API.TransitManager.GetFavoriteStops C# (CSharp) Method

        private static List<FavoriteStop> GetFavoriteStops(BusStaticData staticData, IEnumerable<int> stopIds, LatLong? optionalUserLocation)
        {
            var favoriteStops = stopIds.Where(staticData.Stops.ContainsKey).Select(id =>
            {
                var stop = staticData.Stops[id];
                var distanceFromUser = optionalUserLocation != null
                        ? DistanceTo(optionalUserLocation.Value.Lat, optionalUserLocation.Value.Lon, stop.Lat, stop.Long, 'M')
                        : double.NaN;

                return new FavoriteStop(stop.ID, stop.Name, stop.RouteNames, distanceFromUser, isNearestStop: false);
            })
            .ToList();

            var nearestStop = optionalUserLocation != null
                ? staticData.Stops.Values
                    .Aggregate((s1, s2) =>
                        DistanceTo(optionalUserLocation.Value.Lat, optionalUserLocation.Value.Lon, s1.Lat, s1.Long, 'M') <
                        DistanceTo(optionalUserLocation.Value.Lat, optionalUserLocation.Value.Lon, s2.Lat, s2.Long, 'M') ? s1 : s2)
                : null;

            if (nearestStop != null && !favoriteStops.Any(f => f.Id == nearestStop.ID))
            {
                var distanceFromUser = optionalUserLocation != null
                    ? DistanceTo(optionalUserLocation.Value.Lat, optionalUserLocation.Value.Lon, nearestStop.Lat, nearestStop.Long, 'M')
                    : double.NaN;

                favoriteStops.Add(new FavoriteStop(nearestStop.ID, nearestStop.Name, nearestStop.RouteNames,
                                                   distanceFromUser, isNearestStop: true));
            }

            favoriteStops.Sort((f1, f2) => f1.DistanceFromUser.CompareTo(f2.DistanceFromUser));

            return favoriteStops;
        }