redesign the homepage

apps/homepage/src/lib/demo/idempotency.ts

@@ -0,0 +1,46 @@
+import type { DemoSubmissionResult } from './schema';
+
+interface StoredOperation {
+  expiresAt: number;
+  result: Promise<DemoSubmissionResult>;
+}
+
+const globalStore = globalThis as typeof globalThis & {
+  __rdgDemoIdempotencyStore?: Map<string, StoredOperation>;
+};
+
+const store = globalStore.__rdgDemoIdempotencyStore ?? new Map<string, StoredOperation>();
+globalStore.__rdgDemoIdempotencyStore = store;
+
+function purgeExpired(now: number) {
+  for (const [key, operation] of store) {
+    if (operation.expiresAt <= now) store.delete(key);
+  }
+}
+
+export async function executeIdempotent(
+  key: string,
+  ttlSeconds: number,
+  operation: () => Promise<DemoSubmissionResult>,
+): Promise<DemoSubmissionResult> {
+  const now = Date.now();
+  purgeExpired(now);
+  const existing = store.get(key);
+  if (existing) return existing.result;
+
+  const result = operation();
+  store.set(key, { expiresAt: now + ttlSeconds * 1_000, result });
+
+  try {
+    const settled = await result;
+    if (!settled.ok && settled.retryable) store.delete(key);
+    return settled;
+  } catch (error) {
+    store.delete(key);
+    throw error;
+  }
+}
+
+export function clearIdempotencyStoreForTests() {
+  store.clear();
+}