color.hh

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#pragma once
 
#ifdef _WIN32
#include <io.h>
#else
#include <unistd.h>
#endif
 
#include <string_view>
 
namespace cli {

enum class ColorMode { detect, never, always };

struct HelpPalette {
  std::string_view usage{"\033[1m"};
  std::string_view heading{"\033[1;4;36m"};
  std::string_view option{"\033[1;32m"};
  std::string_view metavar{"\033[36m"};
  std::string_view command{"\033[1;33m"};
  std::string_view metadata{"\033[2m"};
  std::string_view group{"\033[1;33m"};
  std::string_view reset{"\033[0m"};
};
 
inline constexpr HelpPalette default_help_palette{};

struct RecurseHelpTag {};

inline constexpr RecurseHelpTag recurse_help{};
 
namespace detail {

struct AnsiStyle {
  bool enabled;
  HelpPalette palette{};

  [[nodiscard]] constexpr auto bold() const noexcept -> std::string_view {
    return enabled ? "\033[1m" : "";
  }

  [[nodiscard]] constexpr auto underline() const noexcept -> std::string_view {
    return enabled ? "\033[4m" : "";
  }

  [[nodiscard]] constexpr auto reset() const noexcept -> std::string_view {
    return enabled ? palette.reset : "";
  }
 
  [[nodiscard]] constexpr auto usage() const noexcept -> std::string_view {
    return enabled ? palette.usage : "";
  }
 
  [[nodiscard]] constexpr auto heading() const noexcept -> std::string_view {
    return enabled ? palette.heading : "";
  }
 
  [[nodiscard]] constexpr auto option() const noexcept -> std::string_view {
    return enabled ? palette.option : "";
  }
 
  [[nodiscard]] constexpr auto metavar() const noexcept -> std::string_view {
    return enabled ? palette.metavar : "";
  }
 
  [[nodiscard]] constexpr auto command() const noexcept -> std::string_view {
    return enabled ? palette.command : "";
  }
 
  [[nodiscard]] constexpr auto metadata() const noexcept -> std::string_view {
    return enabled ? palette.metadata : "";
  }
 
  [[nodiscard]] constexpr auto group() const noexcept -> std::string_view {
    return enabled ? palette.group : "";
  }
};

inline auto is_tty() noexcept -> bool {
#ifdef _WIN32
  return _isatty(1) != 0;
#else
  return ::isatty(STDOUT_FILENO) != 0;
#endif
}

inline auto resolve_color(ColorMode mode,
                          HelpPalette palette = default_help_palette) noexcept
    -> AnsiStyle {
  const bool on =
      (mode == ColorMode::always) || (mode == ColorMode::detect && is_tty());
  return AnsiStyle{.enabled = on, .palette = palette};
}
 
}  // namespace detail
}  // namespace cli