parselink-old/include/parselink/logging/formatters.h

//-----------------------------------------------------------------------------
//     ___                      __ _       _
//    / _ \__ _ _ __ ___  ___  / /(_)_ __ | | __
//   / /_)/ _` | '__/ __|/ _ \/ / | | '_ \| |/ /
//  / ___/ (_| | |  \__ \  __/ /__| | | | |   <
//  \/    \__,_|_|  |___/\___\____/_|_| |_|_|\_\ .
//
//-----------------------------------------------------------------------------
// Author: Kurt Sassenrath
// Module: Logging
//
// {fmt} formatters for various types that are used throughout the codebase.
// Some are specific, while others depend on traits.
//
// Copyright (c) 2023 Kurt Sassenrath.
//
// License TBD.
//-----------------------------------------------------------------------------

#ifndef logging_formatters_d22a64b1645a8134
#define logging_formatters_d22a64b1645a8134

#include "theme.h"
#include "traits.h"
#include <magic_enum.hpp>

#include <tl/expected.hpp>

// Simple wrapper for error strings to be formatted like any other string_view.
template <>
struct fmt::formatter<parselink::logging::error_str>
        : fmt::formatter<std::string_view> {
    template <typename FormatContext>
    constexpr auto format(auto const& v, FormatContext& ctx) const {
        return fmt::formatter<std::string_view>::format(v.v, ctx);
    }
};

// Support enums. By default, enums print the enum type name as well as the
// enum name for the given value. E.g.
//
//     enum Color { Red, Green, Blue };
//     auto const color = Color::Green;
//
// Logging `color` will yield "Color::Green"
template <typename E>
    requires std::is_enum_v<E>
struct fmt::formatter<E> : fmt::formatter<std::string_view> {
    template <typename FormatContext>
    auto format(E const v, FormatContext& ctx) const {
        auto str = [v] {
            return fmt::format("{}::{}", magic_enum::enum_type_name<E>(),
                    magic_enum::enum_name(v));
        }();
        return fmt::formatter<std::string_view>::format(str, ctx);
    }
};

// Support enums that _only_ print the string "name" of the enum value. Using
// the same example above:
//
//     enum Color { Red, Green, Blue };
//     auto const color = Color::Green;
//
// Logging `enum_name_only{color}` will yield "Green"
template <typename E>
    requires std::is_enum_v<E>
struct fmt::formatter<parselink::logging::enum_name_only<E>>
        : fmt::formatter<std::string_view> {
    using enum_name_only = parselink::logging::enum_name_only<E>;

    template <typename FormatContext>
    auto format(enum_name_only const v, FormatContext& ctx) const {
        return fmt::formatter<std::string_view>::format(
                magic_enum::enum_name(v.v), ctx);
    }
};

template <>
struct fmt::formatter<std::error_code> : fmt::formatter<std::string_view> {
    template <typename FormatContext>
    auto format(auto const& v, FormatContext& ctx) const {
        return fmt::formatter<std::string_view>::format(v.message(), ctx);
    }
};

// Support conversion of typical standard error codes into a human-readable
// string.
template <>
struct fmt::formatter<std::errc> : fmt::formatter<std::error_code> {
    template <typename FormatContext>
    auto format(std::errc const& v, FormatContext& ctx) const {
        return fmt::formatter<std::error_code>::format(
                    std::make_error_code(v), ctx);
    }
};

// Support printing bytes as their hex representation.
template <>
struct fmt::formatter<std::byte> {
    template <typename ParseContext>
    constexpr auto parse(ParseContext& ctx) -> decltype(ctx.begin()) {
        return ctx.begin();
    }

    template <typename FormatContext>
    auto format(std::byte const v, FormatContext& ctx) const {
        return fmt::format_to(ctx.out(), "0x{:0x}", std::uint8_t(v));
    }
};

// Support printing raw/smart pointers without needing to wrap them in fmt::ptr
template <parselink::logging::detail::printable_pointer T>
struct fmt::formatter<T> : fmt::formatter<void const*> {
    template <typename FormatContext>
    auto format(T const& v, FormatContext& ctx) const {
        return fmt::formatter<void const*>::format(fmt::ptr(v), ctx);
    }
};

// TODO(ksassenrath): Re-enable when expected has been integrated
template <typename T, typename Err>
struct fmt::formatter<tl::expected<T, Err>> {
    template <typename ParseContext>
    constexpr auto parse(ParseContext& ctx) -> decltype(ctx.begin()) {
        return ctx.begin();
    }

    template <typename FormatContext>
    auto format(tl::expected<T, Err> const& v, FormatContext& ctx) const {
        if (v) {
            return fmt::format_to(ctx.out(), "{}",
                    parselink::logging::format_arg<T>{v.value()});
        } else {
            return fmt::format_to(ctx.out(), "{}",
                    parselink::logging::format_arg<Err>{v.error()});
        }
    }
};

// Support format_arg wrappers, which will be used to colorize output.
template <typename T>
struct fmt::formatter<parselink::logging::format_arg<T>>
        : fmt::formatter<typename parselink::logging::format_arg<T>::type> {
    using format_arg_type = parselink::logging::format_arg<T>;
    using resolved_type = typename format_arg_type::type;

    template <typename FormatContext>
    auto format(format_arg_type const& v, FormatContext& ctx) const {
        return fmt::formatter<resolved_type>::format(v.v, ctx);
    }
};

#endif // logging_formatters_d22a64b1645a8134