Add "Followers you know" to hovercard (#34769)

app/javascript/mastodon/features/account_timeline/hooks/familiar_followers.ts

@@ -0,0 +1,30 @@
+import { useEffect } from 'react';
+
+import { fetchAccountsFamiliarFollowers } from '@/mastodon/actions/accounts_familiar_followers';
+import { getAccountFamiliarFollowers } from '@/mastodon/selectors/accounts';
+import { useAppDispatch, useAppSelector } from '@/mastodon/store';
+import { me } from 'mastodon/initial_state';
+
+export const useFetchFamiliarFollowers = ({
+  accountId,
+}: {
+  accountId?: string;
+}) => {
+  const dispatch = useAppDispatch();
+  const familiarFollowers = useAppSelector((state) =>
+    accountId ? getAccountFamiliarFollowers(state, accountId) : null,
+  );
+
+  const hasNoData = familiarFollowers === null;
+
+  useEffect(() => {
+    if (hasNoData && accountId && accountId !== me) {
+      void dispatch(fetchAccountsFamiliarFollowers({ id: accountId }));
+    }
+  }, [dispatch, accountId, hasNoData]);
+
+  return {
+    familiarFollowers: hasNoData ? [] : familiarFollowers,
+    isLoading: hasNoData,
+  };
+};