refactor: share backoff helpers

src/infra/backoff.ts

@@ -0,0 +1,26 @@
+import { setTimeout as delay } from "node:timers/promises";
+
+export type BackoffPolicy = {
+  initialMs: number;
+  maxMs: number;
+  factor: number;
+  jitter: number;
+};
+
+export function computeBackoff(policy: BackoffPolicy, attempt: number) {
+  const base = policy.initialMs * policy.factor ** Math.max(attempt - 1, 0);
+  const jitter = base * policy.jitter * Math.random();
+  return Math.min(policy.maxMs, Math.round(base + jitter));
+}
+
+export async function sleepWithAbort(ms: number, abortSignal?: AbortSignal) {
+  if (ms <= 0) return;
+  try {
+    await delay(ms, undefined, { signal: abortSignal });
+  } catch (err) {
+    if (abortSignal?.aborted) {
+      throw new Error("aborted");
+    }
+    throw err;
+  }
+}