1 files changed, 84 insertions, 0 deletions
diff --git a/misc/dist/html/service-worker.js b/misc/dist/html/service-worker.js
new file mode 100644
index 0000000000..d4eaed2b17
--- /dev/null
+++ b/misc/dist/html/service-worker.js
@@ -0,0 +1,84 @@
+// This service worker is required to expose an exported Godot project as a
+// Progressive Web App. It provides an offline fallback page telling the user
+// that they need an Internet conneciton to run the project if desired.
+// Incrementing CACHE_VERSION will kick off the install event and force
+// previously cached resources to be updated from the network.
+const CACHE_VERSION = "@GODOT_VERSION@";
+const CACHE_NAME = "@GODOT_NAME@-cache";
+const OFFLINE_URL = "offline.html";
+// Files that will be cached on load.
+const CACHED_FILES = [
+	"godot.tools.html",
+	"offline.html",
+	"godot.tools.js",
+	"godot.tools.worker.js",
+	"godot.tools.audio.worklet.js",
+	"logo.svg",
+	"favicon.png",
+];
+
+// Files that we might not want the user to preload, and will only be cached on first load.
+const CACHABLE_FILES = [
+	"godot.tools.wasm",
+];
+const FULL_CACHE = CACHED_FILES.concat(CACHABLE_FILES);
+
+self.addEventListener("install", (event) => {
+	event.waitUntil(async function () {
+		const cache = await caches.open(CACHE_NAME);
+		// Clear old cache (including optionals).
+		await Promise.all(FULL_CACHE.map(path => cache.delete(path)));
+		// Insert new one.
+		const done = await cache.addAll(CACHED_FILES);
+		return done;
+	}());
+});
+
+self.addEventListener("activate", (event) => {
+	event.waitUntil(async function () {
+		if ("navigationPreload" in self.registration) {
+			await self.registration.navigationPreload.enable();
+		}
+	}());
+	// Tell the active service worker to take control of the page immediately.
+	self.clients.claim();
+});
+
+self.addEventListener("fetch", (event) => {
+	const isNavigate = event.request.mode === "navigate";
+	const url = event.request.url || "";
+	const referrer = event.request.referrer || "";
+	const base = referrer.slice(0, referrer.lastIndexOf("/") + 1);
+	const local = url.startsWith(base) ? url.replace(base, "") : "";
+	const isCachable = FULL_CACHE.some(v => v === local) || (base === referrer && base.endsWith(CACHED_FILES[0]));
+	if (isNavigate || isCachable) {
+		event.respondWith(async function () {
+			try {
+				// Use the preloaded response, if it's there
+				let request = event.request.clone();
+				let response = await event.preloadResponse;
+				if (!response) {
+					// Or, go over network.
+					response = await fetch(event.request);
+				}
+				if (isCachable) {
+					// Update the cache
+					const cache = await caches.open(CACHE_NAME);
+					cache.put(request, response.clone());
+				}
+				return response;
+			} catch (error) {
+				const cache = await caches.open(CACHE_NAME);
+				if (event.request.mode === "navigate") {
+					// Check if we have full cache.
+					const cached = await Promise.all(FULL_CACHE.map(name => cache.match(name)));
+					const missing = cached.some(v => v === undefined);
+					const cachedResponse = missing ? await caches.match(OFFLINE_URL) : await caches.match(CACHED_FILES[0]);
+					return cachedResponse;
+				}
+				const cachedResponse = await caches.match(event.request);
+				return cachedResponse;
+			}
+		}());
+	}
+});