chore: extract random timeout

Author: fryorcraken

packages/sdk/src/reliable_channel/random_timeout.ts

@@ -0,0 +1,47 @@
+/**
+ * Enables waiting a random time before doing an action (using `setTimeout`),
+ * with possibility to apply a multipliers to manipulate said time.
+ */
+export class RandomTimeout {
+  private timeout: ReturnType<typeof setTimeout> | undefined;
+
+  public constructor(
+    /**
+     * The maximum interval one would wait before the call is made, in milliseconds.
+     */
+    private maxIntervalMs: number,
+    /**
+     * When not zero: Anytime a call is made, then a new call will be rescheduled
+     * using this multiplier
+     */
+    private multiplierOnCall: number,
+    /**
+     * The function to call when the timer is reached
+     */
+    private callback: () => void | Promise<void>
+  ) {}
+
+  /**
+   * Use to start the timer. If a timer was already set, it deletes it and
+   * schedule a new one.
+   * @param multiplier applied to [[maxIntervalMs]]
+   */
+  public restart(multiplier: number = 1): void {
+    this.stop();
+
+    if (this.maxIntervalMs) {
+      const timeoutMs = Math.random() * this.maxIntervalMs * multiplier;
+
+      this.timeout = setTimeout(() => {
+        void this.callback();
+        void this.restart(this.multiplierOnCall);
+      }, timeoutMs);
+    }
+  }
+
+  public stop(): void {
+    if (this.timeout) {
+      clearTimeout(this.timeout);
+    }
+  }
+}

packages/sdk/src/reliable_channel/reliable_channel.ts

@@ -34,6 +34,7 @@ import {
 
 import { ReliableChannelEvent, ReliableChannelEvents } from "./events.js";
 import { MissingMessageRetriever } from "./missing_message_retriever.js";
+import { RandomTimeout } from "./random_timeout.js";
 import { RetryManager } from "./retry_manager.js";
 import { SyncStatus } from "./sync_status.js";
 
@@ -150,8 +151,7 @@ export class ReliableChannel<
     options?: Partial<QueryRequestParams>
   ) => AsyncGenerator<Promise<T | undefined>[]>;
 
-  private readonly syncMinIntervalMs: number;
-  private syncTimeout: ReturnType<typeof setTimeout> | undefined;
+  private syncRandomTimeout: RandomTimeout;
   private sweepInBufInterval: ReturnType<typeof setInterval> | undefined;
   private readonly sweepInBufIntervalMs: number;
   private processTaskTimeout: ReturnType<typeof setTimeout> | undefined;
@@ -205,8 +205,11 @@ export class ReliableChannel<
       }
     }
 
-    this.syncMinIntervalMs =
-      options?.syncMinIntervalMs ?? DEFAULT_SYNC_MIN_INTERVAL_MS;
+    this.syncRandomTimeout = new RandomTimeout(
+      options?.syncMinIntervalMs ?? DEFAULT_SYNC_MIN_INTERVAL_MS,
+      2,
+      this.sendSyncMessage.bind(this)
+    );
 
     this.sweepInBufIntervalMs =
       options?.sweepInBufIntervalMs ?? DEFAULT_SWEEP_IN_BUF_INTERVAL_MS;
@@ -242,7 +245,7 @@ export class ReliableChannel<
 
   /**
    * Emit events when the channel is aware of missing message.
-   * Note that "syncd" may mean some messages are irretrievably lost.
+   * Note that "synced" may mean some messages are irretrievably lost.
    * Check the emitted data for details.
    *
    * @emits [[StatusEvents]]
@@ -547,30 +550,11 @@ export class ReliableChannel<
   }
 
   private restartSync(multiplier: number = 1): void {
-    if (this.syncTimeout) {
-      clearTimeout(this.syncTimeout);
-    }
-    if (this.syncMinIntervalMs) {
-      const timeoutMs = this.random() * this.syncMinIntervalMs * multiplier;
-
-      this.syncTimeout = setTimeout(() => {
-        void this.sendSyncMessage();
-        // Always restart a sync, no matter whether the message was sent.
-        // Set a multiplier so we wait a bit longer to not hog the conversation
-        void this.restartSync(2);
-      }, timeoutMs);
-    }
+    this.syncRandomTimeout.restart(multiplier);
   }
 
   private stopSync(): void {
-    if (this.syncTimeout) {
-      clearTimeout(this.syncTimeout);
-    }
-  }
-
-  // Used to enable overriding when testing
-  private random(): number {
-    return Math.random();
+    this.syncRandomTimeout.stop();
   }
 
   private safeSendEvent<T extends ReliableChannelEvent>(