ETCM-674: added headers consistency with ready blocks validation to fetcher state

Author: pslaski

src/main/scala/io/iohk/ethereum/blockchain/sync/regular/BlockFetcherState.scala

@@ -113,7 +113,7 @@ case class BlockFetcherState(
   }
 
   /**
-    * Validates received headers consistency and their compatibilty with the state
+    * Validates received headers consistency and their compatibility with the state
     * TODO ETCM-370: This needs to be more fine-grained and detailed so blacklisting can be re-enabled
     */
   private def validatedHeaders(headers: Seq[BlockHeader]): Either[String, Seq[BlockHeader]] =
@@ -123,11 +123,18 @@ case class BlockFetcherState(
       headers
         .asRight[String]
         .ensure("Given headers should form a sequence without gaps")(HeadersSeq.areChain)
+        .ensure("Given headers should form a sequence with ready blocks")(checkConsistencyWithReadyBlocks)
         .ensure("Given headers do not form a chain with already stored ones")(headers =>
           (waitingHeaders.lastOption, headers.headOption).mapN(_ isParentOf _).getOrElse(true)
         )
     }
 
+  private def checkConsistencyWithReadyBlocks(headers: Seq[BlockHeader]): Boolean = {
+    if (waitingHeaders.isEmpty) {
+      (readyBlocks.lastOption.map(_.header), headers.headOption).mapN(_ isParentOf _).getOrElse(true)
+    } else true
+  }
+
   def validateNewBlockHashes(hashes: Seq[BlockHash]): Either[String, Seq[BlockHash]] =
     hashes
       .asRight[String]

src/test/scala/io/iohk/ethereum/blockchain/sync/regular/BlockFetcherStateSpec.scala

@@ -60,6 +60,17 @@ class BlockFetcherStateSpec
         }
         assert(result.map(_.knownTop) === Right(blocks.last.number))
       }
+
+      "enqueue requested blocks fails when ready blocks is not forming a sequence with given headers" in {
+
+        val result = BlockFetcherState
+          .initial(importer, validators.blockValidator, 0)
+          .copy(readyBlocks = Queue(blocks.head))
+          .appendHeaders(blocks.map(_.header))
+          .map(_.handleRequestedBlocks(blocks, peer))
+
+        assert(result.map(_.waitingHeaders) === Left("Given headers should form a sequence with ready blocks"))
+      }
     }
 
     "trying to insert block into the queues" should {