#include "utilities_ptime.h"


#include <boost/date_time/posix_time/posix_time_types.hpp>



using boost::posix_time::time_period;
using boost::posix_time::not_a_date_time;

///
/// \brief time_period_span
/// Combines two periods and any gap between them such that
///		begin = min(p1.begin, p2.begin) and
///		end = max(p1.end , p2.end).
/// If one of the periods is invalid, the other period is returned. If both
/// periods are invalid, the returned period is invalid.
///
/// \param left
/// \param right
/// \return
///
auto time_period_span(time_period & left, time_period & right) -> time_period
{
	time_period rv(left);
	if(rv.begin().is_special() || rv.is_null())
	{
		rv = right;
		if(rv.begin().is_special() || rv.is_null())
		{
			// both arguments are not_a_date_time -> set result invalid
			rv.begin() = not_a_date_time;
		}
	}
	else
	{
		if(!(right.begin().is_special() || right.is_null()))
		{
			rv = rv.span(right);
		}
	}

	return rv;
}