//    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/>.

#ifndef OPENVPN_TUN_PERSIST_TUNPERSIST_H
#define OPENVPN_TUN_PERSIST_TUNPERSIST_H

#include <openvpn/common/size.hpp>
#include <openvpn/tun/persist/tunwrap.hpp>
#include <openvpn/tun/client/tunprop.hpp>
#include <openvpn/tun/builder/capture.hpp>

namespace openvpn {

  // TunPersistTemplate adds persistence capabilities onto TunWrapTemplate,
  // in order to implement logic for the persist-tun directive.
  template <typename SCOPED_OBJ, typename STATE=TunProp::State::Ptr>
  class TunPersistTemplate : public TunWrapTemplate<SCOPED_OBJ>
  {
  public:
    typedef RCPtr<TunPersistTemplate> Ptr;

    TunPersistTemplate(const bool enable_persistence, const bool retain_obj, TunBuilderBase* tb)
      : TunWrapTemplate<SCOPED_OBJ>(retain_obj),
	enable_persistence_(enable_persistence),
	tb_(tb),
	use_persisted_tun_(false),
	disconnect(false)
    {
    }

    // Current persisted state
    const STATE& state() const
    {
      return state_;
    }

    virtual ~TunPersistTemplate()
    {
      close_local();
    }

    void invalidate()
    {
      options_.clear();
    }

    void close()
    {
      close_local();
      TunWrapTemplate<SCOPED_OBJ>::close();
    }

    void set_disconnect()
    {
      disconnect = true;
    }

    // Current persisted options
    const std::string& options()
    {
      return options_;
    }

    // Return true if we should use previously persisted
    // tun socket descriptor/handle
    bool use_persisted_tun(const IP::Addr server_addr,
			   const TunProp::Config& tun_prop,
			   const OptionList& opt)
    {
#if OPENVPN_DEBUG_TUN_BUILDER > 0
      {
	TunBuilderCapture::Ptr capture = new TunBuilderCapture();
	try {
	  TunProp::configure_builder(capture.get(), nullptr, nullptr, server_addr, tun_prop, opt, nullptr, true);
	  OPENVPN_LOG("*** TUN BUILDER CAPTURE" << std::endl << capture->to_string());
	}
	catch (const std::exception& e)
	  {
	    OPENVPN_LOG("*** TUN BUILDER CAPTURE exception: " << e.what());
	  }
      }
#endif

      // In tun_persist mode, capture tun builder settings so we can
      // compare them to previous persisted settings.
      if (enable_persistence_)
	{
	  copt_.reset(new TunBuilderCapture());
	  try {
	    TunProp::configure_builder(copt_.get(), nullptr, nullptr, server_addr, tun_prop, opt, nullptr, true);
	  }
	  catch (const std::exception&)
	    {
	      copt_.reset();
	    }
	}

      // Check if previous tun session matches properties of to-be-created session
      use_persisted_tun_ = (TunWrapTemplate<SCOPED_OBJ>::obj_defined()
			    && copt_
			    && !options_.empty()
			    && options_ == copt_->to_string()
			    && (tb_ ? tb_->tun_builder_persist() : true));
      return use_persisted_tun_;
    }

    // Possibly save tunnel fd/handle, state, and options.
    bool persist_tun_state(const typename SCOPED_OBJ::base_type obj,
			   const STATE& state)
    {
      if (!enable_persistence_ || !use_persisted_tun_)
	{
	  TunWrapTemplate<SCOPED_OBJ>::save_replace_sock(obj);
	}
      if (enable_persistence_ && copt_ && !use_persisted_tun_)
	{
	  state_ = state;
	  options_ = copt_->to_string();
	  return true;
	}
      else
	return false;
    }

  private:
    void close_local()
    {
      if (tb_)
	tb_->tun_builder_teardown(disconnect);
      state_.reset();
      options_ = "";
    }

    const bool enable_persistence_;
    TunBuilderBase * const tb_;
    STATE state_;
    std::string options_;

    TunBuilderCapture::Ptr copt_;
    bool use_persisted_tun_;

    bool disconnect;
  };

}
#endif