// (C) Copyright David Abrahams 2002.

// (C) Copyright Jeremy Siek    2002.

// (C) Copyright Thomas Witt    2002.

// Distributed under the Boost Software License, Version 1.0. (See

// accompanying file LICENSE_1_0.txt or copy at

// http://www.boost.org/LICENSE_1_0.txt)

#ifndef BOOST_ITERATOR_ADAPTOR_23022003THW_HPP

#define BOOST_ITERATOR_ADAPTOR_23022003THW_HPP

#include <boost/static_assert.hpp>

#include <boost/iterator.hpp>

#include <boost/detail/iterator.hpp>

#include <boost/iterator/iterator_categories.hpp>

#include <boost/iterator/iterator_facade.hpp>

#include <boost/iterator/detail/enable_if.hpp>

#include <boost/mpl/and.hpp>

#include <boost/mpl/not.hpp>

#include <boost/mpl/or.hpp>

#include <boost/type_traits/is_same.hpp>

#include <boost/type_traits/is_convertible.hpp>

#ifdef BOOST_ITERATOR_REF_CONSTNESS_KILLS_WRITABILITY

# include <boost/type_traits/remove_reference.hpp>

#else 

# include <boost/type_traits/add_reference.hpp>

#endif 

#include <boost/iterator/detail/config_def.hpp>

#include <boost/iterator/iterator_traits.hpp>

namespace boost

{

  // Used as a default template argument internally, merely to

  // indicate "use the default", this can also be passed by users

  // explicitly in order to specify that the default should be used.

  struct use_default;

# ifndef BOOST_NO_TEMPLATE_PARTIAL_SPECIALIZATION

  // the incompleteness of use_default causes massive problems for

  // is_convertible (naturally).  This workaround is fortunately not

  // needed for vc6/vc7.

  template<class To>

  struct is_convertible<use_default,To>

    : mpl::false_ {};

# endif 

  namespace detail

  {

    // 

    // Result type used in enable_if_convertible meta function.

    // This can be an incomplete type, as only pointers to 

    // enable_if_convertible< ... >::type are used.

    // We could have used void for this, but conversion to

    // void* is just to easy.

    //

    struct enable_type;

  }

  //

  // enable_if for use in adapted iterators constructors.

  //

  // In order to provide interoperability between adapted constant and

  // mutable iterators, adapted iterators will usually provide templated

  // conversion constructors of the following form

  //

  // template <class BaseIterator>

  // class adapted_iterator :

  //   public iterator_adaptor< adapted_iterator<Iterator>, Iterator >

  // {

  // public:

  //   

  //   ...

  //

  //   template <class OtherIterator>

  //   adapted_iterator(

  //       OtherIterator const& it

  //     , typename enable_if_convertible<OtherIterator, Iterator>::type* = 0);

  //

  //   ...

  // };

  //

  // enable_if_convertible is used to remove those overloads from the overload

  // set that cannot be instantiated. For all practical purposes only overloads

  // for constant/mutable interaction will remain. This has the advantage that

  // meta functions like boost::is_convertible do not return false positives,

  // as they can only look at the signature of the conversion constructor

  // and not at the actual instantiation.

  //

  // enable_if_interoperable can be safely used in user code. It falls back to

  // always enabled for compilers that don't support enable_if or is_convertible. 

  // There is no need for compiler specific workarounds in user code. 

  //

  // The operators implementation relies on boost::is_convertible not returning

  // false positives for user/library defined iterator types. See comments

  // on operator implementation for consequences.

  //

#  if BOOST_WORKAROUND(BOOST_MSVC, <= 1300)

  template<typename From, typename To>

  struct enable_if_convertible

  {

     typedef typename mpl::if_<

         mpl::or_<

             is_same<From,To>

           , is_convertible<From, To>

         >

      , detail::enable_type

      , int&

     >::type type;

  };

#  elif defined(BOOST_NO_IS_CONVERTIBLE) || defined(BOOST_NO_SFINAE)

  template <class From, class To>

  struct enable_if_convertible

  {

      typedef detail::enable_type type;

  };

#  elif BOOST_WORKAROUND(_MSC_FULL_VER, BOOST_TESTED_AT(13102292)) && BOOST_MSVC > 1300

  // For some reason vc7.1 needs us to "cut off" instantiation

  // of is_convertible in a few cases.

  template<typename From, typename To>

  struct enable_if_convertible

    : iterators::enable_if<

        mpl::or_<

            is_same<From,To>

          , is_convertible<From, To>

        >

      , detail::enable_type

    >

  {};

#  else 

  template<typename From, typename To>

  struct enable_if_convertible

    : iterators::enable_if<

          is_convertible<From, To>

        , detail::enable_type

      >

  {};

# endif

  //

  // Default template argument handling for iterator_adaptor

  //

  namespace detail

  {

    // If T is use_default, return the result of invoking

    // DefaultNullaryFn, otherwise return T.

    template <class T, class DefaultNullaryFn>

    struct ia_dflt_help

      : mpl::eval_if<

            is_same<T, use_default>

          , DefaultNullaryFn

          , mpl::identity<T>

        >

    {

    };

    // A metafunction which computes an iterator_adaptor's base class,

    // a specialization of iterator_facade.

