take_until_view.hpp

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// SPDX-FileCopyrightText: 2006-2026 Knut Reinert & Freie Universität Berlin
// SPDX-FileCopyrightText: 2016-2026 Knut Reinert & MPI für molekulare Genetik
// SPDX-License-Identifier: BSD-3-Clause
 
#pragma once
 
#include <algorithm>
#include <concepts>
#include <iterator>
#include <ranges>
#include <type_traits>
 
#include <seqan3/contrib/std/detail/movable_box.hpp>
#include <seqan3/core/detail/iterator_traits.hpp>
#include <seqan3/core/range/detail/adaptor_from_functor.hpp>
#include <seqan3/core/range/detail/inherited_iterator_base.hpp>
#include <seqan3/core/range/type_traits.hpp>
#include <seqan3/io/exception.hpp>
#include <seqan3/utility/range/concept.hpp>
#include <seqan3/utility/type_traits/detail/transformation_trait_or.hpp>
 
namespace seqan3::detail
{
 
// ============================================================================
//  view_take_until
// ============================================================================
 
template <std::ranges::view urng_t, typename fun_t, bool or_throw, bool and_consume>
class view_take_until : public std::ranges::view_interface<view_take_until<urng_t, fun_t, or_throw, and_consume>>
{
private:
    static_assert(std::invocable<fun_t, std::ranges::range_reference_t<urng_t>>,
                  "The functor type for detail::take_until must model"
                  "std::invocable<fun_t, std::ranges::range_reference_t<urng_t>>.");
    static_assert(std::convertible_to<std::invoke_result_t<fun_t &&, std::ranges::range_reference_t<urng_t>>, bool>,
                  "The result type of the functor for detail::take_until must be a boolean.");
 
    urng_t urange;
 
    seqan::stl::detail::movable_box_t<fun_t> fun;
 
    static constexpr bool const_iterable =
        const_iterable_range<urng_t> && indirect_unary_predicate_on_range<fun_t const, urng_t const>;
 
    template <bool const_range>
    using basic_iterator = seqan3::detail::maybe_const_iterator_t<const_range, urng_t>;
 
    template <bool const_range>
    class basic_sentinel;
 
    template <bool const_range>
    class basic_consume_iterator;
 
    template <bool const_range>
    using basic_consume_sentinel = std::default_sentinel_t;
 
public:
    view_take_until() = default;                                                  
    constexpr view_take_until(view_take_until const & rhs) = default;             
    constexpr view_take_until(view_take_until && rhs) = default;                  
    constexpr view_take_until & operator=(view_take_until const & rhs) = default; 
    constexpr view_take_until & operator=(view_take_until && rhs) = default;      
    ~view_take_until() = default;                                                 
 
    view_take_until(urng_t && _urange, fun_t && _fun) :
        urange{std::forward<urng_t>(_urange)},
        fun{std::forward<fun_t>(_fun)}
    {}
 
    template <std::ranges::viewable_range rng_t>
        requires std::constructible_from<urng_t, std::views::all_t<rng_t>>
    view_take_until(rng_t && _urange, fun_t && _fun) :
        view_take_until{std::views::all(std::forward<rng_t>(_urange)), std::forward<fun_t>(_fun)}
    {}
 
    auto begin() noexcept
    {
        if constexpr (and_consume && !std::ranges::forward_range<urng_t>)
            return basic_consume_iterator<false>{std::ranges::begin(urange), fun, std::ranges::end(urange)};
        else
            return basic_iterator<false>{std::ranges::begin(urange)};
    }
 
    auto begin() const noexcept
        requires const_iterable
    {
        if constexpr (and_consume && !std::ranges::forward_range<urng_t const>)
            return basic_consume_iterator<true>{std::ranges::cbegin(urange), fun, std::ranges::cend(urange)};
        else
            return basic_iterator<true>{std::ranges::begin(urange)};
    }
 
    auto end() noexcept
    {
        if constexpr (and_consume && !std::ranges::forward_range<urng_t>)
            return basic_consume_sentinel<false>{};
        else
            return basic_sentinel<false>{std::ranges::end(urange), fun};
    }
 
    auto end() const noexcept
        requires const_iterable
    {
        if constexpr (and_consume && !std::ranges::forward_range<urng_t const>)
            return basic_consume_sentinel<true>{};
        else
            return basic_sentinel<true>{std::ranges::end(urange), fun};
    }
};
 
template <typename urng_t, typename fun_t, bool or_throw = false, bool and_consume = false>
view_take_until(urng_t &&, fun_t &&) -> view_take_until<std::views::all_t<urng_t>, fun_t, or_throw, and_consume>;
 
template <std::ranges::view urng_t, typename fun_t, bool or_throw, bool and_consume>
template <bool const_range>
class view_take_until<urng_t, fun_t, or_throw, and_consume>::basic_consume_iterator :
    public inherited_iterator_base<basic_consume_iterator<const_range>,
                                   seqan3::detail::maybe_const_iterator_t<const_range, urng_t>>
{
private:
    using underlying_iterator_t = seqan3::detail::maybe_const_iterator_t<const_range, urng_t>;
    using base_t = inherited_iterator_base<basic_consume_iterator, underlying_iterator_t>;
 
