spdlog/include/c11log/sinks/file_sinks.h

#pragma once

#include <fstream>
#include  <iomanip>
#include <mutex>
#include "base_sink.h"
#include "../details/flush_helper.h"

namespace c11log {
namespace sinks {

/*
* Trivial file sink with single file as target
*/
class simple_file_sink : public base_sink {
public:
    explicit simple_file_sink(const std::string &filename,
                              const std::string& extension,
                              const std::chrono::milliseconds &flush_every=std::chrono::milliseconds::zero())
        : _mutex(),
          _ofstream(filename + "." + extension, std::ofstream::binary|std::ofstream::app),
          _flush_helper(flush_every) {
    }
protected:
    void _sink_it(const std::string& msg) override {
        std::lock_guard<std::mutex> lock(_mutex);
        _flush_helper.write(_ofstream, msg);
    }
private:
    std::mutex _mutex;
    std::ofstream _ofstream;
    details::file_flush_helper _flush_helper;
};


/*
 * Thread safe, size limited file sink
*/
class rotating_file_sink : public base_sink {
public:
    rotating_file_sink(const std::string &base_filename, const std::string &extension,
                       size_t max_size, size_t max_files,
                       const std::chrono::milliseconds &flush_every = std::chrono::milliseconds::zero()):
        _base_filename(base_filename),
        _extension(extension),
        _max_size(max_size),
        _max_files(max_files),
        _current_size(0),
        _mutex(),
        _ofstream(_calc_filename(_base_filename, 0, _extension), std::ofstream::binary),
        _flush_helper(flush_every) {
    }

protected:
    void _sink_it(const std::string& msg) override {
        std::lock_guard<std::mutex> lock(_mutex);
        _current_size += msg.length();
        if (_current_size  > _max_size) {
            _rotate();
            _current_size = msg.length();
        }
        _flush_helper.write(_ofstream, msg);
    }


private:
    static std::string _calc_filename(const std::string& filename, std::size_t index, const std::string& extension) {
        std::ostringstream oss;
        if (index)
            oss << filename << "." << index << "." << extension;
        else
            oss << filename << "." << extension;
        return oss.str();
    }


    // Rotate old files:
    // log.n-1.txt -> log.n.txt
    // log n-2.txt -> log.n-1.txt
    // ...
    // log.txt -> log.1.txt
    void _rotate() {
        _ofstream.close();
        //Remove oldest file
        for (auto i = _max_files; i > 0; --i) {
            auto src = _calc_filename(_base_filename, i - 1, _extension);
            auto target = _calc_filename(_base_filename, i, _extension);
            if (i == _max_files)
                std::remove(target.c_str());
            std::rename(src.c_str(), target.c_str());
        }
        _ofstream.open(_calc_filename(_base_filename, 0, _extension));
    }
    std::string _base_filename;
    std::string _extension;
    std::size_t _max_size;
    std::size_t _max_files;
    std::size_t _current_size;
    std::mutex _mutex;
    std::ofstream _ofstream;
    details::file_flush_helper _flush_helper;
};

/*
 * Thread safe file sink that closes the log file at midnight and opens new one
 */
class daily_file_sink:public base_sink {
public:
    explicit daily_file_sink(const std::string& base_filename,
                             const std::string& extension,
                             const std::chrono::milliseconds &flush_every = std::chrono::milliseconds::zero()):
        _base_filename(base_filename),
        _extension(extension),
        _midnight_tp (_calc_midnight_tp() ),
        _mutex(),
        _ofstream(_calc_filename(_base_filename, _extension), std::ofstream::binary|std::ofstream::app),
        _flush_helper(flush_every) {
    }

protected:
    void _sink_it(const std::string& msg) override {
        std::lock_guard<std::mutex> lock(_mutex);
        if (std::chrono::system_clock::now() >= _midnight_tp) {
            _ofstream.close();
            _ofstream.open(_calc_filename(_base_filename, _extension));
            _midnight_tp = _calc_midnight_tp();
        }
        _flush_helper.write(_ofstream, msg);
    }

private:
    // Return next midnight's time_point
    static std::chrono::system_clock::time_point _calc_midnight_tp() {
        using namespace std::chrono;
        auto now = system_clock::now();
        time_t tnow = std::chrono::system_clock::to_time_t(now);
        tm date = c11log::details::os::localtime(tnow);
        date.tm_hour = date.tm_min = date.tm_sec = 0;
        auto midnight = std::chrono::system_clock::from_time_t(std::mktime(&date));
        return system_clock::time_point(midnight + hours(24));
    }

	//Create filename for the form basename.YYYY-MM-DD.extension
    static std::string _calc_filename(const std::string& basename, const std::string& extension) {
        std::tm tm = c11log::details::os::localtime();		
		std::ostringstream oss;
		oss << basename << '.';
		oss << tm.tm_year + 1900 << '-' << std::setw(2) << std::setfill('0') << tm.tm_mon + 1 << '-' << tm.tm_mday;
		oss << '.' << extension;
		return oss.str();
    }

    std::string _base_filename;
    std::string _extension;
    std::chrono::system_clock::time_point _midnight_tp;
    std::mutex _mutex;
    std::ofstream _ofstream;
    details::file_flush_helper _flush_helper;

};
}
}