/**
 * Service Worker for LED Grab PWA.
 *
 * Strategy:
 *   - Static assets (/static/): stale-while-revalidate
 *   - API / config requests: network-only (device control must be live)
 *   - Navigation: network-first with offline fallback
 */

const CACHE_NAME = 'ledgrab-v34';

// Only pre-cache static assets (no auth required).
// Do NOT pre-cache '/' — it requires API key auth and would cache an error page.
const PRECACHE_URLS = [
    '/static/dist/app.bundle.css',
    '/static/dist/app.bundle.js',
    '/static/icons/icon-192.png',
    '/static/icons/icon-512.png',
];

// Install: pre-cache core shell
self.addEventListener('install', (event) => {
    event.waitUntil(
        caches.open(CACHE_NAME)
            .then((cache) => cache.addAll(PRECACHE_URLS))
            .then(() => self.skipWaiting())
    );
});

// Activate: clean old caches
self.addEventListener('activate', (event) => {
    event.waitUntil(
        caches.keys()
            .then((keys) => Promise.all(
                keys.filter((k) => k !== CACHE_NAME).map((k) => caches.delete(k))
            ))
            .then(() => self.clients.claim())
    );
});

// Fetch handler
self.addEventListener('fetch', (event) => {
    const url = new URL(event.request.url);

    // API and config: always network (device control must be live)
    if (url.pathname.startsWith('/api/') || url.pathname.startsWith('/config/')) {
        return; // fall through to default network fetch
    }

    // Static assets: stale-while-revalidate
    if (url.pathname.startsWith('/static/')) {
        event.respondWith(
            caches.open(CACHE_NAME).then((cache) =>
                cache.match(event.request).then((cached) => {
                    const fetchPromise = fetch(event.request).then((response) => {
                        if (response.ok) {
                            cache.put(event.request, response.clone());
                        }
                        return response;
                    }).catch(() => cached);

                    return cached || fetchPromise;
                })
            )
        );
        return;
    }

    // Navigation: network-only (page requires auth, no useful offline fallback)
    if (event.request.mode === 'navigate') {
        event.respondWith(
            fetch(event.request).catch(() =>
                new Response(
                    '<html><body style="font-family:system-ui;text-align:center;padding:60px 20px;background:#1a1a1a;color:#ccc">' +
                    '<h2>LED Grab</h2><p>Cannot reach the server. Check that it is running and you are on the same network.</p>' +
                    '<button onclick="location.reload()" style="margin-top:20px;padding:10px 24px;border-radius:8px;border:none;background:#4CAF50;color:#fff;font-size:1rem;cursor:pointer">Retry</button>' +
                    '</body></html>',
                    { status: 503, headers: { 'Content-Type': 'text/html' } }
                )
            )
        );
        return;
    }
});
