Successfully calculating the wtxid merkle root, and the commitment header inside of a coinbase output

src/main/scala/org/bitcoins/core/consensus/Merkle.scala

@@ -2,7 +2,7 @@ package org.bitcoins.core.consensus
 
 import org.bitcoins.core.crypto.DoubleSha256Digest
 import org.bitcoins.core.protocol.blockchain.Block
-import org.bitcoins.core.protocol.transaction.Transaction
+import org.bitcoins.core.protocol.transaction.{BaseTransaction, Transaction, WitnessTransaction}
 import org.bitcoins.core.util._
 
 import scala.annotation.tailrec
@@ -11,7 +11,7 @@ import scala.annotation.tailrec
   * Created by chris on 5/24/16.
   * This trait contains all functionality related to computing merkle trees
   * Mimics this functionality inside of bitcoin core
-  * https://github.com/bitcoin/bitcoin/blob/master/src/consensus/merkle.cpp
+  * [[https://github.com/bitcoin/bitcoin/blob/master/src/consensus/merkle.cpp]]
   */
 trait Merkle extends BitcoinSLogger {
 
@@ -72,6 +72,28 @@ trait Merkle extends BitcoinSLogger {
     val hash = CryptoUtil.doubleSHA256(bytes)
     Node(hash,tree1,tree2)
   }
+
+  /** Computes the commitment of the block to the wtxids
+    * See the definition of a block commitment in BIP141
+    * [[https://github.com/bitcoin/bips/blob/master/bip-0141.mediawiki#commitment-structure]]
+    * [[https://github.com/bitcoin/bitcoin/blob/7490ae8b699d2955b665cf849d86ff5bb5245c28/src/consensus/merkle.cpp#L168]]
+    */
+  def computeBlockWitnessMerkleTree(block: Block): MerkleTree = {
+    val coinbaseWTxId = CryptoUtil.emptyDoubleSha256Hash
+    val hashes = block.transactions.tail.map {
+      case wtx: WitnessTransaction => wtx.wTxId
+      case btx: BaseTransaction => btx.txId
+    }
+    build(coinbaseWTxId +: hashes)
+  }
+
+  /** Computes the merkle root for the committment inside of a coinbase txs scriptPubKey
+    * See BIP141
+    * [[https://github.com/bitcoin/bips/blob/master/bip-0141.mediawiki#commitment-structure]]
+    * */
+  def computeBlockWitnessMerkleRoot(block: Block): DoubleSha256Digest = {
+    computeBlockWitnessMerkleTree(block).value.get
+  }
 }
 
 object Merkle extends Merkle

src/main/scala/org/bitcoins/core/crypto/TransactionSignatureSerializer.scala

@@ -168,7 +168,7 @@ trait TransactionSignatureSerializer extends RawBitcoinSerializerHelper with Bit
       val isNotSigHashSingle = !(HashType.isSIGHASH_SINGLE(hashType.num))
       val isNotSigHashNone = !(HashType.isSIGHASH_NONE(hashType.num))
       val inputIndexInt = inputIndex.toInt
-      val emptyHash = DoubleSha256Digest("0000000000000000000000000000000000000000000000000000000000000000")
+      val emptyHash = CryptoUtil.emptyDoubleSha256Hash
 
       val outPointHash: Seq[Byte] = if (isNotAnyoneCanPay) {
         val bytes: Seq[Byte] = spendingTx.inputs.flatMap(_.previousOutput.bytes)

src/main/scala/org/bitcoins/core/protocol/blockchain/Block.scala

@@ -10,29 +10,20 @@ import org.bitcoins.core.util.{BitcoinSLogger, Factory}
   * Created by chris on 5/19/16.
   * Represents a block in our blockchain
   * Bitcoin Core implementation:
-  * https://github.com/bitcoin/bitcoin/blob/master/src/primitives/block.h#L73
+  * [[https://github.com/bitcoin/bitcoin/blob/master/src/primitives/block.h#L73]]
   * Bitcoin Developer Reference link:
-  * https://bitcoin.org/en/developer-reference#serialized-blocks
+  * [[https://bitcoin.org/en/developer-reference#serialized-blocks]]
   */
-sealed trait Block extends NetworkElement with BitcoinSLogger {
+sealed trait Block extends NetworkElement {
 
