#include "torrent-manager.hpp"

#include "file-manifest.hpp"
#include "torrent-file.hpp"

#include <boost/filesystem.hpp>
#include <boost/filesystem/fstream.hpp>

#include <ndn-cxx/data.hpp>
#include <ndn-cxx/security/key-chain.hpp>
#include <ndn-cxx/security/signing-helpers.hpp>
#include <ndn-cxx/util/io.hpp>

#include <set>
#include <string>
#include <unordered_map>
#include <vector>

namespace fs = boost::filesystem;

using std::string;
using std::vector;

namespace {
// TODO(msweatt) Move this to a utility
template<typename T>
static vector<T>
load_directory(const string& dirPath,
               ndn::io::IoEncoding encoding = ndn::io::IoEncoding::BASE_64) {
  vector<T> structures;
  std::set<string> fileNames;
  if (fs::exists(dirPath)) {
    for(fs::recursive_directory_iterator it(dirPath);
      it !=  fs::recursive_directory_iterator();
      ++it)
    {
      fileNames.insert(it->path().string());
    }
    for (const auto& f : fileNames) {
      auto data_ptr = ndn::io::load<T>(f, encoding);
      if (nullptr != data_ptr) {
        structures.push_back(*data_ptr);
      }
    }
  }
  structures.shrink_to_fit();
  return structures;
}

} // end anonymous

namespace ndn {
namespace ntorrent {

// TODO(msweatt) Move this to a utility
static vector<ndn::Data>
packetize_file(const fs::path& filePath,
               const ndn::Name& commonPrefix,
               size_t dataPacketSize,
               size_t subManifestSize,
               size_t subManifestNum)
{
  BOOST_ASSERT(0 < dataPacketSize);
  size_t APPROX_BUFFER_SIZE = std::numeric_limits<int>::max(); // 2 * 1024 * 1024 *1024
  auto file_size = fs::file_size(filePath);
  auto start_offset = subManifestNum * subManifestSize * dataPacketSize;
  // determine the number of bytes in this submanifest
  auto subManifestLength = subManifestSize * dataPacketSize;
  auto remainingFileLength = file_size - start_offset;
  subManifestLength = remainingFileLength < subManifestLength
                    ? remainingFileLength
                    : subManifestLength;
  vector<ndn::Data> packets;
  packets.reserve(subManifestLength/dataPacketSize + 1);
  fs::ifstream fs(filePath, fs::ifstream::binary);
  if (!fs) {
    BOOST_THROW_EXCEPTION(FileManifest::Error("IO Error when opening" + filePath.string()));
  }
  // ensure that buffer is large enough to contain whole packets
  // buffer size is either the entire file or the smallest number of data packets >= 2 GB
  auto buffer_size =
    subManifestLength < APPROX_BUFFER_SIZE   ?
    subManifestLength                        :
    APPROX_BUFFER_SIZE % dataPacketSize == 0 ?
    APPROX_BUFFER_SIZE :
    APPROX_BUFFER_SIZE + dataPacketSize - (APPROX_BUFFER_SIZE % dataPacketSize);
  vector<char> file_bytes;
  file_bytes.reserve(buffer_size);
  size_t bytes_read = 0;
  fs.seekg(start_offset);
  while(fs && bytes_read < subManifestLength && !fs.eof()) {
    // read the file into the buffer
    fs.read(&file_bytes.front(), buffer_size);
    auto read_size = fs.gcount();
    if (fs.bad() || read_size < 0) {
      BOOST_THROW_EXCEPTION(FileManifest::Error("IO Error when reading" + filePath.string()));
    }
    bytes_read += read_size;
    char *curr_start = &file_bytes.front();
    for (size_t i = 0u; i < buffer_size; i += dataPacketSize) {
      // Build a packet from the data
      Name packetName = commonPrefix;
      packetName.appendSequenceNumber(packets.size());
      Data d(packetName);
      auto content_length = i + dataPacketSize > buffer_size ? buffer_size - i : dataPacketSize;
      d.setContent(encoding::makeBinaryBlock(tlv::Content, curr_start, content_length));
      curr_start += content_length;
      // append to the collection
      packets.push_back(d);
    }
    file_bytes.clear();
    // recompute the buffer_size
    buffer_size =
      subManifestLength - bytes_read < APPROX_BUFFER_SIZE ?
      subManifestLength - bytes_read                      :
      APPROX_BUFFER_SIZE % dataPacketSize == 0            ?
      APPROX_BUFFER_SIZE                                  :
      APPROX_BUFFER_SIZE + dataPacketSize - (APPROX_BUFFER_SIZE % dataPacketSize);
  }
  fs.close();
  packets.shrink_to_fit();
  ndn::security::KeyChain key_chain;
  // sign all the packets
  for (auto& p : packets) {
    key_chain.sign(p, signingWithSha256());
  }
  return packets;
}

