feat(snap): address comments and suggestions

Author: Vovchyk

rskj-core/src/main/java/co/rsk/net/SnapshotProcessor.java

@@ -299,7 +299,7 @@ public void processSnapStatusResponse(SnapSyncState state, Peer sender, SnapStat
 
         List<BlockDifficulty> difficultiesFromResponse = responseMessage.getDifficulties();
         if (difficultiesFromResponse == null || blocksFromResponse.size() != difficultiesFromResponse.size()) {
-            failSyncing(state, sender, EventType.INVALID_BLOCK, "Blocks and difficulties size mismatch. Blocks: [{}], Difficulties: [{}]", blocksFromResponse.size(), Optional.ofNullable(difficultiesFromResponse).map(List::size));
+            failSyncing(state, sender, EventType.INVALID_BLOCK, "Blocks and difficulties size mismatch. Blocks: [{}], Difficulties: [{}]", blocksFromResponse.size(), Optional.ofNullable(difficultiesFromResponse).map(List::size).map(Object::toString).orElse("<null>"));
             return;
         }
 

rskj-core/src/main/java/co/rsk/net/sync/PeersInformation.java

@@ -31,7 +31,14 @@
 
 import java.security.SecureRandom;
 import java.time.Instant;
-import java.util.*;
+import java.util.Collection;
+import java.util.Comparator;
+import java.util.HashMap;
+import java.util.List;
+import java.util.Map;
+import java.util.Optional;
+import java.util.Random;
+import java.util.Set;
 import java.util.function.Predicate;
 import java.util.stream.Collectors;
 import java.util.stream.Stream;

rskj-core/src/main/java/co/rsk/net/sync/SnapCapablePeerSelectionSyncState.java

@@ -240,23 +240,10 @@ private void selectBestPeerFromValidated() {
             return;
         }
 
-        // Select a peer with the highest cumulative difficulty adjusted with multiplying by the number of peers with the same checkpoint header
-        Map<Keccak256, Integer> headerHashCounts = validatedPeers.values().stream()
-                .map(vh -> vh.header.getHash())
-                .collect(Collectors.toMap(
-                        hash -> hash,
-                        h -> 1,
-                        Integer::sum
-                ));
-        Comparator<ValidatedPeerInfo> comparator = Comparator.comparing(
-                (ValidatedPeerInfo info) -> info.validatedHeader.cumulativeDifficulty.asBigInteger()
-                        .multiply(BigInteger.valueOf(headerHashCounts.get(info.validatedHeader.header.getHash())))
-        ).thenComparing((ValidatedPeerInfo info) -> info.peerStatus.getStatus().getTotalDifficulty());
-
         ValidatedPeerInfo bestPeerInfo = validatedPeers.entrySet().stream()
                 .map(entry -> new ValidatedPeerInfo(entry.getKey(), peersInformation.getPeer(entry.getKey()), entry.getValue()))
                 .filter(info -> isPeerStatusAvailable(info.peerStatus))
-                .max(comparator)
+                .max(peerComparator())
                 .orElse(null);
         if (bestPeerInfo == null) {
             logger.warn("No valid peers found after validation");
@@ -268,6 +255,22 @@ private void selectBestPeerFromValidated() {
         onPeerSelectionComplete(bestPeerInfo.peer, bestPeerInfo.validatedHeader);
     }
 
+    private Comparator<ValidatedPeerInfo> peerComparator() {
+        // Select a peer with the highest cumulative difficulty adjusted with multiplying by the number of peers with the same checkpoint header
+        Map<Keccak256, Integer> headerHashCounts = validatedPeers.values().stream()
+                .map(vh -> vh.header.getHash())
+                .collect(Collectors.toMap(
+                        hash -> hash,
+                        h -> 1,
+                        Integer::sum
+                ));
+
+        return Comparator.comparing(
+                (ValidatedPeerInfo info) -> info.validatedHeader.cumulativeDifficulty.asBigInteger()
+                        .multiply(BigInteger.valueOf(headerHashCounts.get(info.validatedHeader.header.getHash())))
+        ).thenComparing((ValidatedPeerInfo info) -> info.peerStatus.getStatus().getTotalDifficulty());
+    }
+
     private void onPeerSelectionComplete(Peer selectedSnapCapablePeer, @Nullable ValidatedHeader validatedHeader) {
         this.syncEventsHandler.startSnapSync(selectedSnapCapablePeer, Optional.ofNullable(validatedHeader).map(ValidatedHeader::header).orElse(null));
     }

rskj-core/src/main/java/co/rsk/net/sync/SyncConfiguration.java

@@ -23,7 +23,9 @@
 
 import javax.annotation.concurrent.Immutable;
 import java.time.Duration;
-import java.util.*;
+import java.util.Collections;
+import java.util.List;
+import java.util.Set;
 import java.util.stream.Collectors;
 
 @Immutable

rskj-core/src/test/java/co/rsk/net/sync/PeersInformationTest.java

@@ -37,7 +37,11 @@
 import java.math.BigInteger;
 import java.time.Duration;
 import java.time.temporal.ChronoUnit;
-import java.util.*;
+import java.util.HashSet;
+import java.util.List;
+import java.util.Optional;
+import java.util.Random;
+import java.util.Set;
 import java.util.stream.Collectors;
 import java.util.stream.Stream;