/* -*- Mode:C++; c-file-style:"gnu"; indent-tabs-mode:nil; -*- */
/**
 * Copyright (c) 2014,  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 "forwarder.hpp"
#include "core/logger.hpp"
#include "core/random.hpp"
#include "available-strategies.hpp"
#include <boost/random/uniform_int_distribution.hpp>

namespace nfd {

NFD_LOG_INIT("Forwarder");

using fw::Strategy;

const Name Forwarder::LOCALHOST_NAME("ndn:/localhost");

Forwarder::Forwarder()
  : m_faceTable(*this)
  , m_fib(m_nameTree)
  , m_pit(m_nameTree)
  , m_measurements(m_nameTree)
  , m_strategyChoice(m_nameTree, fw::makeDefaultStrategy(*this))
{
  fw::installStrategies(*this);
}

Forwarder::~Forwarder()
{

}

void
Forwarder::onIncomingInterest(Face& inFace, const Interest& interest)
{
  // receive Interest
  NFD_LOG_DEBUG("onIncomingInterest face=" << inFace.getId() <<
                " interest=" << interest.getName());
  const_cast<Interest&>(interest).setIncomingFaceId(inFace.getId());
  m_counters.getNInInterests() ++;

  // /localhost scope control
  bool isViolatingLocalhost = !inFace.isLocal() &&
                              LOCALHOST_NAME.isPrefixOf(interest.getName());
  if (isViolatingLocalhost) {
    NFD_LOG_DEBUG("onIncomingInterest face=" << inFace.getId() <<
                  " interest=" << interest.getName() << " violates /localhost");
    // (drop)
    return;
  }

  // PIT insert
  shared_ptr<pit::Entry> pitEntry = m_pit.insert(interest).first;

  // detect loop and record Nonce
  bool isLoop = ! pitEntry->addNonce(interest.getNonce());
  if (isLoop) {
    // goto Interest loop pipeline
    this->onInterestLoop(inFace, interest, pitEntry);
    return;
  }

  // cancel unsatisfy & straggler timer
  this->cancelUnsatisfyAndStragglerTimer(pitEntry);

  // is pending?
  const pit::InRecordCollection& inRecords = pitEntry->getInRecords();
  bool isPending = inRecords.begin() != inRecords.end();
  if (!isPending) {
    // CS lookup
    const Data* csMatch = m_cs.find(interest);
    if (csMatch != 0) {
      // XXX should we lookup PIT for other Interests that also match csMatch?

      // goto outgoing Data pipeline
      this->onOutgoingData(*csMatch, inFace);
      return;
    }
  }

  // insert InRecord
  pitEntry->insertOrUpdateInRecord(inFace.shared_from_this(), interest);

  // FIB lookup
  shared_ptr<fib::Entry> fibEntry = m_fib.findLongestPrefixMatch(*pitEntry);

  // dispatch to strategy
  this->dispatchToStrategy(pitEntry, bind(&Strategy::afterReceiveInterest, _1,
                                          cref(inFace), cref(interest), fibEntry, pitEntry));
}

void
Forwarder::onInterestLoop(Face& inFace, const Interest& interest,
                          shared_ptr<pit::Entry> pitEntry)
{
  NFD_LOG_DEBUG("onInterestLoop face=" << inFace.getId() <<
                " interest=" << interest.getName());

  // (drop)
}

/** \brief compare two InRecords for picking outgoing Interest
 *  \return true if b is preferred over a
 *
 *  This function should be passed to std::max_element over InRecordCollection.
 *  The outgoing Interest picked is the last incoming Interest
 *  that does not come from outFace.
 *  If all InRecords come from outFace, it's fine to pick that. This happens when
 *  there's only one InRecord that comes from outFace. The legit use is for
 *  vehicular network; otherwise, strategy shouldn't send to the sole inFace.
 */
static inline bool
compare_pickInterest(const pit::InRecord& a, const pit::InRecord& b, const Face* outFace)
{
  bool isOutFaceA = a.getFace().get() == outFace;
  bool isOutFaceB = b.getFace().get() == outFace;

  if (!isOutFaceA && isOutFaceB) {
    return false;
  }
  if (isOutFaceA && !isOutFaceB) {
    return true;
  }

  return a.getLastRenewed() > b.getLastRenewed();
}

void
Forwarder::onOutgoingInterest(shared_ptr<pit::Entry> pitEntry, Face& outFace,
                              bool wantNewNonce)
{
  NFD_LOG_DEBUG("onOutgoingInterest face=" << outFace.getId() <<
                " interest=" << pitEntry->getName());

