// Boost.Range library concept checks
//
//  Copyright Neil Groves 2009. Use, modification and distribution
//  are subject to 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)
//
//  Copyright Daniel Walker 2006. Use, modification and distribution
//  are subject to 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)
//
// For more information, see http://www.boost.org/libs/range/
//

#ifndef BOOST_RANGE_CONCEPTS_HPP
#define BOOST_RANGE_CONCEPTS_HPP

#include <boost/concept_check.hpp>
#include <boost/iterator/iterator_concepts.hpp>
#include <boost/range/begin.hpp>
#include <boost/range/end.hpp>
#include <boost/range/iterator.hpp>
#include <boost/range/value_type.hpp>
#include <boost/range/detail/misc_concept.hpp>
#include <boost/type_traits/remove_reference.hpp>

#include <iterator>

/*!
 * \file
 * \brief Concept checks for the Boost Range library.
 *
 * The structures in this file may be used in conjunction with the
 * Boost Concept Check library to insure that the type of a function
 * parameter is compatible with a range concept. If not, a meaningful
 * compile time error is generated. Checks are provided for the range
 * concepts related to iterator traversal categories. For example, the
 * following line checks that the type T models the ForwardRange
 * concept.
 *
 * \code
 * BOOST_CONCEPT_ASSERT((ForwardRangeConcept<T>));
 * \endcode
 *
 * A different concept check is required to ensure writeable value
 * access. For example to check for a ForwardRange that can be written
 * to, the following code is required.
 *
 * \code
 * BOOST_CONCEPT_ASSERT((WriteableForwardRangeConcept<T>));
 * \endcode
 *
 * \see http://www.boost.org/libs/range/doc/range.html for details
 * about range concepts.
 * \see http://www.boost.org/libs/iterator/doc/iterator_concepts.html
 * for details about iterator concepts.
 * \see http://www.boost.org/libs/concept_check/concept_check.htm for
 * details about concept checks.
 */

namespace boost {

namespace range_detail {

#ifndef BOOST_RANGE_ENABLE_CONCEPT_ASSERT

// List broken compiler versions here:
#ifndef __clang__
#ifdef __GNUC__
// GNUC 4.2 has strange issues correctly detecting compliance with the Concepts
// hence the least disruptive approach is to turn-off the concept checking for
// this version of the compiler.
#if __GNUC__ == 4 && __GNUC_MINOR__ == 2
#define BOOST_RANGE_ENABLE_CONCEPT_ASSERT 0
#endif
#endif

#ifdef __GCCXML__
// GCC XML, unsurprisingly, has the same issues
#if __GCCXML_GNUC__ == 4 && __GCCXML_GNUC_MINOR__ == 2
#define BOOST_RANGE_ENABLE_CONCEPT_ASSERT 0
#endif
#endif
#endif

#ifdef BOOST_BORLANDC
#define BOOST_RANGE_ENABLE_CONCEPT_ASSERT 0
#endif

#ifdef __PATHCC__
#define BOOST_RANGE_ENABLE_CONCEPT_ASSERT 0
#endif

// Default to using the concept asserts unless we have defined it off
// during the search for black listed compilers.
#ifndef BOOST_RANGE_ENABLE_CONCEPT_ASSERT
#define BOOST_RANGE_ENABLE_CONCEPT_ASSERT 1
#endif

#endif

#if BOOST_RANGE_ENABLE_CONCEPT_ASSERT
#define BOOST_RANGE_CONCEPT_ASSERT( x ) BOOST_CONCEPT_ASSERT( x )
#else
#define BOOST_RANGE_CONCEPT_ASSERT( x )
#endif

// Rationale for the inclusion of redefined iterator concept
// classes:
//
// The Range algorithms often do not require that the iterators are
// Assignable or default constructable, but the correct standard
// conformant iterators do require the iterators to be a model of the
// Assignable concept.
// Iterators that contains a functor that is not assignable therefore
// are not correct models of the standard iterator concepts,
// despite being adequate for most algorithms. An example of this
// use case is the combination of the boost::adaptors::filtered
// class with a boost::lambda::bind generated functor.
// Ultimately modeling the range concepts using composition
// with the Boost.Iterator concepts would render the library
// incompatible with many common Boost.Lambda expressions.
template<class Iterator>
struct IncrementableIteratorConcept : CopyConstructible<Iterator>
{
#if BOOST_RANGE_ENABLE_CONCEPT_ASSERT
    typedef BOOST_DEDUCED_TYPENAME iterator_traversal<Iterator>::type traversal_category;

    BOOST_RANGE_CONCEPT_ASSERT((
                                   Convertible<
                                   traversal_category,
                                   incrementable_traversal_tag
                                   >));

