/* -*- 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
 *
 * 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 <ndn-cxx/face.hpp>
#include <ndn-cxx/management/nfd-controller.hpp>
#include <ndn-cxx/security/key-chain.hpp>

#include <sys/types.h>
#include <netinet/in.h>
#include <arpa/nameser.h>
#include <resolv.h>

#ifdef __APPLE__
#include <arpa/nameser_compat.h>
#endif

namespace tools {

class NdnAutoconfig
{
public:
  union QueryAnswer
  {
    HEADER header;
    uint8_t buf[NS_PACKETSZ];
  };

  class Error : public std::runtime_error
  {
  public:
    explicit
    Error(const std::string& what)
      : std::runtime_error(what)
    {
    }
  };

  explicit
  NdnAutoconfig()
    : m_controller(m_face)
  {
  }

  // Start to look for a hub (NDN hub discovery first stage)
  void
  discoverHubStage1()
  {
    ndn::Interest interest(ndn::Name("/localhop/ndn-autoconf/hub"));
    interest.setInterestLifetime(ndn::time::milliseconds(4000)); // 4 seconds
    interest.setMustBeFresh(true);

    std::cerr << "Stage 1: Trying multicast discovery..." << std::endl;
    m_face.expressInterest(interest,
                           ndn::bind(&NdnAutoconfig::onDiscoverHubStage1Success, this, _1, _2),
                           ndn::bind(&NdnAutoconfig::discoverHubStage2, this, _1, "Timeout"));

    m_face.processEvents();
  }

  // First stage OnData Callback
  void
  onDiscoverHubStage1Success(const ndn::Interest& interest, ndn::Data& data)
  {
    const ndn::Block& content = data.getContent();
    content.parse();

    // Get Uri
    ndn::Block::element_const_iterator blockValue = content.find(ndn::tlv::nfd::Uri);
    if (blockValue == content.elements_end())
    {
      discoverHubStage2(interest, "Incorrect reply to stage1");
      return;
    }
    std::string faceMgmtUri(reinterpret_cast<const char*>(blockValue->value()),
                            blockValue->value_size());
    connectToHub(faceMgmtUri);
  }

  // First stage OnTimeout callback - start 2nd stage
  void
  discoverHubStage2(const ndn::Interest& interest, const std::string& message)
  {
    std::cerr << message << std::endl;
    std::cerr << "Stage 2: Trying DNS query with default suffix..." << std::endl;

    _res.retry = 2;
    _res.ndots = 10;

    QueryAnswer queryAnswer;

    int answerSize = res_search("_ndn._udp",
                                ns_c_in,
                                ns_t_srv,
                                queryAnswer.buf,
                                sizeof(queryAnswer));

    // 2nd stage failed - move on to the third stage
    if (answerSize < 0)
    {
      discoverHubStage3("Failed to find NDN router using default suffix DNS query");
    }
    else
    {
      bool isParsed = parseHostAndConnectToHub(queryAnswer, answerSize);
      if (isParsed == false)
      {
        // Failed to parse DNS response, try stage 3
        discoverHubStage3("Failed to parse DNS response");
      }
    }
  }

  // Second stage OnTimeout callback
  void
  discoverHubStage3(const std::string& message)
  {
    std::cerr << message << std::endl;
    std::cerr << "Stage 3: Trying to find home router..." << std::endl;

    ndn::KeyChain keyChain;
    ndn::Name identity = keyChain.getDefaultIdentity();
    std::string serverName = "_ndn._udp.";

    for (ndn::Name::const_reverse_iterator i = identity.rbegin(); i != identity.rend(); i++)
    {
      serverName.append(i->toEscapedString());
      serverName.append(".");
    }
    serverName += "_homehub._autoconf.named-data.net";
    std::cerr << "Stage3: About to query for a home router: " << serverName << std::endl;