    template <

        class Derived

      , class Base

      , class Value

      , class Traversal

      , class Reference

      , class Difference

    >

    struct iterator_adaptor_base

    {

        typedef iterator_facade<

            Derived

# ifdef BOOST_ITERATOR_REF_CONSTNESS_KILLS_WRITABILITY

          , typename detail::ia_dflt_help<

                Value

              , mpl::eval_if<

                    is_same<Reference,use_default>

                  , iterator_value<Base>

                  , remove_reference<Reference>

                >

            >::type

# else

          , typename detail::ia_dflt_help<

                Value, iterator_value<Base>

            >::type

# endif

          , typename detail::ia_dflt_help<

                Traversal

              , iterator_traversal<Base>

            >::type

          , typename detail::ia_dflt_help<

                Reference

              , mpl::eval_if<

                    is_same<Value,use_default>

                  , iterator_reference<Base>

                  , add_reference<Value>

                >

            >::type

          , typename detail::ia_dflt_help<

                Difference, iterator_difference<Base>

            >::type

        >

        type;

    };

    // workaround for aC++ CR JAGaf33512

    template <class Tr1, class Tr2>

    inline void iterator_adaptor_assert_traversal ()

    {

      BOOST_STATIC_ASSERT((is_convertible<Tr1, Tr2>::value));

    }

  }

  //

  // Iterator Adaptor

  //

  // The parameter ordering changed slightly with respect to former

  // versions of iterator_adaptor The idea is that when the user needs

  // to fiddle with the reference type it is highly likely that the

  // iterator category has to be adjusted as well.  Any of the

  // following four template arguments may be ommitted or explicitly

  // replaced by use_default.

  //

  //   Value - if supplied, the value_type of the resulting iterator, unless

  //      const. If const, a conforming compiler strips constness for the

  //      value_type. If not supplied, iterator_traits<Base>::value_type is used

  //

  //   Category - the traversal category of the resulting iterator. If not

  //      supplied, iterator_traversal<Base>::type is used.

  //

  //   Reference - the reference type of the resulting iterator, and in

  //      particular, the result type of operator*(). If not supplied but

  //      Value is supplied, Value& is used. Otherwise

  //      iterator_traits<Base>::reference is used.

  //

  //   Difference - the difference_type of the resulting iterator. If not

  //      supplied, iterator_traits<Base>::difference_type is used.

  //

  template <

      class Derived

    , class Base

    , class Value        = use_default

    , class Traversal    = use_default

    , class Reference    = use_default

    , class Difference   = use_default

  >

  class iterator_adaptor

    : public detail::iterator_adaptor_base<

        Derived, Base, Value, Traversal, Reference, Difference

      >::type

  {

      friend class iterator_core_access;

   protected:

      typedef typename detail::iterator_adaptor_base<

          Derived, Base, Value, Traversal, Reference, Difference

      >::type super_t;

   public:

      iterator_adaptor() {}

      explicit iterator_adaptor(Base const &iter)

          : m_iterator(iter)

      {

      }

      typedef Base base_type;

      Base const& base() const

        { return m_iterator; }

   protected:

      // for convenience in derived classes

      typedef iterator_adaptor<Derived,Base,Value,Traversal,Reference,Difference> iterator_adaptor_;

      //

      // lvalue access to the Base object for Derived

      //

      Base const& base_reference() const

        { return m_iterator; }

      Base& base_reference()

        { return m_iterator; }

   private:

      //

      // Core iterator interface for iterator_facade.  This is private

      // to prevent temptation for Derived classes to use it, which

      // will often result in an error.  Derived classes should use

      // base_reference(), above, to get direct access to m_iterator.

      // 

      typename super_t::reference dereference() const

        { return *m_iterator; }

      template <

      class OtherDerived, class OtherIterator, class V, class C, class R, class D

      >   

      bool equal(iterator_adaptor<OtherDerived, OtherIterator, V, C, R, D> const& x) const

      {

        // Maybe readd with same_distance

        //           BOOST_STATIC_ASSERT(

        //               (detail::same_category_and_difference<Derived,OtherDerived>::value)

        //               );

          return m_iterator == x.base();

      }

      typedef typename iterator_category_to_traversal<

          typename super_t::iterator_category

      >::type my_traversal;

# define BOOST_ITERATOR_ADAPTOR_ASSERT_TRAVERSAL(cat) \

      detail::iterator_adaptor_assert_traversal<my_traversal, cat>();

      void advance(typename super_t::difference_type n)

      {

          BOOST_ITERATOR_ADAPTOR_ASSERT_TRAVERSAL(random_access_traversal_tag)

          m_iterator += n;

      }

      void increment() { ++m_iterator; }

      void decrement() 

      {

          BOOST_ITERATOR_ADAPTOR_ASSERT_TRAVERSAL(bidirectional_traversal_tag)

           --m_iterator;

      }

      template <

          class OtherDerived, class OtherIterator, class V, class C, class R, class D

      >   

      typename super_t::difference_type distance_to(

          iterator_adaptor<OtherDerived, OtherIterator, V, C, R, D> const& y) const

      {

          BOOST_ITERATOR_ADAPTOR_ASSERT_TRAVERSAL(random_access_traversal_tag)

          // Maybe readd with same_distance

          //           BOOST_STATIC_ASSERT(

          //               (detail::same_category_and_difference<Derived,OtherDerived>::value)

          //               );

          return y.base() - m_iterator;

      }

# undef BOOST_ITERATOR_ADAPTOR_ASSERT_TRAVERSAL

   private: // data members

      Base m_iterator;

  };

} // namespace boost

#include <boost/iterator/detail/config_undef.hpp>

#endif // BOOST_ITERATOR_ADAPTOR_23022003THW_HPP