  // scope control
  if (pitEntry->violatesScope(outFace)) {
    NFD_LOG_DEBUG("onOutgoingInterest face=" << outFace.getId() <<
                  " interest=" << pitEntry->getName() << " violates scope");
    return;
  }

  // pick Interest
  const pit::InRecordCollection& inRecords = pitEntry->getInRecords();
  pit::InRecordCollection::const_iterator pickedInRecord = std::max_element(
    inRecords.begin(), inRecords.end(), bind(&compare_pickInterest, _1, _2, &outFace));
  BOOST_ASSERT(pickedInRecord != inRecords.end());
  shared_ptr<Interest> interest = const_pointer_cast<Interest>(
    pickedInRecord->getInterest().shared_from_this());

  if (wantNewNonce) {
    interest = make_shared<Interest>(*interest);
    static boost::random::uniform_int_distribution<uint32_t> dist;
    interest->setNonce(dist(getGlobalRng()));
  }

  // insert OutRecord
  pitEntry->insertOrUpdateOutRecord(outFace.shared_from_this(), *interest);

  // set PIT unsatisfy timer
  this->setUnsatisfyTimer(pitEntry);

  // send Interest
  outFace.sendInterest(*interest);
  m_counters.getNOutInterests() ++;
}

void
Forwarder::onInterestReject(shared_ptr<pit::Entry> pitEntry)
{
  if (pitEntry->hasUnexpiredOutRecords()) {
    NFD_LOG_ERROR("onInterestReject interest=" << pitEntry->getName() <<
                  " cannot reject forwarded Interest");
    return;
  }
  NFD_LOG_DEBUG("onInterestReject interest=" << pitEntry->getName());

  // set PIT straggler timer
  this->setStragglerTimer(pitEntry);
}

void
Forwarder::onInterestUnsatisfied(shared_ptr<pit::Entry> pitEntry)
{
  NFD_LOG_DEBUG("onInterestUnsatisfied interest=" << pitEntry->getName());

  // invoke PIT unsatisfied callback
  this->dispatchToStrategy(pitEntry, bind(&Strategy::beforeExpirePendingInterest, _1,
                                          pitEntry));

  // PIT delete
  this->cancelUnsatisfyAndStragglerTimer(pitEntry);
  m_pit.erase(pitEntry);
}

void
Forwarder::onIncomingData(Face& inFace, const Data& data)
{
  // receive Data
  NFD_LOG_DEBUG("onIncomingData face=" << inFace.getId() << " data=" << data.getName());
  const_cast<Data&>(data).setIncomingFaceId(inFace.getId());
  m_counters.getNInDatas() ++;

  // /localhost scope control
  bool isViolatingLocalhost = !inFace.isLocal() &&
                              LOCALHOST_NAME.isPrefixOf(data.getName());
  if (isViolatingLocalhost) {
    NFD_LOG_DEBUG("onIncomingData face=" << inFace.getId() <<
                  " data=" << data.getName() << " violates /localhost");
    // (drop)
    return;
  }

  // PIT match
  shared_ptr<pit::DataMatchResult> pitMatches = m_pit.findAllDataMatches(data);
  if (pitMatches->begin() == pitMatches->end()) {
    // goto Data unsolicited pipeline
    this->onDataUnsolicited(inFace, data);
    return;
  }

  // CS insert
  m_cs.insert(data);

  std::set<shared_ptr<Face> > pendingDownstreams;
  // foreach PitEntry
  for (pit::DataMatchResult::iterator it = pitMatches->begin();
       it != pitMatches->end(); ++it) {
    shared_ptr<pit::Entry> pitEntry = *it;
    NFD_LOG_DEBUG("onIncomingData matching=" << pitEntry->getName());

    // cancel unsatisfy & straggler timer
    this->cancelUnsatisfyAndStragglerTimer(pitEntry);

