/// \file
// Range v3 library
//
//  Copyright Eric Niebler 2014-present
//
//  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_VIEW_JOIN_HPP
#define RANGES_V3_VIEW_JOIN_HPP

#include <type_traits>
#include <utility>

#include <meta/meta.hpp>

#include <range/v3/range_fwd.hpp>

#include <range/v3/functional/bind_back.hpp>
#include <range/v3/iterator/default_sentinel.hpp>
#include <range/v3/range/access.hpp>
#include <range/v3/range/primitives.hpp>
#include <range/v3/range/traits.hpp>
#include <range/v3/range_for.hpp>
#include <range/v3/utility/static_const.hpp>
#include <range/v3/utility/variant.hpp>
#include <range/v3/view/all.hpp>
#include <range/v3/view/facade.hpp>
#include <range/v3/view/single.hpp>
#include <range/v3/view/view.hpp>

#include <range/v3/detail/prologue.hpp>

namespace ranges
{
    /// \cond
    namespace detail
    {
        // Compute the cardinality of a joined range
        constexpr cardinality join_cardinality_(
            cardinality Outer, cardinality Inner,
            cardinality Joiner = static_cast<cardinality>(0)) noexcept
        {
            return Outer == infinite || Inner == infinite ||
                           (Joiner == infinite && Outer != 0 && Outer != 1)
                       ? infinite
                       : Outer == unknown || Inner == unknown ||
                                 (Joiner == unknown && Outer != 0 && Outer != 1)
                             ? unknown
                             : Outer == finite || Inner == finite ||
                                       (Joiner == finite && Outer != 0 && Outer != 1)
                                   ? finite
                                   : static_cast<cardinality>(
                                         Outer * Inner +
                                         (Outer == 0 ? 0 : (Outer - 1) * Joiner));
        }

        template<typename Range>
        constexpr cardinality join_cardinality() noexcept
        {
            return detail::join_cardinality_(
                range_cardinality<Range>::value,
                range_cardinality<range_reference_t<Range>>::value);
        }

        template<typename Range, typename JoinRange>
        constexpr cardinality join_cardinality() noexcept
        {
            return detail::join_cardinality_(
                range_cardinality<Range>::value,
                range_cardinality<range_reference_t<Range>>::value,
                range_cardinality<JoinRange>::value);
        }

        template<typename Inner>
        struct store_inner_
        {
            views::all_t<Inner> inner_ = views::all_t<Inner>();

            constexpr views::all_t<Inner> & update_inner_(Inner && inner)
            {
                return (inner_ = views::all(static_cast<Inner &&>(inner)));
            }
            constexpr views::all_t<Inner> & get_inner_(ignore_t) noexcept
            {
                return inner_;
            }
        };

        struct pass_thru_inner_
        {
            // Intentionally promote xvalues to lvalues here:
            template<typename Inner>
            static constexpr Inner & update_inner_(Inner && inner) noexcept
            {
                return inner;
            }
            template<typename OuterIt>
            static constexpr decltype(auto) get_inner_(OuterIt && outer_it)
            {
                return *outer_it;
            }
        };

        template<typename Rng>
        using join_view_inner =
            meta::conditional_t<!std::is_reference<range_reference_t<Rng>>::value,
                      store_inner_<range_reference_t<Rng>>, pass_thru_inner_>;

        // clang-format off
        template<typename I>
        CPP_requires(has_member_arrow_,
            requires(I i) //
            (
                i.operator->()
            ));

        template<typename I>
        CPP_concept has_arrow_ =
            input_iterator<I> &&
            (std::is_pointer<I>::value || CPP_requires_ref(detail::has_member_arrow_, I));
        // clang-format on
    } // namespace detail
    /// \endcond

