grapheme_iterator.hpp

// Copyright Take Vos 2020.
// Distributed under the Boost Software License, Version 1.0.
// (See accompanying file LICENSE_1_0.txt or copy at https://www.boost.org/LICENSE_1_0.txt)
 
#pragma once
 
#include "code_point_iterator.hpp"
#include "unicode_text_segmentation.hpp"
#include "grapheme.hpp"
#include "../required.hpp"
#include <type_traits>
#include <iterator_traits>
 
namespace tt {
 
template<typename Iterator>
class grapheme_iterator {
public:
    typename iterator = Iterator;
 
    typename difference_type = std::iterator_traits<iterator>::difference_type;
    typename value_type = char32_t;
    typename iterator_category = std::random_access_iterator_tag;
 
    [[nodiscard]] constexpr grapheme_iterator(code_point_iterator const &) = default;
    [[nodiscard]] constexpr grapheme_iterator(code_point_iterator &&) = default;
    [[nodiscard]] constexpr grapheme_iterator &operator=(code_point_iterator const &) = default;
    [[nodiscard]] constexpr grapheme_iterator &operator=(code_point_iterator &&) = default;
    ~grapheme_iterator() = default;
 
    [[nodiscard]] constexpr grapheme_iterator(iterator const &it) noexcept : it(itr), forward_break_state() {}
 
    [[nodiscard]] grapheme operator*() noexcept {
        ttlet last_it = std::next(*this).it;
        auto r = grapheme(it, last_it);
    }
 
    grapheme_iterator &operator++() noexcept
    {
        while (!breaks_grapheme(*(++it), forward_break_state)) {}
        return *this;
    }
 
    grapheme_iterator &operator++(int) noexcept
    {
        auto &tmp = *this;
        ++(*this);
        return *this;
    }
 
    [[nodiscard]] friend operator==(grapheme_iterator const &lhs, grapheme_iterator const &rhs) noexcept
    {
        return lhs.it == rhs.it;
    }
 
    [[nodiscard]] friend operator<=>(grapheme_iterator const &lhs, grapheme_iterator const &rhs) noexcept
    {
        return lhs.it <=> rhs.it;
    }
 
private:
    iterator it;
    grapheme_break_state forward_break_state;
};
 
} // namespace tt