// Settings → "Your data": download everything as one file, restore from one, and save Bibles for offline.
import { useRef, useState } from 'react';
import { useApp } from '../../context/AppContext.js';
import { useToast } from '../Toasts.jsx';
import { DownloadProgress } from '../OfflineSave.jsx';
import { useOfflineSave } from '../../hooks/useOfflineSave.js';
import { backupFileName, buildBackup, markBackedUp, restoreProjects, validateBackup } from '../../utils/backup.js';
import { saveRemoteProject } from '../../syncService.js';

const btn = 'rounded-xl border border-[var(--r-line)] px-4 py-2 text-sm hover:bg-black/5 disabled:opacity-50';

const plural = (n, one, many = `${one}s`) => `${n} ${n === 1 ? one : many}`;

export default function DataSection() {
  const {
    authUser, readerBookmarks, readerBookmarkNotes, readerTextHighlights, readerColorLabels, readerInkByPage, readingPlansState,
    importReaderMarks, importReadingPlans, refreshProjectIndex, prayers, importPrayers,
  } = useApp();
  const { toast } = useToast();
  const offline = useOfflineSave();
  const fileRef = useRef(null);
  const [pending, setPending] = useState(null); // { name, backup, summary } waiting for "Restore"
  const [error, setError] = useState('');
  const [busy, setBusy] = useState(false);

  const download = () => {
    const backup = buildBackup({
      email: authUser?.email ?? null,
      reader: { bookmarks: readerBookmarks, bookmarkNotes: readerBookmarkNotes, highlights: readerTextHighlights, colorLabels: readerColorLabels, ink: readerInkByPage },
      readingPlans: readingPlansState,
      prayers,
    });
    const url = URL.createObjectURL(new Blob([JSON.stringify(backup, null, 2)], { type: 'application/json' }));
    const link = document.createElement('a');
    link.href = url;
    link.download = backupFileName();
    document.body.appendChild(link);
    link.click();
    link.remove();
    URL.revokeObjectURL(url);
    markBackedUp();
    toast(`Backup downloaded: ${plural(backup.projects.length, 'study', 'studies')} and your reading marks`);
  };

  const choose = async (e) => {
    const file = e.target.files?.[0];
    e.target.value = '';
    setError('');
    setPending(null);
    if (!file) return;
    let data;
    try { data = JSON.parse(await file.text()); } catch { setError('That file couldn’t be read as a backup.'); return; }
    const checked = validateBackup(data);
    if (!checked.ok) { setError(checked.error); return; }
    setPending({ name: file.name, ...checked });
  };

  const restore = async () => {
    setBusy(true);
    const { backup } = pending;
    const written = restoreProjects(backup.projects);
    importReaderMarks(backup.reader);
    importReadingPlans(backup.readingPlans);
    importPrayers?.(backup.prayers);
    refreshProjectIndex();
    // Studies restored here also go to the account, so they follow you to other devices
    if (authUser) await Promise.all(written.map((p) => saveRemoteProject(p)));
    setBusy(false);
    setPending(null);
    toast(`Restored ${plural(written.length, 'study', 'studies')}, plus your bookmarks, highlights and plans`);
  };

  const s = pending?.summary;
  return (
    <section id="backup" aria-label="Your data" className="scroll-mt-16 space-y-5 rounded-2xl border border-[var(--r-line)] bg-[var(--r-bar)] p-6">
      <div>
        <h2 className="text-base font-medium">Your data</h2>
        <p className="mt-1 text-sm text-[var(--r-sub)]">Everything you’ve made — studies and notes, bookmarks, highlights, ink and reading plans — in one file you keep.{authUser ? ' “Download backup” is what’s on this device; “Download from my account” is everything the server holds. The server also keeps a daily snapshot for the administrator.' : ''}</p>
      </div>

      <div className="flex flex-wrap items-center gap-3">
        <button type="button" onClick={download} className={btn}>Download backup</button>
        {authUser && (
          <a href="/api/account/export" download onClick={() => markBackedUp()} className={`${btn} inline-block`} title="Everything saved to your account on the server, including studies from other devices">Download from my account</a>
        )}
        <button type="button" onClick={() => fileRef.current?.click()} className={btn}>Restore from a backup…</button>
        <input ref={fileRef} type="file" accept="application/json,.json" onChange={choose} className="hidden" aria-label="Backup file" />
      </div>
      {error && <p role="alert" className="text-sm text-[var(--r-danger,#b42318)]">{error}</p>}
      {pending && (
        <div className="rounded-xl border border-[var(--r-line)] bg-[var(--r-bg)] p-4 text-sm">
          <p className="font-medium">{pending.name}</p>
          <p className="mt-1 text-[var(--r-sub)]">
            Contains {plural(s.projects, 'study', 'studies')}, {plural(s.bookmarks, 'bookmark')}, {plural(s.highlights, 'highlight')}, {plural(s.inkPages, 'ink page')}, {plural(s.plans, 'reading plan')} and {plural(s.prayers ?? 0, 'prayer')}.
            Restoring adds these to what you have — nothing is deleted, and a study on this device is only replaced if the backup’s copy is newer.
          </p>
          <div className="mt-3 flex gap-2">
            <button type="button" onClick={restore} disabled={busy} className="rounded-xl bg-[var(--r-accent)] px-4 py-2 text-sm font-medium text-[var(--r-on)] hover:opacity-90 disabled:opacity-50">{busy ? 'Restoring…' : 'Restore'}</button>
            <button type="button" onClick={() => setPending(null)} className={btn}>Cancel</button>
          </div>
        </div>
      )}

      <div className="border-t border-[var(--r-line)] pt-4">
        <h3 className="text-sm font-medium">Read offline</h3>
        <p className="mb-3 mt-1 text-sm text-[var(--r-sub)]">Chapters you read are kept automatically. To read anywhere, save a whole Bible while you’re connected (about 4 MB). The ESV, NLT, CSB and NASB can’t be saved: their licences don’t allow it.</p>
        {offline.job ? <DownloadProgress job={offline.job} onCancel={offline.cancel} /> : (
          <div className="flex flex-wrap gap-3">
            {['BSB', 'NET', 'KJV', 'ASV', 'LSV'].map((t) => (
              <button key={t} type="button" onClick={() => offline.saveBible(t)} className={btn}>
                {(offline.saved[t] ?? []).length >= 66 ? `✓ The whole ${t} is saved` : `Save the whole ${t}`}
              </button>
            ))}
          </div>
        )}
      </div>
    </section>
  );
}