From 8627a91f6f9a18b7dd2fdac7a9586309b71c557c Mon Sep 17 00:00:00 2001
From: Nickii Miaro <miaronkirote@gmail.com>
Date: Thu, 5 Sep 2024 19:01:19 +0300
Subject: [PATCH] fix: cached message state mixup (#3278)

* fix cached message state duplication

* ensure only messages in chat available

* check for duplicates in delta messages
---
 .../mgt-chat/src/statefulClient/Caching/MessageCache.ts    | 7 ++++++-
 .../mgt-chat/src/statefulClient/StatefulGraphChatClient.ts | 7 ++++++-
 2 files changed, 12 insertions(+), 2 deletions(-)

diff --git a/packages/mgt-chat/src/statefulClient/Caching/MessageCache.ts b/packages/mgt-chat/src/statefulClient/Caching/MessageCache.ts
index 2efc756607..df8ab09f18 100644
--- a/packages/mgt-chat/src/statefulClient/Caching/MessageCache.ts
+++ b/packages/mgt-chat/src/statefulClient/Caching/MessageCache.ts
@@ -53,7 +53,12 @@ export class MessageCache {
       return data;
     } else {
       // need to iterate through the messages and either push or splice them into the array.
-      messages.forEach(m => this.addMessageToCacheData(m, cachedData));
+      messages.forEach(m => {
+        // ensure that only new messages (those not already in the cache) are added to the cache for the specified chat
+        if (m.chatId === chatId && !cachedData.value.some(cachedMessage => cachedMessage.id === m.id)) {
+          this.addMessageToCacheData(m, cachedData);
+        }
+      });
       if (updateNextLink) {
         cachedData.nextLink = nextLink;
       }
diff --git a/packages/mgt-chat/src/statefulClient/StatefulGraphChatClient.ts b/packages/mgt-chat/src/statefulClient/StatefulGraphChatClient.ts
index dddf3a7bac..578255787c 100644
--- a/packages/mgt-chat/src/statefulClient/StatefulGraphChatClient.ts
+++ b/packages/mgt-chat/src/statefulClient/StatefulGraphChatClient.ts
@@ -494,8 +494,13 @@ class StatefulGraphChatClient extends BaseStatefulClient<GraphChatClient> {
       const deltaMessages = await this.loadDeltaData(this._chatId, cachedMessages.lastModifiedDateTime);
       // add delta messages to cache
       const updatedState = await this._cache.cacheMessages(this._chatId, deltaMessages);
+      // Filters the delta messages based on whether their IDs exist in the updated state.
+      const filteredDeltaMessages = deltaMessages.filter(
+        deltaMessage =>
+          !updatedState.value.some(message => message.id === deltaMessage.id && message.chatId === deltaMessage.chatId)
+      );
       // writeMessagesToState concats with existing state, need to be careful not to create duplicate messages
-      updatedState.value = deltaMessages;
+      updatedState.value = filteredDeltaMessages;
       // update state
       await this.writeMessagesToState(updatedState);
     } else {