mapdata.py

from pathlib import Path
import geopandas
import pickle


def get_mapdata(postcode: int) -> dict:
    assert postcode >= 3000 and postcode < 4000

    root = Path("./")
    jar = root / f"./mapdata-{postcode}.pickle"

    if not jar.exists():
        print(f"No cached data for {postcode}. This will take a minute.")
        postcode_path = f"{root}/postcodes-vic/ll_gda94/sde_shape/whole/VIC/VMADMIN/layer/postcode_polygon.shp"
        print(f"Reading postcode boundaries from {postcode_path}")
        postcode_boundary = (
            geopandas.read_file(postcode_path)
            .query(f'POSTCODE == "{postcode}"')
            .to_crs(epsg=3112)
        )

        # TODO probably quicker to convert reference system *after* clipping to
        # postcode...
        roads_path = f"{root}/roads-vic/ll_gda2020/shape/whole_of_dataset/vic/VMTRANS/TR_ROAD.shp"
        print(f"Reading roads from {roads_path}")
        roads_vic = geopandas.read_file(roads_path).to_crs(epsg=3112)
        roads_buffer = geopandas.clip(roads_vic, postcode_boundary.buffer(500))
        roads_0 = geopandas.clip(roads_buffer, postcode_boundary.buffer(0))

        with jar.open(mode="bw") as dest:
            mapdata = {
                "postcode": postcode_boundary,
                "roads_buffer": roads_buffer,
                "roads_0": roads_0,
            }
            pickle.dump(mapdata, dest)

    else:
        with jar.open(mode="rb") as src:
            mapdata = pickle.load(src)

    return mapdata