private BannerDataHolder PickBannerK(Identity id, BannerQuerySetInfo info)
{
int? indexOfBannerToReturn = null;
double target = ThreadSafeRandom.NextDouble() * info.TotalRemainingImpressionsForTheCurrentTimeSlot;
Stack<int> suitableBannersIndexes = new Stack<int>();
for (int i = 0; i < info.Banners.Count && indexOfBannerToReturn == null; i++)
{
long remainingHits = info.GetRemainingHits(i);
if (remainingHits == 0) { continue; }
target -= remainingHits;
suitableBannersIndexes.Push(i);
if (target <= 0)
{
indexOfBannerToReturn = ReturnFirstBannerThatNeedsAHit(id, suitableBannersIndexes, info);
}
}
if (indexOfBannerToReturn.HasValue)
{
return info.Banners[indexOfBannerToReturn.Value];
}
else
{
return null;
}
}
private void AddBanners(int numberOfBannersToGet, Identity id, BannerQuerySetInfo info, List<BannerDataHolder> chosenBanners)
{
for (int i = 0; i < numberOfBannersToGet - chosenBanners.Count; i++)
{
BannerDataHolder banner = PickBannerK(id, info);
if (banner != null)
{
chosenBanners.Add(banner);
}
}
}
private int? ReturnFirstBannerThatNeedsAHit(Identity id, Stack<int> suitableBanners, BannerQuerySetInfo info)
{
double hitProportion = Common.ThreadSafeRandom.NextDouble();
while (suitableBanners.Count > 0)
{
int index = suitableBanners.Peek();
BannerDataHolder banner = info.Banners[index];
if (BannerHasBeenShownToAParticularIdentityTooManyTimesToday(banner, id) || info.BannerNeedsToDropAHit(index, hitProportion))
{
suitableBanners.Pop();
continue;
}
return suitableBanners.Peek();
}
return null;
}