trace_iterator_base.hpp

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// SPDX-FileCopyrightText: 2006-2024 Knut Reinert & Freie Universität Berlin
// SPDX-FileCopyrightText: 2016-2024 Knut Reinert & MPI für molekulare Genetik
// SPDX-License-Identifier: BSD-3-Clause
 
#pragma once
 
#include <concepts>
#include <ranges>
 
#include <seqan3/alignment/matrix/detail/trace_directions.hpp>
#include <seqan3/alignment/matrix/detail/two_dimensional_matrix_iterator_base.hpp>
#include <seqan3/alignment/matrix/detail/two_dimensional_matrix_iterator_concept.hpp>
 
namespace seqan3::detail
{
 
template <typename derived_t, two_dimensional_matrix_iterator matrix_iter_t>
class trace_iterator_base
{
private:
    static_assert(std::same_as<std::iter_value_t<matrix_iter_t>, trace_directions>,
                  "Value type of the underlying iterator must be seqan3::detail::trace_directions.");
 
    template <typename other_derived_t, two_dimensional_matrix_iterator other_matrix_iter_t>
    friend class trace_iterator_base;
 
    friend derived_t;
 
    constexpr trace_iterator_base() = default;                                        
    constexpr trace_iterator_base(trace_iterator_base const &) = default;             
    constexpr trace_iterator_base(trace_iterator_base &&) = default;                  
    constexpr trace_iterator_base & operator=(trace_iterator_base const &) = default; 
    constexpr trace_iterator_base & operator=(trace_iterator_base &&) = default;      
    ~trace_iterator_base() = default;                                                 
 
    constexpr trace_iterator_base(matrix_iter_t const matrix_iter) noexcept : matrix_iter{matrix_iter}
    {
        set_trace_direction(*matrix_iter);
    }
 
    template <typename other_derived_t, two_dimensional_matrix_iterator other_matrix_iter_t>
        requires std::constructible_from<matrix_iter_t, other_matrix_iter_t>
    constexpr trace_iterator_base(trace_iterator_base<other_derived_t, other_matrix_iter_t> const & other) noexcept :
        trace_iterator_base{other.matrix_iter}
    {}
 
public:
    // Doxygen: https://github.com/seqan/product_backlog/issues/424
    using value_type = trace_directions;
    using reference = trace_directions const &;          
    using pointer = value_type const *;                  
    using difference_type = std::ptrdiff_t;              
    using iterator_category = std::forward_iterator_tag; 
 
    reference operator*() const noexcept
    {
        return current_direction;
    }
 
    pointer operator->() const noexcept
    {
        return &current_direction;
    }
 
    [[nodiscard]] constexpr matrix_coordinate coordinate() const noexcept
    {
        return matrix_iter.coordinate();
    }
 
    constexpr derived_t & operator++() noexcept
    {
        trace_directions old_dir = *matrix_iter;
 
        assert(old_dir != trace_directions::none);
 
        if (current_direction == trace_directions::up)
        {
            derived().go_up(matrix_iter);
            // Set new trace direction if last position was up_open.
            if (static_cast<bool>(old_dir & trace_directions::carry_up_open))
                set_trace_direction(*matrix_iter);
        }
        else if (current_direction == trace_directions::left)
        {
            derived().go_left(matrix_iter);
            // Set new trace direction if last position was left_open.
            if (static_cast<bool>(old_dir & trace_directions::carry_left_open))
                set_trace_direction(*matrix_iter);
        }
        else
        {
            assert(current_direction == trace_directions::diagonal);
 
            derived().go_diagonal(matrix_iter);
            set_trace_direction(*matrix_iter);
        }
        return derived();
    }
 
    constexpr derived_t operator++(int) noexcept
    {
        derived_t tmp{derived()};
        ++(*this);
        return tmp;
    }
 
    constexpr friend bool operator==(derived_t const & lhs, derived_t const & rhs) noexcept
    {
        return lhs.matrix_iter == rhs.matrix_iter;
    }
 
    constexpr friend bool operator==(derived_t const & lhs, std::default_sentinel_t const &) noexcept
    {
        return *lhs.matrix_iter == trace_directions::none;
    }
 
    constexpr friend bool operator==(std::default_sentinel_t const &, derived_t const & rhs) noexcept
    {
        return rhs == std::default_sentinel;
    }
 
    constexpr friend bool operator!=(derived_t const & lhs, derived_t const & rhs) noexcept
    {
        return !(lhs == rhs);
    }
 
    constexpr friend bool operator!=(derived_t const & lhs, std::default_sentinel_t const &) noexcept
    {
        return !(lhs == std::default_sentinel);
    }
 
    constexpr friend bool operator!=(std::default_sentinel_t const &, derived_t const & rhs) noexcept
    {
        return !(rhs == std::default_sentinel);
    }
 
private:
    constexpr void go_left(matrix_iter_t & iter) const noexcept
    {
        iter -= matrix_offset{row_index_type{0}, column_index_type{1}};
    }
 
    constexpr void go_up(matrix_iter_t & iter) const noexcept
    {
        iter -= matrix_offset{row_index_type{1}, column_index_type{0}};
    }
 
    constexpr void go_diagonal(matrix_iter_t & iter) const noexcept
    {
        iter -= matrix_offset{row_index_type{1}, column_index_type{1}};
    }
 
    void set_trace_direction(trace_directions const dir) noexcept
    {
        if (static_cast<bool>(dir & trace_directions::diagonal))
        {
            current_direction = trace_directions::diagonal;
        }
        else if (static_cast<bool>(dir & trace_directions::up))
        {
            current_direction = trace_directions::up;
        }
        else if (static_cast<bool>(dir & trace_directions::left))
        {
            current_direction = trace_directions::left;
        }
        else
        {
            current_direction = trace_directions::none;
        }
    }
 
    constexpr derived_t & derived() noexcept
    {
        return static_cast<derived_t &>(*this);
    }
 
    constexpr derived_t const & derived() const noexcept
    {
        return static_cast<derived_t const &>(*this);
    }
 
    matrix_iter_t matrix_iter{};          
    trace_directions current_direction{}; 
};
 
} // namespace seqan3::detail