packages/frontend/web/sw.js

// Service Worker to intercept and serve cached share assets on-demand
const pendingRequests = new Map();
let requestIdCounter = 0;

self.addEventListener('install', (event) => {
  self.skipWaiting();
});

self.addEventListener('activate', (event) => {
  event.waitUntil(self.clients.claim());
});

self.addEventListener('fetch', (event) => {
  const url = new URL(event.request.url);
  // Intercept requests matching /share/<32-char-hex-hash>/...
  const match = url.pathname.match(/\/share\/([a-f0-9]{32})\/(.*)/);
  if (match) {
    const hash = match[1];
    const filePath = match[2] || 'index.html';

    event.respondWith(
      caches.open(`share-${hash}`).then((cache) => {
        return cache.match(event.request).then((cachedResponse) => {
          if (cachedResponse && filePath !== 'index.html' && filePath !== '') {
            return cachedResponse;
          }

          // Request the file from the client window on-demand
          return new Promise((resolve, reject) => {
            const requestId = ++requestIdCounter;
            pendingRequests.set(requestId, { resolve, reject, cache, request: event.request });

            // Send message to all matching clients
            self.clients.matchAll().then((clients) => {
              if (clients.length === 0) {
                reject(new Error('No active client window found to fetch file'));
                pendingRequests.delete(requestId);
                return;
              }
              clients.forEach((client) => {
                client.postMessage({
                  type: 'FETCH_FILE',
                  requestId: requestId,
                  hash: hash,
                  path: filePath
                });
              });
            });
          });
        });
      })
    );
  }
});

self.addEventListener('message', (event) => {
  if (event.data.type === 'FETCH_FILE_RESPONSE') {
    const pending = pendingRequests.get(event.data.requestId);
    if (pending) {
      pendingRequests.delete(event.data.requestId);
      if (event.data.error) {
        pending.reject(new Error(event.data.error));
      } else {
        const mimeType = event.data.mimeType || 'application/octet-stream';
        const headers = new Headers({
          'content-type': mimeType,
          'access-control-allow-origin': '*'
        });
        const response = new Response(event.data.bytes, { headers });
        // Store in cache for next time
        pending.cache.put(pending.request, response.clone());
        pending.resolve(response);
      }
    }
  }
});