    seqan::stl::detail::movable_box_t<fun_t> const * fun{nullptr};
 
    using underlying_sentinel_t = seqan3::detail::maybe_const_sentinel_t<const_range, urng_t>;
 
    underlying_sentinel_t underlying_sentinel;
 
    bool at_end_gracefully = false;
 
public:
    constexpr basic_consume_iterator() = default;                                               
    constexpr basic_consume_iterator(basic_consume_iterator const & rhs) = default;             
    constexpr basic_consume_iterator(basic_consume_iterator && rhs) = default;                  
    constexpr basic_consume_iterator & operator=(basic_consume_iterator const & rhs) = default; 
    constexpr basic_consume_iterator & operator=(basic_consume_iterator && rhs) = default;      
    ~basic_consume_iterator() = default;                                                        
 
    basic_consume_iterator(underlying_iterator_t it,
                           seqan::stl::detail::movable_box_t<fun_t> const & _fun,
                           underlying_sentinel_t sen) noexcept(noexcept(base_t{it})) :
        base_t{std::move(it)},
        fun{std::addressof(_fun)},
        underlying_sentinel{std::move(sen)}
    {
        if ((this->base() != underlying_sentinel) && fun->operator()(**this))
        {
            at_end_gracefully = true;
            ++(*this);
        }
    }
 
    using difference_type = std::iter_difference_t<underlying_iterator_t>; 
    using value_type = std::iter_value_t<underlying_iterator_t>;           
    using reference = std::iter_reference_t<underlying_iterator_t>;        
    using pointer = detail::iter_pointer_t<underlying_iterator_t>;         
    using iterator_category = std::input_iterator_tag;                     
 
    basic_consume_iterator & operator++()
        noexcept(noexcept(++std::declval<base_t &>())
                 && noexcept(std::declval<underlying_iterator_t &>() != std::declval<underlying_sentinel_t &>())
                 && noexcept(fun->operator()(std::declval<reference>())))
    {
        base_t::operator++();
 
        while ((this->base() != underlying_sentinel) && fun->operator()(**this))
        {
            at_end_gracefully = true;
            base_t::operator++();
        }
 
        return *this;
    }
 
    decltype(auto) operator++(int) noexcept(noexcept(++std::declval<basic_consume_iterator &>())
                                            && (std::same_as<decltype(std::declval<underlying_iterator_t &>()++), void>
                                                || std::is_nothrow_copy_constructible_v<basic_consume_iterator>))
    {
        // if underlying iterator is a C++20 input iterator (i.e. returns void), return void too.
        if constexpr (std::same_as<decltype(std::declval<underlying_iterator_t &>()++), void>)
        {
            ++(*this);
        }
        else
        {
            basic_consume_iterator cpy{*this};
            ++(*this);
            return cpy;
        }
    }
 
    bool operator==(basic_consume_sentinel<const_range> const &) const
        noexcept(!or_throw
                 && noexcept(std::declval<underlying_iterator_t &>() != std::declval<underlying_sentinel_t &>())
                 && noexcept(fun->operator()(std::declval<reference>())))
    {
        if (at_end_gracefully)
            return true;
 
        if (this->base() == underlying_sentinel)
        {
            if constexpr (or_throw)
                throw unexpected_end_of_input{"Reached end of input before functor evaluated to true."};
            else
                return true;
        }
 
        return fun->operator()(**this);
    }
 
    friend bool operator==(basic_consume_sentinel<const_range> const & lhs, basic_consume_iterator const & rhs)
        noexcept(noexcept(rhs == lhs))
    {
        return rhs == lhs;
    }
 
    bool operator!=(basic_consume_sentinel<const_range> const & rhs) const
        noexcept(noexcept(std::declval<basic_consume_iterator &>() == rhs))
    {
        return !(*this == rhs);
    }
 
    friend bool operator!=(basic_consume_sentinel<const_range> const & lhs, basic_consume_iterator const & rhs)
        noexcept(noexcept(rhs != lhs))
    {
        return rhs != lhs;
    }
};
 
template <std::ranges::view urng_t, typename fun_t, bool or_throw, bool and_consume>
template <bool const_range>
class view_take_until<urng_t, fun_t, or_throw, and_consume>::basic_sentinel
{
private:
    using underlying_sentinel_t = seqan3::detail::maybe_const_sentinel_t<const_range, urng_t>;
 
    underlying_sentinel_t underlying_sentinel{};
 
    seqan::stl::detail::movable_box_t<fun_t> const * fun{nullptr};
 
public:
    basic_sentinel() = default;                                   
    basic_sentinel(basic_sentinel const &) = default;             
    basic_sentinel(basic_sentinel &&) = default;                  
    basic_sentinel & operator=(basic_sentinel const &) = default; 
    basic_sentinel & operator=(basic_sentinel &&) = default;      
    ~basic_sentinel() = default;                                  
 
