"""Download Planning Data conservation area polygons.

Source: https://www.planning.data.gov.uk/dataset/conservation-area
License: Open Government Licence v3.0
"""

import argparse
from pathlib import Path

import httpx
import pyogrio
from shapely import from_wkb

URL = "https://files.planning.data.gov.uk/dataset/conservation-area.geojson"


def _geometry_column(metadata: dict, column_names: list[str]) -> str:
    geometry_name = metadata.get("geometry_name")
    if geometry_name:
        return str(geometry_name)
    for name in ("wkb_geometry", "geometry", "geom"):
        if name in column_names:
            return name
    return column_names[-1]


def _validate_conservation_areas(path: Path) -> int:
    info = pyogrio.read_info(path)
    features = info.get("features", 0)
    if features <= 0:
        raise ValueError("Downloaded conservation areas file contains no features")

    metadata, table = pyogrio.read_arrow(path, columns=[], read_geometry=True)
    geometry_name = _geometry_column(metadata, table.column_names)
    geometries = from_wkb(table[geometry_name].combine_chunks().to_pylist())
    polygon_count = sum(
        geom is not None
        and not geom.is_empty
        and geom.geom_type in {"Polygon", "MultiPolygon"}
        for geom in geometries
    )
    if polygon_count <= 0:
        raise ValueError("Downloaded conservation areas file contains no polygons")
    return int(features)


def main() -> None:
    parser = argparse.ArgumentParser(
        description="Download Planning Data conservation area polygons"
    )
    parser.add_argument(
        "--output", type=Path, required=True, help="Output GeoJSON file path"
    )
    args = parser.parse_args()
    args.output.parent.mkdir(parents=True, exist_ok=True)
    tmp_path = args.output.with_name(f"{args.output.stem}.tmp{args.output.suffix}")

    print("Downloading Planning Data conservation areas...")
    with httpx.stream("GET", URL, follow_redirects=True, timeout=300) as response:
        response.raise_for_status()
        with tmp_path.open("wb") as fh:
            for chunk in response.iter_bytes():
                fh.write(chunk)

    features = _validate_conservation_areas(tmp_path)

    tmp_path.replace(args.output)
    size_mb = args.output.stat().st_size / (1024 * 1024)
    print(f"Saved {features} conservation areas to {args.output} ({size_mb:.1f} MB)")


if __name__ == "__main__":
    main()