Implementing OP_PICK script operation

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

@@ -48,6 +48,8 @@ trait ScriptInterpreter extends CryptoInterpreter with StackInterpreter with Con
         case OP_DROP :: t => loop(opDrop(program))
         case OP_IFDUP :: t => loop(opIfDup(program))
         case OP_NIP :: t => loop(opNip(program))
+        case OP_OVER :: t => loop(opOver(program))
+        case OP_PICK :: t => loop(opPick(program))
         //arithmetic operations
         case OP_ADD :: t => loop(opAdd(program))
 

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

@@ -2,6 +2,7 @@ package org.scalacoin.script.stack
 
 import org.scalacoin.script.{ScriptProgramImpl, ScriptProgram}
 import org.scalacoin.script.constant._
+import org.scalacoin.util.ScalacoinUtil
 
 /**
  * Created by chris on 1/6/16.
@@ -99,8 +100,41 @@ trait StackInterpreter {
     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)
+      case h :: _ :: t => ScriptProgramImpl(h :: t, program.script.tail, program.transaction, program.altStack)
+      case h :: t => throw new RuntimeException("Stack must have at least two items on it for OP_NIP")
+      case Nil => throw new RuntimeException("Stack must have at least two items on it for OP_NIP")
     }
   }
 
+
+  /**
+   * Copies the second-to-top stack item to the top.
+   * @param program
+   * @return
+   */
+  def opOver(program : ScriptProgram) : ScriptProgram = {
+    require(program.script.headOption.isDefined && program.script.head == OP_OVER, "Top of script stack must be OP_OVER")
+    require(program.stack.size > 1,"Stack must have at least two items on it for OP_OVER")
+    program.stack match {
+      case _ :: h1 :: _ => ScriptProgramImpl(h1 :: program.stack, program.script.tail, program.transaction, program.altStack)
+      case h :: t => throw new RuntimeException("Stack must have at least two items on it for OP_OVER")
+      case Nil => throw new RuntimeException("Stack must have at least two items on it for OP_OVER")
+    }
+  }
+
+  /**
+   * The item n back in the stack is copied to the top.
+   * @param program
+   * @return
+   */
+  def opPick(program : ScriptProgram) : ScriptProgram = {
+    require(program.script.headOption.isDefined && program.script.head == OP_PICK, "Top of script stack must be OP_PICK")
+    require(program.stack.size > 1,"Stack must have at least two items on it for OP_PICK")
+
+    val n = ScalacoinUtil.hexToInt(program.stack.head.hex)
+    val newStackTop = program.stack.tail(n)
+    ScriptProgramImpl(newStackTop :: program.stack.tail, program.script.tail, program.transaction, program.altStack)
+
+  }
+
 }

src/test/scala/org/scalacoin/marshallers/script/ScriptParserTest.scala

@@ -3,6 +3,7 @@ package org.scalacoin.marshallers.script
 import org.scalacoin.script.arithmetic.OP_ADD
 import org.scalacoin.script.bitwise.OP_EQUAL
 import org.scalacoin.script.constant.{ScriptNumberImpl, OP_1, OP_1NEGATE, ScriptConstantImpl}
+import org.scalacoin.script.stack.OP_PICK
 import org.scalacoin.util.{ScalacoinUtil, TestUtil}
 import org.scalatest.{FlatSpec, MustMatchers}
 
@@ -58,10 +59,10 @@ class ScriptParserTest extends FlatSpec with MustMatchers with ScriptParser with
     parse(str) must equal (List(OP_1NEGATE, ScriptConstantImpl("3e8"), OP_ADD))
   }
 
-/*  it must "parse a decimal number as a ScriptNumber if it is under 75" in {
+  it must "parse an OP_PICK" in {
-    val str = "ADD 21 EQUAL"
+    val str = "PICK"
-    parse(str) must equal (List(OP_ADD, ScriptNumberImpl(21), OP_EQUAL))
+    parse(str) must equal (List(OP_PICK))
-  }*/
+  }
 
 
 

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

@@ -1,6 +1,7 @@
 package org.scalacoin.script.stack
 
 import org.scalacoin.script.ScriptProgramImpl
+import org.scalacoin.script.bitwise.OP_EQUAL
 import org.scalacoin.script.constant.{OP_1, OP_0, ScriptConstantImpl}
 import org.scalacoin.util.{TestUtil, ScalacoinUtil}
 import org.scalatest.{FlatSpec, MustMatchers}
@@ -106,6 +107,26 @@ class StackInterpreterTest extends FlatSpec with MustMatchers with StackInterpre
 
     newProgram.stack must be (List(OP_0))
     newProgram.script.isEmpty must be (true)
+  }
+
+  it must "evaluate an OP_OVER correctly" in {
+    val stack = List(OP_0,OP_1)
+    val script = List(OP_OVER)
+    val program = ScriptProgramImpl(stack,script,TestUtil.transaction,List())
+    val newProgram = opOver(program)
+    newProgram.stack must be (List(OP_1,OP_0,OP_1))
+    newProgram.script.isEmpty must be (true)
+  }
+
+  it must "evaluate an OP_PICK correctly" in {
+    val stack = List(OP_0, ScriptConstantImpl("14"), ScriptConstantImpl("15"), ScriptConstantImpl("16"))
+    val script = List(OP_PICK)
+    val program = ScriptProgramImpl(stack,script,TestUtil.transaction,List())
+    val newProgram = opPick(program)
+
+    newProgram.stack must be (List(ScriptConstantImpl("14"),ScriptConstantImpl("14"),
+      ScriptConstantImpl("15"), ScriptConstantImpl("16")))
+    newProgram.script.isEmpty must be (true)
 
   }
 }