#include <string>
#include <iomanip>
#include <iostream>
#include <sstream>
#include <mutex>
#include <ctime>

enum class lvl {
    MAX,
    FATAL,
    IMPORTANT,
    ERROR,
    WARNING,
    MESSAGE,
    SPAM,
    MIN
};

class log {
public:
    log(lvl level = lvl::MESSAGE) {
        this->level = level;
    }

    /*
     * destroys the logline object. this destructor will output the
     * logline's accumulated content, in a thread-safe way.
     */
    ~log() {
        //thread-safety etc
        std::unique_lock<mutex> lock(globalmutex);
        //in this simplified class, we just output the whole line to
        //stdout, but in the real version there is a log of
        //manipulation of global data structures happening right here.
        if(level <  lvl::WARNING) {
            cout << '[' << time(NULL) << "] ";
            cout << sstr.str() << endl;
        }
    }

    //for writing normal types
    template<typename T>
    log &operator<<(T x) {
        sstr << x;
        return *this;
    }

    //for writing function pointers, such as endl or setw(5).
    template<typename T>
    log &operator<<(T &(*x)(T &)) {
        sstr << x;
        return *this;
    }

private:
    //this particular log line's level.
    lvl level;
    //accumulates all input.
    std::stringstream sstr;
    //to ensure thread-safety
    static std::mutex globalmutex;
};

int main() {
    log(lvl::SPAM) << "main method initialized";
    log(lvl::MESSAGE) << "the time is: " << time(NULL);
    log(lvl::SPAM) << "main method de-initializing";
}