incoming packet from " << sender);
    // This packet won't extend the face lifetime
    return;
  }
  m_hasRecentlyReceived = true;

  static_assert(sizeof(EndpointId) >= ethernet::ADDR_LEN, "EndpointId is too small");
  EndpointId endpoint = 0;
  if (m_destAddress.isMulticast()) {
    std::memcpy(&endpoint, sender.data(), sender.size());
  }

  this->receive(element, endpoint);
}

void
EthernetTransport::handleError(const std::string& errorMessage)
{
  if (getPersistency() == ndn::nfd::FACE_PERSISTENCY_PERMANENT) {
    NFD_LOG_FACE_DEBUG("Permanent face ignores error: " << errorMessage);
    return;
  }

  NFD_LOG_FACE_ERROR(errorMessage);
  this->setState(TransportState::FAILED);
  doClose();
}

} // namespace nfd::face