first commit

.gitignore

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+target/

build.sbt

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+name := "statemachine"
+
+version := "0.0.1"
+
+scalaVersion := "2.9.1"
+
+scalacOptions += "-deprecation"
+
+libraryDependencies += "org.scalatest" %% "scalatest" % "1.8" % "test"
+
+libraryDependencies += "junit" % "junit" % "4.10" % "test"
+
+testOptions in Test += Tests.Argument("-oDF")

src/main/scala/StateMachine.scala

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+package com.conbere.statemachine
+
+trait Event
+trait State
+
+trait StateMachine[Self <: StateMachine[Self]] {
+  type Transition = PartialFunction[(State, Event), Self]
+
+  val transitions: Transition
+  val state: State
+
+  def defaultTransition: Transition
+
+  def trigger(event: Event): Self = {
+    (transitions orElse defaultTransition)((state, event))
+  }
+}
+

src/test/scala/StateMachineSuite.scala

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+import scala.io.Source
+
+import org.scalatest.FunSuite
+import org.scalatest.junit.JUnitRunner
+
+import org.junit.runner.RunWith
+
+import com.conbere.statemachine._
+
+case object Locked extends State
+case object UnLocked extends State
+
+case class Coin(val value: Int) extends Event
+case object Push extends Event
+
+class Turnstile(val value: Int, val state: State)
+extends StateMachine[Turnstile] {
+  def this() = this(0, Locked)
+
+  val requiredPayment = 10
+
+  override def defaultTransition: Transition = {
+    case _ => this
+  }
+
+  val transitions: Transition = {
+    case (Locked, Coin(v)) =>
+      if (value + v >= requiredPayment)
+        new Turnstile(0, UnLocked)
+      else
+        new Turnstile(value + v, state)
+    case (Locked, Push) =>
+      this
+    case (UnLocked, Push) =>
+      new Turnstile()
+    case (UnLocked, Coin(_)) =>
+      this
+  }
+
+  override def toString = "Turnstile: %s: %s".format(state, value)
+}
+
+@RunWith(classOf[JUnitRunner])
+class StateMachineSuite extends FunSuite {
+  trait StateMachineM {
+    val t = new Turnstile()
+  }
+
+  test("turnstile") {
+    new StateMachineM {
+      assert(t.state == Locked)
+      assert(t.value == 0)
+
+      val t2 = t.trigger(Push)
+
+      assert(t2.state == Locked)
+      assert(t2.value == 0)
+
+      val t3 = t2.trigger(Coin(5))
+
+      assert(t3.state == Locked)
+      assert(t3.value == 5)
+
+      val t4 = t3.trigger(Coin(5))
+
+      assert(t4.state == UnLocked)
+      assert(t4.value == 0)
+
+      val t5 = t4.trigger(Push)
+
+      assert(t5.state == Locked)
+      assert(t5.value == 0)
+    }
+  }
+}