Move RSS response headers into app

repub/web.py

@@ -4,7 +4,7 @@ import asyncio
 import hashlib
 from collections.abc import AsyncGenerator, Awaitable, Callable
 from contextlib import suppress
-from datetime import timedelta
+from datetime import UTC, datetime, timedelta
 from pathlib import Path
 from typing import TypedDict, cast
 from urllib.parse import urlparse
@@ -590,7 +590,23 @@ def _load_sidebar_counts(app: Quart) -> dict[str, int]:
 def _rss_feed_response(feed_text: str | None) -> Response:
     if feed_text is None:
         return Response(status=404)
-    return Response(feed_text, mimetype="application/rss+xml")
+    etag = hashlib.sha256(feed_text.encode("utf-8")).hexdigest()
+    if request.if_none_match.contains(etag):
+        response = Response(status=304)
+    else:
+        response = Response(
+            feed_text,
+            content_type="application/rss+xml; charset=utf-8",
+        )
+    response.set_etag(etag)
+    response.cache_control.public = True
+    response.cache_control.max_age = 300
+    response.expires = datetime.now(UTC) + timedelta(minutes=5)
+    response.vary.add("Host")
+    response.headers["Access-Control-Allow-Origin"] = "*"
+    response.headers["Access-Control-Allow-Methods"] = "GET, HEAD, OPTIONS"
+    response.headers["Access-Control-Allow-Headers"] = "*"
+    return response
 
 
 def _read_feed_text(*, feeds_dir: Path, feed_path: str) -> str | None: