const CACHE_NAME = 'trackpull-v1';
const APP_SHELL = [
    '/',
    '/static/favicon.ico',
    '/static/manifest.json',
    '/static/icons/icon-192x192.png',
    '/static/icons/icon-512x512.png',
    '/offline',
];

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

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())
    );
});

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

    // API calls: network only
    if (url.pathname.startsWith('/api/')) {
        return;
    }

    // Navigation requests: network first, cache fallback, then offline page
    if (event.request.mode === 'navigate') {
        event.respondWith(
            fetch(event.request)
                .then(response => {
                    const clone = response.clone();
                    caches.open(CACHE_NAME).then(cache => cache.put(event.request, clone));
                    return response;
                })
                .catch(() => caches.match(event.request).then(r => r || caches.match('/offline')))
        );
        return;
    }

    // Static assets: cache first, network fallback
    if (url.pathname.startsWith('/static/')) {
        event.respondWith(
            caches.match(event.request).then(cached =>
                cached || fetch(event.request).then(response => {
                    const clone = response.clone();
                    caches.open(CACHE_NAME).then(cache => cache.put(event.request, clone));
                    return response;
                })
            )
        );
        return;
    }
});