import { useEffect, useRef } from 'react';
import { useAtom } from 'jotai';
import { aggregateUploadProgress, uploadProgressAtom } from '../state/uploadProgress';
import { invokeTauri, isTauri } from './useTauri';

/** Native updates at most ~4 per second. */
const MIN_INTERVAL_MS = 250;
/** How long a failed upload keeps the bar red before it clears. */
const ERROR_HOLD_MS = 4_000;

/**
 * [cinny-desktop #10] One taskbar progress bar for all uploads: the combined
 * percentage while files upload, indeterminate until a size is known, red for a
 * few seconds after a failure, cleared when done. No-op in the browser.
 */
export function useTauriTaskbarProgress(): void {
  const [entries, setEntries] = useAtom(uploadProgressAtom);
  const lastSent = useRef<string>('');
  const lastAt = useRef(0);
  const pending = useRef<number | undefined>(undefined);
  // The (possibly delayed) send must use the latest uploads, not the ones from
  // when it was scheduled — otherwise the final "done" could be dropped.
  const latest = useRef(entries);
  latest.current = entries;

  useEffect(() => {
    if (!isTauri()) return undefined;
    const send = () => {
      pending.current = undefined;
      const state = aggregateUploadProgress(latest.current.values(), Date.now());
      const key = JSON.stringify(state);
      if (key === lastSent.current) return;
      lastSent.current = key;
      lastAt.current = Date.now();
      invokeTauri('set_taskbar_progress', {
        status: state.status,
        progress: 'progress' in state ? state.progress : null,
      });
    };
    const wait = MIN_INTERVAL_MS - (Date.now() - lastAt.current);
    if (wait <= 0) send();
    else if (pending.current === undefined) pending.current = window.setTimeout(send, wait);
    return undefined;
  }, [entries]);

  // Drop failed entries after a moment so the red bar doesn't stick.
  useEffect(() => {
    const failed = Array.from(entries.values()).some((e) => e.failed);
    if (!failed) return undefined;
    const timer = window.setTimeout(() => {
      setEntries((prev) => new Map(Array.from(prev).filter(([, e]) => !e.failed)));
    }, ERROR_HOLD_MS);
    return () => window.clearTimeout(timer);
  }, [entries, setEntries]);

  useEffect(
    () => () => {
      if (pending.current !== undefined) window.clearTimeout(pending.current);
    },
    [],
  );
}