Refactor WitnessVersion.rebuild() to be Either[ScriptError,ScriptPubKey] to make the taproot implemtation easier (#4382)

core/src/main/scala/org/bitcoins/core/protocol/script/WitnessVersion.scala

@@ -2,11 +2,10 @@ package org.bitcoins.core.protocol.script
 
 import org.bitcoins.core.protocol.CompactSizeUInt
 import org.bitcoins.core.script.constant._
+import org.bitcoins.core.script.result._
 import org.bitcoins.core.util.BytesUtil
 import org.bitcoins.crypto.{CryptoUtil, Sha256Digest, Sha256Hash160Digest}
 
-import scala.util.{Failure, Success, Try}
-
 /** Created by chris on 11/10/16.
   * The version of the [[org.bitcoins.core.protocol.script.WitnessScriptPubKey WitnessScriptPubKey]],
   * this indicates how a [[org.bitcoins.core.protocol.script.ScriptWitness ScriptWitness]] is rebuilt.
@@ -16,11 +15,12 @@ sealed trait WitnessVersion {
 
   /** Rebuilds the full script from the given witness and [[org.bitcoins.core.protocol.script.ScriptPubKey ScriptPubKey]]
     * Either returns the [[org.bitcoins.core.protocol.script.ScriptPubKey ScriptPubKey]]
-    * it needs to be executed against or the failure that was encountered while rebuilding the witness
+    * it needs to be executed against or the [[ScriptError]] that was encountered when
+    * building the rebuild the scriptpubkey from the witness
     */
   def rebuild(
       scriptWitness: ScriptWitness,
-      witnessProgram: Seq[ScriptToken]): Try[ScriptPubKey]
+      witnessProgram: Seq[ScriptToken]): Either[ScriptError, ScriptPubKey]
 
   def version: ScriptNumberOperation
 }
@@ -30,38 +30,34 @@ case object WitnessVersion0 extends WitnessVersion {
   /** Rebuilds a witness version 0 SPK program, see BIP141 */
   override def rebuild(
       scriptWitness: ScriptWitness,
-      witnessProgram: Seq[ScriptToken]): Try[ScriptPubKey] = {
+      witnessProgram: Seq[ScriptToken]): Either[ScriptError, ScriptPubKey] = {
     val programBytes = BytesUtil.toByteVector(witnessProgram)
     programBytes.size match {
       case 20 =>
         //p2wpkh
         val hash = Sha256Hash160Digest(programBytes)
-        Success(P2PKHScriptPubKey(hash))
+        Right(P2PKHScriptPubKey(hash))
       case 32 =>
         //p2wsh
-        if (scriptWitness.stack.isEmpty)
-          Failure(
-            new IllegalArgumentException(
-              "P2WSH cannot be rebuilt without redeem script"))
-        else {
+        if (scriptWitness.stack.isEmpty) {
+          Left(ScriptErrorWitnessProgramWitnessEmpty)
+        } else {
           //need to check if the hashes match
           val stackTop = scriptWitness.stack.head
           val stackHash = CryptoUtil.sha256(stackTop)
           val witnessHash = Sha256Digest(witnessProgram.head.bytes)
           if (stackHash != witnessHash) {
-            Failure(new IllegalArgumentException(
-              s"Witness hash $witnessHash did not match stack hash $stackHash"))
+            Left(ScriptErrorWitnessProgramMisMatch)
           } else {
             val compactSizeUInt =
               CompactSizeUInt.calculateCompactSizeUInt(stackTop)
             val scriptPubKey = ScriptPubKey(compactSizeUInt.bytes ++ stackTop)
-            Success(scriptPubKey)
+            Right(scriptPubKey)
           }
         }
       case _ =>
         //witness version 0 programs need to be 20 bytes or 32 bytes in size
-        Failure(new IllegalArgumentException(
-          s"Witness program had invalid length (${programBytes.length}) for version 0, must be 20 or 30: $witnessProgram"))
+        Left(ScriptErrorWitnessProgramWrongLength)
     }
   }
 
