supercell-wx/wxdata/source/scwx/util/time.cpp

// Prevent redefinition of __cpp_lib_format
#if defined(_MSC_VER)
#   include <yvals_core.h>
#endif

// Enable chrono formatters
#ifndef __cpp_lib_format
#   define __cpp_lib_format 202110L
#endif

#include <scwx/util/time.hpp>

#include <sstream>

#if !defined(_MSC_VER)
#   include <date/date.h>
#endif

namespace scwx
{
namespace util
{

std::chrono::system_clock::time_point TimePoint(uint32_t modifiedJulianDate,
                                                uint32_t milliseconds)
{
   using namespace std::chrono;
   using sys_days       = time_point<system_clock, days>;
   constexpr auto epoch = sys_days {1969y / December / 31d};

   return epoch + (modifiedJulianDate * 24h) +
          std::chrono::milliseconds {milliseconds};
}

std::string TimeString(std::chrono::system_clock::time_point time,
                       const time_zone*                      timeZone,
                       bool                                  epochValid)
{
   using namespace std::chrono;

#if !defined(_MSC_VER)
   using namespace date;
#endif

   auto               timeInSeconds = time_point_cast<seconds>(time);
   std::ostringstream os;

   if (epochValid || time.time_since_epoch().count() != 0)
   {
      if (timeZone != nullptr)
      {
         zoned_time zt = {current_zone(), timeInSeconds};
         os << zt;
      }
      else
      {
         os << timeInSeconds;
      }
   }

   return os.str();
}

template<typename T>
std::optional<std::chrono::sys_time<T>>
TryParseDateTime(const std::string& dateTimeFormat, const std::string& str)
{
   using namespace std::chrono;

#if !defined(_MSC_VER)
   using namespace date;
#endif

   std::optional<std::chrono::sys_time<T>> value = std::nullopt;
   std::chrono::sys_time<T>                dateTime;
   std::istringstream                      ssDateTime {str};

   ssDateTime >> parse(dateTimeFormat, dateTime);

   if (!ssDateTime.fail())
   {
      value = dateTime;
   }

   return value;
}

template std::optional<std::chrono::sys_time<std::chrono::seconds>>
TryParseDateTime<std::chrono::seconds>(const std::string& dateTimeFormat,
                                       const std::string& str);

} // namespace util
} // namespace scwx