Detailed explanation of the use of Qt spdlog log module

#ifndef LOGMANAGER_H
#define LOGMANAGER_H
#include <QObject>
#include <memory>
#include <spdlog/>
class LogManager : public QObject
{
    Q_OBJECT
public:
    static LogManager& instance();
    void initialize(const QString& logDir = "logs",
                    const QString& appName = "app",
                    size_t maxFileSize = 1024 * 1024, // 1MB
                    size_t maxFiles = 10);
    void shutdown();
    template<typename... Args>
    static void log(spdlog::level::level_enum level, const QString& message, Args... args)
    {
        if (instance().m_logger)
        {
            instance().m_logger->log(level, ().c_str(), args...);
        }
    }
    // Convenient method    static void trace(const QString& message)
    {
        log(spdlog::level::trace, message);
    }
    static void debug(const QString& message)
    {
        log(spdlog::level::debug, message);
    }
    static void info(const QString& message)
    {
        log(spdlog::level::info, message);
    }
    static void warn(const QString& message)
    {
        log(spdlog::level::warn, message);
    }
    static void error(const QString& message)
    {
        log(spdlog::level::err, message);
    }
    static void critical(const QString& message)
    {
        log(spdlog::level::critical, message);
    }
private:
    LogManager(QObject* parent = nullptr);
    ~LogManager();
    std::shared_ptr<spdlog::logger> createCustomLogger(const std::string& base_filename,
            size_t max_size,
            size_t max_files);
    std::shared_ptr<spdlog::logger> m_logger;
    std::atomic<bool> m_shuttingDown{false};
signals:
    void aboutToShutdown();
private slots:
    void onAboutToQuit();
};
// Log macro definition#define LOG_TRACE(...)    LogManager::log(spdlog::level::trace, __VA_ARGS__)
#define LOG_DEBUG(...)    LogManager::log(spdlog::level::debug, __VA_ARGS__)
#define LOG_INFO(...)     LogManager::log(spdlog::level::info, __VA_ARGS__)
#define LOG_WARN(...)     LogManager::log(spdlog::level::warn, __VA_ARGS__)
#define LOG_ERROR(...)    LogManager::log(spdlog::level::err, __VA_ARGS__)
#define LOG_CRITICAL(...) LogManager::log(spdlog::level::critical, __VA_ARGS__)
#endif // LOGMANAGER_H

