the-nexus/sw.js

// ◈ The Nexus — Service Worker
// Offline-first caching for sovereign space

const CACHE_VERSION = 'nexus-v1';
const STATIC_CACHE = `${CACHE_VERSION}-static`;
const CDN_CACHE = `${CACHE_VERSION}-cdn`;

// Core local assets — always cache
const STATIC_ASSETS = [
  '/',
  '/index.html',
  '/style.css',
  '/app.js',
  '/manifest.json',
  '/icons/icon-192.png',
  '/icons/icon-512.png',
];

// CDN assets for Three.js — cache on first fetch
const CDN_ORIGINS = [
  'https://cdn.jsdelivr.net',
  'https://fonts.googleapis.com',
  'https://fonts.gstatic.com',
];

// ═══ INSTALL — pre-cache static assets ═══
self.addEventListener('install', event => {
  event.waitUntil(
    caches.open(STATIC_CACHE)
      .then(cache => cache.addAll(STATIC_ASSETS))
      .then(() => self.skipWaiting())
  );
});

// ═══ ACTIVATE — clean up old caches ═══
self.addEventListener('activate', event => {
  event.waitUntil(
    caches.keys()
      .then(keys => Promise.all(
        keys
          .filter(key => key.startsWith('nexus-') && key !== STATIC_CACHE && key !== CDN_CACHE)
          .map(key => caches.delete(key))
      ))
      .then(() => self.clients.claim())
  );
});

// ═══ FETCH — serve from cache, fall back to network ═══
self.addEventListener('fetch', event => {
  const { request } = event;
  const url = new URL(request.url);

  // Skip non-GET requests
  if (request.method !== 'GET') return;

  // CDN resources: cache-first with network fallback
  if (CDN_ORIGINS.some(origin => request.url.startsWith(origin))) {
    event.respondWith(cdnFirst(request));
    return;
  }

  // Same-origin static assets: cache-first
  if (url.origin === self.location.origin) {
    event.respondWith(staticFirst(request));
    return;
  }
});

// Cache-first for CDN (Three.js modules, fonts)
async function cdnFirst(request) {
  const cached = await caches.match(request);
  if (cached) return cached;

  try {
    const response = await fetch(request);
    if (response.ok) {
      const cache = await caches.open(CDN_CACHE);
      cache.put(request, response.clone());
    }
    return response;
  } catch {
    // Offline and not cached — return a minimal error response
    return new Response('/* offline */', {
      headers: { 'Content-Type': 'text/plain' },
    });
  }
}

// Cache-first for local static assets
async function staticFirst(request) {
  const cached = await caches.match(request);
  if (cached) return cached;

  try {
    const response = await fetch(request);
    if (response.ok) {
      const cache = await caches.open(STATIC_CACHE);
      cache.put(request, response.clone());
    }
    return response;
  } catch {
    // Offline fallback: serve index.html for navigation requests
    if (request.mode === 'navigate') {
      const fallback = await caches.match('/index.html');
      if (fallback) return fallback;
    }
    return new Response('Nexus offline — cached assets not found.', {
      status: 503,
      headers: { 'Content-Type': 'text/plain' },
    });
  }
}