// Earlier versions of a single note (Observe, Interpret, Apply…), kept on this device so one note can be rolled
// back without restoring the whole study. A version is saved when you start and when you stop editing a note, so
// whatever was there before a big rewrite is always a click away.
export const MAX_VERSIONS = 12;
const keyFor = (chunkId, field) => `note-history:${chunkId}:${field}`;

// -> [{ at, text }], newest first
export function listNoteVersions(chunkId, field) {
  try {
    const raw = JSON.parse(localStorage.getItem(keyFor(chunkId, field)) || '[]');
    return Array.isArray(raw) ? raw.filter((v) => v && typeof v.text === 'string') : [];
  } catch { return []; }
}

// Keeps `text` as the newest version unless it is blank or the same as the newest one. Returns the list.
export function recordNoteVersion(chunkId, field, text, now = Date.now()) {
  const list = listNoteVersions(chunkId, field);
  const value = text ?? '';
  if (!value.trim() || list[0]?.text === value) return list;
  const next = [{ at: now, text: value }, ...list].slice(0, MAX_VERSIONS);
  try { localStorage.setItem(keyFor(chunkId, field), JSON.stringify(next)); } catch { /* storage full or unavailable */ }
  return next;
}