// Copyright (c) 2009-2010 Satoshi Nakamoto
// Copyright (c) 2009-2020 The Bitcoin Core developers
// Distributed under the MIT software license, see the accompanying
// file COPYING or http://www.opensource.org/licenses/mit-license.php.

#ifndef BITCOIN_LOGGING_TIMER_H
#define BITCOIN_LOGGING_TIMER_H

#include <logging.h>
#include <util/macros.h>
#include <util/time.h>

#include <chrono>
#include <string>


namespace BCLog {

//! RAII-style object that outputs timing information to logs.
template <typename TimeType>
class Timer
{
public:
    //! If log_category is left as the default, end_msg will log unconditionally
    //! (instead of being filtered by category).
    Timer(
        std::string prefix,
        std::string end_msg,
        BCLog::LogFlags log_category = BCLog::LogFlags::ALL) :
            m_prefix(std::move(prefix)),
            m_title(std::move(end_msg)),
            m_log_category(log_category)
    {
        this->Log(strprintf("%s started", m_title));
        m_start_t = GetTime<std::chrono::microseconds>();
    }

    ~Timer()
    {
        this->Log(strprintf("%s completed", m_title));
    }

    void Log(const std::string& msg)
    {
        const std::string full_msg = this->LogMsg(msg);

        if (m_log_category == BCLog::LogFlags::ALL) {
            LogPrintf("%s\n", full_msg);
        } else {
            LogPrint(m_log_category, "%s\n", full_msg);
        }
    }

    std::string LogMsg(const std::string& msg)
    {
        const auto end_time = GetTime<std::chrono::microseconds>() - m_start_t;
        if (m_start_t.count() <= 0) {
            return strprintf("%s: %s", m_prefix, msg);
        }

        std::string units = "";
        float divisor = 1;

        if (std::is_same<TimeType, std::chrono::microseconds>::value) {
            units = "μs";
        } else if (std::is_same<TimeType, std::chrono::milliseconds>::value) {
            units = "ms";
            divisor = 1000.;
        } else if (std::is_same<TimeType, std::chrono::seconds>::value) {
            units = "s";
            divisor = 1000. * 1000.;
        }

        const float time_ms = end_time.count() / divisor;
        return strprintf("%s: %s (%.2f%s)", m_prefix, msg, time_ms, units);
    }

private:
    std::chrono::microseconds m_start_t{};

    //! Log prefix; usually the name of the function this was created in.
    const std::string m_prefix{};

    //! A descriptive message of what is being timed.
    const std::string m_title{};

    //! Forwarded on to LogPrint if specified - has the effect of only
    //! outputting the timing log when a particular debug= category is specified.
    const BCLog::LogFlags m_log_category{};

};

} // namespace BCLog


#define LOG_TIME_MILLIS_WITH_CATEGORY(end_msg, log_category) \
    BCLog::Timer<std::chrono::milliseconds> PASTE2(logging_timer, __COUNTER__)(__func__, end_msg, log_category)
#define LOG_TIME_SECONDS(end_msg) \
    BCLog::Timer<std::chrono::seconds> PASTE2(logging_timer, __COUNTER__)(__func__, end_msg)


#endif // BITCOIN_LOGGING_TIMER_H
