public async Task <List <CovidDataByCounty> > GetCovidDataByCounty(CovidDataRequestEntity request)
{
// In order to calculate new cases for the first day they passed in we need to fetch data for one day before
var covidDataOrdered = await _dbContext.GetCovidDataByCountyOrdered(new CovidDataRequestEntity
{
StartDate = request.StartDate.AddDays(-1),
EndDate = request.EndDate,
Fips = request.Fips
});
if (covidDataOrdered.Count < 2)
{
return(new List <CovidDataByCounty>());
}
var returnList = new List <CovidDataByCounty>();
CovidDataByCountyEntity lastFoundDay = covidDataOrdered.FirstOrDefault(_ => _.Date == request.StartDate.Date);
foreach (var currentDayData in EachDay(request.StartDate, request.EndDate, covidDataOrdered.First()))
{
int?newCases = null;
var today = covidDataOrdered.FirstOrDefault(dto => dto.Date == currentDayData.Date);
if (today == null)
{
if (lastFoundDay != null)
{
// No data for this day
// We have found data before this day, this is a gap
newCases = 0;
}
}
else if (lastFoundDay == null)
{
// We have data today but it is our first data point found
// Need at least 2 days worth of data to calculate newCases
lastFoundDay = today;
}
else
{
// We have found at least 2 days worth of data
newCases = today.CasesCumulative - lastFoundDay.CasesCumulative;
lastFoundDay = today;
}
currentDayData.CasesNew = newCases;
returnList.Add(currentDayData);
}
return(returnList);
}
// https://stackoverflow.com/questions/1847580/how-do-i-loop-through-a-date-range
private IEnumerable <CovidDataByCounty> EachDay(DateTime from, DateTime thru, CovidDataByCountyEntity covidDataByCountyEntity)
{
for (var day = from.Date; day.Date <= thru.Date; day = day.AddDays(1))
{
var covidDataByCounty = _mapper.Map <CovidDataByCounty>(covidDataByCountyEntity);
covidDataByCounty.Date = day.ToUniversalTime().Date;
yield return(covidDataByCounty);
}
}