From 6268dbda4d6e8e991e376f2c51a42dc717c6a779 Mon Sep 17 00:00:00 2001
From: Andras Schmelczer <andras@schmelczer.dev>
Date: Thu, 5 Feb 2026 21:37:34 +0000
Subject: [PATCH] Download postcode geojson

---
 pipeline/download/postcodes.py | 67 ++++++++++++++++++++++++++++++++++
 1 file changed, 67 insertions(+)
 create mode 100644 pipeline/download/postcodes.py

diff --git a/pipeline/download/postcodes.py b/pipeline/download/postcodes.py
new file mode 100644
index 0000000..28099e8
--- /dev/null
+++ b/pipeline/download/postcodes.py
@@ -0,0 +1,67 @@
+"""Download GB postcodes data from MapIt.
+
+Downloads the gb-postcodes-v5.tar.bz2 archive containing UK postcode GeoJSON data
+and extracts it to the specified output directory.
+
+Source: https://postcodes-mapit-static.s3.eu-west-2.amazonaws.com/data/gb-postcodes-v5.tar.bz2
+"""
+
+import argparse
+import shutil
+import tarfile
+import tempfile
+from pathlib import Path
+
+from pipeline.utils import download
+
+URL = "https://postcodes-mapit-static.s3.eu-west-2.amazonaws.com/data/gb-postcodes-v5.tar.bz2"
+
+
+def extract_tar_bz2(archive_path: Path, extract_dir: Path) -> None:
+    """Extract a tar.bz2 archive into the given directory."""
+    extract_dir.mkdir(parents=True, exist_ok=True)
+    print(f"Extracting {archive_path.name}...")
+    with tarfile.open(archive_path, "r:bz2") as tf:
+        tf.extractall(extract_dir, filter="data")
+
+
+def main() -> None:
+    parser = argparse.ArgumentParser(
+        description="Download GB postcodes data from MapIt"
+    )
+    parser.add_argument(
+        "--output",
+        type=Path,
+        required=True,
+        help="Output directory for extracted GeoJSON files",
+    )
+    args = parser.parse_args()
+
+    with tempfile.TemporaryDirectory() as cache_dir:
+        cache = Path(cache_dir)
+        archive_path = cache / "gb-postcodes-v5.tar.bz2"
+        extract_dir = cache / "extracted"
+
+        download(URL, archive_path, timeout=600)
+        extract_tar_bz2(archive_path, extract_dir)
+
+        # Find the extracted directory (gb-postcodes-v5)
+        extracted_contents = list(extract_dir.iterdir())
+        if len(extracted_contents) == 1 and extracted_contents[0].is_dir():
+            source_dir = extracted_contents[0]
+        else:
+            source_dir = extract_dir
+
+        # Move to output directory
+        args.output.parent.mkdir(parents=True, exist_ok=True)
+        if args.output.exists():
+            shutil.rmtree(args.output)
+        shutil.move(str(source_dir), str(args.output))
+
+        # Count extracted files
+        geojson_files = list(args.output.rglob("*.geojson"))
+        print(f"Extracted {len(geojson_files)} GeoJSON files to {args.output}")
+
+
+if __name__ == "__main__":
+    main()