// useSwarmName — the swarm's configured display name from `GET /api/swarm`,
// or `null` until it arrives, when none is configured, or when the fetch
// fails. The label is cosmetic, so a failure is swallowed rather than shown:
// callers fall back to their own default, as an operator who never set a
// name sees. One request per page load, shared by every caller, because the
// header and the start page both ask for it and the name does not change
// within a visit.
import { useEffect, useState } from "preact/hooks";

let pending: Promise<string | null> | null = null;

function fetchSwarmName(): Promise<string | null> {
  if (pending === null) {
    pending = (async () => {
      const r = await fetch("/api/swarm");
      if (!r.ok) return null;
      const data = (await r.json()) as { name: string | null };
      return data.name || null;
    })().catch(() => null);
  }
  return pending;
}

export function useSwarmName(): string | null {
  const [name, setName] = useState<string | null>(null);
  useEffect(() => {
    let cancelled = false;
    void fetchSwarmName().then((n) => {
      if (!cancelled && n !== null) setName(n);
    });
    return () => {
      cancelled = true;
    };
  }, []);
  return name;
}