#include ""
#include <spdlog/sinks/base_sink.h>
#include <spdlog/details/file_helper.h>
#include <mutex>
#include <chrono>
#include <iomanip>
#include <sstream>
#include <vector>
#include <algorithm>
#include <QDir>
#include <QFileInfo>
#include <QDateTime>
#include <QCoreApplication>
#include <csignal>
#include <QDebug>
// Replace the C++11 compatible implementation of std::filesystemnamespace spdlog
{
    class custom_rotating_file_sink : public spdlog::sinks::base_sink<std::mutex>
    {
    public:
        custom_rotating_file_sink(const std::string& base_filename,
                                  std::size_t max_size,
                                  std::size_t max_files)
            : base_filename_(base_filename),
              max_size_(max_size),
              max_files_(max_files)
        {
            file_helper_.open(gen_filename());
        }
    protected:
        void sink_it_(const spdlog::details::log_msg& msg) override
        {
            spdlog::memory_buf_t formatted;
            formatter_->format(msg, formatted);
            if (file_helper_.size() + () > max_size_)
            {
                rotate_();
            }
            file_helper_.write(formatted);
        }
        void flush_() override
        {
            file_helper_.flush();
        }
    private:
        std::string gen_filename()
        {
            QDateTime now = QDateTime::currentDateTime();
            QString timeStr = ("yyyyMMddhhmmss");
            // Add milliseconds part (3 digits)            int ms = ().msec();
            timeStr += QString("_%1").arg(ms, 3, 10, QLatin1Char('0'));
            return base_filename_ + "_" + () + ".log";
        }
        void rotate_()
        {
            file_helper_.close();
            cleanup_old_files();
            file_helper_.open(gen_filename());
        }
        void cleanup_old_files()
        {
            if (max_files_ == 0) return;
            QFileInfo base_info(QString::fromStdString(base_filename_));
            QDir dir = base_info.absoluteDir();
            QString base_name = base_info.fileName();
            QFileInfoList files = (QStringList() << (base_name + "_*.log"),
                                                    QDir::Files, QDir::Time);
            // Delete the oldest file            while (() >= static_cast<int>(max_files_))
            {
                QFile::remove(().absoluteFilePath());
                ();
            }
        }
        std::string base_filename_;
        std::size_t max_size_;
        std::size_t max_files_;
        spdlog::details::file_helper file_helper_;
    };
} // namespace
LogManager::LogManager(QObject* parent) : QObject(parent)
{
    // Connect Qt exit signal    connect(qApp, &QCoreApplication::aboutToQuit, this, &LogManager::onAboutToQuit);
    // Handle exception signals    static auto handleSignal = [](int)
    {
        LogManager::instance().shutdown();
        std::_Exit(1);
    };
    std::signal(SIGTERM, handleSignal);
    std::signal(SIGSEGV, handleSignal);
    std::signal(SIGINT, handleSignal);
    std::signal(SIGABRT, handleSignal);
}
LogManager::~LogManager()
{
    shutdown();
}
LogManager& LogManager::instance()
{
    static LogManager instance;
    return instance;
}
void LogManager::initialize(const QString& logDir, const QString& appName, size_t maxFileSize, size_t maxFiles)
{
    if (m_logger)
    {
        return;
    }
    // Make sure the log directory exists    QDir().mkpath(logDir);
    std::string base_filename = QDir(logDir).absoluteFilePath(appName).toStdString();
    m_logger = createCustomLogger(base_filename, maxFileSize, maxFiles);
    // Set the default log format    m_logger->set_pattern("[%Y-%m-%d %H:%M:%S.%e] [%l] [thread %t] %v");
    m_logger->set_level(spdlog::level::trace);
    spdlog::register_logger(m_logger);
    spdlog::set_default_logger(m_logger);
}
void LogManager::shutdown()
{
    /*
    if (m_logger)
    {
        spdlog::drop(m_logger->name());
        m_logger.reset();
    }
    spdlog::shutdown();
    */
    if (m_shuttingDown) return;
    m_shuttingDown = true;
    emit aboutToShutdown();
    try
    {
        if (m_logger)
        {
            m_logger->flush();
            spdlog::drop(m_logger->name());
        }
        spdlog::shutdown();
        m_logger.reset();
    }
    catch (const spdlog::spdlog_ex& ex)
    {
        qCritical() << "Log shutdown error:" << ();
    }
}
void LogManager::onAboutToQuit()
{
    shutdown();
}
std::shared_ptr<spdlog::logger> LogManager::createCustomLogger(const std::string& base_filename,
        size_t max_size,
        size_t max_files)
{
    auto sink = std::make_shared<spdlog::custom_rotating_file_sink>(base_filename, max_size, max_files);
    auto logger = std::make_shared<spdlog::logger>("qt_logger", sink);
    return logger;
}

#include <QCoreApplication>
#include ""
#include <QTimer>
#include <QDebug>
int main(int argc, char* argv[])
{
    QCoreApplication a(argc, argv);
    // Initialize the log system    LogManager::instance().initialize("logs", "MyAppTest");
    // Connect the shutdown signal for additional cleaning    QObject::connect(&LogManager::instance(), &LogManager::aboutToShutdown, []()
    {
        LOG_INFO("Performing final cleanup before shutdown...");
    });
    for (int i = 0; i < 5000; ++i)
    {
        LOG_INFO("This is a test message to fill up the log file. Iteration: {}", i);
    }
    return ();
}