static vector<TorrentFile>
intializeTorrentSegments(const string& torrentFilePath, const Name& initialSegmentName)
{
  security::KeyChain key_chain;
  Name currSegmentFullName = initialSegmentName;
  vector<TorrentFile> torrentSegments = load_directory<TorrentFile>(torrentFilePath);

  // Starting with the initial segment name, verify the names, loading next name from torrentSegment
  for (auto it = torrentSegments.begin(); it != torrentSegments.end(); ++it) {
    TorrentFile& segment = *it;
    key_chain.sign(segment, signingWithSha256());
    if (segment.getFullName() != currSegmentFullName) {
      vector<TorrentFile> correctSegments(torrentSegments.begin(), it);
      torrentSegments.swap(correctSegments);
      break;
    }
    // load the next full name
    if (nullptr == segment.getTorrentFilePtr()) {
      break;
    }
    currSegmentFullName = *segment.getTorrentFilePtr();
  }
  return torrentSegments;
}

static vector<FileManifest>
intializeFileManifests(const string& manifestPath, vector<TorrentFile> torrentSegments)
{
  security::KeyChain key_chain;

  vector<FileManifest> manifests = load_directory<FileManifest>(manifestPath);

  // sign the manifests
  std::for_each(manifests.begin(), manifests.end(),
                [&key_chain](FileManifest& m){
                  key_chain.sign(m,signingWithSha256());
                });

  // put all names of manifests from the valid torrent files into a set
  std::set<ndn::Name> validManifestNames;
  for (const auto& segment : torrentSegments) {
    const auto& catalog = segment.getCatalog();
    validManifestNames.insert(catalog.begin(), catalog.end());
  }

  // put all names of file manifests from disk into a set
  std::set<ndn::Name> loadedManifestNames;
  std::for_each(manifests.begin(), manifests.end(),
                [&loadedManifestNames](const FileManifest& m){
                  loadedManifestNames.insert(m.getFullName());
                });

  // the set of fileManifests that we have is simply the intersection
  std::set<Name> output;
  std::set_intersection(validManifestNames.begin() , validManifestNames.end(),
                        loadedManifestNames.begin(), loadedManifestNames.end(),
                        std::inserter(output, output.begin()));

  // filter out those manifests that are not in this set
  std::remove_if(manifests.begin(),
                 manifests.end(),
                 [&output](const FileManifest& m) {
                   return (output.end() == output.find(m.name()));
                 });

  // order the manifests in the same order they are in the torrent
  std::vector<Name> catalogNames;
  for (const auto& segment : torrentSegments) {
    const auto& catalog = segment.getCatalog();
    catalogNames.insert(catalogNames.end(), catalog.begin(), catalog.end());
  }
  size_t curr_index = 0;
  for (auto name : catalogNames) {
    auto it = std::find_if(manifests.begin(), manifests.end(),
                          [&name](const FileManifest& m) {
                            return m.getFullName() == name;
                           });
    if (it != manifests.end()) {
      // not already in the correct position
      if (it != manifests.begin() + curr_index) {
        std::swap(manifests[curr_index], *it);
      }
      ++curr_index;
    }
  }

  return manifests;
}

static vector<Data>
intializeDataPackets(const string&      filePath,
                     const FileManifest manifest,
                     const TorrentFile& torrentFile)
{
  vector<Data> packets;
  auto subManifestNum = manifest.submanifest_number();

  packets =  packetize_file(filePath,
                             manifest.name(),
                             manifest.data_packet_size(),
                             manifest.catalog().size(),
                             subManifestNum);

  auto catalog = manifest.catalog();

  // Filter out invalid packet names
  std::remove_if(packets.begin(), packets.end(),
                [&packets, &catalog](const Data& p) {
                  return catalog.end() == std::find(catalog.begin(),
                                                     catalog.end(),
                                                     p.getFullName());
                });
  return packets;
}

static std::pair<std::shared_ptr<fs::fstream>, std::vector<bool>>
initializeFileState(const string& dataPath,
                    const FileManifest& manifest)
{
  // construct the file name
  auto fileName = manifest.file_name();
  auto filePath = dataPath + fileName;
  vector<bool> fileBitMap(manifest.catalog().size());
  auto fbits = fs::fstream::out | fs::fstream::binary;
  // if file exists, use in O/W use concatenate mode
  fbits |= fs::exists(filePath) ? fs::fstream::in : fs::fstream::ate;
  auto s = std::make_shared<fs::fstream>(filePath, fbits);
  if (!*s) {
    BOOST_THROW_EXCEPTION(io::Error("Cannot open: " + dataPath));
  }
  return std::make_pair(s, fileBitMap);
}

void TorrentManager::Initialize()
{
  // .../<torrent_name>/torrent-file/<implicit_digest>
  string dataPath = ".appdata/" + m_torrentFileName.get(-3).toUri();
  string manifestPath = dataPath +"/manifests";
  string torrentFilePath = dataPath +"/torrent_files";

  // get the torrent file segments and manifests that we have.
  if (!fs::exists(torrentFilePath)) {
    return;
  }
  m_torrentSegments = intializeTorrentSegments(torrentFilePath, m_torrentFileName);
  if (m_torrentSegments.empty()) {
    return;
  }
  m_fileManifests   = intializeFileManifests(manifestPath, m_torrentSegments);
  auto currTorrentFile_it = m_torrentSegments.begin();
  for (const auto& m : m_fileManifests) {
    // find the appropriate torrent file
    auto currCatalog = currTorrentFile_it->getCatalog();
    while (currCatalog.end() == std::find(currCatalog.begin(), currCatalog.end(), m.getFullName()))
    {
      ++currTorrentFile_it;
      currCatalog = currTorrentFile_it->getCatalog();
    }
    // construct the file name
    auto fileName = m.file_name();
    fs::path filePath = m_dataPath + fileName;
    // If there are any valid packets, add corresponding state to manager
    if (!fs::exists(filePath)) {
      boost::filesystem::create_directories(filePath.parent_path());
      continue;
    }
    auto packets = intializeDataPackets(filePath.string(), m, *currTorrentFile_it);
    if (!packets.empty()) {
      m_fileStates[m.getFullName()] = initializeFileState(m_dataPath, m);
      auto& fileBitMap = m_fileStates[m.getFullName()].second;
      auto read_it = packets.begin();
      size_t i = 0;
      for (auto name : m.catalog()) {
        if (name == read_it->getFullName()) {
          ++read_it;
          fileBitMap[i] = true;
        }
        ++i;
      }
      for (const auto& d : packets) {
        seed(d);
      }
    }
  }
  for (const auto& t : m_torrentSegments) {
    seed(t);
  }
  for (const auto& m : m_fileManifests) {
    seed(m);
  }
}

