mijin2/source/mijin/logging/formatting.hpp

#pragma once

#if !defined(MIJIN_LOGGING_FORMATTING_HPP_INCLUDED)
#define MIJIN_LOGGING_FORMATTING_HPP_INCLUDED 1

#include <flat_map>
#include <format>
#include <variant>
#include "./logger.hpp"
#include "../memory/dynamic_pointer.hpp"
#include "../memory/memutil.hpp"
#include "../memory/virtual_allocator.hpp"
#include "../util/annot.hpp"
#include "../util/concepts.hpp"

namespace mijin
{
template<allocator_type_for<char> TAllocator = std::allocator<char>>
class LogFormatter
{
public:
    using string_t = std::basic_string<char, std::char_traits<char>, TAllocator>;

    virtual ~LogFormatter() noexcept = default;

    virtual void format(const LogMessage& message, string_t& outFormatted) noexcept = 0;
};

template<allocator_type_for<char> TAllocator = std::allocator<char>>
class SimpleLogFormatter : public LogFormatter<TAllocator>
{
public:
    using typename LogFormatter<TAllocator>::string_t;
private:
    string_t mFormat;
public:
    explicit SimpleLogFormatter(string_t format) MIJIN_NOEXCEPT : mFormat(std::move(format)) {}

    void format(const LogMessage& message, string_t& outFormatted) noexcept override;
};

template<template<typename> typename TAllocator = std::allocator,
                            deleter_type<LogFormatter<TAllocator<char>>> TDeleter = AllocatorDeleter<TAllocator<LogFormatter<TAllocator<char>>>>>
        requires(allocator_type<TAllocator<char>>)
class FormattingLogSink : public LogSink
{
public:
    using allocator_t = TAllocator<char>;
    using formatter_t = LogFormatter<allocator_t>;
    using formatter_deleter_t = TDeleter;
    using formatter_ptr_t = DynamicPointer<formatter_t, formatter_deleter_t>;
    using string_t = formatter_t::string_t;
private:
    not_null_t<formatter_ptr_t> mFormatter;
    string_t mBuffer;
public:
    explicit FormattingLogSink(not_null_t<formatter_ptr_t> formatter, TAllocator<char> allocator = {})
        MIJIN_NOEXCEPT_IF(std::is_nothrow_move_constructible_v<TAllocator<char>>)
        : mFormatter(std::move(formatter)), mBuffer(std::move(allocator))
    {}

    virtual void handleMessageFormatted(const LogMessage& message, const char* formatted) MIJIN_NOEXCEPT = 0;

    void handleMessage(const LogMessage& message) noexcept override
    {
        mBuffer.clear();
        mFormatter->format(message, mBuffer);
        handleMessageFormatted(message, mBuffer.c_str());
    }
};

template<allocator_type_for<char> TAllocator>
void SimpleLogFormatter<TAllocator>::format(const LogMessage& message, string_t& outFormatted) noexcept
{
    for (auto pos = mFormat.begin(); pos != mFormat.end(); ++pos)
    {
        if (*pos == '{')
        {
            ++pos;
            if (*pos == '{')
            {
                // double {
                outFormatted += '{';
                continue;
            }
            const auto argStart = pos;
            static const std::string_view endChars = ":}";
            pos = std::find_first_of(pos, mFormat.end(), endChars.begin(), endChars.end());
            MIJIN_ASSERT(pos != mFormat.end(), "Invalid format.");

            const std::string_view argName(argStart, pos);
            std::string argFormat;
            if (*pos == ':')
            {
                const auto formatStart = pos;
                pos = std::find(pos, mFormat.end(), '}');
                MIJIN_ASSERT(pos != mFormat.end(), "Invalid format.");
                argFormat = std::string_view(formatStart, pos);
            }

            // small utility that uses the provided string buffer for storing the format string
            auto formatInline = [&](const auto& value)
            {
                using type_t = std::decay_t<decltype(value)>;

                // if there is no format, just directly print the value
                if (argFormat.empty())
                {
                    if constexpr (std::is_arithmetic_v<type_t>)
                    {
                        std::format_to(std::back_inserter(outFormatted), "{}", value);
                    }
                    else
                    {
                        outFormatted += value;
                    }
                    return;
                }
                // first copy the format string + braces into the buffer
                const auto formatStart = outFormatted.size();
                outFormatted += '{';
                outFormatted += argFormat;
                outFormatted += '}';
                const auto formatEnd = outFormatted.size();
                auto format = std::string_view(outFormatted).substr(formatStart, formatEnd - formatStart);

                // then append the formatted text
                std::vformat_to(std::back_inserter(outFormatted), format, std::make_format_args(value));

                // and then remove the format from the buffer again
                outFormatted.erase(formatStart, formatEnd - formatStart);
            };

            if (argName == "text")
            {
                formatInline(message.text);
            }
            else if (argName == "channel")
            {
                formatInline(message.channel->name);
            }
            else if (argName == "file")
            {
                formatInline(message.sourceLocation.file_name());
            }
            else if (argName == "function")
            {
                formatInline(message.sourceLocation.function_name());
            }
            else if (argName == "line")
            {
                formatInline(message.sourceLocation.line());
            }
            else if (argName == "column")
            {
                formatInline(message.sourceLocation.column());
            }
            else if (argName == "level")
            {
                formatInline(message.level->name);
            }
            else
            {
                MIJIN_ERROR("Invalid format argument name.");
            }
        }
        else
        {
            outFormatted += *pos;
        }
    }
}
} // namespace mijin

#endif // !defined(MIJIN_LOGGING_FORMATTING_HPP_INCLUDED)