#ifndef NULLABLE_INCLUDED
#define NULLABLE_INCLUDED

/*
   Copyright (c) 2014, 2017, Oracle and/or its affiliates. All rights reserved.

   This program is free software; you can redistribute it and/or modify
   it under the terms of the GNU General Public License, version 2.0,
   as published by the Free Software Foundation.

   This program is also distributed with certain software (including
   but not limited to OpenSSL) that is licensed under separate terms,
   as designated in a particular file or component or in included license
   documentation.  The authors of MySQL hereby grant you an additional
   permission to link the program and your derivative works with the
   separately licensed software that they have included with MySQL.

   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 General Public License, version 2.0, for more details.

   You should have received a copy of the GNU General Public License
   along with this program; if not, write to the Free Software
   Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301  USA
*/

/**
  @file include/nullable.h
*/

#include "my_dbug.h"

namespace Mysql {

/**
  Class for storing value or NULL value.
*/
template <typename T_value>
class Nullable {
 public:
  Nullable() : m_has_value(false) {}

  Nullable(T_value value) : m_has_value(true), m_value(value) {}

  Nullable(const Nullable<T_value> &other)
      : m_has_value(other.m_has_value), m_value(other.m_value) {}

  /**
    Assigns value from another Nullable<> object.
  */
  Nullable<T_value> &operator=(const Nullable<T_value> &other) {
    this->m_has_value = other.m_has_value;
    if (this->m_has_value) {
      this->m_value = other.m_value;
    }
    return *this;
  }

  /**
    Compares two Nullable<> objects for equality.
  */
  bool operator==(const Nullable<T_value> &other) const {
    if (this->has_value() != other.has_value())
      return false;
    else if (this->has_value() && this->value() != other.value())
      return false;
    return true;
  }

  /**
    Compares two Nullable<> objects for in-equality.
  */
  bool operator!=(const Nullable<T_value> &other) const {
    return !(*this == other);
  }

  /**
    Returns true if object has not-NULL value assigned. If this is false, one
    should not try to get value by value().
  */
  bool has_value() const { return this->m_has_value; }

  /**
    Returns actual value of object. Do not call this method if has_value()
    returns false.
  */
  const T_value &value() const {
    DBUG_ASSERT(this->m_has_value);
    return this->m_value;
  }

 private:
  /**
    Specifies if this object represents NULL value. If this is false, one
    should not try to get value by value().
  */
  bool m_has_value;
  /**
    Actual value, if m_has_value is true. Undefined if m_has_value is false.
  */
  T_value m_value{};
};

}  // namespace Mysql

#endif  // NULLABLE_INCLUDED