default_printer.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 <functional>
#include <iosfwd>
#include <tuple>
#include <utility>
 
#include <seqan3/core/platform.hpp>
 
namespace seqan3
{
 
// clang-format off
struct no_printer_found{};
template <typename> struct advanceable_alignment_coordinate_printer {};
template <typename> struct alignment_matrix_printer {};
template <typename> struct alignment_printer {};
template <typename> struct alignment_result_printer {};
template <typename> struct alphabet_printer {};
template <typename> struct cigar_printer {};
template <typename> struct debug_stream_printer {};
template <typename> struct dynamic_bitset_printer {};
template <typename> struct enumeration_printer {};
template <typename> struct input_range_printer {};
template <typename> struct integer_sequence_printer {};
template <typename> struct integral_printer {};
template <typename> struct mask_printer {};
template <typename> struct optional_printer {};
template <typename> struct sam_flag_printer {};
template <typename> struct sequence_printer {};
template <typename> struct search_result_printer {};
template <typename> struct simd_printer {};
template <typename> struct std_byte_printer {};
template <typename> struct std_variant_printer {};
template <typename> struct std_printer {};
template <typename> struct strong_type_printer {};
template <typename> struct char_sequence_printer {};
template <typename> struct trace_directions_printer {};
template <typename> struct tuple_printer {};
// clang-format on
 
template <typename printer_t, typename stream_t, typename arg_t>
concept printable_with = std::invocable<printer_t, stream_t, arg_t>;
 
template <typename type_t>
    requires requires (std::ostream & cout, type_t const & value) {
        { cout << value };
    }
struct std_printer<type_t>
{
    template <typename stream_t, typename arg_t>
        requires requires (stream_t & stream) { stream.stream; }
    constexpr void operator()(stream_t & stream, arg_t && arg) const
    {
        *stream.stream << arg;
    }
};
 
template <std::integral integral_t>
struct integral_printer<integral_t>
{
    template <typename stream_t>
    constexpr void operator()(stream_t & stream, integral_t const arg) const
    {
        // note that we assume here that we always can print all std::integral's,
        // but this is not correct since std::cout << char32_t{5}; is not possible.
        // since char32_t is also an alphabet, we avoid infinite recursion here.
        if constexpr (printable_with<std_printer<integral_t>, stream_t &, integral_t>)
            std::invoke(std_printer<integral_t>{}, stream, arg);
        else
            static_assert(std::same_as<integral_t *, void>, "This type is not printable.");
        // We actually want `static_assert(false, "This type is not printable.");`.
        // But this only works starting with GCC13. Before that, also the `if constexpr` branches that are not taken
        // are evaluated and `static_assert(false)` will always result in an error. As a pre-GCC13 workaround,
        // we can make the `false` dependent on some template type, which then will only be evaluated if the branch is
        // taken.
    }
};
 
template <template <typename> typename... printer_templates_t>
struct printer_order
{
protected:
    template <typename stream_t, typename arg_t, typename... printers_t>
    static constexpr size_t find_index()
    {
        size_t i = 0;
        return ((printable_with<printers_t, stream_t, arg_t> ? false : ++i) && ...) ? sizeof...(printer_templates_t)
                                                                                    : i;
    }
 
    template <typename stream_t,
              typename arg_t,
              size_t i = find_index<stream_t, arg_t, printer_templates_t<arg_t>...>()>
    using printer_for_t =
        // first: the index of the printer that can print the arguments or sizeof...(printers_t) if no printer was found
        // second: the tuple of instantiated printers extended with no_printer_found
        std::tuple_element_t<i, std::tuple<printer_templates_t<arg_t>..., no_printer_found>>;
};
 
struct default_printer :
    public printer_order<
        debug_stream_printer,
        alignment_result_printer,                 // type seqan3::alignment_result<>
        search_result_printer,                    // type seqan3::search_result<>
        alignment_printer,                        // concept seqan3::tuple_like<>
        advanceable_alignment_coordinate_printer, // type seqan3::detail::advanceable_alignment_coordinate<>
        alignment_matrix_printer,                 // concept seqan3::detail::matrix<>
        trace_directions_printer,                 // type seqan3::detail::trace_directions
        mask_printer,                             // type seqan3::mask
        integral_printer,                         // concept std::integral
        cigar_printer,                            // type seqan3::cigar
        // NOTE: alphabet_printer needs the integral_printer overload, otherwise it might have infinite recursion due to
        // char and uint being an alphabet
        alphabet_printer,       // concept seqan3::alphabet
        sam_flag_printer,       // type seqan3::sam_flag
        simd_printer,           // concept simd::simd_concept<>
        dynamic_bitset_printer, // type seqan3::dynamic_bitset<>
        // NOTE: In C++26, std::optional<T> is a view (and hence models std::ranges::input_range<>).
        // So it needs to have priority over char_sequence_printer, integer_sequence_printer, and input_range_printer.
        optional_printer,         // type std::optional<> or std::nullopt_t
        char_sequence_printer,    // concept std::range::input_range<> with char value_type
        integer_sequence_printer, // concept std::range::input_range<> with std::integral value_type
        sequence_printer, // concept seqan3::sequence<>, i.e. std::range::input_range<> with seqan3::alphabet value_type
        input_range_printer, // concept std::range::input_range<>
        strong_type_printer, // concept seqan3::detail::derived_from_strong_type<>
        enumeration_printer, // types for which seqan3::enumeration_names is overloaded
        tuple_printer,       // concept seqan3::tuple_like<>
        std_byte_printer,    // type std::byte
        std_variant_printer, // type std::variant<>
        std_printer          // anything that can be printed by std::ostream
        >
{
public:
    template <typename stream_t, typename arg_t>
        requires printable_with<printer_for_t<stream_t &, std::remove_cvref_t<arg_t>>, stream_t &, arg_t>
    constexpr void operator()(stream_t & stream, arg_t && arg) const
    {
        using printer_t = printer_for_t<stream_t &, std::remove_cvref_t<arg_t>>;
        std::invoke(printer_t{}, stream, std::forward<arg_t>(arg));
    }
};
 
} // namespace seqan3