[Perf] Chat List: Some optimizations

src/components/left/main/ChatList.tsx

@@ -14,7 +14,9 @@ import { ALL_CHATS_PRELOAD_DISABLED, CHAT_HEIGHT_PX, CHAT_LIST_SLICE } from '../
 import { IS_ANDROID, IS_MAC_OS, IS_PWA } from '../../../util/environment';
 import usePrevious from '../../../hooks/usePrevious';
 import { mapValues, pick } from '../../../util/iteratees';
-import { getChatOrder, prepareChatList, prepareFolderListIds } from '../../../modules/helpers';
+import {
+  getChatOrder, prepareChatList, prepareFolderListIds, reduceChatList,
+} from '../../../modules/helpers';
 import {
   selectChatFolder, selectNotifyExceptions, selectNotifySettings,
 } from '../../../modules/selectors';
@@ -80,19 +82,20 @@ const ChatList: FC<OwnProps & StateProps & DispatchProps> = ({
       : [listIds, orderedPinnedIds];
   }, [folderType, chatFolder, chatsById, usersById, notifySettings, notifyExceptions, listIds, orderedPinnedIds]);
 
-  const [orderById, orderedIds] = useMemo(() => {
+  const [orderById, orderedIds, chatArrays] = useMemo(() => {
     if (!currentListIds || (folderType === 'folder' && !chatFolder)) {
       return [];
     }
+
     const newChatArrays = prepareChatList(chatsById, currentListIds, currentPinnedIds, folderType);
-    const singleList = [...newChatArrays.pinnedChats, ...newChatArrays.otherChats];
+    const singleList = ([] as ApiChat[]).concat(newChatArrays.pinnedChats, newChatArrays.otherChats);
     const newOrderedIds = singleList.map(({ id }) => id);
     const newOrderById = singleList.reduce((acc, chat, i) => {
       acc[chat.id] = i;
       return acc;
     }, {} as Record<string, number>);
 
-    return [newOrderById, newOrderedIds];
+    return [newOrderById, newOrderedIds, newChatArrays];
   }, [currentListIds, currentPinnedIds, folderType, chatFolder, chatsById]);
 
   const prevOrderById = usePrevious(orderById);
@@ -119,8 +122,13 @@ const ChatList: FC<OwnProps & StateProps & DispatchProps> = ({
     folderType === 'all' && !ALL_CHATS_PRELOAD_DISABLED,
   );
 
-  // TODO Refactor to not call `prepareChatList` twice
-  const chatArrays = viewportIds && prepareChatList(chatsById, viewportIds, currentPinnedIds, folderType);
+  const viewportChatArrays = useMemo(() => {
+    if (!viewportIds || !chatArrays) {
+      return undefined;
+    }
+
+    return reduceChatList(chatArrays, viewportIds);
+  }, [chatArrays, viewportIds]);
 
   useEffect(() => {
     if (lastSyncTime && folderType === 'all') {
@@ -133,7 +141,7 @@ const ChatList: FC<OwnProps & StateProps & DispatchProps> = ({
 
   function renderChats() {
     const viewportOffset = orderedIds!.indexOf(viewportIds![0]);
-    const pinnedOffset = viewportOffset + chatArrays!.pinnedChats.length;
+    const pinnedOffset = viewportOffset + viewportChatArrays!.pinnedChats.length;
 
     return (
       <div
@@ -142,7 +150,7 @@ const ChatList: FC<OwnProps & StateProps & DispatchProps> = ({
         style={IS_ANDROID ? `height: ${orderedIds!.length * CHAT_HEIGHT_PX}px` : undefined}
         teactFastList
       >
-        {chatArrays!.pinnedChats.map(({ id }, i) => (
+        {viewportChatArrays!.pinnedChats.map(({ id }, i) => (
           <Chat
             key={id}
             teactOrderKey={i}
@@ -155,7 +163,7 @@ const ChatList: FC<OwnProps & StateProps & DispatchProps> = ({
             style={`top: ${(viewportOffset + i) * CHAT_HEIGHT_PX}px;`}
           />
         ))}
-        {chatArrays!.otherChats.map((chat, i) => (
+        {viewportChatArrays!.otherChats.map((chat, i) => (
           <Chat
             key={chat.id}
             teactOrderKey={getChatOrder(chat)}
@@ -210,7 +218,7 @@ const ChatList: FC<OwnProps & StateProps & DispatchProps> = ({
       noFastList
       noScrollRestore
     >
-      {viewportIds?.length && chatArrays ? (
+      {viewportIds?.length && viewportChatArrays ? (
         renderChats()
       ) : viewportIds && !viewportIds.length ? (
         (

src/components/left/main/hooks/useChatAnimationType.ts

@@ -24,8 +24,8 @@ export function useChatAnimationType(orderDiffById: Record<string, number>) {
     if (
       orderDiff === Infinity
       || orderDiff === -Infinity
-      || (movesUp(chatId) && numberOfUp <= numberOfDown)
-      || (movesDown(chatId) && numberOfDown < numberOfUp)
+      || (numberOfUp <= numberOfDown && movesUp(chatId))
+      || (numberOfDown < numberOfUp && movesDown(chatId))
     ) {
       return ChatAnimationTypes.Opacity;
     }

src/components/main/DownloadManager.tsx

@@ -23,7 +23,7 @@ type DispatchProps = Pick<GlobalActions, 'cancelMessageMediaDownload'>;
 
 const startedDownloads = new Set<string>();
 
