// Drives "Save for offline": one download at a time, with progress for the button to show,
// a cancel, and a toast when it finishes.
import { useCallback, useEffect, useRef, useState } from 'react';
import { useToast } from '../components/Toasts.jsx';
import { bibleRefs, bookRefs, downloadChapters, loadSavedBooks, markBookSaved } from '../utils/offline.js';

export function useOnline() {
  const [online, setOnline] = useState(() => (typeof navigator === 'undefined' ? true : navigator.onLine !== false));
  useEffect(() => {
    const up = () => setOnline(true);
    const down = () => setOnline(false);
    window.addEventListener('online', up);
    window.addEventListener('offline', down);
    return () => { window.removeEventListener('online', up); window.removeEventListener('offline', down); };
  }, []);
  return online;
}

export function useOfflineSave() {
  const { toast } = useToast();
  const [saved, setSaved] = useState(loadSavedBooks);
  const [job, setJob] = useState(null); // { label, done, total } while downloading
  const controller = useRef(null);
  useEffect(() => () => controller.current?.abort(), []);

  const run = useCallback(async (label, translation, refs, { bookKeys = [] } = {}) => {
    if (controller.current) return; // one at a time
    const abort = new AbortController();
    controller.current = abort;
    setJob({ label, done: 0, total: refs.length });
    const result = await downloadChapters(translation, refs, { signal: abort.signal, onProgress: (done, total) => setJob({ label, done, total }) });
    controller.current = null;
    setJob(null);
    if (abort.signal.aborted) { toast('Download stopped'); return; }
    if (result.failed === 0) {
      bookKeys.forEach((b) => markBookSaved(translation, b));
      setSaved(loadSavedBooks());
      toast(`Saved ${label} for offline`);
    } else {
      toast(`Saved ${result.done} of ${refs.length} chapters — check your connection and try again`, { tone: 'error' });
    }
  }, [toast]);

  return {
    saved, job,
    isSaved: (translation, book) => (saved[translation] ?? []).includes(book),
    saveBook: (translation, book, name) => run(name, translation, bookRefs(book), { bookKeys: [book] }),
    saveBible: (translation) => run(`The whole ${translation}`, translation, bibleRefs(), { bookKeys: [...new Set(bibleRefs().map((r) => r.book))] }),
    saveRefs: (label, translation, refs) => run(label, translation, refs),
    cancel: () => controller.current?.abort(),
  };
}