BlockGenerator: make difficulty consensus-polymorphic

Author: Christos KK Loverdos

src/main/scala/io/iohk/ethereum/consensus/atomixraft/blocks/AtomixRaftBlockGenerator.scala

@@ -20,6 +20,8 @@ class AtomixRaftBlockGenerator(
   blockTimestampProvider
 ) {
 
+  protected def calculateDifficulty(blockNumber: BigInt, parent: Block, blockTimestamp: Long): BigInt = 0
+
   def withBlockTimestampProvider(blockTimestampProvider: BlockTimestampProvider): AtomixRaftBlockGenerator =
     new AtomixRaftBlockGenerator(
       blockchain,

src/main/scala/io/iohk/ethereum/consensus/blocks/BlockGeneratorSkeleton.scala

@@ -38,12 +38,12 @@ abstract class BlockGeneratorSkeleton(
 
   protected val blockCacheSize = consensusConfig.blockCacheSize
 
-  protected val difficulty = new DifficultyCalculator(blockchainConfig)
-
   protected val cache: AtomicReference[List[PendingBlockAndState]] = new AtomicReference(Nil)
 
   protected def newBlockBody(transactions: Seq[SignedTransaction], x: X): BlockBody
 
+  protected def calculateDifficulty(blockNumber: BigInt, parent: Block, blockTimestamp: Long): BigInt
+
   protected def defaultPrepareHeader(
     blockNumber: BigInt,
     parent: Block,
@@ -60,7 +60,7 @@ abstract class BlockGeneratorSkeleton(
         transactionsRoot = ByteString.empty,
         receiptsRoot = ByteString.empty,
         logsBloom = ByteString.empty,
-        difficulty = difficulty.calculateDifficulty(blockNumber, blockTimestamp, parent.header),
+        difficulty = calculateDifficulty(blockNumber, parent, blockTimestamp),
         number = blockNumber,
         gasLimit = calculateGasLimit(parent.header.gasLimit),
         gasUsed = 0,

src/main/scala/io/iohk/ethereum/consensus/ethash/blocks/EthashBlockGenerator.scala

@@ -38,6 +38,11 @@ class EthashBlockGeneratorImpl(
   blockTimestampProvider
 ) with EthashBlockGenerator {
 
+  protected val difficulty = new DifficultyCalculator(blockchainConfig)
+
+  protected def calculateDifficulty(blockNumber: BigInt, parent: Block, blockTimestamp: Long): BigInt =
+    difficulty.calculateDifficulty(blockNumber, blockTimestamp, parent.header)
+
   protected def newBlockBody(transactions: Seq[SignedTransaction], x: Ommers): BlockBody =
     BlockBody(transactions, x)