From 17cfb5b6c2ddb4faa5b37f5cbdc7440e9ba8822a Mon Sep 17 00:00:00 2001
From: Chris Stewart <stewart.chris1234@gmail.com>
Date: Wed, 6 Jan 2016 19:26:37 -0600
Subject: [PATCH] Implmenting OP_VERIFY operation

---
 .../ControlOperationsInterpreter.scala        | 22 +++++++++
 .../ControlOperationsInterpreterTest.scala    | 46 +++++++++++++++++++
 2 files changed, 68 insertions(+)
 create mode 100644 src/main/scala/org/scalacoin/script/control/ControlOperationsInterpreter.scala
 create mode 100644 src/test/scala/org/scalacoin/script/control/ControlOperationsInterpreterTest.scala

diff --git a/src/main/scala/org/scalacoin/script/control/ControlOperationsInterpreter.scala b/src/main/scala/org/scalacoin/script/control/ControlOperationsInterpreter.scala
new file mode 100644
index 0000000000..1131e662d0
--- /dev/null
+++ b/src/main/scala/org/scalacoin/script/control/ControlOperationsInterpreter.scala
@@ -0,0 +1,22 @@
+package org.scalacoin.script.control
+
+import org.scalacoin.script.ScriptOperation
+
+/**
+ * Created by chris on 1/6/16.
+ */
+trait ControlOperationsInterpreter {
+
+
+  /**
+   * Marks transaction as invalid if top stack value is not true.
+   * @param stack
+   * @param script
+   * @return
+   */
+  def verify(stack : List[String], script : List[ScriptOperation]) : Boolean = {
+    require(stack.size > 0, "Stack must not be empty to verify it")
+    require(script.headOption.isDefined && script.head == OP_VERIFY, "Top of script stack must be OP_VERIFY")
+    if (stack.head == "1") true else false
+  }
+}
diff --git a/src/test/scala/org/scalacoin/script/control/ControlOperationsInterpreterTest.scala b/src/test/scala/org/scalacoin/script/control/ControlOperationsInterpreterTest.scala
new file mode 100644
index 0000000000..a1f5b30401
--- /dev/null
+++ b/src/test/scala/org/scalacoin/script/control/ControlOperationsInterpreterTest.scala
@@ -0,0 +1,46 @@
+package org.scalacoin.script.control
+
+import org.scalatest.{MustMatchers, FlatSpec}
+
+/**
+ * Created by chris on 1/6/16.
+ */
+class ControlOperationsInterpreterTest extends FlatSpec with MustMatchers with ControlOperationsInterpreter {
+
+  "ControlOperationsInterpreter" must "have OP_VERIFY evaluate to true with '1' on the stack" in {
+    val stack = List("1")
+    val script = List(OP_VERIFY)
+    val result = verify(stack,script)
+    result must be (true)
+  }
+
+  it must "have OP_VERIFY evaluate to false with '0' on the stack" in {
+    val stack = List("0")
+    val script = List(OP_VERIFY)
+    val result = verify(stack,script)
+    result must be (false)
+  }
+
+  it must "have OP_VERIFY evaluate to false with '2' on the stack" in {
+    val stack = List("2")
+    val script = List(OP_VERIFY)
+    val result = verify(stack,script)
+    result must be (false)
+  }
+
+  it must "fail for OP_VERIFY when there is nothing on the stack" in {
+    intercept[IllegalArgumentException]  {
+      val stack = List()
+      val script = List(OP_VERIFY)
+      val result = verify(stack,script)
+    }
+  }
+
+  it must "fail for verify when there is nothing on the script stack" in {
+    intercept[IllegalArgumentException]  {
+      val stack = List("1")
+      val script = List()
+      val result = verify(stack,script)
+    }
+  }
+}