/* -*- 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/>.
 */

#ifndef NFD_DAEMON_FW_ASF_PROBING_MODULE_HPP
#define NFD_DAEMON_FW_ASF_PROBING_MODULE_HPP

#include "asf-measurements.hpp"

namespace nfd::fw::asf {

/** \brief ASF Probing Module
 */
class ProbingModule
{
public:
  explicit
  ProbingModule(AsfMeasurements& measurements);

  void
  scheduleProbe(const fib::Entry& fibEntry, time::milliseconds interval);

  Face*
  getFaceToProbe(const Face& inFace, const Interest& interest,
                 const fib::Entry& fibEntry, const Face& faceUsed);

  bool
  isProbingNeeded(const fib::Entry& fibEntry, const Name& interestName);

  void
  afterForwardingProbe(const fib::Entry& fibEntry, const Name& interestName);

  void
  setProbingInterval(time::milliseconds probingInterval);

  time::milliseconds
  getProbingInterval() const
  {
    return m_probingInterval;
  }

private:
  // Used to associate FaceInfo with the face in a NextHop
  using FaceInfoFacePair = std::pair<FaceInfo*, Face*>;

  struct FaceInfoCompare
  {
    bool
    operator()(const FaceInfoFacePair& leftPair, const FaceInfoFacePair& rightPair) const
    {
      const FaceInfo& lhs = *leftPair.first;
      const FaceInfo& rhs = *rightPair.first;

      // Sort by RTT: if a face has timed-out, rank it behind non-timed-out faces
      return (!lhs.hasTimeout() && rhs.hasTimeout()) ||
             (lhs.hasTimeout() == rhs.hasTimeout() && lhs.getSrtt() < rhs.getSrtt());
    }
  };

  using FaceInfoFacePairSet = std::set<FaceInfoFacePair, FaceInfoCompare>;

  static Face*
  chooseFace(const FaceInfoFacePairSet& rankedFaces);

  static double
  getProbingProbability(uint64_t rank, uint64_t rankSum, uint64_t nFaces);

public:
  static constexpr time::milliseconds DEFAULT_PROBING_INTERVAL = 1_min;
  static constexpr time::milliseconds MIN_PROBING_INTERVAL = 1_s;

private:
  time::milliseconds m_probingInterval;
  AsfMeasurements& m_measurements;
};

} // namespace nfd::fw::asf

#endif // NFD_DAEMON_FW_ASF_PROBING_MODULE_HPP