#pragma once

#include <chrono>
#include <ctime>
#include <iomanip>
#include <ostream>

#include <fmt/format.h>

#include "utils/datetime/datetime_error.hpp"
#include "utils/total_ordering.hpp"

class Timestamp : public TotalOrdering<Timestamp>
{
public:
    Timestamp() : Timestamp(0, 0) {}

    Timestamp(std::time_t time, long nsec = 0) : unix_time(time), nsec(nsec)
    {
        auto result = gmtime_r(&time, &this->time);

        if(result == nullptr)
            throw DatetimeError("Unable to construct from {}", time);
    }

    Timestamp(const Timestamp&) = default;
    Timestamp(Timestamp&&) = default;

    static Timestamp now()
    {
        timespec time;
        clock_gettime(CLOCK_REALTIME, &time);

        return {time.tv_sec, time.tv_nsec};
    }

    long year() const
    {
        return time.tm_year + 1900;
    }

    long month() const
    {
        return time.tm_mon + 1;
    }

    long day() const
    {
        return time.tm_mday;
    }

    long hour() const
    {
        return time.tm_hour;
    }

    long min() const
    {
        return time.tm_min;
    }

    long sec() const
    {
        return time.tm_sec;
    }

    long subsec() const
    {
        return nsec / 10000;
    }

    const std::string to_iso8601() const
    {
        return fmt::format(fiso8601, year(), month(), day(), hour(),
                           min(), sec(), subsec());
    }

    friend std::ostream& operator<<(std::ostream& stream, const Timestamp& ts)
    {
        return stream << ts.to_iso8601();
    }

    operator std::string() const
    {
        return to_iso8601();
    }

    constexpr friend bool operator==(const Timestamp& a, const Timestamp& b)
    {
        return a.unix_time == b.unix_time && a.nsec == b.nsec;
    }

    constexpr friend bool operator<(const Timestamp& a, const Timestamp& b)
    {
        return a.unix_time < b.unix_time
            || (a.unix_time == b.unix_time && a.nsec < b.nsec);
    }

private:
    std::tm time;

    std::time_t unix_time;
    long nsec;

    static constexpr auto fiso8601 =
        "{:04d}-{:02d}-{:02d}T{:02d}:{:02d}:{:02d}.{:05d}Z";
};