//    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/>.

// Client-side code to handle pushed option list "continuations".
// This is where multiple option lists are pushed by the server,
// if an option list doesn't fit into the standard 1024 byte buffer.
// This class will aggregate the options.

#pragma once

#include <openvpn/common/exception.hpp>
#include <openvpn/common/options.hpp>

namespace openvpn {

  struct PushOptionsBase : public RC<thread_unsafe_refcount>
  {
    typedef RCPtr<PushOptionsBase> Ptr;

    OptionList multi;
    OptionList singleton;
  };

  // Aggregate pushed option continuations into a singular option list.
  // Note that map is not updated until list is complete.
  class OptionListContinuation : public OptionList
  {
  public:
    OPENVPN_SIMPLE_EXCEPTION(olc_complete); // add called when object is already complete

    OptionListContinuation(const PushOptionsBase::Ptr& push_base_arg)
      : push_base(push_base_arg)
    {
      // Prepend from base where multiple options of the same type can aggregate,
      // so that server-pushed options will be at the end of list.
      if (push_base)
	extend(push_base->multi, nullptr);
    }

    OptionListContinuation()
    {
    }

    // call with option list fragments
    void add(const OptionList& other, OptionList::FilterBase* filt)
    {
      if (!complete_)
	{
	  partial_ = true;
	  extend(other, filt);
	  if (!continuation(other))
	    {
	      if (push_base)
		{
		  // Append from base where only a single instance of each option makes sense,
		  // provided that option wasn't already pushed by server.
		  update_map();
		  extend_nonexistent(push_base->singleton);
		}
	      update_map();
	      complete_ = true;
	    }
	}
      else
	throw olc_complete();
    }

    // returns true if add() was called at least once
    bool partial() const { return partial_; }

    // returns true if option list is complete
    bool complete() const { return complete_; }

  private:
    static bool continuation(const OptionList& opt)
    {
      const Option *o = opt.get_ptr("push-continuation");
      return o && o->size() >= 2 && o->ref(1) == "2";
    }

    bool partial_ = false;
    bool complete_ = false;

    PushOptionsBase::Ptr push_base;
  };

}