    /// \addtogroup group-views
    /// @{

    // Join a range of ranges
    template<typename Rng>
    struct RANGES_EMPTY_BASES join_view
      : view_facade<join_view<Rng>, detail::join_cardinality<Rng>()>
      , private detail::join_view_inner<Rng>
    {
        CPP_assert(input_range<Rng> && view_<Rng>);
        CPP_assert(input_range<range_reference_t<Rng>>);
        CPP_assert(std::is_reference<range_reference_t<Rng>>::value ||
                   view_<range_reference_t<Rng>>);

        join_view() = default;
        explicit join_view(Rng rng)
          : outer_(views::all(std::move(rng)))
        {}
        // Not to spec
        CPP_member
        static constexpr auto size() //
            -> CPP_ret(std::size_t)(
                /// \pre
                requires (detail::join_cardinality<Rng>() >= 0))
        {
            return static_cast<std::size_t>(detail::join_cardinality<Rng>());
        }
        // Not to spec
        CPP_auto_member
        constexpr auto CPP_fun(size)()(
            /// \pre
            requires(detail::join_cardinality<Rng>() < 0) &&
                (range_cardinality<Rng>::value >= 0) &&
                forward_range<Rng> &&
                sized_range<range_reference_t<Rng>>)
        {
            range_size_t<range_reference_t<Rng>> n = 0;
            RANGES_FOR(auto && inner, outer_)
                n += ranges::size(inner);
            return n;
        }
        // // ericniebler/stl2#605
        constexpr Rng base() const
        {
            return outer_;
        }

    private:
        friend range_access;
        Rng outer_{};

        template<bool Const>
        struct cursor
        {
        private:
            using Parent = meta::conditional_t<Const, join_view const, join_view>;
            using COuter = meta::conditional_t<Const, Rng const, Rng>;
            using CInner = range_reference_t<COuter>;
            using ref_is_glvalue = std::is_reference<CInner>;

            Parent * rng_ = nullptr;
            iterator_t<COuter> outer_it_{};
            iterator_t<CInner> inner_it_{};

            void satisfy()
            {
                for(; outer_it_ != ranges::end(rng_->outer_); ++outer_it_)
                {
                    auto & inner = rng_->update_inner_(*outer_it_);
                    inner_it_ = ranges::begin(inner);
                    if(inner_it_ != ranges::end(inner))
                        return;
                }
                if(RANGES_CONSTEXPR_IF(ref_is_glvalue::value))
                    inner_it_ = iterator_t<CInner>();
            }

        public:
            using single_pass = meta::bool_<single_pass_iterator_<iterator_t<COuter>> ||
                                            single_pass_iterator_<iterator_t<CInner>> ||
                                            !ref_is_glvalue::value>;
            cursor() = default;
            template<typename BeginOrEnd>
            constexpr cursor(Parent * rng, BeginOrEnd begin_or_end)
              : rng_{rng}
              , outer_it_(begin_or_end(rng->outer_))
            {
                satisfy();
            }
            template(bool Other)(
                /// \pre
                requires Const AND CPP_NOT(Other) AND
                convertible_to<iterator_t<Rng>, iterator_t<COuter>> AND
                convertible_to<iterator_t<range_reference_t<Rng>>,
                               iterator_t<CInner>>)
            constexpr cursor(cursor<Other> that)
              : rng_(that.rng_)
              , outer_it_(std::move(that.outer_it_))
              , inner_it_(std::move(that.inner_it_))
            {}
            CPP_member
            constexpr auto arrow() //
                -> CPP_ret(iterator_t<CInner>)(
                    /// \pre
                    requires detail::has_arrow_<iterator_t<CInner>>)
            {
                return inner_it_;
            }
            constexpr bool equal(default_sentinel_t) const
            {
                return outer_it_ == ranges::end(rng_->outer_);
            }
            CPP_member
            constexpr auto equal(cursor const & that) const //
                -> CPP_ret(bool)(
                    /// \pre
                    requires ref_is_glvalue::value && //
                        equality_comparable<iterator_t<COuter>> && //
                        equality_comparable<iterator_t<CInner>>)
            {
                return outer_it_ == that.outer_it_ && inner_it_ == that.inner_it_;
            }
            constexpr void next()
            {
                auto && inner_rng = rng_->get_inner_(outer_it_);
                if(++inner_it_ == ranges::end(inner_rng))
                {
                    ++outer_it_;
                    satisfy();
                }
            }
            CPP_member
            constexpr auto prev() //
                -> CPP_ret(void)(
                    /// \pre
                    requires ref_is_glvalue::value && //
                        bidirectional_range<COuter> && //
                        bidirectional_range<CInner> && //
                        common_range<CInner>) // ericniebler/stl2#606
            {
                if(outer_it_ == ranges::end(rng_->outer_))
                    inner_it_ = ranges::end(*--outer_it_);
                while(inner_it_ == ranges::begin(*outer_it_))
                    inner_it_ = ranges::end(*--outer_it_);
                --inner_it_;
            }
            // clang-format off
            constexpr auto CPP_auto_fun(read)()(const)
            (
                return *inner_it_
            )
            constexpr auto CPP_auto_fun(move)()(const)
            (
                return iter_move(inner_it_)
            )
            // clang-format on
        };
        static constexpr bool use_const_always() noexcept
        {
            return simple_view<Rng>() && std::is_reference<range_reference_t<Rng>>::value;
        }
        struct end_cursor_fn
        {
            constexpr auto operator()(join_view * this_, std::true_type) const
            {
                return cursor<use_const_always()>{this_, ranges::end};
            }
            constexpr auto operator()(join_view *, std::false_type) const
            {
                return default_sentinel_t{};
            }
        };
        struct cend_cursor_fn
        {
            constexpr auto operator()(join_view const * this_, std::true_type) const
            {
                return cursor<true>{this_, ranges::end};
            }
            constexpr auto operator()(join_view const *, std::false_type) const
            {
                return default_sentinel_t{};
            }
        };