@@ -72,7 +68,7 @@ case object WitnessVersion1 extends WitnessVersion {
 
   override def rebuild(
       scriptWitness: ScriptWitness,
-      witnessProgram: Seq[ScriptToken]): Try[ScriptPubKey] = {
+      witnessProgram: Seq[ScriptToken]): Either[ScriptError, ScriptPubKey] = {
     throw new UnsupportedOperationException("Taproot is not yet supported")
   }
 
@@ -89,10 +85,8 @@ case class UnassignedWitness(version: ScriptNumberOperation)
 
   override def rebuild(
       scriptWitness: ScriptWitness,
-      witnessProgram: Seq[ScriptToken]): Try[ScriptPubKey] =
-    Failure(
-      new UnsupportedOperationException(
-        s"Rebuilding is not defined for version $version yet."))
+      witnessProgram: Seq[ScriptToken]): Either[ScriptError, ScriptPubKey] =
+    Left(ScriptErrorDiscourageUpgradeableWitnessProgram)
 }
 
 object WitnessVersion {

core/src/main/scala/org/bitcoins/core/script/interpreter/ScriptInterpreter.scala

@@ -415,9 +415,10 @@ sealed abstract class ScriptInterpreter {
           if (witness.stack.size != 2) {
             Left(ScriptErrorWitnessProgramMisMatch)
           } else {
-            Right(
-              (witness.stack.map(ScriptConstant(_)),
-               WitnessVersion0.rebuild(witness, program).get))
+            for {
+              rebuilt <- WitnessVersion0.rebuild(witness, program)
+              r <- Right((witness.stack.map(ScriptConstant(_)), rebuilt))
+            } yield r
           }
         case 32 =>
           //p2wsh
@@ -425,10 +426,9 @@ sealed abstract class ScriptInterpreter {
             Left(ScriptErrorWitnessProgramWitnessEmpty)
           else {
             WitnessVersion0.rebuild(witness, program) match {
-              case Success(rebuilt) =>
+              case Right(rebuilt) =>
                 Right((witness.stack.tail.map(ScriptConstant(_)), rebuilt))
-              case Failure(_) =>
-                Left(ScriptErrorWitnessProgramMisMatch)
+              case Left(err) => Left(err)
             }
           }
         case _ =>

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

@@ -440,9 +440,9 @@ trait BitcoinScriptUtil {
       case w: WitnessScriptPubKey =>
         txSignatureComponent match {
           case wtxSigComponent: WitnessTxSigComponent =>
-            val scriptT = w.witnessVersion.rebuild(wtxSigComponent.witness,
+            val scriptE = w.witnessVersion.rebuild(wtxSigComponent.witness,
                                                    w.witnessProgram)
-            parseScriptTry(scriptT)
+            parseScriptEither(scriptE)
           case rWTxSigComponent: WitnessTxSigComponentRebuilt =>
             rWTxSigComponent.scriptPubKey.asm
           case _: BaseTxSigComponent =>
@@ -493,7 +493,7 @@ trait BitcoinScriptUtil {
         val wtx = spendingTransaction.asInstanceOf[WitnessTransaction]
         val scriptT =
           w.witnessVersion.rebuild(wtx.witness.witnesses(idx), w.witnessProgram)
-        parseScriptTry(scriptT)
+        parseScriptEither(scriptT)
 
       case _: P2PKHScriptPubKey | _: P2PKScriptPubKey |
           _: P2PKWithTimeoutScriptPubKey | _: MultiSignatureScriptPubKey |
@@ -553,10 +553,13 @@ trait BitcoinScriptUtil {
     } else program.originalScript
   }
 
-  private def parseScriptTry(scriptT: Try[ScriptPubKey]): Seq[ScriptToken] =
+  private def parseScriptEither(
+      scriptT: Either[ScriptError, ScriptPubKey]): Seq[ScriptToken] =
     scriptT match {
-      case Success(scriptPubKey) => scriptPubKey.asm
-      case Failure(err)          => throw err
+      case Right(scriptPubKey) => scriptPubKey.asm
+      case Left(err) =>
+        throw new IllegalArgumentException(
+          s"Could not parse witness script, got err=$err")
     }
 
   /** Casts the given script token to a boolean value