[NC-2058] initial scaffolding re block propagation (PegaSysEng#860)

* o

* add test

* clean up

* scaffolding

* update

* update

* comments

* add test

* update

* update

* update

ethereum/eth/src/main/java/tech/pegasys/pantheon/ethereum/eth/manager/EthPeer.java

@@ -14,6 +14,7 @@
 
 import static com.google.common.base.Preconditions.checkArgument;
 
+import tech.pegasys.pantheon.ethereum.core.Block;
 import tech.pegasys.pantheon.ethereum.core.Hash;
 import tech.pegasys.pantheon.ethereum.eth.manager.ChainState.EstimatedHeightListener;
 import tech.pegasys.pantheon.ethereum.eth.manager.RequestManager.ResponseStream;
@@ -23,6 +24,7 @@
 import tech.pegasys.pantheon.ethereum.eth.messages.GetBlockHeadersMessage;
 import tech.pegasys.pantheon.ethereum.eth.messages.GetNodeDataMessage;
 import tech.pegasys.pantheon.ethereum.eth.messages.GetReceiptsMessage;
+import tech.pegasys.pantheon.ethereum.eth.messages.NewBlockMessage;
 import tech.pegasys.pantheon.ethereum.p2p.api.MessageData;
 import tech.pegasys.pantheon.ethereum.p2p.api.PeerConnection;
 import tech.pegasys.pantheon.ethereum.p2p.api.PeerConnection.PeerNotConnected;
@@ -130,6 +132,15 @@ public ResponseStream send(final MessageData messageData) throws PeerNotConnecte
     }
   }
 
+  public void propagateBlock(final Block block, final UInt256 totalDifficulty) {
+    final NewBlockMessage newBlockMessage = NewBlockMessage.create(block, totalDifficulty);
+    try {
+      connection.sendForProtocol(protocolName, newBlockMessage);
+    } catch (PeerNotConnected e) {
+      LOG.trace("Failed to broadcast new block to peer", e);
+    }
+  }
+
   public ResponseStream getHeadersByHash(
       final Hash hash, final int maxHeaders, final int skip, final boolean reverse)
       throws PeerNotConnected {

ethereum/eth/src/main/java/tech/pegasys/pantheon/ethereum/eth/sync/BlockPropagationManager.java

@@ -144,13 +144,23 @@ private void onBlockAdded(final BlockAddedEvent blockAddedEvent, final Blockchai
     }
   }
 
-  private void handleNewBlockFromNetwork(final EthMessage message) {
+  void broadcastBlock(final Block block, final UInt256 difficulty) {
+    ethContext
+        .getEthPeers()
+        .availablePeers()
+        .forEach(ethPeer -> ethPeer.propagateBlock(block, difficulty));
+  }
+
+  void handleNewBlockFromNetwork(final EthMessage message) {
     final Blockchain blockchain = protocolContext.getBlockchain();
     final NewBlockMessage newBlockMessage = NewBlockMessage.readFrom(message.getData());
     try {
       final Block block = newBlockMessage.block(protocolSchedule);
       final UInt256 totalDifficulty = newBlockMessage.totalDifficulty(protocolSchedule);
 
+      // TODO: Extract broadcast functionality to independent class.
+      // broadcastBlock(block, totalDifficulty);
+
       message.getPeer().chainState().updateForAnnouncedBlock(block.getHeader(), totalDifficulty);
 
       // Return early if we don't care about this block