broadcast-areas: add a script to build sqlite db

import the raw datasets into a vendored sqlite3 db which can be queried
and versioned with code

Signed-off-by: Toby Lorne <toby.lornewelch-richards@digital.cabinet-office.gov.uk>

notifications_utils/broadcast_areas/create-broadcast-areas-db.py

@@ -0,0 +1,78 @@
+#!/usr/bin/env python
+
+import geojson
+from pathlib import Path
+
+package_path = Path(__file__).resolve().parent
+
+db_filepath = package_path / "broadcast-areas.sqlite3"
+os.remove(str(db_filepath))
+conn = sqlite3.connect(str(db_filepath))
+conn.execute("""
+CREATE TABLE broadcast_areas (
+    id TEXT PRIMARY KEY,
+    name TEXT NOT NULL,
+    dataset TEXT NOT NULL,
+    feature_geojson TEXT NOT NULL
+)""")
+conn.execute("""
+CREATE INDEX broadcast_areas_dataset
+ON broadcast_areas (dataset);
+""")
+conn.commit()
+
+simple_datasets = [
+    ("Countries", "ctry19nm"),
+    ("Regions of England", "rgn18nm"),
+    ("Counties and Unitary Authorities in England and Wales", "ctyua16nm"),
+]
+for dataset_name, name_field in simple_datasets:
+    filepath = package_path / "{}.geojson".format(dataset_name)
+    dataset_geojson = geojson.loads(filepath.read_text())
+
+    q = """
+    INSERT INTO broadcast_areas (id, name, dataset, feature_geojson)
+    VALUES (?, ?, ?, ?)
+    """
+
+    for feature in dataset_geojson["features"]:
+        f_name = feature["properties"][name_field]
+        f_id = make_string_safe_for_id(f_name)
+        conn.execute(q, (f_id, f_name, dataset_name, geojson.dumps(feature)))
+
+    conn.commit()
+
+# https://geoportal.statistics.gov.uk/datasets/wards-may-2020-boundaries-uk-bgc
+# Converted to geojson manually from SHP because of GeoJSON download limits
+wards_filepath = package_path / "Electoral Wards May 2020.geojson"
+
+# http://geoportal.statistics.gov.uk/datasets/ward-to-westminster-parliamentary-constituency-to-local-authority-district-december-2019-lookup-in-the-united-kingdom/data
+las_filepath = package_path / "Electoral Wards and Local Authorities 2020.geojson"
+
+ward_code_to_la_mapping = {
+    f["properties"]["WD19CD"]: f["properties"]["LAD19NM"]
+    for f in geojson.loads(las_filepath.read_text())["features"]
+}
+
+for f in geojson.loads(wards_filepath.read_text())["features"]:
+    dataset_name = "Electoral Wards of the United Kingdom"
+
+    ward_code = f["properties"]["wd20cd"]
+    ward_name = f["properties"]["wd20nm"]
+
+    try:
+        la_name = ward_code_to_la_mapping[ward_code]
+
+        f_name = "{} - {}".format(la_name, ward_name)
+        f_id = make_string_safe_for_id(f_name)
+
+        q = """
+        INSERT INTO broadcast_areas (id, name, dataset, feature_geojson)
+        VALUES (?, ?, ?, ?)
+        """
+        conn.execute(q, (f_id, f_name, dataset_name, geojson.dumps(f)))
+
+    except KeyError:
+        print("Skipping", ward_code, ward_name)  # noqa: T001
+
+conn.commit()