/*

Copyright (c) 2015-2016, Steven Siloti

Copyright (c) 2016, Alden Torres

Copyright (c) 2016, 2018-2019, Arvid Norberg

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/kademlia/msg.hpp"

#include "libtorrent/bdecode.hpp"

#include "libtorrent/entry.hpp"

namespace libtorrent { namespace dht {

bool verify_message_impl(bdecode_node const& message, span<key_desc_t const> desc

  , span<bdecode_node> ret, span<char> error)

{

  TORRENT_ASSERT(desc.size() == ret.size());

  auto const size = ret.size();

  // get a non-root bdecode_node that still

  // points to the root. message should not be copied

  bdecode_node msg = message.non_owning();

  // clear the return buffer

  for (int i = 0; i < size; ++i)

    ret[i].clear();

  // when parsing child nodes, this is the stack

  // of bdecode_nodes to return to

  bdecode_node stack[5];

  int stack_ptr = -1;

  if (msg.type() != bdecode_node::dict_t)

  {

    std::snprintf(error.data(), static_cast<std::size_t>(error.size()), "not a dictionary");

    return false;

  }

  ++stack_ptr;

  stack[stack_ptr] = msg;

  for (int i = 0; i < size; ++i)

  {

    key_desc_t const& k = desc[i];

    //    std::fprintf(stderr, "looking for %s in %s\n", k.name, print_entry(*msg).c_str());

    ret[i] = msg.dict_find(k.name);

    // none_t means any type

    if (ret[i] && ret[i].type() != k.type && k.type != bdecode_node::none_t)

      ret[i].clear();

    if (!ret[i] && (k.flags & key_desc_t::optional) == 0)

    {

      // the key was not found, and it's not an optional key

      std::snprintf(error.data(), static_cast<std::size_t>(error.size()), "missing '%s' key", k.name);

      return false;

    }

    if (k.size > 0

      && ret[i]

      && k.type == bdecode_node::string_t)

    {

      bool const invalid = (k.flags & key_desc_t::size_divisible)

        ? (ret[i].string_length() % k.size) != 0

        : ret[i].string_length() != k.size;

      if (invalid)

      {

        // the string was not of the required size

        ret[i].clear();

        if ((k.flags & key_desc_t::optional) == 0)

        {

          std::snprintf(error.data(), static_cast<std::size_t>(error.size())

            , "invalid value for '%s'", k.name);

          return false;

        }

      }

    }

    if (k.flags & key_desc_t::parse_children)

    {

      TORRENT_ASSERT(k.type == bdecode_node::dict_t);

      if (ret[i])

      {

        ++stack_ptr;

        TORRENT_ASSERT(stack_ptr < int(sizeof(stack) / sizeof(stack[0])));

        msg = ret[i];

        stack[stack_ptr] = msg;

      }

      else

      {

        // skip all children

        while (i < size && (desc[i].flags & key_desc_t::last_child) == 0) ++i;

        // if this assert is hit, desc is incorrect

        TORRENT_ASSERT(i < size);

      }

    }

    else if (k.flags & key_desc_t::last_child)

    {

      TORRENT_ASSERT(stack_ptr > 0);

      // this can happen if the specification passed

      // in is unbalanced. i.e. contain more last_child

      // nodes than parse_children

      if (stack_ptr == 0) return false;

      --stack_ptr;

      msg = stack[stack_ptr];

    }

  }

  return true;

}

} }