Cache friend list

app/src/providers/feed/feed.ts

@@ -6,6 +6,8 @@ import { P2pStorageIpfsProvider } from "../p2p-storage-ipfs/p2p-storage-ipfs";
 
 @Injectable()
 export class FeedProvider {
+  friends;
+
   constructor(
     private http: HttpClient,
     private twitter: TwitterApiProvider,
@@ -65,7 +67,7 @@ export class FeedProvider {
     const intervalEnd: Date = this.getOldestTweetTimestamp(tweets);
 
     // Fetch user's friends
-    const friends = await this.twitter.fetchFriends(userId);
+    const friends = await this.getCachedFriends(userId);
 
     let privateTweetHashs = [];
     friends.forEach(async friend => {
@@ -136,4 +138,15 @@ export class FeedProvider {
       return 0;
     }
   }
+
+  private async getCachedFriends(userId) {
+    // Cache friends for 15 minutes to avoid unnecessary  API calls
+    if (!this.friends || (Date.now() - this.friends.lastUpdate) / 900000 > 15) {
+      this.friends = {
+        friendList: await this.twitter.fetchFriends(userId),
+        lastUpdate: Date.now()
+      };
+    }
+    return this.friends.friendList;
+  }
 }