//********************************************************
// The following code example is taken from the book
//  C++20 - The Complete Guide
//  by Nicolai M. Josuttis (www.josuttis.com)
//  http://www.cppstd20.com
//
// The code is licensed under a
//  Creative Commons Attribution 4.0 International License
//  http://creativecommons.org/licenses/by/4.0/
//********************************************************


#include <chrono>
#include <string>
#include <sstream>
#include <cassert>

// parse year-month-day with optional hour:minute and optional :sec
// - returns a time_point<> of the passed clock (default: system_clock)
//   in seconds
template<typename Clock = std::chrono::system_clock>
auto parseDateTime(const std::string& s)
{
  // return value:
  std::chrono::time_point<Clock, std::chrono::seconds> tp;

  // string stream to read from:
  std::istringstream sstrm{s};  // no string_view support

  auto posColon = s.find(":");
  if (posColon != std::string::npos) {
    if (posColon != s.rfind(":")) {
      // multiple colons:
      std::chrono::from_stream(sstrm, "%F %T", tp);
    }
    else {
      // one colon:
      std::chrono::from_stream(sstrm, "%F %R", tp);
    }
  }
  else {
    // no colon:
    std::chrono::from_stream(sstrm, "%F", tp);
  }

  // handle invalid formats:
  assert((!sstrm.fail()));

  return tp;
}