colour_help_formatter.hpp

// Copyright (C) 2022-2023 by Camden Mannett.
// Distributed under the Boost Software License, Version 1.0.
// (See accompanying file LICENSE or copy at https://www.boost.org/LICENSE_1_0.txt)
 
#pragma once
 
#include "arg_router/policy/default_help_formatter.hpp"
 
namespace arg_router::policy
{
namespace help_formatter_component
{
template <std::size_t Indent>
class colour_line_formatter
{
    static_assert(Indent > 0, "Indent must be greater than zero");
 
    constexpr static auto reset_colour = std::string_view{"\033[0m"};
    constexpr static auto red_colour = std::string_view{"\033[31m"};
    constexpr static auto green_colour = std::string_view{"\033[32m"};
 
public:
    template <std::size_t DescStart, std::size_t Depth, typename HelpData>
    void format(std::ostream& stream, std::size_t columns)
    {
        if constexpr (!HelpData::label::empty()) {
            constexpr auto indent = indent_size<Depth>();
            stream << red_colour << utility::create_sequence_cts_t<indent, ' '>::get()
                   << HelpData::label::get();
 
            if constexpr (!HelpData::description::empty()) {
                static_assert(HelpData::description::get().find('\t') == std::string_view::npos,
                              "Help descriptions cannot contain tabs");
 
                constexpr auto gap =
                    DescStart - indent - utility::utf8::terminal_width(HelpData::label::get());
 
                // Spacing between the end of the args label and start of description
                stream << green_colour << utility::create_sequence_cts_t<gap, ' '>::get();
 
                // Print the description, breaking if a word will exceed the terminal width
                for (auto it = utility::utf8::line_iterator{HelpData::description::get(),
                                                            columns - DescStart};
                     it != utility::utf8::line_iterator{};) {
                    stream << *it;
 
                    // If there's more data to follow, then add the offset
                    if (++it != utility::utf8::line_iterator{}) {
                        stream << '\n' << utility::create_sequence_cts_t<DescStart, ' '>::get();
                    }
                }
            }
 
            stream << "\n" << reset_colour;
        }
    }
 
    void format(std::ostream& stream,
                std::size_t desc_start,
                std::size_t depth,
                std::size_t columns,
                const runtime_help_data& help_data)
    {
        if (!help_data.label.empty()) {
            const auto indent = depth * Indent;
            stream << red_colour << std::setw(indent) << ' ' << help_data.label;
 
            if (!help_data.description.empty()) {
                const auto gap =
                    desc_start - indent - utility::utf8::terminal_width(help_data.label);
 
                // Spacing between the end of the args label and start of description
                stream << green_colour << std::setw(gap) << ' ';
 
                // Print the description, breaking if a word will exceed the terminal width
                for (auto it =
                         utility::utf8::line_iterator{help_data.description, columns - desc_start};
                     it != utility::utf8::line_iterator{};) {
                    stream << *it;
 
                    // If there's more data to follow, then add the offset
                    if (++it != utility::utf8::line_iterator{}) {
                        stream << '\n' << std::setw(desc_start) << ' ';
                    }
                }
            }
 
            stream << "\n" << reset_colour;
        }
    }
 
private:
    template <std::size_t Depth>
    [[nodiscard]] constexpr static std::size_t indent_size() noexcept
    {
        return Depth * Indent;
    }
};
}  // namespace help_formatter_component
 
template <typename Indent = traits::integral_constant<std::size_t{4}>,
          typename DescColumnOffset = traits::integral_constant<Indent{} * 2>,
          typename PreambleFormatter = help_formatter_component::default_preamble_formatter,
          typename AddendumFormatter = help_formatter_component::default_addendum_formatter>
using colour_help_formatter_t =
    default_help_formatter_t<Indent,
                             DescColumnOffset,
                             help_formatter_component::colour_line_formatter<Indent{}>,
                             PreambleFormatter,
                             AddendumFormatter>;
 
constexpr auto colour_help_formatter = colour_help_formatter_t<>{};
}  // namespace arg_router::policy