Remove the unnecessary getHistory calls

Part of #70

Author: Finesse

src/cache/fastStorages/indices/messageHistory.ts

@@ -9,7 +9,11 @@ interface IdsChunkReference {
   readonly history: BehaviorSubject<IdsChunk>;
 
   // Returns <0 if the message is older than chunk, =0 if inside chunk, >0 if newer than chunk, null when unknown.
-  getMessagePosition(messageId: number): number | null;
+  getMessageRelation(messageId: number): number | null;
+
+  // Returns the message index in the `history` property.
+  // A fractional number means that the message isn't in the chunk, but if it was, it would stand in the given intermediate position.
+  getMessageIndex(messageId: number): number;
 
   // The chunk must intersect or directly touch the referenced chunk
   putChunk(chunk: IdsChunk): void;
@@ -94,7 +98,7 @@ function compareChunksAndIdForOrder(chunk: IdsChunk, id: number): number {
 
   if (process.env.NODE_ENV !== 'production') {
     // eslint-disable-next-line no-console
-    console.error('Unexpected empty chunk (no ids and not oldest or newest)');
+    console.error('Unexpected empty chunk (no ids and neither oldest nor newest)');
   }
   return -1;
 }
@@ -228,7 +232,8 @@ class PeerIndex {
     const chunkReference = {
       isRevoked: false,
       history: new BehaviorSubject({ ids: [] }),
-      getMessagePosition: (messageId: number) => compareChunksAndId(chunkReference.history.value, messageId),
+      getMessageRelation: (messageId: number) => compareChunksAndId(chunkReference.history.value, messageId),
+      getMessageIndex: (messageId: number) => findInIdsList(chunkReference.history.value.ids, messageId),
       putChunk: (chunk: IdsChunk) => {
         if (chunkReference.isRevoked) {
           if (process.env.NODE_ENV !== 'production') {
@@ -392,7 +397,8 @@ export default function messageHistory(collection: Collection<Message, any>) {
       const messagesChunkReference = {
         isRevoked: false,
         history: idsChunkReference.history,
-        getMessagePosition: idsChunkReference.getMessagePosition,
+        getMessageRelation: idsChunkReference.getMessageRelation,
+        getMessageIndex: idsChunkReference.getMessageIndex,
         putChunk(chunk: MessagesChunk) {
           try {
             isUpdatingByThisIndex = true;

src/services/message/message.ts

@@ -84,7 +84,7 @@ export default class MessagesService {
     if (isPeerChanged) {
       isChunkChanged = true;
     } else if (this.currentChunk && messageId) {
-      const messagePosition = this.currentChunk.getMessagePosition(messageId);
+      const messagePosition = this.currentChunk.getMessageRelation(messageId);
       if (messagePosition !== 0) {
         isChunkChanged = true;
         if (messagePosition !== null) {
@@ -102,7 +102,7 @@ export default class MessagesService {
         if (!isPeerChanged && this.currentChunk) {
           // Keep the current chunk until the next is loaded
           // Don't recreate the next chunk if it contains the target message
-          if (!this.nextChunk || this.nextChunk.getMessagePosition(messageId!) !== 0) {
+          if (!this.nextChunk || this.nextChunk.getMessageRelation(messageId!) !== 0) {
             if (this.nextChunk) {
               this.nextChunk.destroy();
             }

src/services/message/message_chunk.ts

@@ -14,7 +14,7 @@ export interface MessageChunkService {
   readonly history: BehaviorSubject<MessageHistoryChunk>;
 
   // Returns <0 if the message is older than chunk, =0 if inside chunk, >0 if newer than chunk, null when unknown.
-  getMessagePosition(messageId: number): number | null;
+  getMessageRelation(messageId: number): number | null;
 
   loadMore(direction: Direction.Newer | Direction.Older): void;
 
@@ -69,22 +69,20 @@ export default function makeMessageChunk(peer: Peer, messageId: Exclude<number,
         return;
       }
 
-      if (isDestroyed) {
-        return;
-      }
-
       try {
         isUpdatingCacheChunk = true;
         cacheChunkRef.putChunk(result);
       } finally {
         isUpdatingCacheChunk = false;
       }
     } finally {
-      historySubject.next({
-        ...cacheChunkRef.history.value,
-        loadingOlder: direction === Direction.Around || direction === Direction.Older ? false : historySubject.value.loadingOlder,
-        loadingNewer: direction === Direction.Around || direction === Direction.Newer ? false : historySubject.value.loadingNewer,
-      });
+      if (!isDestroyed) {
+        historySubject.next({
+          ...cacheChunkRef.history.value,
+          loadingOlder: direction === Direction.Around || direction === Direction.Older ? false : historySubject.value.loadingOlder,
+          loadingNewer: direction === Direction.Around || direction === Direction.Newer ? false : historySubject.value.loadingNewer,
+        });
+      }
     }
   }
 
@@ -129,22 +127,39 @@ export default function makeMessageChunk(peer: Peer, messageId: Exclude<number,
     cacheChunkRef.revoke();
   }
 
-  if (messageId === Infinity) {
-    const { ids } = historySubject.value;
-    if (ids.length < LOAD_CHUNK_LENGTH) {
-      loadMessages(Direction.Older, ids[0] /* undefined is welcome here */);
+  function makeSureChunkHasMessages() {
+    const { ids, newestReached, oldestReached } = cacheChunkRef.history.value;
+
+    if (messageId === Infinity) {
+      if (ids.length < LOAD_CHUNK_LENGTH && !oldestReached) {
+        loadMessages(Direction.Older, ids.length ? ids[ids.length - 1] : undefined);
+      }
+      return;
     }
-    if (ids.length > 0) {
-      loadMessages(Direction.Newer, ids[0], 0);
+
+    if (messageId === -Infinity) {
+      if (ids.length < LOAD_CHUNK_LENGTH && !newestReached) {
+        loadMessages(Direction.Older, ids.length ? ids[0] : undefined);
+      }
+      return;
+    }
+
+    const messageIndex = cacheChunkRef.getMessageIndex(messageId);
+    const minSideCount = Math.floor(LOAD_CHUNK_LENGTH / 2) - 1;
+    if (
+      (messageIndex < minSideCount && !newestReached)
+      || (ids.length - messageIndex - 1 < minSideCount && !oldestReached)
+    ) {
+      loadMessages(Direction.Around, messageId);
     }
-  } else {
-    loadMessages(Direction.Around, messageId);
   }
 
+  makeSureChunkHasMessages();
+
   return {
     history: historySubject,
     loadMore,
-    getMessagePosition: cacheChunkRef.getMessagePosition,
+    getMessageRelation: cacheChunkRef.getMessageRelation,
     destroy,
   };
 }