fix: cache canonical GTIN page without redirects

scripts/build-site.py

@@ -14,6 +14,7 @@ from __future__ import annotations
 
 import base64
 import datetime as dt
+import hashlib
 import io
 import json
 import shutil
@@ -285,6 +286,7 @@ def build_html(table: dict[str, dict]) -> list[tuple[str, str]]:
         print(f"  [html] {rel}")
     shutil.rmtree(SITE / "gtin", ignore_errors=True)
     shutil.copytree(SRC / "gtin", SITE / "gtin")
+    version_gtin_service_worker()
     print("  [html] gtin/ (unlisted browser tool and standalone legal pages)")
     not_found = pages.not_found().replace("og-desfoto.jpg", "og-desfoto.jpg")
     (SITE / "404.html").write_text(not_found, encoding="utf-8")
@@ -292,6 +294,26 @@ def build_html(table: dict[str, dict]) -> list[tuple[str, str]]:
     return written
 
 
+def version_gtin_service_worker() -> None:
+    """Give each GTIN source release its own offline cache."""
+    digest = hashlib.sha256()
+    source_root = SRC / "gtin"
+    for path in sorted(source_root.rglob("*")):
+        if not path.is_file():
+            continue
+        digest.update(path.relative_to(source_root).as_posix().encode("utf-8"))
+        digest.update(b"\0")
+        digest.update(path.read_bytes())
+        digest.update(b"\0")
+
+    worker = SITE / "gtin" / "sw.js"
+    script = worker.read_text(encoding="utf-8")
+    marker = "__BUILD_VERSION__"
+    if script.count(marker) != 1:
+        raise RuntimeError("GTIN service worker cache version marker is missing or duplicated")
+    worker.write_text(script.replace(marker, digest.hexdigest()[:12]), encoding="utf-8")
+
+
 def build_meta_files(routes: list[tuple[str, str]]) -> None:
     today = dt.date.today().isoformat()
     urls = []