From 071d5e71e49ee0eb87f10461fbe3a9eb83087054 Mon Sep 17 00:00:00 2001
From: Andy Uhnak <andyuhnak@gmail.com>
Date: Wed, 30 Nov 2022 10:24:28 +0000
Subject: [PATCH] Resume to-device message queue after resumed sync

---
 src/ToDeviceMessageQueue.ts | 16 +++++++++++++++-
 1 file changed, 15 insertions(+), 1 deletion(-)

diff --git a/src/ToDeviceMessageQueue.ts b/src/ToDeviceMessageQueue.ts
index e78c46ba2..986eb5a9f 100644
--- a/src/ToDeviceMessageQueue.ts
+++ b/src/ToDeviceMessageQueue.ts
@@ -16,9 +16,10 @@ limitations under the License.
 
 import { ToDeviceMessageId } from "./@types/event";
 import { logger } from "./logger";
-import { MatrixError, MatrixClient } from "./matrix";
+import { MatrixError, MatrixClient, ClientEvent } from "./matrix";
 import { IndexedToDeviceBatch, ToDeviceBatch, ToDeviceBatchWithTxnId, ToDevicePayload } from "./models/ToDeviceMessage";
 import { MatrixScheduler } from "./scheduler";
+import { SyncState } from "./sync";
 
 const MAX_BATCH_SIZE = 20;
 
@@ -37,12 +38,14 @@ export class ToDeviceMessageQueue {
     public start(): void {
         this.running = true;
         this.sendQueue();
+        this.client.on(ClientEvent.Sync, this.onResumedSync);
     }
 
     public stop(): void {
         this.running = false;
         if (this.retryTimeout !== null) clearTimeout(this.retryTimeout);
         this.retryTimeout = null;
+        this.client.removeListener(ClientEvent.Sync, this.onResumedSync);
     }
 
     public async queueBatch(batch: ToDeviceBatch): Promise<void> {
@@ -132,4 +135,15 @@ export class ToDeviceMessageQueue {
 
         await this.client.sendToDevice(batch.eventType, contentMap, batch.txnId);
     }
+
+    /**
+     * Listen to sync state changes and automatically resend any pending events
+     * once syncing is resumed
+     */
+    private onResumedSync = (state: SyncState | null, oldState: SyncState | null): void => {
+        if (state === SyncState.Syncing && oldState !== SyncState.Syncing) {
+            logger.info(`Resuming queue after resumed sync`);
+            this.sendQueue();
+        }
+    };
 }