/// \file
// Range v3 library
//
//  Copyright Eric Niebler 2014-present
//  Copyright Casey Carter 2015
//
//  Use, modification and distribution is 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)
//
// Project home: https://github.com/ericniebler/range-v3
//
#ifndef RANGES_V3_ALGORITHM_MINMAX_HPP
#define RANGES_V3_ALGORITHM_MINMAX_HPP

#include <initializer_list>

#include <range/v3/range_fwd.hpp>

#include <range/v3/algorithm/result_types.hpp>
#include <range/v3/functional/comparisons.hpp>
#include <range/v3/functional/identity.hpp>
#include <range/v3/functional/invoke.hpp>
#include <range/v3/iterator/concepts.hpp>
#include <range/v3/iterator/traits.hpp>
#include <range/v3/range/access.hpp>
#include <range/v3/range/concepts.hpp>
#include <range/v3/range/traits.hpp>
#include <range/v3/utility/static_const.hpp>

namespace ranges
{
    /// \addtogroup group-algorithms
    /// @{
    template<typename T>
    using minmax_result = detail::min_max_result<T, T>;

    RANGES_BEGIN_NIEBLOID(minmax)

        /// \brief function template \c minmax
        template<typename T, typename C = less, typename P = identity>
        constexpr auto RANGES_FUN_NIEBLOID(minmax)(
            T const & a, T const & b, C pred = C{}, P proj = P{}) //
            ->CPP_ret(minmax_result<T const &>)(                  //
                requires indirect_strict_weak_order<C, projected<T const *, P>>)
        {
            using R = minmax_result<T const &>;
            return invoke(pred, invoke(proj, b), invoke(proj, a)) ? R{b, a} : R{a, b};
        }

        /// \overload
        template<typename Rng, typename C = less, typename P = identity>
        constexpr auto RANGES_FUN_NIEBLOID(minmax)(
            Rng && rng, C pred = C{}, P proj = P{})       //
            ->CPP_ret(minmax_result<range_value_t<Rng>>)( //
                requires input_range<Rng> &&
                indirect_strict_weak_order<C, projected<iterator_t<Rng>, P>> &&
                indirectly_copyable_storable<iterator_t<Rng>, range_value_t<Rng> *>)
        {
            using R = minmax_result<range_value_t<Rng>>;
            auto first = ranges::begin(rng);
            auto last = ranges::end(rng);
            RANGES_EXPECT(first != last);
            auto result = R{*first, *first};
            if(++first != last)
            {
                {
                    auto && tmp = *first;
                    if(invoke(pred, invoke(proj, tmp), invoke(proj, result.min)))
                        result.min = (decltype(tmp) &&)tmp;
                    else
                        result.max = (decltype(tmp) &&)tmp;
                }
                while(++first != last)
                {
                    range_value_t<Rng> tmp1 = *first;
                    if(++first == last)
                    {
                        if(invoke(pred, invoke(proj, tmp1), invoke(proj, result.min)))
                            result.min = std::move(tmp1);
                        else if(!invoke(
                                    pred, invoke(proj, tmp1), invoke(proj, result.max)))
                            result.max = std::move(tmp1);
                        break;
                    }

                    auto && tmp2 = *first;
                    if(invoke(pred, invoke(proj, tmp2), invoke(proj, tmp1)))
                    {
                        if(invoke(pred, invoke(proj, tmp2), invoke(proj, result.min)))
                            result.min = (decltype(tmp2) &&)tmp2;
                        if(!invoke(pred, invoke(proj, tmp1), invoke(proj, result.max)))
                            result.max = std::move(tmp1);
                    }
                    else
                    {
                        if(invoke(pred, invoke(proj, tmp1), invoke(proj, result.min)))
                            result.min = std::move(tmp1);
                        if(!invoke(pred, invoke(proj, tmp2), invoke(proj, result.max)))
                            result.max = (decltype(tmp2) &&)tmp2;
                    }
                }
            }
            return result;
        }

        /// \overload
        template<typename T, typename C = less, typename P = identity>
        constexpr auto RANGES_FUN_NIEBLOID(minmax)(
            std::initializer_list<T> const && rng, C pred = C{}, P proj = P{}) //
            ->CPP_ret(minmax_result<T>)(                                       //
                requires copyable<T> &&
                indirect_strict_weak_order<C, projected<T const *, P>>)
        {
            return (*this)(rng, std::move(pred), std::move(proj));
        }

    RANGES_END_NIEBLOID(minmax)

    namespace cpp20
    {
        using ranges::minmax;
        using ranges::minmax_result;
    } // namespace cpp20
    /// @}
} // namespace ranges

#endif // include guard