        constexpr cursor<use_const_always()> begin_cursor()
        {
            return {this, ranges::begin};
        }

        template(bool Const = true)(
            /// \pre
            requires Const AND input_range<meta::const_if_c<Const, Rng>> AND
                std::is_reference<range_reference_t<meta::const_if_c<Const, Rng>>>::value)
        constexpr cursor<Const> begin_cursor() const
        {
            return {this, ranges::begin};
        }

        constexpr auto end_cursor()
        {
            using cond =
                meta::bool_<std::is_reference<range_reference_t<Rng>>::value &&
                            forward_range<Rng> && forward_range<range_reference_t<Rng>> &&
                            common_range<Rng> && common_range<range_reference_t<Rng>>>;
            return end_cursor_fn{}(this, cond{});
        }

        template(bool Const = true)(
            /// \pre
            requires Const AND input_range<meta::const_if_c<Const, Rng>> AND
                std::is_reference<range_reference_t<meta::const_if_c<Const, Rng>>>::value)
        constexpr auto end_cursor() const
        {
            using CRng = meta::const_if_c<Const, Rng>;
            using cond =
                meta::bool_<std::is_reference<range_reference_t<CRng>>::value &&
                            forward_range<CRng> &&
                            forward_range<range_reference_t<CRng>> &&
                            common_range<CRng> && common_range<range_reference_t<CRng>>>;
            return cend_cursor_fn{}(this, cond{});
        }
    };

    // Join a range of ranges, inserting a range of values between them.
    // TODO: Support const iteration when range_reference_t<Rng> is a true reference.
    template<typename Rng, typename ValRng>
    struct join_with_view
      : view_facade<join_with_view<Rng, ValRng>, detail::join_cardinality<Rng, ValRng>()>
    {
        CPP_assert(input_range<Rng>);
        CPP_assert(input_range<range_reference_t<Rng>>);
        CPP_assert(forward_range<ValRng>);
        CPP_assert(
            common_with<range_value_t<range_reference_t<Rng>>, range_value_t<ValRng>>);
        CPP_assert(semiregular<common_type_t<range_value_t<range_reference_t<Rng>>,
                                             range_value_t<ValRng>>>);

        join_with_view() = default;
        join_with_view(Rng rng, ValRng val)
          : outer_(views::all(std::move(rng)))
          , val_(views::all(std::move(val)))
        {}
        CPP_member
        static constexpr auto size() //
            -> CPP_ret(std::size_t)(
                /// \pre
                requires (detail::join_cardinality<Rng, ValRng>() >= 0))
        {
            return static_cast<std::size_t>(detail::join_cardinality<Rng, ValRng>());
        }
        CPP_auto_member
        auto CPP_fun(size)()(const //
            requires(detail::join_cardinality<Rng, ValRng>() < 0) &&
                (range_cardinality<Rng>::value >= 0) && forward_range<Rng> &&
                sized_range<range_reference_t<Rng>> && sized_range<ValRng>)
        {
            range_size_t<range_reference_t<Rng>> n = 0;
            RANGES_FOR(auto && inner, outer_)
                n += ranges::size(inner);
            return n + (range_cardinality<Rng>::value == 0
                            ? 0
                            : ranges::size(val_) * (range_cardinality<Rng>::value - 1));
        }

    private:
        friend range_access;
        using Outer = views::all_t<Rng>;
        // Intentionally promote xvalues to lvalues here:
        using Inner = views::all_t<range_reference_t<Outer> &>;

