import fs from 'node:fs';
import path from 'node:path';

/** Only the app shell; route data is downloaded separately on explicit request. */
export function offlineManifest(publicDirectory) {
  const resources = new Set(['/']);
  const appDirectories = new Set(['css', 'js', 'vendor', 'assets', 'images']);
  function visit(directory, prefix = '') {
    for (const entry of fs.readdirSync(directory, { withFileTypes: true })) {
      if (entry.name.startsWith('.')) continue;
      if (!prefix && entry.isDirectory() && !appDirectories.has(entry.name)) continue;
      if (prefix === '/images' && entry.isDirectory() && !['icons', 'group-symbols'].includes(entry.name)) continue;
      const relative = `${prefix}/${encodeURIComponent(entry.name)}`;
      if (entry.isDirectory()) visit(path.join(directory, entry.name), relative);
      else if (entry.isFile() && /\.(?:html|css|js|svg|png|webp|jpg|jpeg|gif|ico|woff2?)$/i.test(entry.name)) resources.add(relative);
    }
  }
  visit(publicDirectory);
  return { resources: [...resources].sort((left, right) => left.localeCompare(right, 'en')) };
}