Add cache-busted static asset URLs

repub/web.py

@@ -90,6 +90,9 @@ DEFAULT_PANGEA_CONTENT_FORMAT = "MOBILE_3"
 DEFAULT_PANGEA_CONTENT_TYPE = "articles"
 DEFAULT_PANGEA_MAX_ARTICLES = "10"
 DEFAULT_PANGEA_OLDEST_ARTICLE = "3"
+STATIC_DIR = Path(__file__).resolve().parent / "static"
+CACHE_BUSTED_STATIC_ASSETS = frozenset({"app.css"})
+CACHE_BUSTED_HASH_LENGTH = 12
 
 
 def _render_shim_page(
@@ -106,6 +109,24 @@ def _render_shim_page(
     return body, etag
 
 
+def versioned_static_asset_filename(filename: str) -> str:
+    _require_cache_busted_static_asset(filename)
+    asset_path = STATIC_DIR / filename
+    truncated_hash = hashlib.sha256(asset_path.read_bytes()).hexdigest()[
+        :CACHE_BUSTED_HASH_LENGTH
+    ]
+    return f"{asset_path.stem}-{truncated_hash}{asset_path.suffix}"
+
+
+def versioned_static_asset_href(filename: str) -> str:
+    return f"/static/{versioned_static_asset_filename(filename)}"
+
+
+def _require_cache_busted_static_asset(filename: str) -> None:
+    if filename not in CACHE_BUSTED_STATIC_ASSETS:
+        raise ValueError(f"Unsupported cache-busted static asset: {filename}")
+
+
 def create_app(*, dev_mode: bool = False) -> Quart:
     app = Quart(__name__)
     app.config["REPUB_DB_PATH"] = str(initialize_database())
@@ -127,6 +148,22 @@ def create_app(*, dev_mode: bool = False) -> Quart:
             response.mimetype = "application/rss+xml"
         return response
 
+    @app.get("/static/<string:asset_name>-<string:asset_hash>.<string:extension>")
+    async def versioned_static_asset(
+        asset_name: str, asset_hash: str, extension: str
+    ) -> Response:
+        logical_filename = f"{asset_name}.{extension}"
+        requested_filename = f"{asset_name}-{asset_hash}.{extension}"
+        if logical_filename in CACHE_BUSTED_STATIC_ASSETS:
+            response = await send_from_directory(str(STATIC_DIR), logical_filename)
+            response.cache_control.public = True
+            response.cache_control.max_age = 31536000
+            response.cache_control.immutable = True
+            return response
+
+        response = await send_from_directory(str(STATIC_DIR), requested_filename)
+        return response
+
     @app.get("/")
     @app.get("/sources")
     @app.get("/sources/create")
@@ -141,7 +178,7 @@ def create_app(*, dev_mode: bool = False) -> Quart:
     ) -> Response:
         del slug, job_id, execution_id
         body, etag = _render_shim_page(
-            stylesheet_href=url_for("static", filename="app.css"),
+            stylesheet_href=versioned_static_asset_href("app.css"),
             datastar_src=url_for("static", filename="datastar@1.0.0-RC.8.js"),
             current_path=request.path,
         )