/*

Copyright (c) 2015-2019, 2022, Arvid Norberg

Copyright (c) 2016-2017, Alden Torres

All rights reserved.

Redistribution and use in source and binary forms, with or without

modification, are permitted provided that the following conditions

are met:

    * Redistributions of source code must retain the above copyright

      notice, this list of conditions and the following disclaimer.

    * Redistributions in binary form must reproduce the above copyright

      notice, this list of conditions and the following disclaimer in

      the documentation and/or other materials provided with the distribution.

    * Neither the name of the author nor the names of its

      contributors may be used to endorse or promote products derived

      from this software without specific prior written permission.

THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"

AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE

IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE

ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE

LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR

CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF

SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS

INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN

CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)

ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE

POSSIBILITY OF SUCH DAMAGE.

*/

#include "libtorrent/resolve_links.hpp"

#include "libtorrent/torrent_info.hpp"

#include "libtorrent/aux_/numeric_cast.hpp"

namespace libtorrent {

#ifndef TORRENT_DISABLE_MUTABLE_TORRENTS

resolve_links::resolve_links(std::shared_ptr<torrent_info> ti)

  : m_torrent_file(std::move(ti))

{

  TORRENT_ASSERT(m_torrent_file);

  int const piece_size = m_torrent_file->piece_length();

  bool const v1 = m_torrent_file->v1();

  bool const v2 = m_torrent_file->v2();

  file_storage const& fs = m_torrent_file->files();

  m_file_sizes.reserve(aux::numeric_cast<std::size_t>(fs.num_files()));

  for (auto const i : fs.file_range())

  {

    // don't match pad-files, and don't match files that aren't aligned to

    // pieces. Files are matched by comparing piece hashes, so pieces must

    // be aligned and the same size

    if (fs.pad_file_at(i)) continue;

    if ((fs.file_offset(i) % piece_size) != 0) continue;

    if (v1)

      m_file_sizes.insert({fs.file_size(i), i});

    if (v2)

      m_file_roots.insert({fs.root(i), i});

  }

  m_links.resize(m_torrent_file->num_files());

}

void resolve_links::match(std::shared_ptr<const torrent_info> const& ti

  , std::string const& save_path)

{

  if (!ti) return;

  if (m_torrent_file->v2() && ti->v2())

  {

    match_v2(ti, save_path);

  }

  if (m_torrent_file->v1() && ti->v1())

  {

    match_v1(ti, save_path);

  }

}

void resolve_links::match_v1(std::shared_ptr<const torrent_info> const& ti

  , std::string const& save_path)

{

  // only torrents with the same piece size

  if (ti->piece_length() != m_torrent_file->piece_length()) return;

  int const piece_size = ti->piece_length();

  file_storage const& fs = ti->files();

  for (auto const i : fs.file_range())

  {

    // for every file in the other torrent, see if we have one that match

    // it in m_torrent_file

    // if the file base is not aligned to pieces, we're not going to match

    // it anyway (we only compare piece hashes)

    if ((fs.file_offset(i) % piece_size) != 0) continue;

    if (fs.pad_file_at(i)) continue;

    std::int64_t const file_size = fs.file_size(i);

    auto const range = m_file_sizes.equal_range(file_size);

    for (auto iter = range.first; iter != range.second; ++iter)

    {

      auto const idx = iter->second;

      TORRENT_ASSERT(idx >= file_index_t(0));

      TORRENT_ASSERT(idx < m_torrent_file->files().end_file());

      // if we already have found a duplicate for this file, no need

      // to keep looking

      if (m_links[idx].ti) continue;

      // files are aligned and have the same size, now start comparing

      // piece hashes, to see if the files are identical

      // the pieces of the incoming file

      piece_index_t their_piece = fs.map_file(i, 0, 0).piece;

      // the pieces of "this" file (from m_torrent_file)

      piece_index_t our_piece = m_torrent_file->files().map_file(

        idx, 0, 0).piece;

      int const num_pieces = int((file_size + piece_size - 1) / piece_size);

      bool match = true;

      for (int p = 0; p < num_pieces; ++p, ++their_piece, ++our_piece)

      {

        if (m_torrent_file->hash_for_piece(our_piece)

          != ti->hash_for_piece(their_piece))

        {

          match = false;

          break;

        }

      }

      if (!match) continue;

      m_links[idx].ti = ti;

      m_links[idx].save_path = save_path;

      m_links[idx].file_idx = i;

      // since we have a duplicate for this file, we may as well remove

      // it from the file-size map, so we won't find it again.

      m_file_sizes.erase(iter);

      break;

    }

  }

}

void resolve_links::match_v2(std::shared_ptr<const torrent_info> const& ti

  , std::string const& save_path)

{

  file_storage const& fs = ti->files();

  for (auto const i : fs.file_range())

  {

    // for every file in the other torrent, see if we have one that match

    // it in m_torrent_file

    if (fs.pad_file_at(i)) continue;

    auto const iter = m_file_roots.find(fs.root(i));

    if (iter == m_file_roots.end()) continue;

    auto const idx = iter->second;

    TORRENT_ASSERT(idx >= file_index_t(0));

    TORRENT_ASSERT(idx < m_torrent_file->files().end_file());

    // if we already have found a duplicate for this file, no need

    // to keep looking

    if (m_links[idx].ti) continue;

    m_links[idx].ti = ti;

    m_links[idx].save_path = save_path;

    m_links[idx].file_idx = i;

    // since we have a duplicate for this file, we may as well remove

    // it from the file-size map, so we won't find it again.

    m_file_roots.erase(iter);

  }

}

#endif // TORRENT_DISABLE_MUTABLE_TORRENTS

} // namespace libtorrent