Support usage of last* methods in pattern guards

- closes #205

src/main/scala/com/rbmhtechnology/eventuate/EventsourcedView.scala

@@ -206,12 +206,17 @@ trait EventsourcedView extends Actor with Stash with ActorLogging {
    */
   private[eventuate] def receiveEvent(event: DurableEvent): Unit = {
     val behavior = _eventContext.current
-    if (behavior.isDefinedAt(event.payload)) try {
-      _eventHandling = true
-      receiveEventInternal(event)
-      behavior(event.payload)
-      if (!recovering) conditionChanged(currentVectorTime)
-    } finally _eventHandling = false
+    val previous = lastHandledEvent
+
+    _lastHandledEvent = event
+    if (behavior.isDefinedAt(event.payload)) {
+      try {
+        _eventHandling = true
+        receiveEventInternal(event)
+        behavior(event.payload)
+        if (!recovering) conditionChanged(currentVectorTime)
+      } finally _eventHandling = false
+    } else _lastHandledEvent = previous
   }
 
   /**

src/test/scala/com/rbmhtechnology/eventuate/EventsourcedViewSpec.scala

@@ -140,6 +140,25 @@ object EventsourcedViewSpec {
       add orElse change(eventContext)
   }
 
+  class TestGuardingView(
+    val logProbe: ActorRef,
+    val msgProbe: ActorRef) extends EventsourcedView {
+
+    val id = emitterIdA
+    val eventLog = logProbe
+
+    override def onCommand = {
+      case "last" => msgProbe ! lastHandledEvent
+    }
+
+    override def onEvent = {
+      case "e1" if lastEmitterId == "x" =>
+        msgProbe ! "handled"
+      case "e2" if lastEmitterId == "y" =>
+        msgProbe ! "handled"
+    }
+  }
+
   val event1a = event("a", 1L)
   val event1b = event("b", 2L)
   val event1c = event("c", 3L)
@@ -195,6 +214,9 @@ class EventsourcedViewSpec extends TestKit(ActorSystem("test")) with WordSpecLik
   def recoveredBehaviorView(): ActorRef =
     processRecover(system.actorOf(Props(new TestBehaviorView(logProbe.ref, msgProbe.ref))))
 
+  def recoveredGuardingView(): ActorRef =
+    processRecover(system.actorOf(Props(new TestGuardingView(logProbe.ref, msgProbe.ref))))
+
   def processRecover(actor: ActorRef, instanceId: Int = instanceId): ActorRef = {
     logProbe.expectMsg(LoadSnapshot(emitterIdA, instanceId))
     logProbe.sender() ! LoadSnapshotSuccess(None, instanceId)
@@ -473,5 +495,27 @@ class EventsourcedViewSpec extends TestKit(ActorSystem("test")) with WordSpecLik
       system.stop(logProbe.ref)
       expectTerminated(actor)
     }
+    "support usage of last* methods in pattern guards when guard evaluates to true" in {
+      val actor = recoveredGuardingView()
+      val event1 = event("e1", 1L).copy(emitterId = "x")
+
+      actor ! Written(event1)
+      msgProbe.expectMsg("handled")
+
+      actor ! "last"
+      msgProbe.expectMsgType[DurableEvent].payload should be("e1")
+    }
+    "support usage of last* methods in pattern guards when guard evaluates to false" in {
+      val actor = recoveredGuardingView()
+      val event1 = event("e1", 1L).copy(emitterId = "x")
+      val event2 = event("e2", 1L).copy(emitterId = "x")
+
+      actor ! Written(event1)
+      actor ! Written(event2)
+      msgProbe.expectMsg("handled")
+
+      actor ! "last"
+      msgProbe.expectMsgType[DurableEvent].payload should be("e1")
+    }
   }
 }