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packages/taler-wallet-core/src/util/retries.ts

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+/*
+ This file is part of GNU Taler
+ (C) 2020 Taler Systems S.A.
+
+ GNU Taler is free software; you can redistribute it and/or modify it under the
+ terms of the GNU General Public License as published by the Free Software
+ Foundation; either version 3, or (at your option) any later version.
+
+ GNU Taler is distributed in the hope that it will be useful, but WITHOUT ANY
+ WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR
+ A PARTICULAR PURPOSE.  See the GNU General Public License for more details.
+
+ You should have received a copy of the GNU General Public License along with
+ GNU Taler; see the file COPYING.  If not, see <http://www.gnu.org/licenses/>
+ */
+
+/**
+ * Helpers for dealing with retry timeouts.
+ */
+
+/**
+ * Imports.
+ */
+import { Timestamp, Duration, getTimestampNow } from "./time";
+
+export interface RetryInfo {
+  firstTry: Timestamp;
+  nextRetry: Timestamp;
+  retryCounter: number;
+  active: boolean;
+}
+
+export interface RetryPolicy {
+  readonly backoffDelta: Duration;
+  readonly backoffBase: number;
+}
+
+const defaultRetryPolicy: RetryPolicy = {
+  backoffBase: 1.5,
+  backoffDelta: { d_ms: 200 },
+};
+
+export function updateRetryInfoTimeout(
+  r: RetryInfo,
+  p: RetryPolicy = defaultRetryPolicy,
+): void {
+  const now = getTimestampNow();
+  if (now.t_ms === "never") {
+    throw Error("assertion failed");
+  }
+  if (p.backoffDelta.d_ms === "forever") {
+    r.nextRetry = { t_ms: "never" };
+    return;
+  }
+  r.active = true;
+  const t =
+    now.t_ms + p.backoffDelta.d_ms * Math.pow(p.backoffBase, r.retryCounter);
+  r.nextRetry = { t_ms: t };
+}
+
+export function getRetryDuration(
+  r: RetryInfo,
+  p: RetryPolicy = defaultRetryPolicy,
+): Duration {
+  if (p.backoffDelta.d_ms === "forever") {
+    return { d_ms: "forever" };
+  }
+  const t = p.backoffDelta.d_ms * Math.pow(p.backoffBase, r.retryCounter);
+  return { d_ms: t };
+}
+
+export function initRetryInfo(
+  active = true,
+  p: RetryPolicy = defaultRetryPolicy,
+): RetryInfo {
+  if (!active) {
+    return {
+      active: false,
+      firstTry: { t_ms: Number.MAX_SAFE_INTEGER },
+      nextRetry: { t_ms: Number.MAX_SAFE_INTEGER },
+      retryCounter: 0,
+    };
+  }
+  const info = {
+    firstTry: getTimestampNow(),
+    active: true,
+    nextRetry: { t_ms: 0 },
+    retryCounter: 0,
+  };
+  updateRetryInfoTimeout(info, p);
+  return info;
+}