export const BEFORE_PAGE_REFRESH = "app:before-page-refresh";
export type PageRefreshRequest = {
  save: (action: () => Promise<void>) => void;
  block: (message: string) => void;
};

export async function preparePageRefresh() {
  const actions: Array<() => Promise<void>> = [];
  let blocked = "";
  window.dispatchEvent(new CustomEvent<PageRefreshRequest>(BEFORE_PAGE_REFRESH, {
    detail: { save: action => actions.push(action), block: message => { blocked ||= message; } },
  }));
  if (blocked) throw new Error(blocked);
  for (const action of actions) await action();
}