//    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_ADDR_RANGE_H
#define OPENVPN_ADDR_RANGE_H

#include <string>
#include <sstream>

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

#include <openvpn/addr/ip.hpp>

namespace openvpn {
  namespace IP {

    // Denote a range of IP addresses with a start and extent,
    // where A represents an address class.
    // A should be a network address class such as IP::Addr, IPv4::Addr, or IPv6::Addr.

    template <typename ADDR>
    class RangeType
    {
    public:
      class Iterator
      {
	friend class RangeType;
      public:
	bool more() const { return remaining_ > 0; }

	const ADDR& addr() const { return addr_; }

	void next()
	{
	  if (more())
	    {
	      ++addr_;
	      --remaining_;
	    }
	}

      private:
	Iterator(const RangeType& range)
	  : addr_(range.start_), remaining_(range.extent_) {}

	ADDR addr_;
	size_t remaining_;
      };

      RangeType() : extent_(0) {}

      RangeType(const ADDR& start, const size_t extent)
	: start_(start), extent_(extent) {}

      Iterator iterator() const { return Iterator(*this); }

      const bool defined() const { return extent_ > 0; }
      const ADDR& start() const { return start_; }
      size_t extent() const { return extent_; }

      RangeType pull_front(size_t extent)
      {
	if (extent > extent_)
	  extent = extent_;
	RangeType ret(start_, extent);
	start_ += extent;
	extent_ -= extent;
	return ret;
      }

      std::string to_string() const
      {
	std::ostringstream os;
	os << start_.to_string() << '[' << extent_ << ']';
	return os.str();
      }

    private:
      ADDR start_;
      size_t extent_;
    };

    template <typename ADDR>
    class RangePartitionType
    {
    public:
      RangePartitionType(const RangeType<ADDR>& src_range, const size_t n_partitions)
	: range(src_range),
	  remaining(n_partitions)
      {
      }

      bool next(RangeType<ADDR>& r)
      {
	if (remaining)
	  {
	    if (remaining > 1)
	      r = range.pull_front(range.extent() / remaining);
	    else
	      r = range;
	    --remaining;
	    return r.defined();
	  }
	else
	  return false;
      }

    private:
      RangeType<ADDR> range;
      size_t remaining;
    };

    typedef RangeType<IP::Addr> Range;
    typedef RangePartitionType<IP::Addr> RangePartition;
  }
}

#endif