move app logic into templates (#444)

templates/src/client/prefetchRoutes/index.ts

@@ -0,0 +1,14 @@
+import { manifest, load_component } from "../app";
+
+export default function prefetchRoutes(pathnames: string[]) {
+	if (!manifest) throw new Error(`You must call init() first`);
+
+	return manifest.pages
+		.filter(route => {
+			if (!pathnames) return true;
+			return pathnames.some(pathname => route.pattern.test(pathname));
+		})
+		.reduce((promise: Promise<any>, route) => promise.then(() => {
+			return Promise.all(route.parts.map(part => part && load_component(part.component)));
+		}), Promise.resolve());
+}