Faster WebSocket reconnects

ts/util/BackOff.ts

@@ -0,0 +1,33 @@
+// Copyright 2021 Signal Messenger, LLC
+// SPDX-License-Identifier: AGPL-3.0-only
+
+export class BackOff {
+  private count = 0;
+
+  constructor(private readonly timeouts: ReadonlyArray<number>) {}
+
+  public get(): number {
+    return this.timeouts[this.count];
+  }
+
+  public getAndIncrement(): number {
+    const result = this.get();
+    if (!this.isFull()) {
+      this.count += 1;
+    }
+
+    return result;
+  }
+
+  public reset(): void {
+    this.count = 0;
+  }
+
+  public isFull(): boolean {
+    return this.count === this.timeouts.length - 1;
+  }
+
+  public getIndex(): number {
+    return this.count;
+  }
+}