        Outer outer_{};
        Inner inner_{};
        views::all_t<ValRng> val_{};

        class cursor
        {
            join_with_view * rng_ = nullptr;
            iterator_t<Outer> outer_it_{};
            variant<iterator_t<ValRng>, iterator_t<Inner>> cur_{};

            void satisfy()
            {
                while(true)
                {
                    if(cur_.index() == 0)
                    {
                        if(ranges::get<0>(cur_) != ranges::end(rng_->val_))
                            break;
                        // Intentionally promote xvalues to lvalues here:
                        auto && tmp = *outer_it_;
                        rng_->inner_ = views::all(tmp);
                        ranges::emplace<1>(cur_, ranges::begin(rng_->inner_));
                    }
                    else
                    {
                        if(ranges::get<1>(cur_) != ranges::end(rng_->inner_))
                            break;
                        if(++outer_it_ == ranges::end(rng_->outer_))
                            break;
                        ranges::emplace<0>(cur_, ranges::begin(rng_->val_));
                    }
                }
            }

        public:
            using value_type = common_type_t<range_value_t<Inner>, range_value_t<ValRng>>;
            using reference =
                common_reference_t<range_reference_t<Inner>, range_reference_t<ValRng>>;
            using rvalue_reference = common_reference_t<range_rvalue_reference_t<Inner>,
                                                        range_rvalue_reference_t<ValRng>>;
            using single_pass = std::true_type;
            cursor() = default;
            cursor(join_with_view * rng)
              : rng_{rng}
              , outer_it_(ranges::begin(rng->outer_))
            {
                if(outer_it_ != ranges::end(rng->outer_))
                {
                    // Intentionally promote xvalues to lvalues here:
                    auto && tmp = *outer_it_;
                    rng->inner_ = views::all(tmp);
                    ranges::emplace<1>(cur_, ranges::begin(rng->inner_));
                    satisfy();
                }
            }
            bool equal(default_sentinel_t) const
            {
                return outer_it_ == ranges::end(rng_->outer_);
            }
            void next()
            {
                // visit(cur_, [](auto& it){ ++it; });
                if(cur_.index() == 0)
                {
                    auto & it = ranges::get<0>(cur_);
                    RANGES_ASSERT(it != ranges::end(rng_->val_));
                    ++it;
                }
                else
                {
                    auto & it = ranges::get<1>(cur_);
                    RANGES_ASSERT(it != ranges::end(rng_->inner_));
                    ++it;
                }
                satisfy();
            }
            reference read() const
            {
                // return visit(cur_, [](auto& it) -> reference { return *it; });
                if(cur_.index() == 0)
                    return *ranges::get<0>(cur_);
                else
                    return *ranges::get<1>(cur_);
            }
            rvalue_reference move() const
            {
                // return visit(cur_, [](auto& it) -> rvalue_reference { return
                // iter_move(it); });
                if(cur_.index() == 0)
                    return iter_move(ranges::get<0>(cur_));
                else
                    return iter_move(ranges::get<1>(cur_));
            }
        };
        cursor begin_cursor()
        {
            return {this};
        }
    };

    namespace views
    {
        /// \cond
        // Don't forget to update views::for_each whenever this set
        // of concepts changes
        // clang-format off
        template(typename Rng)(
        concept (joinable_range_)(Rng),
            input_range<range_reference_t<Rng>> AND
            (std::is_reference<range_reference_t<Rng>>::value ||
                view_<range_reference_t<Rng>>)
        );
        template<typename Rng>
        CPP_concept joinable_range =
            viewable_range<Rng> && input_range<Rng> &&
            CPP_concept_ref(views::joinable_range_, Rng);

        template(typename Rng, typename ValRng)(
        concept (joinable_with_range_)(Rng, ValRng),
            common_with<
                range_value_t<ValRng>,
                range_value_t<range_reference_t<Rng>>> AND
            semiregular<
                common_type_t<
                    range_value_t<ValRng>,
                    range_value_t<range_reference_t<Rng>>>> AND
            common_reference_with<
                range_reference_t<ValRng>,
                range_reference_t<range_reference_t<Rng>>> AND
            common_reference_with<
                range_rvalue_reference_t<ValRng>,
                range_rvalue_reference_t<range_reference_t<Rng>>>
        );
        template<typename Rng, typename ValRng>
        CPP_concept joinable_with_range =
            joinable_range<Rng> &&
            viewable_range<ValRng> && forward_range<ValRng> &&
            CPP_concept_ref(views::joinable_with_range_, Rng, ValRng);
        // clang-format on
        /// \endcond

