Refactor clawx (#344)

Co-authored-by: ashione <skyzlxuan@gmail.com>

src/lib/host-events.ts

@@ -0,0 +1,25 @@
+import { createHostEventSource } from './host-api';
+
+let eventSource: EventSource | null = null;
+
+function getEventSource(): EventSource {
+  if (!eventSource) {
+    eventSource = createHostEventSource();
+  }
+  return eventSource;
+}
+
+export function subscribeHostEvent<T = unknown>(
+  eventName: string,
+  handler: (payload: T) => void,
+): () => void {
+  const source = getEventSource();
+  const listener = (event: Event) => {
+    const payload = JSON.parse((event as MessageEvent).data) as T;
+    handler(payload);
+  };
+  source.addEventListener(eventName, listener);
+  return () => {
+    source.removeEventListener(eventName, listener);
+  };
+}