-  /**
-    * The block header for this block
-    * @return
-    */
+  /** The block header for this block */
   def blockHeader : BlockHeader
 
-  /**
-    * The total number of transactions in this block,
-    * including the coinbase transaction.
-    * @return
-    */
+  /** The total number of transactions in this block,
+    * including the coinbase transaction. */
   def txCount : CompactSizeUInt
 
-  /**
-    * The transactions contained in this block
-    * @return
-    */
+  /** The transactions contained in this block */
   def transactions : Seq[Transaction]
 
   override def hex = RawBlockSerializer.write(this)

src/main/scala/org/bitcoins/core/util/CryptoUtil.scala

@@ -60,6 +60,8 @@ trait CryptoUtil {
     messageDigest.doFinal(out, 0)
     RipeMd160Digest(out.toList)
   }
+
+  val emptyDoubleSha256Hash = DoubleSha256Digest("0000000000000000000000000000000000000000000000000000000000000000")
 }
 
 object CryptoUtil extends CryptoUtil

src/test/scala/org/bitcoins/core/protocol/transaction/TransactionTest.scala

@@ -7,7 +7,7 @@ import org.bitcoins.core.script.ScriptProgram
 import org.bitcoins.core.script.interpreter.ScriptInterpreter
 import org.bitcoins.core.script.result.ScriptOk
 import org.bitcoins.core.serializers.transaction.RawBaseTransactionParser
-import org.bitcoins.core.util.{BitcoinSLogger, BitcoinSUtil, TestUtil}
+import org.bitcoins.core.util.{BitcoinSLogger, BitcoinSUtil, CryptoUtil, TestUtil}
 import org.scalatest.{FlatSpec, MustMatchers}
 import spray.json._
 
@@ -58,12 +58,11 @@ class TransactionTest extends FlatSpec with MustMatchers with BitcoinSLogger {
     val hex = "0100000000010115e180dc28a2327e687facc33f10f2a20da717e5548406f7ae8b4c811072f8560100000000ffffffff0100b4f505000000001976a9141d7cd6c75c2e86f4cbf98eaed221b30bd9a0b92888ac02483045022100df7b7e5cda14ddf91290e02ea10786e03eb11ee36ec02dd862fe9a326bbcb7fd02203f5b4496b667e6e281cc654a2da9e4f08660c620a1051337fa8965f727eb19190121038262a6c6cec93c2d3ecd6c6072efea86d02ff8e3328bbd0242b20af3425990ac00000000"
     val wtx = WitnessTransaction(hex)
     wtx.txId.hex must be (BitcoinSUtil.flipEndianness("d869f854e1f8788bcff294cc83b280942a8c728de71eb709a2c29d10bfe21b7c"))
+    wtx.wTxId must be (CryptoUtil.doubleSHA256(hex))
   }
 
 
   it must "read all of the tx_valid.json's contents and return ScriptOk" in {
-
-
     val source = Source.fromURL(getClass.getResource("/tx_valid.json"))
 
 

src/test/scala/org/bitcoins/core/script/constant/ConstantInterpreterTest.scala

@@ -1,16 +1,13 @@
 package org.bitcoins.core.script.constant
 
-import org.bitcoins.core.script.crypto.OP_CHECKMULTISIGVERIFY
-import org.bitcoins.core.script.interpreter.ScriptInterpreter
-import org.bitcoins.core.script.{ScriptOperation, ScriptProgram}
+import org.bitcoins.core.script.ScriptProgram
 import org.bitcoins.core.script.bitwise.OP_EQUAL
-import org.bitcoins.core.script.flag.{ScriptVerifyMinimalData, ScriptFlag}
-import org.bitcoins.core.script.result.{ScriptErrorMinimalData, ScriptErrorBadOpCode}
+import org.bitcoins.core.script.crypto.OP_CHECKMULTISIGVERIFY
+import org.bitcoins.core.script.flag.{ScriptFlag, ScriptVerifyMinimalData}
+import org.bitcoins.core.script.result.{ScriptErrorBadOpCode, ScriptErrorMinimalData}
 import org.bitcoins.core.util.{ScriptProgramTestUtil, TestUtil}
 import org.scalatest.{FlatSpec, MustMatchers}
 
-import scala.util.Try
-
 /**
  * Created by chris on 1/24/16.
  */