good changes

pipeline/download/os_greenspace.py

@@ -0,0 +1,127 @@
+"""Download OS Open Greenspace and extract site centroids.
+
+Downloads the OS Open Greenspace dataset as ESRI Shapefile, computes
+WGS84 centroids for each greenspace site polygon, and outputs a parquet
+with lat/lng/category columns compatible with the POI proximity pipeline.
+
+Source: https://osdatahub.os.uk/downloads/open/OpenGreenspace
+License: Open Government Licence v3.0
+"""
+
+import argparse
+import tempfile
+from pathlib import Path
+
+import numpy as np
+import polars as pl
+import shapefile as shp
+from pyproj import Transformer
+from shapely.geometry import shape as to_shapely
+
+from pipeline.utils.download import download, extract_zip
+
+URL = "https://api.os.uk/downloads/v1/products/OpenGreenspace/downloads?area=GB&format=ESRI%C2%AE+Shapefile&redirect"
+
+_to_wgs84 = Transformer.from_crs("EPSG:27700", "EPSG:4326", always_xy=True)
+
+
+def download_greenspace(output: Path) -> None:
+    output.parent.mkdir(parents=True, exist_ok=True)
+
+    with tempfile.TemporaryDirectory() as cache_dir:
+        zip_path = Path(cache_dir) / "greenspace.zip"
+        extract_dir = Path(cache_dir) / "extracted"
+
+        download(URL, zip_path, timeout=300)
+        extract_zip(zip_path, extract_dir)
+
+        # Find the GreenspaceSite shapefile (not the AccessPoint one)
+        shp_files = list(extract_dir.rglob("*GreenspaceSite*.shp"))
+        if not shp_files:
+            shp_files = [
+                f
+                for f in extract_dir.rglob("*.shp")
+                if "AccessPoint" not in f.name
+            ]
+        if not shp_files:
+            raise FileNotFoundError(
+                "No GreenspaceSite shapefile found in download"
+            )
+
+        print(f"Reading {shp_files[0].name}...")
+        reader = shp.Reader(str(shp_files[0]), encoding="latin-1")
+
+        # Find the "function" field (greenspace type)
+        field_names = [f[0] for f in reader.fields[1:]]  # skip deletion flag
+        func_field = None
+        for name in field_names:
+            if "funct" in name.lower():
+                func_field = name
+                break
+        if func_field is None:
+            raise ValueError(
+                f"No 'function' field found. Available: {field_names}"
+            )
+        func_idx = field_names.index(func_field)
+
+        # Find a name field if available
+        name_idx = None
+        for name in field_names:
+            if "distname" in name.lower():
+                name_idx = field_names.index(name)
+                break
+
+        lats = []
+        lngs = []
+        categories = []
+        names = []
+
+        for sr in reader.shapeRecords():
+            func = sr.record[func_idx]
+            site_name = sr.record[name_idx] if name_idx is not None else ""
+
+            try:
+                geom = to_shapely(sr.shape.__geo_interface__)
+                if geom.is_empty or not geom.is_valid:
+                    continue
+                centroid = geom.centroid
+                lng, lat = _to_wgs84.transform(centroid.x, centroid.y)
+            except Exception:
+                continue
+
+            lats.append(lat)
+            lngs.append(lng)
+            categories.append(func)
+            names.append(site_name or "")
+
+    df = pl.DataFrame(
+        {
+            "lat": np.array(lats, dtype=np.float64),
+            "lng": np.array(lngs, dtype=np.float64),
+            "category": categories,
+            "name": names,
+        }
+    )
+
+    df.write_parquet(output)
+    size_mb = output.stat().st_size / (1024 * 1024)
+    print(f"Wrote {output} ({size_mb:.1f} MB, {len(df):,} greenspace sites)")
+
+    counts = df.group_by("category").len().sort("len", descending=True)
+    for row in counts.iter_rows(named=True):
+        print(f"  {row['category']}: {row['len']:,}")
+
+
+def main() -> None:
+    parser = argparse.ArgumentParser(
+        description="Download OS Open Greenspace site centroids"
+    )
+    parser.add_argument(
+        "--output", type=Path, required=True, help="Output parquet file path"
+    )
+    args = parser.parse_args()
+    download_greenspace(args.output)
+
+
+if __name__ == "__main__":
+    main()