From 0b08fc9e1f54cb14e9c9968dad6decc38e9f052e Mon Sep 17 00:00:00 2001
From: Scott Nonnenberg <scott@signal.org>
Date: Thu, 2 Nov 2023 06:28:49 -0700
Subject: [PATCH] Use sender+timestamp to cache receipts and read syncs

---
 ts/messageModifiers/MessageReceipts.ts  | 16 ++++++++++++++--
 ts/messageModifiers/ReadSyncs.ts        | 18 +++++++++++++++---
 ts/messageModifiers/generateCacheKey.ts | 16 ++++++++++++++++
 3 files changed, 45 insertions(+), 5 deletions(-)
 create mode 100644 ts/messageModifiers/generateCacheKey.ts

diff --git a/ts/messageModifiers/MessageReceipts.ts b/ts/messageModifiers/MessageReceipts.ts
index f3ba1564e00..f3ca3fb0857 100644
--- a/ts/messageModifiers/MessageReceipts.ts
+++ b/ts/messageModifiers/MessageReceipts.ts
@@ -24,6 +24,7 @@ import { getSourceServiceId } from '../messages/helpers';
 import { queueUpdateMessage } from '../util/messageBatcher';
 import { getMessageSentTimestamp } from '../util/getMessageSentTimestamp';
 import { getMessageIdForLogging } from '../util/idForLogging';
+import { generateCacheKey } from './generateCacheKey';
 
 const { deleteSentProtoRecipient } = dataInterface;
 
@@ -78,7 +79,12 @@ const deleteSentProtoBatcher = createWaitBatcher({
 });
 
 function remove(receipt: MessageReceiptAttributesType): void {
-  receipts.delete(receipt.envelopeId);
+  receipts.delete(
+    generateCacheKey({
+      sender: receipt.sourceServiceId,
+      timestamp: receipt.messageSentAt,
+    })
+  );
   receipt.removeFromMessageReceiverCache();
 }
 
@@ -341,7 +347,13 @@ async function updateMessageSendState(
 export async function onReceipt(
   receipt: MessageReceiptAttributesType
 ): Promise<void> {
-  receipts.set(receipt.envelopeId, receipt);
+  receipts.set(
+    generateCacheKey({
+      sender: receipt.sourceServiceId,
+      timestamp: receipt.messageSentAt,
+    }),
+    receipt
+  );
 
   const { messageSentAt, sourceConversationId, sourceServiceId, type } =
     receipt;
diff --git a/ts/messageModifiers/ReadSyncs.ts b/ts/messageModifiers/ReadSyncs.ts
index 17f81756788..39e75411b50 100644
--- a/ts/messageModifiers/ReadSyncs.ts
+++ b/ts/messageModifiers/ReadSyncs.ts
@@ -14,6 +14,7 @@ import { isMessageUnread } from '../util/isMessageUnread';
 import { notificationService } from '../services/notifications';
 import { queueUpdateMessage } from '../util/messageBatcher';
 import { strictAssert } from '../util/assert';
+import { generateCacheKey } from './generateCacheKey';
 
 export type ReadSyncAttributesType = {
   envelopeId: string;
@@ -25,10 +26,15 @@ export type ReadSyncAttributesType = {
   timestamp: number;
 };
 
-const readSyncs = new Map<number, ReadSyncAttributesType>();
+const readSyncs = new Map<string, ReadSyncAttributesType>();
 
 function remove(sync: ReadSyncAttributesType): void {
-  readSyncs.delete(sync.timestamp);
+  readSyncs.delete(
+    generateCacheKey({
+      sender: sync.senderId,
+      timestamp: sync.timestamp,
+    })
+  );
   sync.removeFromMessageReceiverCache();
 }
 
@@ -99,7 +105,13 @@ export function forMessage(
 }
 
 export async function onSync(sync: ReadSyncAttributesType): Promise<void> {
-  readSyncs.set(sync.timestamp, sync);
+  readSyncs.set(
+    generateCacheKey({
+      sender: sync.senderId,
+      timestamp: sync.timestamp,
+    }),
+    sync
+  );
 
   const logId = `ReadSyncs.onSync(timestamp=${sync.timestamp})`;
 
diff --git a/ts/messageModifiers/generateCacheKey.ts b/ts/messageModifiers/generateCacheKey.ts
new file mode 100644
index 00000000000..87b0f0e4d18
--- /dev/null
+++ b/ts/messageModifiers/generateCacheKey.ts
@@ -0,0 +1,16 @@
+// Copyright 2016 Signal Messenger, LLC
+// SPDX-License-Identifier: AGPL-3.0-only
+
+// This function is necessary because the only thing we can guarantee will be unique is
+//  three pieces of data: sender, deviceId, and timestamp.
+// Because we don't care which device interacted with our message, we collapse this down
+//  to: sender + timestamp.
+export function generateCacheKey({
+  sender,
+  timestamp,
+}: {
+  sender: string;
+  timestamp: number;
+}): string {
+  return `cacheKey-${sender}-${timestamp}`;
+}