// file      : odb/nullable.hxx
// author    : Boris Kolpackov <boris@codesynthesis.com>
// copyright : Copyright (c) 2009-2011 Code Synthesis Tools CC
// license   : GNU GPL v2; see accompanying LICENSE file

#ifndef ODB_NULLABLE_HXX
#define ODB_NULLABLE_HXX

#include <odb/pre.hxx>

namespace odb
{
  template <typename T>
  class nullable
  {
  public:
    typedef T value_type;

    nullable ();
    nullable (const T&);
    nullable (const nullable&);
    template <typename Y> explicit nullable (const nullable<Y>&);

    nullable& operator= (const T&);
    nullable& operator= (const nullable&);
    template <typename Y> nullable& operator= (const nullable<Y>&);

    void swap (nullable&);

    bool null () const;

    T&       get ();
    const T& get () const;

    T*       operator-> ();
    const T* operator-> () const;

    T&       operator* ();
    const T& operator* () const;

    typedef void (nullable::*bool_convertible) ();
    operator bool_convertible () const
    {
      return null_ ? 0 : &nullable<T>::true_value;
    }

    void reset ();

  private:
    void true_value () {};

    T value_;
    bool null_;
  };

  namespace core
  {
    using odb::nullable;
  }

  template <typename T>
  inline nullable<T>::
  nullable ()
      : null_ (true)
  {
  }

  template <typename T>
  inline nullable<T>::
  nullable (const T& v)
      : value_ (v), null_ (false)
  {
  }

  template <typename T>
  inline nullable<T>::
  nullable (const nullable& y)
      : value_ (y.value_), null_ (y.null_)
  {
  }

  template <typename T>
  template <typename Y>
  inline nullable<T>::
  nullable (const nullable<Y>& y)
      : value_ (y.value_), null_ (y.null_)
  {
  }

  template <typename T>
  inline nullable<T>& nullable<T>::
  operator= (const T& v)
  {
    value_ = v;
    null_ = false;
    return *this;
  }

  template <typename T>
  inline nullable<T>& nullable<T>::
  operator= (const nullable& y)
  {
    if (this != &y)
    {
      if (!y.null_)
        value_ = y.value_;

      null_ = y.null_;
    }

    return *this;
  }

  template <typename T>
  template <typename Y>
  inline nullable<T>& nullable<T>::
  operator= (const nullable<Y>& y)
  {
    if (!y.null_)
      value_ = y.value_;

    null_ = y.null_;
    return *this;
  }

  template <typename T>
  inline void nullable<T>::
  swap (nullable& y)
  {
    T v (value_);
    bool n (null_);

    value_ = y.value_;
    null_ = y.null_;

    y.value_ = v;
    y.null_ = n;
  }

  template <typename T>
  inline bool nullable<T>::
  null () const
  {
    return null_;
  }

  template <typename T>
  inline T& nullable<T>::
  get ()
  {
    return value_;
  }

  template <typename T>
  inline const T& nullable<T>::
  get () const
  {
    return value_;
  }

  template <typename T>
  inline T* nullable<T>::
  operator-> ()
  {
    return null_ ? 0 : &value_;
  }

  template <typename T>
  inline const T* nullable<T>::
  operator-> () const
  {
    return null_ ? 0 : &value_;
  }

  template <typename T>
  inline T& nullable<T>::
  operator* ()
  {
    return value_;
  }

  template <typename T>
  inline const T& nullable<T>::
  operator* () const
  {
    return value_;
  }

  template <typename T>
  inline void nullable<T>::
  reset ()
  {
    null_ = true;
  }
}

#include <odb/post.hxx>

#endif // ODB_NULLABLE_HXX