const STUDIO_FLUSH_PENDING_EDITS_EVENT = "hf-studio-flush-pending-edits";

interface StudioFlushPendingEditsDetail {
  promises: Array<Promise<unknown>>;
}

const pendingEditPromises = new Set<Promise<unknown>>();

export function trackStudioPendingEdit(
  result: Promise<unknown> | unknown,
): Promise<unknown> | undefined {
  if (!result) return undefined;
  const promise = Promise.resolve(result);
  pendingEditPromises.add(promise);
  promise.then(
    () => pendingEditPromises.delete(promise),
    () => pendingEditPromises.delete(promise),
  );
  return promise;
}

export async function flushStudioPendingEdits(): Promise<void> {
  const detail: StudioFlushPendingEditsDetail = { promises: [] };
  window.dispatchEvent(
    new CustomEvent<StudioFlushPendingEditsDetail>(STUDIO_FLUSH_PENDING_EDITS_EVENT, { detail }),
  );
  while (detail.promises.length > 0 || pendingEditPromises.size > 0) {
    const promises = [...detail.promises, ...pendingEditPromises];
    detail.promises = [];
    await Promise.allSettled(promises);
  }
}

export function addStudioPendingEditFlushListener(
  handler: () => Promise<unknown> | unknown,
): () => void {
  const listener = (event: Event) => {
    const detail = (event as CustomEvent<StudioFlushPendingEditsDetail>).detail;
    if (!detail?.promises) return;
    const promise = trackStudioPendingEdit(handler());
    if (promise) detail.promises.push(promise);
  };
  window.addEventListener(STUDIO_FLUSH_PENDING_EDITS_EVENT, listener);
  return () => window.removeEventListener(STUDIO_FLUSH_PENDING_EDITS_EVENT, listener);
}