//    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_BUFFER_SAFESTR_H
#define OPENVPN_BUFFER_SAFESTR_H

#include <cstring> // for std::strlen, and std::memset
#include <ostream>

#include <openvpn/common/memneq.hpp>
#include <openvpn/buffer/buffer.hpp>
#include <openvpn/buffer/bufstr.hpp>

namespace openvpn {
  class SafeString
  {
    static constexpr size_t INITIAL_CAPACITY = 32;
    static constexpr unsigned int BUF_FLAGS = BufferAllocated::DESTRUCT_ZERO|BufferAllocated::GROW;

  public:
    SafeString()
    {
    }

    SafeString(const char *str, const size_t size)
      : data(size+1, BUF_FLAGS)
    {
      data.write((unsigned char *)str, size);
      trail();
    }

    SafeString(const char *str)
      : SafeString(str, std::strlen(str))
    {
    }

    SafeString(const std::string& str)
      : SafeString(str.c_str(), str.length())
    {
    }

    const char *c_str() const
    {
      if (data.defined())
	return (const char *)data.c_data();
      else
	return "";
    }

    // Note: unsafe because of conversion to std::string
    std::string to_string() const
    {
      return buf_to_string(data);
    }

    size_t length() const
    {
      return data.size();
    }

    bool empty() const
    {
      return !length();
    }

    char& operator[](size_t pos)
    {
      return *reinterpret_cast<char *>(data.index(pos));
    }

    const char& operator[](size_t pos) const
    {
      return *reinterpret_cast<const char *>(data.c_index(pos));
    }

    bool operator==(const char *str) const
    {
      const size_t len = std::strlen(str);
      if (len != length())
	return false;
      return !crypto::memneq(str, c_str(), len);
    }

    bool operator!=(const char *str) const
    {
      return !operator==(str);
    }

    SafeString& operator+=(char c)
    {
      alloc();
      data.push_back((unsigned char)c);
      trail();
      return *this;
    }

    SafeString& operator+=(const char* s)
    {
      return append(s);
    }

    SafeString& operator+=(const SafeString& str)
    {
      return append(str);
    }

    SafeString& append(const char* s)
    {
      alloc();
      data.write((unsigned char *)s, std::strlen(s));
      trail();
      return *this;
    }

    SafeString& append(const SafeString& str)
    {
      alloc();
      data.append(str.data);
      trail();
      return *this;
    }

    SafeString& append(const SafeString& str, size_t subpos, size_t sublen)
    {
      alloc();
      data.append(str.data.range(subpos, sublen));
      trail();
      return *this;
    }

    void reserve(const size_t n)
    {
      if (data.allocated())
	data.reserve(n+1);
      else
	data.init(n+1, BUF_FLAGS);
    }

    void wipe()
    {
      data.clear();
    }

  private:
    void alloc()
    {
      if (!data.allocated())
	data.init(INITIAL_CAPACITY, BUF_FLAGS);
    }

    void trail()
    {
      data.set_trailer(0);
    }

    BufferAllocated data;
  };

  template <typename Elem, typename Traits>
  std::basic_ostream<Elem, Traits>& operator<<(
    std::basic_ostream<Elem, Traits>& os, const SafeString& ss)
  {
    os << ss.c_str();
    return os;
  }
}

#endif