web: support installing as progressive web app™

1 files changed, 68 insertions, 0 deletions

diff --git a/web/static/sw.js b/web/static/sw.js
new file mode 100644
index 0000000..3a92eb3
--- /dev/null
+++ b/web/static/sw.js
@@ -0,0 +1,68 @@
+const CACHE_PREFIX = 'dartboat-'
+const CACHE_VERSION = '1';
+const CACHE_NAME = `${CACHE_PREFIX}${CACHE_VERSION}`;
+
+const FILES = [
+	'./',
+	'dartboat.js',
+	'dartboat_wasm.js',
+	'dartboat_wasm.wasm',
+	'style.css',
+	'icons.woff2',
+	'inter-num.woff2',
+	'dartboat_16.png',
+	'dartboat_32.png',
+	'dartboat_64.png',
+	'dartboat_96.png',
+	'dartboat_128.png',
+	'dartboat_192.png',
+	'dartboat_256.png',
+	'dartboat_512.png'
+]
+
+function swlog(str) {
+	console.log(`[service worker] ${str}`);
+}
+
+self.addEventListener('install', e => {
+	swlog('installing');
+
+	e.waitUntil((async() => {
+		swlog(`initialising cache ${CACHE_NAME}`);
+		const cache = await caches.open(CACHE_NAME);
+		await cache.addAll(FILES);
+	})());
+
+	swlog('installed');
+});
+
+self.addEventListener('activate', e => {
+	e.waitUntil(caches.keys().then((keys) => {
+		return Promise.all(keys.map((k) => {
+			if (k === CACHE_NAME ||	!k.startsWith(CACHE_PREFIX))
+				return;
+
+			swlog(`deleting cache ${k}`);
+			return caches.delete(k);
+		}));
+	}));
+});
+
+self.addEventListener('fetch', e => {
+	e.respondWith((async () => {
+		const cache = await caches.open(CACHE_NAME);
+
+		const cached = await cache.match(e.request);
+		swlog(`${cached ? 'hit' : 'miss'} ${e.request.url}`);
+		if (cached)
+			return cached;
+
+		if (!(resp = await fetch(e.request)).ok) {
+			swlog(`ignore status:${resp.status} ${e.request.url}`);
+		} else {
+			swlog(`put ${e.request.url}`);
+			cache.put(e.request, resp.clone());
+		}
+		return resp;
+	})());
+});