time_point.hpp

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// Andrew Naplavkov
 
#ifndef BOAT_DB_ADAPTED_TIME_POINT_HPP
#define BOAT_DB_ADAPTED_TIME_POINT_HPP
 
#include <boat/db/variant.hpp>
#include <boat/detail/string.hpp>
#include <chrono>
#include <regex>
 
namespace boat::db {

template <class Clock, class Duration>
void read(variant const& in, std::chrono::time_point<Clock, Duration>& out)
{
    if (!in.has_value()) {
        out = {};
        return;
    }
    // std::chrono::parse("%F %T", out)
    namespace sc = std::chrono;
    static auto const regex = std::regex{
        R"(^(\d{4})-(\d{2})-(\d{2}) (\d{2}):(\d{2}):(\d{2})(\.(\d+))?$)"};
    auto& str = std::get<std::string>(in);
    auto m = std::cmatch{};
    check(std::regex_match(str.data(), str.data() + str.size(), m, regex), str);
    auto ymd = sc::year_month_day(
        sc::year(from_chars<int>(m[1].first, m[1].length())),
        sc::month(from_chars<int>(m[2].first, m[2].length())),
        sc::day(from_chars<int>(m[3].first, m[3].length())));
    auto h = from_chars<int>(m[4].first, m[4].length());
    auto min = from_chars<int>(m[5].first, m[5].length());
    auto s = from_chars<int>(m[6].first, m[6].length());
    auto fraction = m[8].str();
    fraction.resize(6, '0');
    auto us = from_chars<int>(fraction.data(), fraction.size());
    check(ymd.ok() && h < 24 && min < 60 && s < 60, str.data());
    out = sc::time_point_cast<Duration>(
        sc::time_point<Clock, sc::microseconds>{
            sc::duration_cast<sc::microseconds>(
                sc::sys_days(ymd).time_since_epoch())} +
        sc::hours{h} + sc::minutes{min} + sc::seconds{s} +
        sc::microseconds{us});
}

template <class Clock, class Duration>
void write(variant& out, std::chrono::time_point<Clock, Duration> in)
{
    // std::format("{:L%F %T}", in)
    namespace sc = std::chrono;
    auto epoch = in.time_since_epoch();
    auto days = sc::floor<sc::days>(epoch);
    auto ymd = sc::year_month_day{sc::sys_days(days)};
    auto hms = sc::hh_mm_ss{sc::duration_cast<sc::microseconds>(epoch - days)};
    auto os = std::ostringstream{};
    os.imbue(std::locale::classic());
    os << std::setfill('0') << std::setw(4) << static_cast<int>(ymd.year())
       << "-" << std::setw(2) << static_cast<unsigned>(ymd.month()) << "-"
       << std::setw(2) << static_cast<unsigned>(ymd.day()) << " " << hms;
    auto& str = out.emplace<std::string>(std::move(os).str());
    str.erase(str.find_last_not_of('0') + 1);
    if (str.ends_with('.'))
        str.pop_back();
}
 
template <specialized<std::chrono::time_point> T>
struct kind<T> {
    static constexpr auto value = "timestamp";
};
 
}  // namespace boat::db
 
#endif  // BOAT_DB_ADAPTED_TIME_POINT_HPP