implmenting OP_NIP and OP_IFDUP

src/main/scala/org/scalacoin/script/interpreter/ScriptInterpreter.scala

@@ -46,6 +46,8 @@ trait ScriptInterpreter extends CryptoInterpreter with StackInterpreter with Con
         case OP_TOALTSTACK :: t => loop(opToAltStack(program))
         case OP_FROMALTSTACK :: t => loop(opFromAltStack(program))
         case OP_DROP :: t => loop(opDrop(program))
+        case OP_IFDUP :: t => loop(opIfDup(program))
+        case OP_NIP :: t => loop(opNip(program))
         //arithmetic operations
         case OP_ADD :: t => loop(opAdd(program))
 

src/main/scala/org/scalacoin/script/stack/StackInterpreter.scala

@@ -25,6 +25,20 @@ trait StackInterpreter {
     }
   }
 
+  /**
+   * If the top stack value is not 0, duplicate it.
+   * @param program
+   * @return
+   */
+  def opIfDup(program : ScriptProgram) : ScriptProgram = {
+    require(program.script.headOption.isDefined && program.script.head == OP_IFDUP, "Top of the script stack must be OP_DUP")
+    require(program.stack.headOption.isDefined, "Cannot duplicate the top element on an empty stack")
+    if (program.stack.head == OP_0) {
+      ScriptProgramImpl(program.stack,program.script.tail, program.transaction,program.altStack)
+    } else ScriptProgramImpl(program.stack.head :: program.stack,
+      program.script.tail, program.transaction,program.altStack)
+  }
+
   /**
    * Puts the number of stack items onto the stack.
    * @param program
@@ -75,4 +89,18 @@ trait StackInterpreter {
     ScriptProgramImpl(program.stack.tail,program.script.tail,program.transaction,program.altStack)
   }
 
+
+  /**
+   * Removes the second-to-top stack item
+   * @param program
+   * @return
+   */
+  def opNip(program : ScriptProgram) : ScriptProgram = {
+    require(program.script.headOption.isDefined && program.script.head == OP_NIP, "Top of script stack must be OP_NIP")
+    require(program.stack.size > 1,"Stack must have at least two items on it for OP_NIP")
+    program.stack match {
+      case h :: h1 :: t => ScriptProgramImpl(h :: t, program.script.tail, program.transaction, program.altStack)
+    }
+  }
+
 }

src/test/scala/org/scalacoin/script/interpreter/ScriptInterpreterTest.scala

@@ -54,13 +54,13 @@ class ScriptInterpreterTest extends FlatSpec with MustMatchers with ScriptInterp
     val source = scala.io.Source.fromFile("src/test/scala/org/scalacoin/script/interpreter/script_valid.json")
 
       //use this to represent a single test case from script_valid.json
-      val lines =
-      """
-        |
-        |[["10 0 11 TOALTSTACK DROP FROMALTSTACK", "ADD 21 EQUAL", "P2SH,STRICTENC"]]
-      """.stripMargin
+/*    val lines =
+    """
+      |
+      |[["10 0 11 TOALTSTACK DROP FROMALTSTACK", "ADD 21 EQUAL", "P2SH,STRICTENC"]]
+    """.stripMargin*/
 
-    //val lines = try source.getLines.filterNot(_.isEmpty).map(_.trim) mkString "\n" finally source.close()
+    val lines = try source.getLines.filterNot(_.isEmpty).map(_.trim) mkString "\n" finally source.close()
     val json = lines.parseJson
     val testCasesOpt : Seq[Option[CoreTestCase]] = json.convertTo[Seq[Option[CoreTestCase]]]
     val testCases : Seq[CoreTestCase] = testCasesOpt.flatten

src/test/scala/org/scalacoin/script/stack/StackInterpreterTest.scala

@@ -1,7 +1,7 @@
 package org.scalacoin.script.stack
 
 import org.scalacoin.script.ScriptProgramImpl
-import org.scalacoin.script.constant.{OP_0, ScriptConstantImpl}
+import org.scalacoin.script.constant.{OP_1, OP_0, ScriptConstantImpl}
 import org.scalacoin.util.{TestUtil, ScalacoinUtil}
 import org.scalatest.{FlatSpec, MustMatchers}
 
@@ -78,4 +78,34 @@ class StackInterpreterTest extends FlatSpec with MustMatchers with StackInterpre
     newProgram.stack.isEmpty must be (true)
     newProgram.script.isEmpty must be (true)
   }
+
+  it must "evaluate an OP_IFDUP correctly" in {
+    val stack = List(OP_0)
+    val script = List(OP_IFDUP)
+    val program = ScriptProgramImpl(stack,script,TestUtil.transaction, List())
+    val newProgram = opIfDup(program)
+
+    newProgram.stack must be (stack)
+    newProgram.script.isEmpty must be (true)
+
+    val stack1 = List(OP_1)
+    val program1 = ScriptProgramImpl(stack1,script,TestUtil.transaction,List())
+    val newProgram1 = opIfDup(program1)
+    newProgram1.stack must be (List(OP_1,OP_1))
+    newProgram1.script.isEmpty must be (true)
+
+  }
+
+  it must "evaluate an OP_NIP correctly" in {
+    val stack = List(OP_0,OP_1)
+    val script = List(OP_NIP)
+
+    val program = ScriptProgramImpl(stack,script,TestUtil.transaction,List())
+
+    val newProgram = opNip(program)
+
+    newProgram.stack must be (List(OP_0))
+    newProgram.script.isEmpty must be (true)
+
+  }
 }