    BOOST_CONCEPT_USAGE(IncrementableIteratorConcept)
    {
        ++i;
        (void)i++;
    }
  private:
    Iterator i;
#endif
};

template<class Iterator>
struct SinglePassIteratorConcept
    : IncrementableIteratorConcept<Iterator>
    , EqualityComparable<Iterator>
{
#if BOOST_RANGE_ENABLE_CONCEPT_ASSERT
    BOOST_RANGE_CONCEPT_ASSERT((
                                   Convertible<
                                   BOOST_DEDUCED_TYPENAME SinglePassIteratorConcept::traversal_category,
                                   single_pass_traversal_tag
                                   >));

    BOOST_CONCEPT_USAGE(SinglePassIteratorConcept)
    {
        Iterator i2(++i);
        boost::ignore_unused_variable_warning(i2);

        // deliberately we are loose with the postfix version for the single pass
        // iterator due to the commonly poor adherence to the specification means that
        // many algorithms would be unusable, whereas actually without the check they
        // work
        (void)(i++);

        BOOST_DEDUCED_TYPENAME std::iterator_traits<Iterator>::reference r1(*i);
        boost::ignore_unused_variable_warning(r1);

        BOOST_DEDUCED_TYPENAME std::iterator_traits<Iterator>::reference r2(*(++i));
        boost::ignore_unused_variable_warning(r2);
    }
  private:
    Iterator i;
#endif
};

template<class Iterator>
struct ForwardIteratorConcept
    : SinglePassIteratorConcept<Iterator>
    , DefaultConstructible<Iterator>
{
#if BOOST_RANGE_ENABLE_CONCEPT_ASSERT
    typedef BOOST_DEDUCED_TYPENAME std::iterator_traits<Iterator>::difference_type difference_type;

    BOOST_MPL_ASSERT((is_integral<difference_type>));
    BOOST_MPL_ASSERT_RELATION(std::numeric_limits<difference_type>::is_signed, ==, true);

    BOOST_RANGE_CONCEPT_ASSERT((
                                   Convertible<
                                   BOOST_DEDUCED_TYPENAME ForwardIteratorConcept::traversal_category,
                                   forward_traversal_tag
                                   >));

    BOOST_CONCEPT_USAGE(ForwardIteratorConcept)
    {
        // See the above note in the SinglePassIteratorConcept about the handling of the
        // postfix increment. Since with forward and better iterators there is no need
        // for a proxy, we can sensibly require that the dereference result
        // is convertible to reference.
        Iterator i2(i++);
        boost::ignore_unused_variable_warning(i2);
        BOOST_DEDUCED_TYPENAME std::iterator_traits<Iterator>::reference r(*(i++));
        boost::ignore_unused_variable_warning(r);
    }
  private:
    Iterator i;
#endif
};

template<class Iterator>
struct BidirectionalIteratorConcept
    : ForwardIteratorConcept<Iterator>
{
#if BOOST_RANGE_ENABLE_CONCEPT_ASSERT
    BOOST_RANGE_CONCEPT_ASSERT((
                                   Convertible<
                                   BOOST_DEDUCED_TYPENAME BidirectionalIteratorConcept::traversal_category,
                                   bidirectional_traversal_tag
                                   >));

    BOOST_CONCEPT_USAGE(BidirectionalIteratorConcept)
    {
        --i;
        (void)i--;
    }
  private:
    Iterator i;
#endif
};

template<class Iterator>
struct RandomAccessIteratorConcept
    : BidirectionalIteratorConcept<Iterator>
{
#if BOOST_RANGE_ENABLE_CONCEPT_ASSERT
    BOOST_RANGE_CONCEPT_ASSERT((
                                   Convertible<
                                   BOOST_DEDUCED_TYPENAME RandomAccessIteratorConcept::traversal_category,
                                   random_access_traversal_tag
                                   >));

    BOOST_CONCEPT_USAGE(RandomAccessIteratorConcept)
    {
        i += n;
        i = i + n;
        i = n + i;
        i -= n;
        i = i - n;
        n = i - j;
    }
  private:
    BOOST_DEDUCED_TYPENAME BidirectionalIteratorConcept<Iterator>::difference_type n;
    Iterator i;
    Iterator j;
#endif
};

} // namespace range_detail

//! Check if a type T models the SinglePassRange range concept.
template<class T>
struct SinglePassRangeConcept
{
#if BOOST_RANGE_ENABLE_CONCEPT_ASSERT
    // A few compilers don't like the rvalue reference T types so just
    // remove it.
    typedef BOOST_DEDUCED_TYPENAME remove_reference<T>::type Rng;

    typedef BOOST_DEDUCED_TYPENAME range_iterator<
    Rng const
    >::type const_iterator;

    typedef BOOST_DEDUCED_TYPENAME range_iterator<Rng>::type iterator;

