//

// Created by gelldur on 04.01.2020.

//

#include "to_string.hpp"

#include <array>

#include <cassert>

#include <functional>

#include <string_view>

namespace gcpp::string::to_string

{

using namespace std::chrono;

// size return +1 char as extra \0, len = 19 + 1

static constexpr auto LENGTH_OF_DATE = std::size("2020-01-01 00:00:00");

// len = 23 + 1

static constexpr auto LENGTH_OF_DATE_WITH_FRAC = std::size("2020-01-01 00:00:00.000");

static void ISO8601(std::chrono::system_clock::time_point timePointUTC,

bool withFractional,

const std::function<void(std::string_view)>& callback)

{

const auto timeInfo = system_clock::to_time_t(timePointUTC);

std::tm result{};

/// https://linux.die.net/man/3/gmtime_r as std::gmtime is not thread safe

gmtime_r(&timeInfo, &result); // gmtime_r is not portable, if needed please fix.

std::array<char, LENGTH_OF_DATE_WITH_FRAC> buffer{}; // Example date: "2020-01-04 10:43:44.000"

auto length = std::strftime(buffer.data(), buffer.size(), "%F %T", &result);

if(withFractional)

{

auto ms = duration_cast<milliseconds>(timePointUTC.time_since_epoch());

unsigned fractionalSeconds = ms.count() % 1000;

length += std::sprintf(buffer.data() + length, ".%.3u", fractionalSeconds);

}

assert(buffer.at(length) == '\0');

callback(std::string_view{buffer.data(), length});

}

std::string formatTimeISO8601(std::chrono::system_clock::time_point timePointUTC,

bool withFractional)

{

std::string returned((withFractional ? LENGTH_OF_DATE_WITH_FRAC : LENGTH_OF_DATE), '\0');

ISO8601(timePointUTC, withFractional, [&returned](std::string_view data) {

returned.assign(data.data(), data.length());

});

assert(returned.capacity() == (withFractional ? LENGTH_OF_DATE_WITH_FRAC : LENGTH_OF_DATE));

assert(returned.size() == (withFractional ? LENGTH_OF_DATE_WITH_FRAC - 1 : LENGTH_OF_DATE - 1));

return returned;

}

std::ostream& asISO8601(std::ostream& stream,

std::chrono::system_clock::time_point timePointUTC,

bool withFractional)

{

ISO8601(timePointUTC, withFractional, [&stream](std::string_view data) { stream << data; });

return stream;

}

} // namespace gcpp::string::to_string