// constants

// holidays or vacations, date format must be the same
Set HOLIDAYS = new HashSet(['02.02.2019', '03.02.2019']);

// date format need by date check
def SIMPLE_DATE_FORMAT = new SimpleDateFormat('dd.MM.YYYY');

// time/date constants
long DAY = 24 * 60 * 60 * 1000, HOUR = 60 * 60 * 1000;
int START_WORK_HOURS = 07, END_WORK_HOURS = 16;
int WORK_DAY_HOURS = END_WORK_HOURS - START_WORK_HOURS;
long WORK_DAY_AS_MILLIS = WORK_DAY_HOURS * HOUR;

long diff = 0;

// date value definition and extraction

def createdAt = doc['created_at'];
def firstRespondedAt = doc['stats.first_responded_at'];

// handling for corrupt or invalid data

if(createdAt==null || firstRespondedAt== null){
     return -1L;
}
if (firstRespondedAt.size() == 0) {
   return -1L;
}

// initialisation of calendar's, necessary for iteration over calendar

Date dateStart = new Date(createdAt.date.millis);
Calendar startCalendar = new GregorianCalendar();
startCalendar.setTime(dateStart);

Date dateEnd = new Date(firstRespondedAt.date.millis);
Calendar endCalendar = new GregorianCalendar();
endCalendar.setTime(dateEnd);

// simple check: are date values in the same day

boolean sameDay = startCalendar.get(Calendar.DAY_OF_YEAR) == endCalendar.get(Calendar.DAY_OF_YEAR) && endCalendar.get(Calendar.YEAR) == endCalendar.get(Calendar.YEAR);
Date resultTemp = startCalendar.getTime();

String resultDate = SIMPLE_DATE_FORMAT.format(resultTemp);

//calculation of expected start work hours for start date
Calendar startCalendarExpected = (Calendar) endCalendar.clone();
startCalendarExpected.set(Calendar.HOUR_OF_DAY, START_WORK_HOURS);
startCalendarExpected.set(Calendar.MINUTE, 0);
startCalendarExpected.set(Calendar.SECOND, 0);

//calculation of expected end work hours for start date
Calendar endCalendarExpected = (Calendar) startCalendar.clone();
endCalendarExpected.set(Calendar.HOUR_OF_DAY, END_WORK_HOURS);
endCalendarExpected.set(Calendar.MINUTE, 0);
endCalendarExpected.set(Calendar.SECOND, 0);

if(!HOLIDAYS.contains(resultDate)) {
   if(sameDay){
      if(endCalendar.getTimeInMillis()>endCalendarExpected.getTimeInMillis()&&startCalendar.getTimeInMillis()>endCalendarExpected.getTimeInMillis()){
         return 0L;
       }else if(startCalendar.getTimeInMillis()<startCalendarExpected.getTimeInMillis()&&endCalendar.getTimeInMillis()<startCalendarExpected.getTimeInMillis()){
          return 0L;
       }else{
           long start = startCalendar.getTimeInMillis()<startCalendarExpected.getTimeInMillis()? startCalendarExpected.getTimeInMillis() : startCalendar.getTimeInMillis();
           long end =   endCalendar.getTimeInMillis()>endCalendarExpected.getTimeInMillis()? endCalendarExpected.getTimeInMillis() : endCalendar.getTimeInMillis();
           return end - start;
       }
     }
   long tempDiff = endCalendarExpected.getTimeInMillis() - startCalendar.getTimeInMillis();
   if (tempDiff > 0) {
      diff += tempDiff > WORK_DAY_AS_MILLIS ? WORK_DAY_AS_MILLIS : tempDiff;
    }
  }
  startCalendar.add(Calendar.DATE, 1);
  while (sameDay && startCalendar.before(endCalendar)) {
           resultTemp = startCalendar.getTime();
                resultDate = SIMPLE_DATE_FORMAT.format(resultTemp);
                if (!HOLIDAYS.contains(resultDate)) {
                    diff += WORK_DAY_AS_MILLIS;

                }
                startCalendar.add(Calendar.DATE, 1);
            }

 Date result = endCalendar.getTime();
 resultDate = SIMPLE_DATE_FORMAT.format(result);
 if (!HOLIDAYS.contains(resultDate)) {
     long tempDiff = endCalendar.getTimeInMillis() - startCalendarExpected.getTimeInMillis();
     if (tempDiff > 0) {
         diff += tempDiff > WORK_DAY_AS_MILLIS ? WORK_DAY_AS_MILLIS : tempDiff;
      }
 }
return diff;