    BOOST_RANGE_CONCEPT_ASSERT((
                                   range_detail::SinglePassIteratorConcept<iterator>));

    BOOST_RANGE_CONCEPT_ASSERT((
                                   range_detail::SinglePassIteratorConcept<const_iterator>));

    BOOST_CONCEPT_USAGE(SinglePassRangeConcept)
    {
        // This has been modified from assigning to this->i
        // (where i was a member variable) to improve
        // compatibility with Boost.Lambda
        iterator i1 = boost::begin(*m_range);
        iterator i2 = boost::end(*m_range);

        boost::ignore_unused_variable_warning(i1);
        boost::ignore_unused_variable_warning(i2);

        const_constraints(*m_range);
    }

  private:
    void
    const_constraints(const Rng& const_range)
    {
        const_iterator ci1 = boost::begin(const_range);
        const_iterator ci2 = boost::end(const_range);

        boost::ignore_unused_variable_warning(ci1);
        boost::ignore_unused_variable_warning(ci2);
    }

    // Rationale:
    // The type of m_range is T* rather than T because it allows
    // T to be an abstract class. The other obvious alternative of
    // T& produces a warning on some compilers.
    Rng* m_range;
#endif
};

//! Check if a type T models the ForwardRange range concept.
template<class T>
struct ForwardRangeConcept : SinglePassRangeConcept<T>
{
#if BOOST_RANGE_ENABLE_CONCEPT_ASSERT
    BOOST_RANGE_CONCEPT_ASSERT((range_detail::ForwardIteratorConcept<BOOST_DEDUCED_TYPENAME ForwardRangeConcept::iterator>));
    BOOST_RANGE_CONCEPT_ASSERT((range_detail::ForwardIteratorConcept<BOOST_DEDUCED_TYPENAME ForwardRangeConcept::const_iterator>));
#endif
};

template<class T>
struct WriteableRangeConcept
{
#if BOOST_RANGE_ENABLE_CONCEPT_ASSERT
    typedef BOOST_DEDUCED_TYPENAME range_iterator<T>::type iterator;

    BOOST_CONCEPT_USAGE(WriteableRangeConcept)
    {
        *i = v;
    }
  private:
    iterator i;
    BOOST_DEDUCED_TYPENAME range_value<T>::type v;
#endif
};

//! Check if a type T models the WriteableForwardRange range concept.
template<class T>
struct WriteableForwardRangeConcept
    : ForwardRangeConcept<T>
    , WriteableRangeConcept<T>
{
};

//! Check if a type T models the BidirectionalRange range concept.
template<class T>
struct BidirectionalRangeConcept : ForwardRangeConcept<T>
{
#if BOOST_RANGE_ENABLE_CONCEPT_ASSERT
    BOOST_RANGE_CONCEPT_ASSERT((range_detail::BidirectionalIteratorConcept<BOOST_DEDUCED_TYPENAME BidirectionalRangeConcept::iterator>));
    BOOST_RANGE_CONCEPT_ASSERT((range_detail::BidirectionalIteratorConcept<BOOST_DEDUCED_TYPENAME BidirectionalRangeConcept::const_iterator>));
#endif
};

//! Check if a type T models the WriteableBidirectionalRange range concept.
template<class T>
struct WriteableBidirectionalRangeConcept
    : BidirectionalRangeConcept<T>
    , WriteableRangeConcept<T>
{
};

//! Check if a type T models the RandomAccessRange range concept.
template<class T>
struct RandomAccessRangeConcept : BidirectionalRangeConcept<T>
{
#if BOOST_RANGE_ENABLE_CONCEPT_ASSERT
    BOOST_RANGE_CONCEPT_ASSERT((range_detail::RandomAccessIteratorConcept<BOOST_DEDUCED_TYPENAME RandomAccessRangeConcept::iterator>));
    BOOST_RANGE_CONCEPT_ASSERT((range_detail::RandomAccessIteratorConcept<BOOST_DEDUCED_TYPENAME RandomAccessRangeConcept::const_iterator>));
#endif
};

//! Check if a type T models the WriteableRandomAccessRange range concept.
template<class T>
struct WriteableRandomAccessRangeConcept
    : RandomAccessRangeConcept<T>
    , WriteableRangeConcept<T>
{
};

} // namespace boost

#endif // BOOST_RANGE_CONCEPTS_HPP
