sw.js

const CACHE_NAME = 'ledger-cache-v1';

// We explicitly cache these core files upon installation
const STATIC_ASSETS = [
    './',
    './index.html',
    './manifest.json',
    './icon.svg',
    'https://cdn.tailwindcss.com',
    'https://unpkg.com/leaflet@1.9.4/dist/leaflet.css',
    'https://unpkg.com/leaflet@1.9.4/dist/leaflet.js'
];

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

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

self.addEventListener('fetch', event => {
    // Only intercept standard GET requests
    if (event.request.method !== 'GET') return;
    
    event.respondWith(
        // Network-First Strategy: Always try the network to get the freshest data
        fetch(event.request).then(response => {
            // If network succeeds, clone the fresh response into the cache for future offline use
            const responseClone = response.clone();
            caches.open(CACHE_NAME).then(cache => cache.put(event.request, responseClone));
            return response;
        }).catch(() => {
            // If the network completely fails (e.g. offline), fall back to the cache
            return caches.match(event.request);
        })
    );
});