Finished @ROUTES.put(f"/api/assets/{{id:{UUID_RE}}}/preview")

app/assets/database/queries.py

@@ -810,3 +810,25 @@ def remove_missing_tag_for_asset_id(
             AssetInfoTag.tag_name == "missing",
         )
     )
+
+def set_asset_info_preview(
+    session: Session,
+    *,
+    asset_info_id: str,
+    preview_asset_id: str | None = None,
+) -> None:
+    """Set or clear preview_id and bump updated_at. Raises on unknown IDs."""
+    info = session.get(AssetInfo, asset_info_id)
+    if not info:
+        raise ValueError(f"AssetInfo {asset_info_id} not found")
+
+    if preview_asset_id is None:
+        info.preview_id = None
+    else:
+        # validate preview asset exists
+        if not session.get(Asset, preview_asset_id):
+            raise ValueError(f"Preview Asset {preview_asset_id} not found")
+        info.preview_id = preview_asset_id
+
+    info.updated_at = utcnow()
+    session.flush()