-const DownloadsManager: FC<StateProps & DispatchProps> = ({
+const DownloadManager: FC<StateProps & DispatchProps> = ({
   activeDownloads,
   messages,
   cancelMessageMediaDownload,
@@ -78,4 +78,4 @@ export default memo(withGlobal(
     };
   },
   (setGlobal, actions): DispatchProps => pick(actions, ['cancelMessageMediaDownload']),
-)(DownloadsManager));
+)(DownloadManager));

src/modules/helpers/chats.ts

@@ -223,11 +223,7 @@ export function getChatSlowModeOptions(chat?: ApiChat) {
 }
 
 export function getChatOrder(chat: ApiChat) {
-  return Math.max(
-    chat.joinDate || 0,
-    chat.draftDate || 0,
-    chat.lastMessage ? chat.lastMessage.date : 0,
-  );
+  return Math.max(chat.joinDate || 0, chat.draftDate || 0, chat.lastMessage?.date || 0);
 }
 
 export function isChatArchived(chat: ApiChat) {
@@ -370,52 +366,66 @@ export function prepareChatList(
   orderedPinnedIds?: string[],
   folderType: 'all' | 'archived' | 'folder' = 'all',
 ) {
-  function chatFilter(chat?: ApiChat) {
-    if (!chat || !chat.lastMessage || chat.migratedTo) {
-      return false;
-    }
-
-    switch (folderType) {
-      case 'all':
-        if (isChatArchived(chat)) {
-          return false;
-        }
-        break;
-      case 'archived':
-        if (!isChatArchived(chat)) {
-          return false;
-        }
-        break;
-    }
-
-    return !chat.isRestricted && !chat.isNotJoined;
-  }
-
-  const listedChats = listIds
-    .map((id) => chatsById[id])
-    .filter(chatFilter);
-
   const listIdsSet = new Set(listIds);
-  const pinnedChats = orderedPinnedIds
-    ? (
-      orderedPinnedIds
-        .map((id) => chatsById[id])
-        .filter(chatFilter)
-        .filter((chat) => listIdsSet.has(chat.id))
-    )
-    : [];
+  const orderedPinnedIdsSet = orderedPinnedIds ? new Set(orderedPinnedIds) : undefined;
 
-  const otherChats = orderBy(
-    orderedPinnedIds
-      ? listedChats.filter((chat) => !orderedPinnedIds.includes(chat.id))
-      : listedChats,
-    getChatOrder,
-    'desc',
-  );
+  const pinnedChats = orderedPinnedIds?.reduce((acc, id) => {
+    const chat = chatsById[id];
+
+    if (chat && listIdsSet.has(chat.id) && chatFilter(chat, folderType)) {
+      acc.push(chat);
+    }
+
+    return acc;
+  }, [] as ApiChat[]) || [];
+
+  const otherChats = listIds.reduce((acc, id) => {
+    const chat = chatsById[id];
+
+    if (chat && (!orderedPinnedIdsSet || !orderedPinnedIdsSet.has(chat.id)) && chatFilter(chat, folderType)) {
+      acc.push(chat);
+    }
+
+    return acc;
+  }, [] as ApiChat[]);
+  const otherChatsOrdered = orderBy(otherChats, getChatOrder, 'desc');
 
   return {
     pinnedChats,
-    otherChats,
+    otherChats: otherChatsOrdered,
+  };
+}
+
+function chatFilter(chat: ApiChat, folderType: 'all' | 'archived' | 'folder') {
+  if (!chat.lastMessage || chat.migratedTo) {
+    return false;
+  }
+
+  switch (folderType) {
+    case 'all':
+      if (isChatArchived(chat)) {
+        return false;
+      }
+      break;
+    case 'archived':
+      if (!isChatArchived(chat)) {
+        return false;
+      }
+      break;
+  }
+
+  return !chat.isRestricted && !chat.isNotJoined;
+}
+
+export function reduceChatList(
+  chatArrays: { pinnedChats: ApiChat[]; otherChats: ApiChat[] },
+  filteredIds: string[],
+) {
+  const filteredIdsSet = new Set(filteredIds);
+
+  return {
+    pinnedChats: chatArrays.pinnedChats.filter(({ id }) => filteredIdsSet.has(id)),
+    otherChats: chatArrays.otherChats.filter(({ id }) => filteredIdsSet.has(id)),
   };
 }