bool TorrentManager::writeData(const Data& packet)
{
  // find correct manifest
  const auto& packetName = packet.getName();
  auto manifest_it = std::find_if(m_fileManifests.begin(), m_fileManifests.end(),
                                 [&packetName](const FileManifest& m) {
                                   return m.getName().isPrefixOf(packetName);
                                 });
  if (m_fileManifests.end() == manifest_it) {
    return false;
  }
  // get file state out
  auto& fileState = m_fileStates[manifest_it->getFullName()];
  // if there is no open stream to the file
  if (nullptr == fileState.first) {
    fileState = initializeFileState(m_dataPath, *manifest_it);
  }
  auto packetNum = packetName.get(packetName.size() - 1).toSequenceNumber();
  // if we already have the packet, do not rewrite it.
  if (fileState.second[packetNum]) {
    return false;
  }
  auto packetOffset = packetNum * manifest_it->data_packet_size();
  // write data to disk
  fileState.first->seekg(packetOffset);
  try {
    auto content = packet.getContent();
    std::vector<char> data(content.value_begin(), content.value_end());
    fileState.first->write(&data[0], data.size());
  }
  catch (io::Error &e) {
    std::cerr << e.what() << std::endl;
    return false;
  }
  // update bitmap
  fileState.second[packetNum] = true;
  return true;
}

bool TorrentManager::writeTorrentSegment(const TorrentFile& segment, const std::string& path)
{
  // validate that this torrent segment belongs to our torrent
  auto torrentPrefix = m_torrentFileName.getSubName(0, m_torrentFileName.size() - 1);
  if (!torrentPrefix.isPrefixOf(segment.getName())) {
    return false;
  }

  auto segmentNum = segment.getSegmentNumber();
  // check if we already have it
  if (m_torrentSegments.end() != std::find(m_torrentSegments.begin(), m_torrentSegments.end(),
                                           segment))
  {
    return false;
  }
  // write to disk at path
  if (!fs::exists(path)) {
    fs::create_directories(path);
  }
  auto filename = path + to_string(segmentNum);
  // if there is already a file on disk for this torrent segment, determine if we should override
  if (fs::exists(filename)) {
    auto segmentOnDisk_ptr = io::load<TorrentFile>(filename);
    if (nullptr != segmentOnDisk_ptr && *segmentOnDisk_ptr == segment) {
      return false;
    }
  }
  io::save(segment, filename);
  // add to collection
  auto it = std::find_if(m_torrentSegments.begin(), m_torrentSegments.end(),
                         [segmentNum](const TorrentFile& t){
                           return t.getSegmentNumber() > segmentNum;
                        });
  m_torrentSegments.insert(it, segment);
  return true;
}

bool TorrentManager::writeFileManifest(const FileManifest& manifest, const std::string& path)
{
  auto subManifestNum = manifest.submanifest_number();
  fs::path filename = path + manifest.file_name() + "/" + to_string(subManifestNum);
  // check if we already have it
  if (m_fileManifests.end() != std::find(m_fileManifests.begin(), m_fileManifests.end(),
                                         manifest))
  {
    return false;
  }

  // write to disk at path
  if (!fs::exists(filename.parent_path())) {
    boost::filesystem::create_directories(filename.parent_path());
  }
  // if there is already a file on disk for this torrent segment, determine if we should override
  if (fs::exists(filename)) {
    auto submanifestOnDisk_ptr = io::load<FileManifest>(filename.string());
    if (nullptr != submanifestOnDisk_ptr && *submanifestOnDisk_ptr == manifest) {
      return false;
    }
  }
  io::save(manifest, filename.string());
  // add to collection
  // add to collection
  auto it = std::find_if(m_fileManifests.begin(), m_fileManifests.end(),
                         [&manifest](const FileManifest& m){
                           return m.file_name() >  manifest.file_name()
                           ||    (m.file_name() == manifest.file_name()
                              && (m.submanifest_number() > manifest.submanifest_number()));
                        });
  m_fileManifests.insert(it, manifest);
  return true;
}

void TorrentManager::seed(const Data& data) const {
  // TODO(msweatt) IMPLEMENT ME
}

