Prototype commit

web/src/lib/precache.svelte.ts

@@ -0,0 +1,51 @@
+import { browser } from '$app/environment';
+import { stops } from './stops';
+
+export type PrecacheState = 'idle' | 'running' | 'complete' | 'unsupported';
+
+let state: PrecacheState = $state('idle');
+let done = $state(0);
+let total = $state(0);
+
+export function precacheState() {
+	return { state, done, total };
+}
+
+export async function precacheAll(): Promise<void> {
+	if (!browser) return;
+	if (!('serviceWorker' in navigator)) {
+		state = 'unsupported';
+		return;
+	}
+	if (state === 'running' || state === 'complete') return;
+
+	const reg = await navigator.serviceWorker.ready.catch(() => null);
+	const target = reg?.active ?? navigator.serviceWorker.controller;
+	if (!target) {
+		state = 'unsupported';
+		return;
+	}
+
+	const urls = stops.flatMap((s) => [s.audio, s.image]);
+
+	state = 'running';
+	done = 0;
+	total = urls.length;
+
+	const onMessage = (event: MessageEvent) => {
+		const data = event.data;
+		if (!data || typeof data !== 'object') return;
+		if (data.type === 'precache-progress') {
+			done = data.done;
+			total = data.total;
+		} else if (data.type === 'precache-done') {
+			done = data.done;
+			total = data.total;
+			state = 'complete';
+			navigator.serviceWorker.removeEventListener('message', onMessage);
+		}
+	};
+	navigator.serviceWorker.addEventListener('message', onMessage);
+
+	target.postMessage({ type: 'precache-stops', urls });
+}