// ============================================================================
// Service Worker — Homelab Automation Dashboard PWA
// ============================================================================

const CACHE_VERSION = 'v1';
const STATIC_CACHE = `homelab-static-${CACHE_VERSION}`;
const DYNAMIC_CACHE = `homelab-dynamic-${CACHE_VERSION}`;

// App shell — resources to pre-cache on install
const APP_SHELL = [
    '/',
    '/static/main.js',
    '/static/containers_page.js',
    '/static/dashboard_core.js',
    '/static/docker_section.js',
    '/static/favorites_manager.js',
    '/static/icon_picker.js',
    '/static/playbook_editor.js',
    '/static/container_customizations_manager.js',
    '/manifest.json',
    '/static/icons/icon-192x192.png',
    '/static/icons/icon-512x512.png',
];

// External CDN resources to cache on first fetch
const CDN_PATTERNS = [
    'cdn.tailwindcss.com',
    'cdnjs.cloudflare.com',
    'fonts.googleapis.com',
    'fonts.gstatic.com',
    'cdn.jsdelivr.net',
];

// ---- INSTALL: pre-cache app shell ----
self.addEventListener('install', (event) => {
    console.log('[SW] Installing...');
    event.waitUntil(
        caches.open(STATIC_CACHE)
            .then((cache) => cache.addAll(APP_SHELL))
            .then(() => self.skipWaiting())
            .catch((err) => console.warn('[SW] Pre-cache failed for some resources:', err))
    );
});

// ---- ACTIVATE: clean up old caches ----
self.addEventListener('activate', (event) => {
    console.log('[SW] Activating...');
    event.waitUntil(
        caches.keys()
            .then((keys) =>
                Promise.all(
                    keys
                        .filter((key) => key !== STATIC_CACHE && key !== DYNAMIC_CACHE)
                        .map((key) => {
                            console.log('[SW] Removing old cache:', key);
                            return caches.delete(key);
                        })
                )
            )
            .then(() => self.clients.claim())
    );
});

// ---- FETCH: routing strategies ----
self.addEventListener('fetch', (event) => {
    const { request } = event;
    const url = new URL(request.url);

    // Skip non-GET requests
    if (request.method !== 'GET') return;

    // Skip WebSocket upgrades
    if (url.protocol === 'ws:' || url.protocol === 'wss:') return;

    // Skip /docs and /redoc (Swagger UI) — always network
    if (url.pathname.startsWith('/docs') || url.pathname.startsWith('/redoc')) return;

    // --- API calls: Network First ---
    if (url.pathname.startsWith('/api/')) {
        event.respondWith(networkFirst(request, DYNAMIC_CACHE));
        return;
    }

    // --- CDN resources: Cache First ---
    if (CDN_PATTERNS.some((pattern) => url.hostname.includes(pattern))) {
        event.respondWith(cacheFirst(request, STATIC_CACHE));
        return;
    }

    // --- Static assets & app shell: Cache First ---
    if (
        url.pathname.startsWith('/static/') ||
        url.pathname === '/manifest.json' ||
        url.pathname === '/favicon.ico' ||
        url.pathname === '/sw.js'
    ) {
        event.respondWith(cacheFirst(request, STATIC_CACHE));
        return;
    }

    // --- HTML pages (/, etc.): Network First ---
    event.respondWith(networkFirst(request, DYNAMIC_CACHE));
});

// ============================================================================
// Caching strategies
// ============================================================================

/**
 * Cache First — try cache, fall back to network (and cache the response).
 */
async function cacheFirst(request, cacheName) {
    const cached = await caches.match(request);
    if (cached) return cached;

    try {
        const response = await fetch(request);
        if (response.ok) {
            const cache = await caches.open(cacheName);
            cache.put(request, response.clone());
        }
        return response;
    } catch {
        // If both cache and network fail, return a basic offline page
        return new Response('Offline', {
            status: 503,
            statusText: 'Service Unavailable',
            headers: { 'Content-Type': 'text/plain' },
        });
    }
}

/**
 * Network First — try network, fall back to cache.
 */
async function networkFirst(request, cacheName) {
    try {
        const response = await fetch(request);
        if (response.ok) {
            const cache = await caches.open(cacheName);
            cache.put(request, response.clone());
        }
        return response;
    } catch {
        const cached = await caches.match(request);
        if (cached) return cached;

        // For HTML navigations, serve the cached root page
        if (request.headers.get('Accept')?.includes('text/html')) {
            const fallback = await caches.match('/');
            if (fallback) return fallback;
        }

        return new Response('Offline', {
            status: 503,
            statusText: 'Service Unavailable',
            headers: { 'Content-Type': 'text/plain' },
        });
    }
}