Extract legend toggle logic into reusable useHiddenKeys hook

Author: Roman Snapko

packages/ui-components/src/ui/chart/use-hidden-keys.ts

@@ -0,0 +1,22 @@
+import { useCallback, useState } from 'react';
+
+export function useHiddenKeys(): {
+  hiddenKeys: Set<string>;
+  toggleKey: (key: string) => void;
+} {
+  const [hiddenKeys, setHiddenKeys] = useState<Set<string>>(new Set());
+
+  const toggleKey = useCallback((key: string) => {
+    setHiddenKeys((prev) => {
+      const next = new Set(prev);
+      if (next.has(key)) {
+        next.delete(key);
+      } else {
+        next.add(key);
+      }
+      return next;
+    });
+  }, []);
+
+  return { hiddenKeys, toggleKey };
+}