export type CacheStrategy = 'shell' | 'network-first' | 'images' | 'network-only';

type RequestShape = { url: string; method: string };

// Pure function — sole decision-maker for "which strategy for this request?".
// Called by the service worker for every fetch event.
export function resolveStrategy(req: RequestShape): CacheStrategy {
  // All write methods: never cache.
  if (req.method !== 'GET' && req.method !== 'HEAD') return 'network-only';

  // Reduce URL to pathname — query string not needed for matching
  // except that online-only endpoints need no special handling here.
  const path = req.url.startsWith('http') ? new URL(req.url).pathname : req.url.split('?')[0];

  // Explicitly online-only GETs
  if (
    path === '/api/recipes/import' ||
    path === '/api/recipes/preview' ||
    path === '/api/recipes/extract-from-photo' ||
    path.startsWith('/api/recipes/search/web') ||
    path.startsWith('/api/shopping-list')
  ) {
    return 'network-only';
  }

  // Images
  if (path.startsWith('/images/')) return 'images';

  // App-shell: build assets and known static files
  if (
    path.startsWith('/_app/') ||
    path === '/manifest.webmanifest' ||
    path === '/icon.svg' ||
    path === '/icon-192.png' ||
    path === '/icon-512.png' ||
    path === '/favicon.ico' ||
    path === '/robots.txt'
  ) {
    return 'shell';
  }

  // Everything else: recipe pages, API reads, lists — network-first with
  // timeout fallback to cache (handled in service-worker.ts).
  return 'network-first';
}