//    OpenVPN -- An application to securely tunnel IP networks
//               over a single port, with support for SSL/TLS-based
//               session authentication and key exchange,
//               packet encryption, packet authentication, and
//               packet compression.
//
//    Copyright (C) 2012-2020 OpenVPN Inc.
//
//    This program is free software: you can redistribute it and/or modify
//    it under the terms of the GNU Affero General Public License Version 3
//    as published by the Free Software Foundation.
//
//    This program 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 Affero General Public License for more details.
//
//    You should have received a copy of the GNU Affero General Public License
//    along with this program in the COPYING file.
//    If not, see <http://www.gnu.org/licenses/>.

#pragma once

#include <algorithm>

#include <openvpn/random/randapi.hpp>
#include <openvpn/addr/ip.hpp>

namespace openvpn {
  namespace WS {

    // These methods become no-ops unless building with a patched Asio and C++14 or higher.
    // Define ASIO_RESOLVER_RESULTS_DATA_REQUIRED to force an error if these methods
    // cannot be compiled.

#if defined(HAVE_ASIO_RESOLVER_RESULTS_DATA) && __cplusplus >= 201402L

    template <typename RESULTS>
    inline void randomize_results(RESULTS& results, RandomAPI& prng)
    {
      auto* data = results.data();
      if (!data)
	return;
      std::shuffle(data->begin(), data->end(), prng);
    }

    template <typename RESULTS>
    inline void filter_by_ip_version(RESULTS& results, const IP::Addr::Version ip_ver)
    {
      auto* data = results.data();
      if (!data)
	return;

      bool v4;
      switch (ip_ver)
	{
	case IP::Addr::V4:
	  v4 = true;
	  break;
	case IP::Addr::V6:
	  v4 = false;
	  break;
	default:
	  return;
	}

      // the "auto" lambda parameter makes this C++14 code
      data->erase(std::remove_if(data->begin(), data->end(),
				 [v4](auto& e)
				 {
				   return e.endpoint().address().is_v4() != v4;
				 }),
		  data->end());
    }

#elif defined(ASIO_RESOLVER_RESULTS_DATA_REQUIRED)
#error ASIO_RESOLVER_RESULTS_DATA_REQUIRED is defined but Asio results data are not available or compiler is pre-C++14
#else

    template <typename RESULTS>
    inline void randomize_results(RESULTS& results, RandomAPI& prng)
    {
    }

    template <typename RESULTS>
    inline void filter_by_ip_version(RESULTS& results, const IP::Addr::Version ip_ver)
    {
    }

#endif

  }
}