/// <summary>
/// polyfill takes a given GeoJSON-like data structure and preallocated,
/// zeroed memory, and fills it with the hexagons that are contained by
/// the GeoJSON-like data structure.
///
/// This implementation traces the GeoJSON geofence(s) in cartesian space with
/// hexagons, tests them and their neighbors to be contained by the geofence(s),
/// and then any newly found hexagons are used to test again until no new
/// hexagons are found.
/// </summary>
/// <param name="polygon">The geofence and holes defining the relevant area</param>
/// <param name="res">The Hexagon resolution (0-15)</param>
/// <returns>List of H3Index that compose the polyfill</returns>
/// <!--
/// algos.c
/// void H3_EXPORT(polyfill)
/// -->
public static List <H3Index> Polyfill(this GeoPolygon polygon, int res)
{
// TODO: Eliminate this wrapper with the H3 4.0.0 release
(int failure, var result) = polygon.PolyFillInternal(res);
if (failure == 0)
{
return(result.Where(r => r != 0).ToList());
}
// The polyfill algorithm can theoretically fail if the allocated memory is
// not large enough for the polygon, but this should be impossible given the
// conservative overestimation of the number of hexagons possible.
int numHexagons = polygon.MaxPolyFillSize(res);
return(new H3Index[numHexagons].ToList());
}