Add parallel server action utilities

src/lib/utils/parallelAction.ts

@@ -0,0 +1,46 @@
+/**
+ * Parallel Server Action utilities.
+ *
+ * Server Actions are dispatched sequentially per client in Next.js.
+ * `createParallelAction` wraps a server function so its outer wrapper
+ * returns immediately without awaiting the inner work, freeing the
+ * dispatch queue. The real work continues asynchronously on the server,
+ * and the result is streamed back via React Flight.
+ *
+ * Usage:
+ *
+ *   // server (in a "use server" file):
+ *   export const getData = createParallelAction(async (id: string) => {
+ *     return await fetchExpensiveData(id);
+ *   });
+ *
+ *   // client:
+ *   const result = await runParallelAction(getData("abc"));
+ *
+ * Multiple calls can run in parallel — each outer Action returns instantly,
+ * so the Next.js serial queue does not block subsequent calls.
+ *
+ * @see https://github.com/icflorescu/next-server-actions-parallel
+ */
+
+/**
+ * Wrap an async server function so it returns immediately without awaiting
+ * the inner work. The outer function completes instantly (returning a
+ * Flight-wrapped promise tuple), so the Next.js Server Action dispatch
+ * queue is freed for the next call.
+ */
+export function createParallelAction<T, U extends unknown[]>(
+  action: (...args: U) => Promise<T>,
+) {
+  return async (...args: U) => [action(...args)] as const;
+}
+
+/**
+ * Await the result of a parallel Server Action created by
+ * {@link createParallelAction}. Call this on the client side.
+ */
+export async function runParallelAction<T>(
+  result: Promise<readonly [Promise<T>]>,
+) {
+  return (await result)[0];
+}