//    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_ADDRPAIR_H
#define OPENVPN_ADDR_ADDRPAIR_H

#include <sstream>

#include <openvpn/common/exception.hpp>
#include <openvpn/common/number.hpp>
#include <openvpn/common/split.hpp>
#include <openvpn/addr/ip.hpp>

namespace openvpn {
  namespace IP {

    // AddrMaskPair is basically an object that combines an IP address (v4 or v6)
    // with a netmask or prefix length.
    struct AddrMaskPair
    {
    public:
      OPENVPN_EXCEPTION(addr_pair_mask_parse_error);

      class StringPair {
      public:
	OPENVPN_SIMPLE_EXCEPTION(addr_pair_string_error);

	StringPair()
	  : size_(0)
	{
	}

	explicit StringPair(const std::string& s1)
	  : size_(1)
	{
	  data[0] = s1;
	}

	explicit StringPair(const std::string& s1, const std::string& s2)
	  : size_(2)
	{
	  data[0] = s1;
	  data[1] = s2;
	}

	void push_back(const std::string& s)
	{
	  if (size_ < 2)
	    data[size_++] = s;
	  else
	    throw addr_pair_string_error();
	}

	const std::string& operator[](const size_t i) const
	{
	  if (i >= 2)
	    throw addr_pair_string_error();
	  return data[i];
	}

	std::string& operator[](const size_t i)
	{
	  if (i >= 2)
	    throw addr_pair_string_error();
	  return data[i];
	}

	size_t size() const { return size_; }

	std::string render() const
	{
	  switch (size_)
	    {
	    case 1:
	      return data[0];
	    case 2:
	      return data[0] + "/" + data[1];
	    default:
	      return "";
	    }
	}

      private:
	std::string data[2];
	unsigned int size_;
      };

      static AddrMaskPair from_string(const std::string& s1, const std::string& s2, const char *title = nullptr)
      {
	try {
	  if (s2.empty())
	    {
	      const StringPair pair = Split::by_char<StringPair, NullLex, Split::NullLimit>(s1, '/');
	      return from_string_impl(pair, title);
	    }
	  else
	    {
	      const StringPair pair(s1, s2);
	      return from_string_impl(pair, title);
	    }
	}
	catch (const std::exception& e)
	  {
	    const StringPair pair(s1, s2);
	    error(e, pair.render(), title);
	  }
	return AddrMaskPair(); // NOTREACHED
      }

      static AddrMaskPair from_string(const std::string& s, const char *title = nullptr)
      {
	try {
	  const StringPair pair = Split::by_char<StringPair, NullLex, Split::NullLimit>(s, '/');
	  return from_string_impl(pair, title);
	}
	catch (const std::exception& e)
	  {
	    error(e, s, title);
	  }
	return AddrMaskPair(); // NOTREACHED
      }

      static AddrMaskPair from_string(const StringPair& pair, const char *title = nullptr)
      {
	try {
	  return from_string_impl(pair, title);
	}
	catch (const std::exception& e)
	  {
	    error(e, pair.render(), title);
	  }
	return AddrMaskPair(); // NOTREACHED
      }

      std::string to_string(const bool netmask_form=false) const
      {
	std::ostringstream os;
	if (netmask_form)
	  os << addr.to_string() << '/' << netmask.to_string();
	else
	  os << addr.to_string() << '/' << netmask.prefix_len();
	return os.str();
      }

      bool is_canonical() const
      {
	return (addr & netmask) == addr;
      }

      Addr::Version version() const
      {
	const Addr::Version v1 = addr.version();
	const Addr::Version v2 = netmask.version();
	if (v1 == v2)
	  return v1;
	else
	  return Addr::UNSPEC;
      }

      Addr addr;
      Addr netmask;

    private:
      static void error(const std::exception& e, const std::string& s, const char *title)
      {
	if (!title)
	  title = "";
	OPENVPN_THROW(addr_pair_mask_parse_error, "AddrMaskPair parse error '" << title << "': " << s << " : " << e.what());
      }

      static AddrMaskPair from_string_impl(const StringPair& pair, const char *title = nullptr)
      {
	AddrMaskPair ret;
	if (pair.size() == 1 || pair.size() == 2)
	  {
	    ret.addr = Addr::from_string(pair[0], title);
	    if (pair.size() == 2 && !pair[1].empty())
	      {
		if (is_number(pair[1].c_str()))
		  ret.netmask = Addr::netmask_from_prefix_len(ret.addr.version(),
							      parse_number_throw<unsigned int>(pair[1], "prefix length"));
		else
		  ret.netmask = Addr::from_string(pair[1]);
		ret.netmask.prefix_len(); // verify that netmask is ok
	      }
	    else
	      ret.netmask = Addr::from_zero_complement(ret.addr.version());
	    ret.addr.verify_version_consistency(ret.netmask);
	  }
	else
	  throw addr_pair_mask_parse_error("only one or two address terms allowed");
	return ret;
      }

    };
    OPENVPN_OSTREAM(AddrMaskPair, to_string)
  }
}

#endif