CppDemo1/Logger.h

//
// Created by 张衡 on 25-7-8.
//

#ifndef LOGGER_H
#define LOGGER_H

#include <queue>
#include <mutex>
#include <string>
#include <condition_variable>
#include <thread>
#include <fstream>
#include <atomic>
#include <sstream>
#include <vector>
#include <stdexcept>



//辅助函数，多个参数转化字符串
template <typename T>
std::string to_string_helper(T&& arg) {
    std::ostringstream oss;
    oss << std::forward<T>(arg);
    return oss.str();
}

class LogQueue {
public:
    void push(const std::string& msg) {
        std::lock_guard<std::mutex> lock(mutex_);
        queue_.push(msg);
        //构造好自动加锁，析构自动解锁
        cond_var_.notify_all();
    }; //字符串放队列中
    bool pop(std::string& msg) {
        std::unique_lock<std::mutex> lock(mutex_);
        //条件变量唤醒之后直接加锁
        cond_var_.wait(lock, [this]() {
           return !queue_.empty() || is_shutdown_; //返回true就继续往下走
        });
        //消费逻辑
        //队列不为空or已经关闭
        if (is_shutdown_ && queue_.empty()) {
            return false;
        }
        //保证队列的数据被清空掉
        // while (is_shutdown_ && !queue_.empty()) {
        //     msg = queue_.front();
        //     queue_.pop();
        //     return false;
        // }
        msg = queue_.front(); //返回消息给msg指针
        queue_.pop();
        return true;
    };
    void shutdown() {
        std::lock_guard<std::mutex> lock(mutex_);
        is_shutdown_ = true;
        cond_var_.notify_all();
    };
private:
    std::queue<std::string> queue_;
    std::mutex mutex_;
    std::condition_variable cond_var_;
    bool is_shutdown_ = false;
};

enum class Loglevel {
    INFO,
    DEBUG,
    WARNING,
    ERROR
};

class Logger {
public:
    Logger(const std::string& filename) : log_file_(filename, std::ios::out | std::ios::app)
    , exit_flag_(false) {
        if (!log_file_.is_open()) {
            throw std::runtime_error("Failed to open log file");
        }

        worker_thread_ = std::thread([this]() {
            std::string msg;
            while (log_queue_.pop(msg)) {
                log_file_ << msg << std::endl;
            }
        });
    };
    ~Logger() {
        exit_flag_ = true;
        log_queue_.shutdown();
        //如果日志结束了，说明主线程退出，这里是优雅退出，等待其他主线程
        if (worker_thread_.joinable()) {
            worker_thread_.join();
        }

        if (log_file_.is_open()) {
            log_file_.close();
        }
    };

    template<typename ... Args>
    void log(Loglevel loglevel, const std::string& format, Args&& ...args) {
        std::string level_str;
        switch (loglevel) {
            case Loglevel::INFO:
                level_str = "[INFO] ";
                break;
            case Loglevel::DEBUG:
                level_str = "[DEBUG] ";
                break;
            case Loglevel::WARNING:
                level_str = "[WARNING] ";
                break;
            case Loglevel::ERROR:
                level_str = "[ERROR] ";
                break;
        }
        log_queue_.push(level_str + formatMessage(format, std::forward<Args>(args)...));
    };

private:

    std::string GetTimeStamp() {
        std::time_t now = std::time(nullptr);
        std::tm* local_time = std::localtime(&now);
        char buffer[80];
        std::strftime(buffer, sizeof(buffer), "%Y-%m-%d %H:%M:%S", local_time);
        return std::string(buffer);
    }

    template<typename ... Args>
    std::string formatMessage(const std::string& format, Args&&...args) {
        std::vector<std::string> arg_strings = {to_string_helper(std::forward<Args>(args))...};
        std::ostringstream oss;
        size_t arg_index = 0;
        size_t pos = 0;
        size_t placeholder = format.find("{}", pos);

        oss << GetTimeStamp() << " ";

        while (placeholder != std::string::npos) {
            oss << format.substr(pos, placeholder - pos);
            if (arg_index < arg_strings.size()) {
                oss << arg_strings[arg_index];
            } else {
                oss << "{}";
                //如果占位符没有对应参数，保留占位符
            }
            arg_strings[arg_index++];
            pos = placeholder + 2;
            placeholder = format.find("{}", pos);
        }


        oss << format.substr(pos);
        while (arg_index < arg_strings.size()) {
            oss << arg_strings[arg_index++];
        }
        return oss.str();
    }

    LogQueue log_queue_;
    std::thread worker_thread_;
    std::ofstream log_file_;
    std::atomic<bool> exit_flag_;
};




#endif //LOGGER_H