/// <reference no-default-lib="true"/>
/// <reference lib="esnext" />
/// <reference lib="webworker" />
/// <reference types="@sveltejs/kit" />

import { build, files, version } from '$service-worker';

// This gives `self` the correct types
const sw = /** @type {ServiceWorkerGlobalScope} */ (/** @type {unknown} */ (globalThis.self));

// Create a unique cache name for this deployment
const CACHE = `cache-${version}`;

// Assets to cache immediately (app shell)
const ASSETS = [
	...build, // the app itself
	...files // everything in static
];

// Install: cache app shell
sw.addEventListener('install', (event) => {
	async function addFilesToCache() {
		const cache = await caches.open(CACHE);
		// In dev mode, ASSETS is empty - skip caching
		if (ASSETS.length > 0) {
			await cache.addAll(ASSETS);
		}
	}

	event.waitUntil(addFilesToCache());
});

// Activate: clean up old caches
sw.addEventListener('activate', (event) => {
	async function deleteOldCaches() {
		for (const key of await caches.keys()) {
			if (key !== CACHE) await caches.delete(key);
		}
	}

	event.waitUntil(deleteOldCaches());
});

// Fetch: network-first with cache fallback for pages, cache-first for assets
sw.addEventListener('fetch', (event) => {
	// Only handle GET requests
	if (event.request.method !== 'GET') return;

	const url = new URL(event.request.url);

	// Skip cross-origin requests
	if (url.origin !== sw.location.origin) return;

	// Skip API routes - always go to network
	if (url.pathname.startsWith('/api/')) return;

	async function respond() {
		const cache = await caches.open(CACHE);

		// For static assets (build/files), serve from cache first
		if (ASSETS.includes(url.pathname)) {
			const cached = await cache.match(url.pathname);
			if (cached) return cached;
		}

		// For pages, try network first, fall back to cache
		try {
			const response = await fetch(event.request);

			// if we're offline, fetch can return a value that is not a Response
			if (!(response instanceof Response)) {
				throw new Error('invalid response from fetch');
			}

			// Cache successful responses
			if (response.status === 200) {
				cache.put(event.request, response.clone());
			}

			return response;
		} catch (err) {
			// Offline: try to serve from cache
			const cached = await cache.match(event.request);
			if (cached) return cached;

			// If no cache and it's a navigation request, show offline page
			if (event.request.mode === 'navigate') {
				const offlinePage = await cache.match('/');
				if (offlinePage) return offlinePage;
			}

			throw err;
		}
	}

	event.respondWith(respond());
});