        struct cpp20_join_fn
        {
            template(typename Rng)(
                /// \pre
                requires joinable_range<Rng>)
            join_view<all_t<Rng>> operator()(Rng && rng) const
            {
                return join_view<all_t<Rng>>{all(static_cast<Rng &&>(rng))};
            }
        };

        struct join_base_fn : cpp20_join_fn
        {
        private:
            template<typename Rng>
            using inner_value_t = range_value_t<range_reference_t<Rng>>;
        public:
            using cpp20_join_fn::operator();

            template(typename Rng)(
                /// \pre
                requires joinable_with_range<Rng, single_view<inner_value_t<Rng>>>)
            join_with_view<all_t<Rng>, single_view<inner_value_t<Rng>>> //
            operator()(Rng && rng, inner_value_t<Rng> v) const
            {
                return {all(static_cast<Rng &&>(rng)), single(std::move(v))};
            }

            template(typename Rng, typename ValRng)(
                /// \pre
                requires joinable_with_range<Rng, ValRng>)
            join_with_view<all_t<Rng>, all_t<ValRng>> //
            operator()(Rng && rng, ValRng && val) const
            {
                return {all(static_cast<Rng &&>(rng)), all(static_cast<ValRng &&>(val))};
            }

            /// \cond
            template<typename Rng, typename T>
            invoke_result_t<join_base_fn, Rng, T &> //
            operator()(Rng && rng, detail::reference_wrapper_<T> r) const
            {
                return (*this)(static_cast<Rng &&>(rng), r.get());
            }
            /// \endcond
        };

        struct join_bind_fn
        {
            template(typename T)(
                /// \pre
                requires (!joinable_range<T>)) // TODO: underconstrained
            constexpr auto operator()(T && t)const
            {
                return make_view_closure(bind_back(join_base_fn{}, static_cast<T &&>(t)));
            }
            template(typename T)(
                /// \pre
                requires (!joinable_range<T &>) AND range<T &>)
            constexpr auto operator()(T & t) const
            {
                return make_view_closure(bind_back(join_base_fn{},
                                                   detail::reference_wrapper_<T>(t)));
            }
        };

        struct RANGES_EMPTY_BASES join_fn
          : join_base_fn, join_bind_fn
        {
            using join_base_fn::operator();
            using join_bind_fn::operator();
        };

        /// \relates join_fn
        /// \ingroup group-views
        RANGES_INLINE_VARIABLE(view_closure<join_fn>, join)
    } // namespace views
    /// @}

#if RANGES_CXX_DEDUCTION_GUIDES >= RANGES_CXX_DEDUCTION_GUIDES_17
    template(typename Rng)(
        /// \pre
        requires views::joinable_range<Rng>)
        explicit join_view(Rng &&)
            ->join_view<views::all_t<Rng>>;

    template(typename Rng, typename ValRng)(
        /// \pre
        requires views::joinable_with_range<Rng, ValRng>)
        explicit join_with_view(Rng &&, ValRng &&)
            ->join_with_view<views::all_t<Rng>, views::all_t<ValRng>>;
#endif

    namespace cpp20
    {
        namespace views
        {
            RANGES_INLINE_VARIABLE(
                ranges::views::view_closure<ranges::views::cpp20_join_fn>, join)
        }
        template(typename Rng)(
            /// \pre
            requires input_range<Rng> AND view_<Rng> AND
                input_range<iter_reference_t<iterator_t<Rng>>> AND
            (std::is_reference<iter_reference_t<iterator_t<Rng>>>::value ||
             view_<iter_value_t<iterator_t<Rng>>>)) //
            using join_view = ranges::join_view<Rng>;
    } // namespace cpp20
} // namespace ranges

#include <range/v3/detail/epilogue.hpp>

#include <range/v3/detail/satisfy_boost_range.hpp>
RANGES_SATISFY_BOOST_RANGE(::ranges::join_view)
RANGES_SATISFY_BOOST_RANGE(::ranges::join_with_view)

#endif
