first commit

apps/gateway/src/ws/assistTxnDeduper.ts

@@ -0,0 +1,35 @@
+export interface AssistTxnDeduperOptions {
+  ttlMs: number;
+  cacheLimit: number;
+}
+
+export function createAssistTxnDeduper(options: AssistTxnDeduperOptions): (source?: string, txnId?: string) => boolean {
+  const seenAt = new Map<string, number>();
+
+  return (source?: string, txnId?: string): boolean => {
+    if (source !== "assist" || !txnId) {
+      return false;
+    }
+
+    const now = Date.now();
+    for (const [id, at] of seenAt.entries()) {
+      if (now - at > options.ttlMs) {
+        seenAt.delete(id);
+      }
+    }
+
+    if (seenAt.has(txnId)) {
+      return true;
+    }
+
+    seenAt.set(txnId, now);
+    if (seenAt.size > options.cacheLimit) {
+      const oldestId = seenAt.keys().next().value as string | undefined;
+      if (oldestId) {
+        seenAt.delete(oldestId);
+      }
+    }
+
+    return false;
+  };
+}