Use read sync timestamp to do unread bookkeeping

ts/messageModifiers/ReadSyncs.ts

@@ -115,6 +115,7 @@ export async function onSync(sync: ReadSyncAttributesType): Promise<void> {
 
     const message = window.MessageController.register(found.id, found);
     const readAt = Math.min(sync.readAt, Date.now());
+    const newestSentAt = sync.timestamp;
 
     // If message is unread, we mark it read. Otherwise, we update the expiration
     //   timer to the time specified by the read sync if it's earlier than
@@ -127,7 +128,11 @@ export async function onSync(sync: ReadSyncAttributesType): Promise<void> {
         // onReadMessage may result in messages older than this one being
         //   marked read. We want those messages to have the same expire timer
         //   start time as this one, so we pass the readAt value through.
-        drop(message.getConversation()?.onReadMessage(message, readAt));
+        drop(
+          message
+            .getConversation()
+            ?.onReadMessage(message, readAt, newestSentAt)
+        );
       };
 
       // only available during initialization

ts/models/conversations.ts

@@ -3306,7 +3306,11 @@ export class ConversationModel extends window.Backbone
     );
   }
 
-  async onReadMessage(message: MessageModel, readAt?: number): Promise<void> {
+  async onReadMessage(
+    message: MessageModel,
+    readAt?: number,
+    newestSentAt?: number
+  ): Promise<void> {
     // We mark as read everything older than this message - to clean up old stuff
     //   still marked unread in the database. If the user generally doesn't read in
     //   the desktop app, so the desktop app only gets read syncs, we can very
@@ -3321,7 +3325,7 @@ export class ConversationModel extends window.Backbone
     return this.queueJob('onReadMessage', () =>
       // eslint-disable-next-line @typescript-eslint/no-non-null-assertion
       this.markRead(message.get('received_at')!, {
-        newestSentAt: message.get('sent_at'),
+        newestSentAt: newestSentAt || message.get('sent_at'),
         sendReadReceipts: false,
         readAt,
       })

ts/util/modifyTargetMessage.ts

@@ -19,6 +19,7 @@ import { SeenStatus } from '../MessageSeenStatus';
 import { SendActionType, sendStateReducer } from '../messages/MessageSendState';
 import { canConversationBeUnarchived } from './canConversationBeUnarchived';
 import { deleteForEveryone } from './deleteForEveryone';
+import { drop } from './drop';
 import { handleEditMessage } from './handleEditMessage';
 import { isGroup } from './whatTypeOfConversation';
 import { isStory, isTapToView } from '../state/selectors/message';
@@ -167,6 +168,7 @@ export async function modifyTargetMessage(
     if (!isFirstRun && message.getPendingMarkRead()) {
       const markReadAt = message.getPendingMarkRead();
       message.setPendingMarkRead(undefined);
+      const newestSentAt = readSync?.timestamp;
 
       // This is primarily to allow the conversation to mark all older
       // messages as read, as is done when we receive a read sync for
@@ -175,7 +177,11 @@ export async function modifyTargetMessage(
       // We run message when `isFirstRun` is false so that it triggers when the
       // message and the other ones accompanying it in the batch are fully in
       // the database.
-      void message.getConversation()?.onReadMessage(message, markReadAt);
+      drop(
+        message
+          .getConversation()
+          ?.onReadMessage(message, markReadAt, newestSentAt)
+      );
     }
 
     // Check for out-of-order view once open syncs