void
TorrentManager::downloadTorrentFile(const std::string& path,
                                    TorrentFileReceivedCallback onSuccess,
                                    FailedCallback onFailed)
{
  shared_ptr<Name> searchRes = this->findTorrentFileSegmentToDownload();
  auto manifestNames = make_shared<std::vector<Name>>();
  if (searchRes == nullptr) {
    this->findFileManifestsToDownload(*manifestNames);
    if (manifestNames->empty()) {
      auto packetNames = make_shared<std::vector<Name>>();
      this->findAllMissingDataPackets(*packetNames);
      onSuccess(*packetNames);
      return;
    }
    else {
      onSuccess(*manifestNames);
      return;
    }
  }
  this->downloadTorrentFileSegment(*searchRes, path, manifestNames,
                                   true, onSuccess, onFailed);
}

std::vector<Name>
TorrentManager::downloadTorrentFile(const std::string& path)
{
  shared_ptr<Name> searchRes = this->findTorrentFileSegmentToDownload();
  auto manifestNames = make_shared<std::vector<Name>>();
  if (searchRes == nullptr) {
    this->findFileManifestsToDownload(*manifestNames);
    if (manifestNames->empty()) {
      auto packetNames = make_shared<std::vector<Name>>();
      this->findAllMissingDataPackets(*packetNames);
      return *packetNames;
    }
    else {
      return *manifestNames;
    }
  }
  this->downloadTorrentFileSegment(m_torrentFileName, path, manifestNames,
                                  false, {}, {});
  return *manifestNames;
}

void
TorrentManager::downloadTorrentFileSegment(const ndn::Name& name,
                                           const std::string& path,
                                           std::shared_ptr<std::vector<Name>> manifestNames,
                                           bool async,
                                           TorrentFileReceivedCallback onSuccess,
                                           FailedCallback onFailed)
{
  shared_ptr<Interest> interest = createInterest(name);

  auto dataReceived = [manifestNames, path, async, onSuccess, onFailed, this]
                                            (const Interest& interest, const Data& data) {
      // Stats Table update here...
      m_stats_table_iter->incrementReceivedData();
      m_retries = 0;

      if (async) {
        manifestNames->clear();
      }

      TorrentFile file(data.wireEncode());

      // Write the torrent file segment to disk...
      writeTorrentSegment(file, path);

      const std::vector<Name>& manifestCatalog = file.getCatalog();
      manifestNames->insert(manifestNames->end(), manifestCatalog.begin(), manifestCatalog.end());

      shared_ptr<Name> nextSegmentPtr = file.getTorrentFilePtr();

      if (async) {
        onSuccess(*manifestNames);
      }
      if (nextSegmentPtr != nullptr) {
        this->downloadTorrentFileSegment(*nextSegmentPtr, path, manifestNames,
                                         async, onSuccess, onFailed);
      }
  };

  auto dataFailed = [manifestNames, path, name, async, onSuccess, onFailed, this]
                                                (const Interest& interest) {
    ++m_retries;
    if (m_retries >= MAX_NUM_OF_RETRIES) {
      ++m_stats_table_iter;
      if (m_stats_table_iter == m_statsTable.end()) {
        m_stats_table_iter = m_statsTable.begin();
      }
    }
    if (async) {
      onFailed(interest.getName(), "Unknown error");
    }
    this->downloadTorrentFileSegment(name, path, manifestNames, async, onSuccess, onFailed);
  };

  m_face.expressInterest(*interest, dataReceived, dataFailed);

  if (!async) {
    m_face.processEvents();
  }
}


void
TorrentManager::download_file_manifest(const Name&              manifestName,
                                       const std::string&       path,
                                       TorrentManager::ManifestReceivedCallback onSuccess,
                                       TorrentManager::FailedCallback           onFailed)
{
  shared_ptr<Name> searchRes = findManifestSegmentToDownload(manifestName);
  auto packetNames = make_shared<std::vector<Name>>();
  if (searchRes == nullptr) {
    this->findDataPacketsToDownload(manifestName, *packetNames);
    onSuccess(*packetNames);
    return;
  }
  this->downloadFileManifestSegment(*searchRes, path, packetNames, onSuccess, onFailed);
}

