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// (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

#include <boost/config.hpp>
#include <boost/config/workaround.hpp>
#include <boost/iterator/detail/enable_if.hpp>
#include <boost/iterator/iterator_adaptor.hpp>
#include <boost/iterator/iterator_categories.hpp>
#include <boost/type_traits/function_traits.hpp>
#include <boost/type_traits/is_const.hpp>
#include <boost/type_traits/is_class.hpp>
#include <boost/type_traits/is_function.hpp>
#include <boost/type_traits/is_reference.hpp>
#include <boost/type_traits/remove_const.hpp>
#include <boost/type_traits/remove_reference.hpp>
#include <boost/utility/result_of.hpp>

#include <iterator>

#include <boost/type_traits/is_base_and_derived.hpp>

#include <boost/static_assert.hpp>

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

namespace boost {
namespace iterators {

  template <class UnaryFunction, class Iterator, class Reference = use_default, class Value = use_default>
  class transform_iterator;

  namespace detail
    // Compute the iterator_adaptor instantiation to be used for transform_iterator
    template <class UnaryFunc, class Iterator, class Reference, class Value>
    struct transform_iterator_base
        // By default, dereferencing the iterator yields the same as
        // the function.
        typedef typename ia_dflt_help<
          , result_of<const UnaryFunc(typename std::iterator_traits<Iterator>::reference)>
          , result_of<const UnaryFunc&(typename std::iterator_traits<Iterator>::reference)>
        >::type reference;

        // To get the default for Value: remove any reference on the
        // result type, but retain any constness to signal
        // non-writability.  Note that if we adopt Thomas' suggestion
        // to key non-writability *only* on the Reference argument,
        // we'd need to strip constness here as well.
        typedef typename ia_dflt_help<
          , remove_reference<reference>
        >::type cv_value_type;

        typedef iterator_adaptor<
            transform_iterator<UnaryFunc, Iterator, Reference, Value>
          , Iterator
          , cv_value_type
          , use_default    // Leave the traversal category alone
          , reference
        > type;

  template <class UnaryFunc, class Iterator, class Reference, class Value>
  class transform_iterator
    : public boost::iterators::detail::transform_iterator_base<UnaryFunc, Iterator, Reference, Value>::type
    typedef typename
    boost::iterators::detail::transform_iterator_base<UnaryFunc, Iterator, Reference, Value>::type

    friend class iterator_core_access;

    transform_iterator() { }

    transform_iterator(Iterator const& x, UnaryFunc f)
      : super_t(x), m_f(f) { }

    explicit transform_iterator(Iterator const& x)
      : super_t(x)
        // Pro8 is a little too aggressive about instantiating the
        // body of this function.
        // don't provide this constructor if UnaryFunc is a
        // function pointer type, since it will be 0.  Too dangerous.

    template <
        class OtherUnaryFunction
      , class OtherIterator
      , class OtherReference
      , class OtherValue>
         transform_iterator<OtherUnaryFunction, OtherIterator, OtherReference, OtherValue> const& t
       , typename enable_if_convertible<OtherIterator, Iterator>::type* = 0
       , typename enable_if_convertible<OtherUnaryFunction, UnaryFunc>::type* = 0
      : super_t(t.base()), m_f(t.functor())

    UnaryFunc functor() const
      { return m_f; }

    typename super_t::reference dereference() const
    { return m_f(*this->base()); }

    // Probably should be the initial base class so it can be
    // optimized away via EBO if it is an empty class.
    UnaryFunc m_f;

  template <class UnaryFunc, class Iterator>
  inline transform_iterator<UnaryFunc, Iterator>
  make_transform_iterator(Iterator it, UnaryFunc fun)
      return transform_iterator<UnaryFunc, Iterator>(it, fun);

  // Version which allows explicit specification of the UnaryFunc
  // type.
  // This generator is not provided if UnaryFunc is a function
  // pointer type, because it's too dangerous: the default-constructed
  // function pointer in the iterator be 0, leading to a runtime
  // crash.
  template <class UnaryFunc, class Iterator>
  inline typename iterators::enable_if<
      is_class<UnaryFunc>   // We should probably find a cheaper test than is_class<>
    , transform_iterator<UnaryFunc, Iterator>
  make_transform_iterator(Iterator it)
      return transform_iterator<UnaryFunc, Iterator>(it, UnaryFunc());

  template <class Return, class Argument, class Iterator>
  inline transform_iterator< Return (*)(Argument), Iterator, Return>
  make_transform_iterator(Iterator it, Return (*fun)(Argument))
    return transform_iterator<Return (*)(Argument), Iterator, Return>(it, fun);

} // namespace iterators

using iterators::transform_iterator;
using iterators::make_transform_iterator;

} // namespace boost

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