import type { QueryClient } from "@tanstack/react-query";
import { api, type TakeoutStatus } from "../../lib/api";
import { qk } from "../../lib/queryKeys";

// A Takeout import, watched to its end: its status is asked again until no run is queued or going,
// then the lists it changed are read afresh. It lives outside the section on purpose: the user may
// leave Settings while the import runs, and the feed they go to must not keep showing as new what
// the import has just marked watched.

const POLL_MS = 1500;

export const importBusy = (s: TakeoutStatus | undefined): boolean =>
  !!s && (s.queued || s.run?.status === "running");

let watching = false;

const pause = () => new Promise<void>((done) => setTimeout(done, POLL_MS));

async function read(qc: QueryClient): Promise<TakeoutStatus | undefined> {
  try {
    return await qc.fetchQuery({
      queryKey: qk.takeout(),
      queryFn: api.takeoutStatus,
      staleTime: 0,
    });
  } catch {
    // A read that failed is the section's to say (its query holds the error); the watch asks again.
    return qc.getQueryData<TakeoutStatus>(qk.takeout());
  }
}

/** Mark stale everything an import may have changed: the feed and its counts, Watch later, and the
 *  playlists that show its size. */
export function invalidateImported(qc: QueryClient): void {
  for (const queryKey of [
    qk.feed(),
    qk.feedSummary(),
    qk.feedYears(),
    qk.playlist(),
    qk.playlists(),
  ])
    void qc.invalidateQueries({ queryKey });
}

/** Watch the user's import until it is done (once: a second call while it watches is that watch),
 *  then mark stale what it changed. */
export async function watchTakeout(qc: QueryClient): Promise<void> {
  if (watching) return;
  watching = true;
  let status = qc.getQueryData<TakeoutStatus>(qk.takeout());
  while (importBusy(status)) {
    await pause();
    status = await read(qc);
  }
  watching = false;
  invalidateImported(qc);
}