    QueryAnswer queryAnswer;

    int answerSize = res_query(serverName.c_str(),
                               ns_c_in,
                               ns_t_srv,
                               queryAnswer.buf,
                               sizeof(queryAnswer));


    // 3rd stage failed - abort
    if (answerSize < 0)
    {
      std::cerr << "Failed to find a home router" << std::endl;
      std::cerr << "exit" << std::endl;
    }
    else
    {
      bool isParsed = parseHostAndConnectToHub(queryAnswer, answerSize);
      if (isParsed == false)
      {
        // Failed to parse DNS response
        throw Error("Failed to parse DNS response");
      }
    }

  }

  void
  connectToHub(const std::string& uri)
  {
    std::cerr << "about to connect to: " << uri << std::endl;

    m_controller.start<ndn::nfd::FaceCreateCommand>(
      ndn::nfd::ControlParameters()
        .setUri(uri),
      bind(&NdnAutoconfig::onHubConnectSuccess, this, _1),
      bind(&NdnAutoconfig::onHubConnectError, this, _1, _2)
    );
  }

  void
  onHubConnectSuccess(const ndn::nfd::ControlParameters& resp)
  {
    std::cerr << "Successfully created face: " << resp << std::endl;
  }

  void
  onHubConnectError(uint32_t code, const std::string& error)
  {
    std::ostringstream os;
    os << "Failed to create face: " << error << " (code: " << code << ")";
    throw Error(os.str());
  }


  bool parseHostAndConnectToHub(QueryAnswer& queryAnswer, int answerSize)
  {
    // The references of the next classes are:
    // http://www.diablotin.com/librairie/networking/dnsbind/ch14_02.htm
    // https://gist.github.com/mologie/6027597

    struct rechdr
    {
      uint16_t type;
      uint16_t iclass;
      uint32_t ttl;
      uint16_t length;
    };

    struct srv_t
    {
      uint16_t priority;
      uint16_t weight;
      uint16_t port;
      uint8_t* target;
    };

    if (ntohs(queryAnswer.header.ancount) == 0)
    {
      std::cerr << "No records found\n" << std::endl;
      return false;
    }

    uint8_t* blob = queryAnswer.buf + NS_HFIXEDSZ;

    blob += dn_skipname(blob, queryAnswer.buf + answerSize) + NS_QFIXEDSZ;

    for (int i = 0; i < ntohs(queryAnswer.header.ancount); i++)
    {
      char srvName[NS_MAXDNAME];
      int serverNameSize = dn_expand(queryAnswer.buf,               // message pointer
                                     queryAnswer.buf + answerSize,  // end of message
                                     blob,                          // compressed server name
                                     srvName,                       // expanded server name
                                     NS_MAXDNAME);
      if (serverNameSize < 0)
      {
        return false;
      }

      srv_t* server = reinterpret_cast<srv_t*>(&blob[sizeof(rechdr)]);
      uint16_t convertedPort = be16toh(server->port);

      blob += serverNameSize + NS_HFIXEDSZ + NS_QFIXEDSZ;

      char hostName[NS_MAXDNAME];
      int hostNameSize = dn_expand(queryAnswer.buf,               // message pointer
                                   queryAnswer.buf + answerSize,  // end of message
                                   blob,                          // compressed host name
                                   hostName,                      // expanded host name
                                   NS_MAXDNAME);
      if (hostNameSize < 0)
      {
        return false;
      }

      std::string uri = "udp://";
      uri.append(hostName);
      uri.append(":");
      uri.append(boost::lexical_cast<std::string>(convertedPort));

      connectToHub(uri);
      return true;
    }

    return false;
  }

private:
  ndn::Face m_face;
  ndn::nfd::Controller m_controller;
};

} // namespace tools

int
main()
{
  try
    {
      tools::NdnAutoconfig autoConfigInstance;

      autoConfigInstance.discoverHubStage1();
    }
  catch (const std::exception& error)
    {
      std::cerr << "ERROR: " << error.what() << std::endl;
    }
  return 0;
}