void
TorrentManager::downloadFileManifestSegment(const Name& manifestName,
                                            const std::string& path,
                                            std::shared_ptr<std::vector<Name>> packetNames,
                                            TorrentManager::ManifestReceivedCallback onSuccess,
                                            TorrentManager::FailedCallback onFailed)
{
  shared_ptr<Interest> interest = this->createInterest(manifestName);

  auto dataReceived = [packetNames, path, onSuccess, onFailed, this]
                                          (const Interest& interest, const Data& data) {
    // Stats Table update here...
    m_stats_table_iter->incrementReceivedData();
    m_retries = 0;

    FileManifest file(data.wireEncode());

    // Write the file manifest segment to disk...
    writeFileManifest(file, path);

    const std::vector<Name>& packetsCatalog = file.catalog();
    packetNames->insert(packetNames->end(), packetsCatalog.begin(), packetsCatalog.end());
    shared_ptr<Name> nextSegmentPtr = file.submanifest_ptr();
    if (nextSegmentPtr != nullptr) {
      this->downloadFileManifestSegment(*nextSegmentPtr, path, packetNames, onSuccess, onFailed);
    }
    else
      onSuccess(*packetNames);
  };

  auto dataFailed = [packetNames, path, manifestName, onFailed, this]
                                                (const Interest& interest) {
    m_retries++;
    if (m_retries >= MAX_NUM_OF_RETRIES) {
      m_stats_table_iter++;
      if (m_stats_table_iter == m_statsTable.end())
        m_stats_table_iter = m_statsTable.begin();
    }
    onFailed(interest.getName(), "Unknown failure");
  };

  m_face.expressInterest(*interest, dataReceived, dataFailed);
}

void
TorrentManager::download_data_packet(const Name& packetName,
                                     DataReceivedCallback onSuccess,
                                     FailedCallback onFailed)
{
  if (this->dataAlreadyDownloaded(packetName)) {
    onSuccess(packetName);
    return;
  }

  shared_ptr<Interest> interest = this->createInterest(packetName);

  auto dataReceived = [onSuccess, onFailed, this]
                                          (const Interest& interest, const Data& data) {
    // Write data to disk...
    writeData(data);

    // Stats Table update here...
    m_stats_table_iter->incrementReceivedData();
    m_retries = 0;
    onSuccess(data.getName());
  };
  auto dataFailed = [onFailed, this]
                             (const Interest& interest) {
    m_retries++;
    if (m_retries >= MAX_NUM_OF_RETRIES) {
      m_stats_table_iter++;
      if (m_stats_table_iter == m_statsTable.end())
        m_stats_table_iter = m_statsTable.begin();
    }
    onFailed(interest.getName(), "Unknown failure");
  };

  m_face.expressInterest(*interest, dataReceived, dataFailed);
}

shared_ptr<Interest>
TorrentManager::createInterest(Name name)
{
  shared_ptr<Interest> interest = make_shared<Interest>(name);
  interest->setInterestLifetime(time::milliseconds(2000));
  interest->setMustBeFresh(true);

  // Select routable prefix
  Link link(name, { {1, m_stats_table_iter->getRecordName()} });
  m_keyChain->sign(link, signingWithSha256());
  Block linkWire = link.wireEncode();

  // Stats Table update here...
  m_stats_table_iter->incrementSentInterests();

  m_sortingCounter++;
  if (m_sortingCounter >= SORTING_INTERVAL) {
    m_sortingCounter = 0;
    m_statsTable.sort();
    m_stats_table_iter = m_statsTable.begin();
    m_retries = 0;
  }

  interest->setLink(linkWire);

  return interest;
}

shared_ptr<Name>
TorrentManager::findTorrentFileSegmentToDownload()
{
  // if we have no segments
  if (m_torrentSegments.empty()) {
    return make_shared<Name>(m_torrentFileName);
  }
  // otherwise just return the next segment ptr of the last segment we have
  return m_torrentSegments.back().getTorrentFilePtr();
}

shared_ptr<Name>
TorrentManager::findManifestSegmentToDownload(const Name& manifestName)
{
  //sequentially find whether we have downloaded any segments of this manifest file
  Name manifestPrefix = manifestName.getSubName(0, manifestName.size() - 2);
  auto it = std::find_if(m_fileManifests.rbegin(), m_fileManifests.rend(),
                      [&manifestPrefix] (const FileManifest& f) {
                        return manifestPrefix.isPrefixOf(f.getName());
                      });

