Backfill watchlist alternative titles lazily

app.py

@@ -1875,6 +1875,54 @@ class WatchlistStore:
                 continue
         return {"items": updated}
 
+    def ensure_alt_titles(self, show_id, force=False):
+        item = self.get(show_id)
+        if not force and (item.get("alt_titles") or item.get("english_title")):
+            return item
+        parsed = fetch_allmanga_alternative_titles(item["show_id"], item.get("title"), timeout=self._refresh_request_timeout())
+        updated_at = now_iso()
+        alt_titles_json = json.dumps(unique_title_values(parsed.get("alt_titles") or [], item.get("title")))
+        with self.lock, self._connect() as conn:
+            conn.execute(
+                """
+                UPDATE watchlist
+                SET english_title = ?, alt_titles_json = ?, updated_at = ?
+                WHERE show_id = ?
+                """,
+                (
+                    parsed.get("english_title") or None,
+                    alt_titles_json,
+                    updated_at,
+                    item["show_id"],
+                ),
+            )
+        return self.get(show_id)
+
+    def ensure_alt_titles_many(self, show_ids, limit=6, force=False):
+        normalized = []
+        for show_id in show_ids:
+            text = str(show_id or "").strip()
+            if text and text not in normalized:
+                normalized.append(text)
+        updated = []
+        for show_id in normalized[: max(1, min(int(limit or 6), 10))]:
+            try:
+                item = self.get(show_id)
+            except KeyError:
+                continue
+            if not force and (item.get("alt_titles") or item.get("english_title")):
+                updated.append(item)
+                continue
+            try:
+                updated.append(self.ensure_alt_titles(show_id, force=force))
+            except Exception as exc:
+                debug_log("watchlist.alt_titles.ensure_failed", show_id=show_id, error=exc)
+                try:
+                    updated.append(self.get(show_id))
+                except KeyError:
+                    continue
+        return {"items": updated}
+
 
 def add_to_watchlist(payload):
     ensure_runtime()