adaptor_base.hpp

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// SPDX-FileCopyrightText: 2006-2025 Knut Reinert & Freie Universität Berlin
// SPDX-FileCopyrightText: 2016-2025 Knut Reinert & MPI für molekulare Genetik
// SPDX-License-Identifier: BSD-3-Clause
 
#pragma once
 
#include <ranges>
#include <tuple>
 
#include <seqan3/core/platform.hpp>
 
namespace seqan3::detail
{
 
// ============================================================================
//  forwards
// ============================================================================
 
template <typename left_adaptor_t, typename right_adaptor_t>
class combined_adaptor;
 
// ============================================================================
//  adaptor_base
// ============================================================================
 
template <typename derived_type, typename... stored_args_ts>
class adaptor_base
{
private:
    std::tuple<stored_args_ts...> arguments;
 
    template <typename urng_t, size_t... Is>
    constexpr auto pass_args_to_impl(urng_t && urange, std::index_sequence<Is...> const &) const &
    {
        // std::get returns lvalue-reference to value, but we need to copy the values
        // so that the view does not depend on the functor
        return static_cast<derived_type const &>(*this).impl(
            std::forward<urng_t>(urange),
            std::tuple_element_t<Is, std::tuple<stored_args_ts...>>(std::get<Is>(arguments))...);
    }
 
    template <typename urng_t, size_t... Is>
    constexpr auto pass_args_to_impl(urng_t && urange, std::index_sequence<Is...> const &) &&
    {
        // move out values, because we don't need them anymore (*this is temporary)
        return static_cast<derived_type &&>(*this).impl(
            std::forward<urng_t>(urange),
            std::tuple_element_t<Is, std::tuple<stored_args_ts...>>(std::get<Is>(std::move(arguments)))...);
    }
 
    friend derived_type;
 
public:
    // a default constructor is not provided, however the constructor below might be one.
    constexpr adaptor_base(adaptor_base const &) noexcept = default;             
    constexpr adaptor_base(adaptor_base &&) noexcept = default;                  
    constexpr adaptor_base & operator=(adaptor_base const &) noexcept = default; 
    constexpr adaptor_base & operator=(adaptor_base &&) noexcept = default;      
    ~adaptor_base() noexcept = default;                                          
 
    constexpr adaptor_base(stored_args_ts... args)
        noexcept(noexcept(std::tuple<stored_args_ts...>{std::forward<stored_args_ts>(args)...})) :
        arguments{std::forward<stored_args_ts>(args)...}
    {}
 
    template <std::ranges::input_range urng_t>
    constexpr auto operator()(urng_t && urange) const &
    {
        return pass_args_to_impl(std::forward<urng_t>(urange), std::make_index_sequence<sizeof...(stored_args_ts)>{});
    }
 
    template <std::ranges::input_range urng_t>
    constexpr auto operator()(urng_t && urange) &&
    {
        return std::move(*this).pass_args_to_impl(std::forward<urng_t>(urange),
                                                  std::make_index_sequence<sizeof...(stored_args_ts)>{});
    }
 
    template <typename arg_t>
    constexpr friend auto operator|(arg_t && arg, derived_type const & me)
    {
        if constexpr (std::ranges::input_range<arg_t>)
            return me(std::forward<arg_t>(arg));
        else
            return combined_adaptor{std::forward<arg_t>(arg), me};
    }
 
    template <typename arg_t>
    constexpr friend auto operator|(arg_t && arg, derived_type && me)
    {
        if constexpr (std::ranges::input_range<arg_t>)
            return std::move(me)(std::forward<arg_t>(arg));
        else
            return combined_adaptor{std::forward<arg_t>(arg), std::move(me)};
    }
 
    template <typename arg_t>
    constexpr friend auto operator|(adaptor_base const & me, arg_t && arg)
    {
        return combined_adaptor{static_cast<derived_type const &>(me), std::forward<arg_t>(arg)};
    }
 
    template <typename arg_t>
    constexpr friend auto operator|(adaptor_base && me, arg_t && arg)
    {
        return combined_adaptor{static_cast<derived_type &&>(me), std::forward<arg_t>(arg)};
    }
};
 
// ============================================================================
//  combined_adaptor
// ============================================================================
 
template <typename left_adaptor_t, typename right_adaptor_t>
class combined_adaptor :
    public adaptor_base<combined_adaptor<left_adaptor_t, right_adaptor_t>, left_adaptor_t, right_adaptor_t>
{
private:
    using base_type = adaptor_base<combined_adaptor<left_adaptor_t, right_adaptor_t>, left_adaptor_t, right_adaptor_t>;
 
    friend base_type;
 
    template <std::ranges::input_range urng_t, typename left_adaptor_t_, typename right_adaptor_t_>
    static auto impl(urng_t && urange, left_adaptor_t_ && left_adaptor, right_adaptor_t_ && right_adaptor)
    {
        return std::forward<urng_t>(urange) | std::forward<left_adaptor_t_>(left_adaptor)
             | std::forward<right_adaptor_t_>(right_adaptor);
    }
 
public:
    constexpr combined_adaptor() = default;                                              
    constexpr combined_adaptor(combined_adaptor const &) noexcept = default;             
    constexpr combined_adaptor(combined_adaptor &&) noexcept = default;                  
    constexpr combined_adaptor & operator=(combined_adaptor const &) noexcept = default; 
    constexpr combined_adaptor & operator=(combined_adaptor &&) noexcept = default;      
    ~combined_adaptor() noexcept = default;                                              
 
    using base_type::base_type;
 
    constexpr combined_adaptor(left_adaptor_t l, right_adaptor_t r) :
        base_type{std::forward<left_adaptor_t>(l), std::forward<right_adaptor_t>(r)}
    {}
};
 
} // namespace seqan3::detail