  // if we do not have any segments of the file manifest
  if (it == m_fileManifests.rend()) {
    return make_shared<Name>(manifestName);
  }

  // if we already have the requested segment of the file manifest
  if (it->submanifest_number() >= manifestName.get(manifestName.size() - 2).toSequenceNumber()) {
    return it->submanifest_ptr();
  }
  // if we do not have the requested segment
  else {
    return make_shared<Name>(manifestName);
  }
}

bool
TorrentManager::dataAlreadyDownloaded(const Name& dataName)
{

  auto manifest_it = std::find_if(m_fileManifests.begin(), m_fileManifests.end(),
                                 [&dataName](const FileManifest& m) {
                                   return m.getName().isPrefixOf(dataName);
                                 });

  // if we do not have the file manifest, just return false
  if (manifest_it == m_fileManifests.end()) {
    return false;
  }

  // find the pair of (std::shared_ptr<fs::fstream>, std::vector<bool>)
  // that corresponds to the specific submanifest
  auto& fileState = m_fileStates[manifest_it->getFullName()];

  auto dataNum = dataName.get(dataName.size() - 2).toSequenceNumber();

  // find whether we have the requested packet from the bitmap
  return fileState.second[dataNum];
}

void
TorrentManager::findFileManifestsToDownload(std::vector<Name>& manifestNames)
{
  std::vector<Name> manifests;
  // insert the first segment name of all the file manifests to the vector
  for (auto i = m_torrentSegments.begin(); i != m_torrentSegments.end(); i++) {
    manifests.insert(manifests.end(), i->getCatalog().begin(), i->getCatalog().end());
  }
  // for each file
  for (const auto& manifestName : manifests) {
    // find the first (if any) segment we are missing
    shared_ptr<Name> manifestSegmentName = findManifestSegmentToDownload(manifestName);
    if (nullptr != manifestSegmentName) {
      manifestNames.push_back(*manifestSegmentName);
    }
  }
}

void
TorrentManager::findDataPacketsToDownload(const Name& manifestName, std::vector<Name>& packetNames)
{
  auto manifest_it = std::find_if(m_fileManifests.begin(), m_fileManifests.end(),
                                 [&manifestName](const FileManifest& m) {
                                   return m.name().getSubName(0, m.name().size()
                                                              - 1).isPrefixOf(manifestName);
                                 });

  for (auto j = manifest_it; j != m_fileManifests.end(); j++) {
    auto& fileState = m_fileStates[j->getFullName()];
    for (size_t dataNum = 0; dataNum < j->catalog().size(); ++dataNum) {
      if (!fileState.second[dataNum]) {
        packetNames.push_back(j->catalog()[dataNum]);
      }
    }

    // check that the next manifest in the vector refers to the next segment of the same file
    if ((j + 1) != m_fileManifests.end() && (j+1)->file_name() != manifest_it->file_name()) {
      break;
    }
  }
}

void
TorrentManager::findAllMissingDataPackets(std::vector<Name>& packetNames)
{
  for (auto j = m_fileManifests.begin(); j != m_fileManifests.end(); j++) {
    auto& fileState = m_fileStates[j->getFullName()];
    for (auto i = j->catalog().begin(); i != j->catalog().end(); i++) {
      auto dataNum = i->get(i->size() - 2).toSequenceNumber();
      if (!fileState.second[dataNum]) {
        packetNames.push_back(*i);
      }
    }
  }
}

}  // end ntorrent
}  // end ndn