fix: bound Horizon payment-lookup latency so large-dataset queries fail fast (Closes #2)

backend/src/stellar/horizon.ts

@@ -15,6 +15,27 @@ import { Horizon, Networks, Asset } from "@stellar/stellar-sdk";
 export const HORIZON_URL =
   process.env.HORIZON_URL ?? "https://horizon-testnet.stellar.org";
 
+// Hard cap on how long a single Horizon read (e.g. fetching a large account's
+// payment history) may take. Horizon can be slow for accounts with very large
+// payment datasets; without a bound this can hang a request until the caller
+// times out (issue #2). Failing fast with a clear error is better than dropping.
+export const HORIZON_REQUEST_TIMEOUT_MS = 10_000;
+
+/**
+ * Rejects `promise` if it does not settle within `ms`, with a clear timeout
+ * error. Otherwise resolves/rejects with the original result.
+ */
+export function withTimeout<T>(promise: Promise<T>, ms: number): Promise<T> {
+  let timer: ReturnType<typeof setTimeout>;
+  const timeout = new Promise<never>((_, reject) => {
+    timer = setTimeout(
+      () => reject(new Error(`Horizon request timed out after ${ms}ms`)),
+      ms
+    );
+  });
+  return Promise.race([promise, timeout]).finally(() => clearTimeout(timer));
+}
+
 export const NETWORK_PASSPHRASE =
   process.env.STELLAR_NETWORK === "mainnet"
     ? Networks.PUBLIC
@@ -124,12 +145,15 @@ export async function fetchRecentPayments(
   limit = 20
 ): Promise<StellarPayment[]> {
   try {
-    const records = await getHorizon()
-      .payments()
-      .forAccount(accountId)
-      .order("desc")
-      .limit(limit)
-      .call();
+    const records = await withTimeout(
+      getHorizon()
+        .payments()
+        .forAccount(accountId)
+        .order("desc")
+        .limit(limit)
+        .call(),
+      HORIZON_REQUEST_TIMEOUT_MS
+    );
 
     return records.records
       .filter((r: any) => r.type === "payment" && r.to === accountId)

backend/src/tests/horizon.test.ts

@@ -0,0 +1,40 @@
+import { describe, it, expect, vi } from "vitest";
+import { withTimeout, HORIZON_REQUEST_TIMEOUT_MS } from "../stellar/horizon";
+
+const never = new Promise<never>(() => {});
+
+describe("Horizon withTimeout helper", () => {
+  it("resolves with the inner promise's value when it settles within the timeout", async () => {
+    const value = { id: "p1", amount: "10.0000000" };
+    const inner = Promise.resolve(value);
+
+    await expect(withTimeout(inner, 100)).resolves.toBe(value);
+  });
+
+  it("rejects with a clear timeout error when the inner promise never settles (large/slow dataset)", async () => {
+    await expect(withTimeout(never, 10)).rejects.toThrow(
+      "Horizon request timed out after 10ms"
+    );
+  });
+
+  it("still rejects with the inner promise's own error when it fails before the deadline", async () => {
+    const inner = Promise.reject(new Error("Horizon down"));
+
+    await expect(withTimeout(inner, 100)).rejects.toThrow("Horizon down");
+  });
+
+  it("clears its internal timer once the inner promise settles (no leaked handle)", async () => {
+    // spyOn global setTimeout/clearTimeout to confirm cleanup after resolution
+    const clearSpy = vi.spyOn(globalThis, "clearTimeout");
+
+    await withTimeout(Promise.resolve(1), 100);
+
+    expect(clearSpy).toHaveBeenCalled();
+    clearSpy.mockRestore();
+  });
+
+  it("exposes a bounded, positive Horizon timeout", () => {
+    expect(HORIZON_REQUEST_TIMEOUT_MS).toBeGreaterThan(0);
+    expect(HORIZON_REQUEST_TIMEOUT_MS).toBeLessThanOrEqual(60_000);
+  });
+});