    explicit basic_sentinel(underlying_sentinel_t underlying_sentinel,
                            seqan::stl::detail::movable_box_t<fun_t> const & _fun) :
        underlying_sentinel{std::move(underlying_sentinel)},
        fun{std::addressof(_fun)}
    {}
 
    basic_sentinel(basic_sentinel<!const_range> other)
        requires const_range && std::convertible_to<std::ranges::sentinel_t<urng_t>, underlying_sentinel_t>
        : underlying_sentinel{std::move(other.underlying_sentinel)}, fun{other.fun}
    {}
 
    friend bool operator==(basic_iterator<const_range> const & lhs, basic_sentinel const & rhs)
    {
        // Actual comparison delegated to lhs base
        if (lhs == rhs.underlying_sentinel)
        {
            if constexpr (or_throw)
                throw unexpected_end_of_input{"Reached end of input before functor evaluated to true."};
            else
                return true;
        }
 
        return rhs.fun->operator()(*lhs);
    }
 
    friend bool operator==(basic_sentinel const & lhs, basic_iterator<const_range> const & rhs)
    {
        return rhs == lhs;
    }
 
    friend bool operator!=(basic_iterator<const_range> const & lhs, basic_sentinel const & rhs)
    {
        return !(lhs == rhs);
    }
 
    friend bool operator!=(basic_sentinel const & lhs, basic_iterator<const_range> const & rhs)
    {
        return rhs != lhs;
    }
 
    template <bool other_const_range = !const_range>
        requires (std::sentinel_for<underlying_sentinel_t, basic_iterator<other_const_range>>)
    friend bool operator==(basic_iterator<other_const_range> const & lhs, basic_sentinel const & rhs)
    {
        // Actual comparison delegated to lhs base
        if (lhs == rhs.underlying_sentinel)
        {
            if constexpr (or_throw)
                throw unexpected_end_of_input{"Reached end of input before functor evaluated to true."};
            else
                return true;
        }
 
        return rhs.fun->operator()(*lhs);
    }
 
    template <bool other_const_range = !const_range>
        requires (std::sentinel_for<underlying_sentinel_t, basic_iterator<other_const_range>>)
    friend bool operator==(basic_sentinel const & lhs, basic_iterator<other_const_range> const & rhs)
    {
        return rhs == lhs;
    }
 
    template <bool other_const_range = !const_range>
        requires (std::sentinel_for<underlying_sentinel_t, basic_iterator<other_const_range>>)
    friend bool operator!=(basic_iterator<other_const_range> const & lhs, basic_sentinel const & rhs)
    {
        return !(lhs == rhs);
    }
 
    template <bool other_const_range = !const_range>
        requires (std::sentinel_for<underlying_sentinel_t, basic_iterator<other_const_range>>)
    friend bool operator!=(basic_sentinel const & lhs, basic_iterator<other_const_range> const & rhs)
    {
        return rhs != lhs;
    }
};
 
// ============================================================================
//  take_until_fn (adaptor definition)
// ============================================================================
 
template <bool or_throw, bool and_consume>
struct take_until_fn
{
    template <typename fun_t>
    constexpr auto operator()(fun_t && fun) const
    {
        return adaptor_from_functor{*this, std::forward<fun_t>(fun)};
    }
 
    template <std::ranges::viewable_range urng_t, typename fun_t>
    constexpr auto operator()(urng_t && urange, fun_t && fun) const
    {
        return view_take_until<std::views::all_t<urng_t>, fun_t, or_throw, and_consume>{
            std::views::all(std::forward<urng_t>(urange)),
            std::forward<fun_t>(fun)};
    }
};
 
} // namespace seqan3::detail
 
// ============================================================================
//  detail::take_until (adaptor instance definition)
// ============================================================================
 
namespace seqan3::detail
{
inline constexpr auto take_until = take_until_fn<false, false>{};
 
// ============================================================================
//  detail::take_until_or_throw (adaptor instance definition)
// ============================================================================
 
inline constexpr auto take_until_or_throw = take_until_fn<true, false>{};
 
// ============================================================================
//  detail::take_until_and_consume (adaptor instance definition)
// ============================================================================
 
inline constexpr auto take_until_and_consume = take_until_fn<false, true>{};
 
// ============================================================================
//  detail::take_until_or_throw_and_consume (adaptor instance definition)
// ============================================================================
 
inline constexpr auto take_until_or_throw_and_consume = take_until_fn<true, true>{};
 
} // namespace seqan3::detail
 
namespace std::ranges
{
template <std::ranges::view urng_t, typename fun_t, bool or_throw, bool and_consume>
inline constexpr bool enable_borrowed_range<seqan3::detail::view_take_until<urng_t, fun_t, or_throw, and_consume>> =
    enable_borrowed_range<urng_t>;
} // namespace std::ranges