const CACHE_NAME = 'bsc-student-cache-v1';

// We explicitly cache critical assets to allow the app shell to boot offline.
// The data embedding logic from template.html doesn't require separate API calls, 
// so caching the HTML is sufficient for offline usage of the already-embedded repo.
const ASSETS = [
    './',
    './bsc',
    './assets/logo-bsc.svg',
    './assets/manifest-bsc.json',
    'https://cdn.tailwindcss.com',
    'https://fonts.googleapis.com/css2?family=Material+Symbols+Rounded:opsz,wght,FILL,GRAD@24,400,0,0',
    'https://cdnjs.cloudflare.com/ajax/libs/codemirror/5.65.16/codemirror.min.css',
    'https://cdnjs.cloudflare.com/ajax/libs/codemirror/5.65.16/theme/dracula.min.css',
    'https://cdnjs.cloudflare.com/ajax/libs/codemirror/5.65.16/codemirror.min.js',
    'https://cdnjs.cloudflare.com/ajax/libs/codemirror/5.65.16/addon/dialog/dialog.min.css',
    'https://cdnjs.cloudflare.com/ajax/libs/codemirror/5.65.16/addon/dialog/dialog.min.js',
    'https://cdnjs.cloudflare.com/ajax/libs/codemirror/5.65.16/addon/search/searchcursor.min.js',
    'https://cdnjs.cloudflare.com/ajax/libs/codemirror/5.65.16/addon/search/search.min.js',
    'https://cdnjs.cloudflare.com/ajax/libs/codemirror/5.65.16/addon/search/jump-to-line.min.js'
];

self.addEventListener('install', (event) => {
    event.waitUntil(
        caches.open(CACHE_NAME).then((cache) => cache.addAll(ASSETS))
    );
    self.skipWaiting();
});

self.addEventListener('activate', (event) => {
    event.waitUntil(
        caches.keys().then((cacheNames) => {
            return Promise.all(
                cacheNames.map((cacheName) => {
                    if (cacheName !== CACHE_NAME) {
                        return caches.delete(cacheName);
                    }
                })
            );
        })
    );
    self.clients.claim();
});

self.addEventListener('fetch', (event) => {
    // Strategy: Stale-While-Revalidate for app shell & CDNs
    event.respondWith(
        caches.match(event.request).then((cachedResponse) => {
            const fetchPromise = fetch(event.request).then((networkResponse) => {
                // Dynamically cache scripts/styles we might have missed
                if (event.request.method === 'GET' && networkResponse.status === 200) {
                    caches.open(CACHE_NAME).then((cache) => {
                        cache.put(event.request, networkResponse.clone());
                    });
                }
                return networkResponse;
            }).catch(() => {
                // If network fails and we don't have it, fallback silently
                // (Handled automatically by the catch structure if offline)
            });
            
            return cachedResponse || fetchPromise;
        })
    );
});