unicode_bidi.hpp

// Copyright Take Vos 2020-2022.
// 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 "unicode_bidi_class.hpp"
#include "unicode_description.hpp"
#include "../assert.hpp"
 
namespace hi::inline v1 {
 
struct unicode_bidi_context {
    enum class mode_type : uint8_t { LTR, RTL, auto_LTR, auto_RTL };
 
    mode_type direction_mode = mode_type::auto_LTR;
    bool enable_mirrored_brackets = true;
    bool enable_line_separator = true;
 
    constexpr unicode_bidi_context() noexcept = default;
    constexpr unicode_bidi_context(unicode_bidi_context const&) noexcept = default;
    constexpr unicode_bidi_context(unicode_bidi_context&&) noexcept = default;
    constexpr unicode_bidi_context& operator=(unicode_bidi_context const&) noexcept = default;
    constexpr unicode_bidi_context& operator=(unicode_bidi_context&&) noexcept = default;
 
    constexpr unicode_bidi_context(unicode_bidi_class text_direction) noexcept {
        if (text_direction == unicode_bidi_class::L) {
            direction_mode = mode_type::auto_LTR;
        } else if (text_direction == unicode_bidi_class::R) {
            direction_mode = mode_type::auto_RTL;
        } else {
            hi_no_default();
        }
    }
};
 
namespace detail {
 
struct unicode_bidi_char_info {
    std::size_t index;
 
    unicode_description const *description;
 
    char32_t code_point;
 
    int8_t embedding_level;
 
    unicode_bidi_class direction;
 
    unicode_bidi_class bidi_class;
 
    [[nodiscard]] unicode_bidi_char_info(std::size_t index, char32_t code_point, unicode_description const *description) noexcept
        :
        index(index),
        description(description),
        code_point(code_point),
        embedding_level(0),
        direction(description->bidi_class()),
        bidi_class(description->bidi_class())
    {
    }
 
    [[nodiscard]] unicode_bidi_char_info(std::size_t index, unicode_bidi_class bidi_class) noexcept :
        index(index),
        code_point(U'\ufffd'),
        direction(bidi_class),
        bidi_class(bidi_class),
        embedding_level(0),
        description(nullptr)
    {
    }
};
 
using unicode_bidi_char_info_vector = std::vector<unicode_bidi_char_info>;
using unicode_bidi_char_info_iterator = unicode_bidi_char_info_vector::iterator;
using unicode_bidi_char_info_const_iterator = unicode_bidi_char_info_vector::const_iterator;
 
struct unicode_bidi_paragraph {
    using characters_type = std::vector<unicode_bidi_char_info>;
 
    characters_type characters;
 
    template<typename... Args>
    void emplace_character(Args&&...args) noexcept
    {
        characters.emplace_back(std::forward<Args>(args)...);
    }
};
 
template<typename OutputIt, typename SetCodePoint, typename SetTextDirection>
static void unicode_bidi_L4(
    unicode_bidi_char_info_iterator first,
    unicode_bidi_char_info_iterator last,
    OutputIt output_it,
    SetCodePoint set_code_point,
    SetTextDirection set_text_direction) noexcept
{
    for (auto it = first; it != last; ++it, ++output_it) {
        hilet text_direction = it->embedding_level % 2 == 0 ? unicode_bidi_class::L : unicode_bidi_class::R;
        set_text_direction(*output_it, text_direction);
        if (it->direction == unicode_bidi_class::R && it->description->bidi_bracket_type() != unicode_bidi_bracket_type::n) {
            set_code_point(*output_it, it->description->bidi_mirroring_glyph());
        }
    }
}
 
[[nodiscard]] std::pair<int8_t, unicode_bidi_class> unicode_bidi_P2_P3(
    unicode_bidi_char_info_iterator first,
    unicode_bidi_char_info_iterator last,
    unicode_bidi_context const& context = {}) noexcept;
 
[[nodiscard]] std::pair<unicode_bidi_char_info_iterator, std::vector<unicode_bidi_class>> unicode_bidi_P1(
    unicode_bidi_char_info_iterator first,
    unicode_bidi_char_info_iterator last,
    unicode_bidi_context const& context = {}) noexcept;
 
} // namespace detail
 
template<typename It, typename GetDescription, typename SetCodePoint, typename SetTextDirection>
std::pair<It, std::vector<unicode_bidi_class>> unicode_bidi(
    It first,
    It last,
    GetDescription get_description,
    SetCodePoint set_code_point,
    SetTextDirection set_text_direction,
    unicode_bidi_context const& context = {})
{
    auto proxy = detail::unicode_bidi_char_info_vector{};
    proxy.reserve(std::distance(first, last));
 
    std::size_t index = 0;
    for (auto it = first; it != last; ++it) {
        hilet[code_point, description_ptr] = get_description(*it);
        proxy.emplace_back(index++, code_point, description_ptr);
    }
 
    auto [proxy_last, paragraph_directions] = detail::unicode_bidi_P1(begin(proxy), end(proxy), context);
    last = shuffle_by_index(first, last, begin(proxy), proxy_last, [](hilet& item) {
        return item.index;
    });
 
    detail::unicode_bidi_L4(
        begin(proxy),
        proxy_last,
        first,
        std::forward<SetCodePoint>(set_code_point),
        std::forward<SetTextDirection>(set_text_direction));
    return {last, std::move(paragraph_directions)};
}
 
template<typename It, typename GetDescription>
[[nodiscard]] unicode_bidi_class
unicode_bidi_direction(It first, It last, GetDescription get_description, unicode_bidi_context const& context = {})
{
    auto proxy = detail::unicode_bidi_char_info_vector{};
    proxy.reserve(std::distance(first, last));
 
    std::size_t index = 0;
    for (auto it = first; it != last; ++it) {
        hilet[code_point, description_ptr] = get_description(*it);
        proxy.emplace_back(index++, code_point, description_ptr);
        if (proxy.back().direction == unicode_bidi_class::B) {
            // Break early when end-of-paragraph symbol is found.
            break;
        }
    }
 
    return detail::unicode_bidi_P2_P3(begin(proxy), end(proxy), context).second;
}
 
template<typename It, typename EndIt, typename DescriptionFunc>
It unicode_bidi_control_filter(It first, EndIt last, DescriptionFunc const& description_func)
{
    return std::remove_if(first, last, [&](hilet& item) {
        return is_control(description_func(item).bidi_class());
    });
}
 
} // namespace hi::inline v1