/**
 * Service Worker for 2026 Challenge Calendar
 * Enables offline functionality and caching
 */

const CACHE_NAME = '2026-challenges-v1';
const ASSETS_TO_CACHE = [
    '/',
    '/index.html',
    '/styles.css',
    '/app.js',
    '/challenges.json',
    '/manifest.json',
    '/icons/icon-192.png',
    '/icons/icon-512.png',
    '/icons/apple-touch-icon.png'
];

// Install event - cache assets
self.addEventListener('install', (event) => {
    event.waitUntil(
        caches.open(CACHE_NAME)
            .then((cache) => {
                console.log('Caching app assets');
                return cache.addAll(ASSETS_TO_CACHE);
            })
            .then(() => {
                // Activate immediately
                return self.skipWaiting();
            })
    );
});

// Activate event - clean up old caches
self.addEventListener('activate', (event) => {
    event.waitUntil(
        caches.keys()
            .then((cacheNames) => {
                return Promise.all(
                    cacheNames.map((cacheName) => {
                        if (cacheName !== CACHE_NAME) {
                            console.log('Deleting old cache:', cacheName);
                            return caches.delete(cacheName);
                        }
                    })
                );
            })
            .then(() => {
                // Take control of all pages immediately
                return self.clients.claim();
            })
    );
});

// Fetch event - serve from cache, fallback to network
self.addEventListener('fetch', (event) => {
    // Skip non-GET requests
    if (event.request.method !== 'GET') {
        return;
    }

    event.respondWith(
        caches.match(event.request)
            .then((cachedResponse) => {
                if (cachedResponse) {
                    // Return cached version
                    return cachedResponse;
                }

                // Not in cache - fetch from network
                return fetch(event.request)
                    .then((networkResponse) => {
                        // Don't cache if not a valid response
                        if (!networkResponse || networkResponse.status !== 200 || networkResponse.type !== 'basic') {
                            return networkResponse;
                        }

                        // Clone the response (can only be consumed once)
                        const responseToCache = networkResponse.clone();

                        // Add to cache for future use
                        caches.open(CACHE_NAME)
                            .then((cache) => {
                                cache.put(event.request, responseToCache);
                            });

                        return networkResponse;
                    })
                    .catch(() => {
                        // Network failed and not in cache
                        // Return a fallback for HTML pages
                        if (event.request.headers.get('accept').includes('text/html')) {
                            return caches.match('/index.html');
                        }
                    });
            })
    );
});

// Handle messages from the main app
self.addEventListener('message', (event) => {
    if (event.data.action === 'skipWaiting') {
        self.skipWaiting();
    }
});