Function AirportGetNearestTown

src/station_cmd.cpp:2554–2588

* Finds the town nearest to given airport. Based on minimal manhattan distance to any airport's tile. * If two towns have the same distance, town with lower index is returned. * @param as airport's description * @param rotation airport's rotation * @param tile origin tile (top corner of the airport) * @param it An iterator over all airport tiles (consumed) * @param[out] mindist Minimum dista

 * @return nearest town to airport
 */
Town *AirportGetNearestTown(const AirportSpec *as, Direction rotation, TileIndex tile, TileIterator &&it, uint &mindist)
{
	assert(Town::GetNumItems() > 0);

	Town *nearest = nullptr;

	auto width = as->size_x;
	auto height = as->size_y;
	if (rotation == DIR_E || rotation == DIR_W) std::swap(width, height);

	uint perimeter_min_x = TileX(tile);
	uint perimeter_min_y = TileY(tile);
	uint perimeter_max_x = perimeter_min_x + width - 1;
	uint perimeter_max_y = perimeter_min_y + height - 1;

	mindist = UINT_MAX - 1; // prevent overflow

	for (TileIndex cur_tile = *it; cur_tile != INVALID_TILE; cur_tile = ++it) {
		assert(IsInsideBS(TileX(cur_tile), perimeter_min_x, width));
		assert(IsInsideBS(TileY(cur_tile), perimeter_min_y, height));
		if (TileX(cur_tile) == perimeter_min_x || TileX(cur_tile) == perimeter_max_x || TileY(cur_tile) == perimeter_min_y || TileY(cur_tile) == perimeter_max_y) {
			Town *t = CalcClosestTownFromTile(cur_tile, mindist + 1);
			if (t == nullptr) continue;

			uint dist = DistanceManhattan(t->xy, cur_tile);
			if (dist == mindist && t->index < nearest->index) nearest = t;
			if (dist < mindist) {
				nearest = t;
				mindist = dist;
			}
		}
	}

	return nearest;
}

/**
 * Finds the town nearest to given existing airport. Based on minimal manhattan distance to any airport's tile.