    // remember pending downstreams
    const pit::InRecordCollection& inRecords = pitEntry->getInRecords();
    for (pit::InRecordCollection::const_iterator it = inRecords.begin();
                                                 it != inRecords.end(); ++it) {
      if (it->getExpiry() > time::steady_clock::now()) {
        pendingDownstreams.insert(it->getFace());
      }
    }

    // invoke PIT satisfy callback
    this->dispatchToStrategy(pitEntry, bind(&Strategy::beforeSatisfyPendingInterest, _1,
                                            pitEntry, cref(inFace), cref(data)));

    // mark PIT satisfied
    pitEntry->deleteInRecords();
    pitEntry->deleteOutRecord(inFace.shared_from_this());

    // set PIT straggler timer
    this->setStragglerTimer(pitEntry);
  }

  // foreach pending downstream
  for (std::set<shared_ptr<Face> >::iterator it = pendingDownstreams.begin();
      it != pendingDownstreams.end(); ++it) {
    shared_ptr<Face> pendingDownstream = *it;
    if (pendingDownstream.get() == &inFace) {
      continue;
    }
    // goto outgoing Data pipeline
    this->onOutgoingData(data, *pendingDownstream);
  }
}

void
Forwarder::onDataUnsolicited(Face& inFace, const Data& data)
{
  // accept to cache?
  bool acceptToCache = inFace.isLocal();
  if (acceptToCache) {
    // CS insert
    m_cs.insert(data, true);
  }

  NFD_LOG_DEBUG("onDataUnsolicited face=" << inFace.getId() <<
                " data=" << data.getName() <<
                (acceptToCache ? " cached" : " not cached"));
}

void
Forwarder::onOutgoingData(const Data& data, Face& outFace)
{
  NFD_LOG_DEBUG("onOutgoingData face=" << outFace.getId() << " data=" << data.getName());

  // /localhost scope control
  bool isViolatingLocalhost = !outFace.isLocal() &&
                              LOCALHOST_NAME.isPrefixOf(data.getName());
  if (isViolatingLocalhost) {
    NFD_LOG_DEBUG("onOutgoingData face=" << outFace.getId() <<
                  " data=" << data.getName() << " violates /localhost");
    // (drop)
    return;
  }

  // TODO traffic manager

  // send Data
  outFace.sendData(data);
  m_counters.getNOutDatas() ++;
}

static inline bool
compare_InRecord_expiry(const pit::InRecord& a, const pit::InRecord& b)
{
  return a.getExpiry() < b.getExpiry();
}

void
Forwarder::setUnsatisfyTimer(shared_ptr<pit::Entry> pitEntry)
{
  const pit::InRecordCollection& inRecords = pitEntry->getInRecords();
  pit::InRecordCollection::const_iterator lastExpiring =
    std::max_element(inRecords.begin(), inRecords.end(),
    &compare_InRecord_expiry);

  time::steady_clock::TimePoint lastExpiry = lastExpiring->getExpiry();
  time::nanoseconds lastExpiryFromNow = lastExpiry  - time::steady_clock::now();
  if (lastExpiryFromNow <= time::seconds(0)) {
    // TODO all InRecords are already expired; will this happen?
  }

  scheduler::cancel(pitEntry->m_unsatisfyTimer);
  pitEntry->m_unsatisfyTimer = scheduler::schedule(lastExpiryFromNow,
    bind(&Forwarder::onInterestUnsatisfied, this, pitEntry));
}

void
Forwarder::setStragglerTimer(shared_ptr<pit::Entry> pitEntry)
{
  if (pitEntry->hasUnexpiredOutRecords()) {
    NFD_LOG_DEBUG("setStragglerTimer " << pitEntry->getName() <<
                  " cannot set StragglerTimer when an OutRecord is pending");
    return;
  }

  time::nanoseconds stragglerTime = time::milliseconds(100);

  scheduler::cancel(pitEntry->m_stragglerTimer);
  pitEntry->m_stragglerTimer = scheduler::schedule(stragglerTime,
    bind(&Pit::erase, &m_pit, pitEntry));
}

void
Forwarder::cancelUnsatisfyAndStragglerTimer(shared_ptr<pit::Entry> pitEntry)
{
  scheduler::cancel(pitEntry->m_unsatisfyTimer);
  scheduler::cancel(pitEntry->m_stragglerTimer);
}

} // namespace nfd