// Decides what a saved schedule needs after the catalog was read again.
// Runs in the browser; kept free of DOM code so the rules are testable in Node.

const escape = (s) => s.replace(/[.*+?^${}()|[\]\\]/g, "\\$&");
const time = (value) => Date.parse(value || "") || 0;

/** "23-БА" matches "23-ЛГ_23-БА.docx" but not "23-БАз" or "123-БА". */
export function namesGroup(fileName, group) {
  if (!group) return false;
  const base = fileName.replace(/\.docx?$/i, "");
  return new RegExp(
    `(^|[^0-9A-Za-zА-ЯЁа-яё])${escape(group)}(?![0-9A-Za-zА-ЯЁа-яё])`,
    "iu",
  ).test(base);
}

/**
 * changed: the same document was republished, or parsed by an older parser than the server's
 *          (`catalog.parserVersion`, from API version 10) — reload it quietly.
 * newer:   another document for this group appeared later, e.g. the next semester — offer it.
 * missing: the document left the catalog, e.g. a new academic year began.
 */
export function scheduleUpdate(saved, catalog, group, options = {}) {
  // A server without parserVersion never asks for a re-read: comparing with a guess could
  // reload the same document on every check.
  const { dismissed = [], schemaVersion = catalog?.parserVersion ?? 0 } = options;
  const fileId = saved?.source?.fileId;
  if (!fileId || !catalog?.files || catalog.stale) return null;
  const current = catalog.files.find((f) => f.id === fileId) || null;
  const savedTime = time(saved.source.modified) || time(saved.source.importedAt);
  const newer =
    catalog.files
      .filter(
        (f) =>
          f.id !== fileId &&
          !dismissed.includes(f.id) &&
          namesGroup(f.name, group) &&
          time(f.modified) > savedTime &&
          (!saved.source.faculty || f.faculty === saved.source.faculty),
      )
      .sort((a, b) => time(b.modified) - time(a.modified))[0] || null;
  const changed =
    current &&
    (current.modified !== saved.source.modified ||
      (saved.schemaVersion || 0) < schemaVersion)
      ? current
      : null;
  if (!changed && !newer && current) return null;
  return { changed, newer, missing: !current };
}