/* -*- Mode:C++; c-file-style:"gnu"; indent-tabs-mode:nil; -*- */
/**
 * Copyright (c) 2014-2016,  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 "strategy.hpp"
#include "forwarder.hpp"
#include "core/logger.hpp"
#include "core/random.hpp"
#include <boost/range/adaptor/map.hpp>
#include <boost/range/algorithm/copy.hpp>

namespace nfd {
namespace fw {

NFD_LOG_INIT("Strategy");

Strategy::Registry&
Strategy::getRegistry()
{
  static Registry registry;
  return registry;
}

Strategy::Registry::const_iterator
Strategy::find(const Name& strategyName)
{
  const Registry& registry = getRegistry();
  Registry::const_iterator candidate = registry.end();
  for (auto it = registry.lower_bound(strategyName);
       it != registry.end() && strategyName.isPrefixOf(it->first); ++it) {
    switch (it->first.size() - strategyName.size()) {
      case 0: // exact match
        return it;
      case 1: // unversioned strategyName matches versioned strategy
        candidate = it;
        break;
    }
  }
  return candidate;
  ///\todo #3868 if exact version unavailable, choose closest higher version
  ///\todo #3868 allow parameter component
}

bool
Strategy::canCreate(const Name& strategyName)
{
  return Strategy::find(strategyName) != getRegistry().end();
}

unique_ptr<Strategy>
Strategy::create(const Name& strategyName, Forwarder& forwarder)
{
  auto found = Strategy::find(strategyName);
  if (found == getRegistry().end()) {
    NFD_LOG_DEBUG("create " << strategyName << " not-found");
    return nullptr;
  }

  NFD_LOG_DEBUG("create " << strategyName << " found=" << found->first);
  ///\todo #3868 pass parameters to strategy constructor
  return found->second(forwarder, found->first);
}

std::set<Name>
Strategy::listRegistered()
{
  std::set<Name> strategyNames;
  boost::copy(getRegistry() | boost::adaptors::map_keys,
              std::inserter(strategyNames, strategyNames.end()));
  return strategyNames;
}

Strategy::Strategy(Forwarder& forwarder, const Name& name)
  : afterAddFace(forwarder.getFaceTable().afterAdd)
  , beforeRemoveFace(forwarder.getFaceTable().beforeRemove)
  , m_name(name)
  , m_forwarder(forwarder)
  , m_measurements(m_forwarder.getMeasurements(), m_forwarder.getStrategyChoice(), *this)
{
}

Strategy::~Strategy() = default;

void
Strategy::beforeSatisfyInterest(const shared_ptr<pit::Entry>& pitEntry,
                                const Face& inFace, const Data& data)
{
  NFD_LOG_DEBUG("beforeSatisfyInterest pitEntry=" << pitEntry->getName() <<
                " inFace=" << inFace.getId() << " data=" << data.getName());
}

void
Strategy::beforeExpirePendingInterest(const shared_ptr<pit::Entry>& pitEntry)
{
  NFD_LOG_DEBUG("beforeExpirePendingInterest pitEntry=" << pitEntry->getName());
}

void
Strategy::afterReceiveNack(const Face& inFace, const lp::Nack& nack,
                           const shared_ptr<pit::Entry>& pitEntry)
{
  NFD_LOG_DEBUG("afterReceiveNack inFace=" << inFace.getId() <<
                " pitEntry=" << pitEntry->getName());
}

void
Strategy::sendNacks(const shared_ptr<pit::Entry>& pitEntry, const lp::NackHeader& header,
                    std::initializer_list<const Face*> exceptFaces)
{
  // populate downstreams with all downstreams faces
  std::unordered_set<const Face*> downstreams;
  std::transform(pitEntry->in_begin(), pitEntry->in_end(), std::inserter(downstreams, downstreams.end()),
                 [] (const pit::InRecord& inR) { return &inR.getFace(); });

  // delete excluded faces
  // .erase in a loop is more efficient than std::set_difference because that requires sorted range
  for (const Face* exceptFace : exceptFaces) {
    downstreams.erase(exceptFace);
  }

  // send Nacks
  for (const Face* downstream : downstreams) {
    this->sendNack(pitEntry, *downstream, header);
  }
  // warning: don't loop on pitEntry->getInRecords(), because in-record is deleted when sending Nack
}

const fib::Entry&
Strategy::lookupFib(const pit::Entry& pitEntry) const
{
  const Fib& fib = m_forwarder.getFib();
  const NetworkRegionTable& nrt = m_forwarder.getNetworkRegionTable();

  const Interest& interest = pitEntry.getInterest();
  // has Link object?
  if (!interest.hasLink()) {
    // FIB lookup with Interest name
    const fib::Entry& fibEntry = fib.findLongestPrefixMatch(pitEntry);
    NFD_LOG_TRACE("lookupFib noLinkObject found=" << fibEntry.getPrefix());
    return fibEntry;
  }

  const Link& link = interest.getLink();

  // in producer region?
  if (nrt.isInProducerRegion(link)) {
    // FIB lookup with Interest name
    const fib::Entry& fibEntry = fib.findLongestPrefixMatch(pitEntry);
    NFD_LOG_TRACE("lookupFib inProducerRegion found=" << fibEntry.getPrefix());
    return fibEntry;
  }

  // has SelectedDelegation?
  if (interest.hasSelectedDelegation()) {
    // FIB lookup with SelectedDelegation
    Name selectedDelegation = interest.getSelectedDelegation();
    const fib::Entry& fibEntry = fib.findLongestPrefixMatch(selectedDelegation);
    NFD_LOG_TRACE("lookupFib hasSelectedDelegation=" << selectedDelegation << " found=" << fibEntry.getPrefix());
    return fibEntry;
  }

  // FIB lookup with first delegation Name
  const fib::Entry& fibEntry0 = fib.findLongestPrefixMatch(link.getDelegations().begin()->second);
  // in default-free zone?
  bool isDefaultFreeZone = !(fibEntry0.getPrefix().size() == 0 && fibEntry0.hasNextHops());
  if (!isDefaultFreeZone) {
    NFD_LOG_TRACE("lookupFib inConsumerRegion found=" << fibEntry0.getPrefix());
    return fibEntry0;
  }

  // choose and set SelectedDelegation
  for (const std::pair<uint32_t, Name>& delegation : link.getDelegations()) {
    const Name& delegationName = delegation.second;
    const fib::Entry& fibEntry = fib.findLongestPrefixMatch(delegationName);
    if (fibEntry.hasNextHops()) {
      /// \todo Don't modify in-record Interests.
      ///       Set SelectedDelegation in outgoing Interest pipeline.
      std::for_each(pitEntry.in_begin(), pitEntry.in_end(),
        [&delegationName] (const pit::InRecord& inR) {
          const_cast<Interest&>(inR.getInterest()).setSelectedDelegation(delegationName);
        });
      NFD_LOG_TRACE("lookupFib enterDefaultFreeZone setSelectedDelegation=" << delegationName);
      return fibEntry;
    }
  }
  BOOST_ASSERT(false);
  return fibEntry0;
}

} // namespace fw
} // namespace nfd