Krever · April 2, 2024 05:23 · Apr 2, 2024 · Mar 31, 2024
diff --git a/wio.scala b/wio.scala
@@ -20,7 +20,7 @@ trait WorkflowContext {
 }
 
 
-object WithdrawalContext {
+object WithdrawalContext extends WorkflowContext {
   type Event = WithdrawalEvent
   type State = WithdrawalState
 }

diff --git a/wio.scala b/wio.scala
@@ -0,0 +1,41 @@
+// This is a very minimal example showcasing how we can levarage type members to capture fixed types without the need
+// to introduce more type parameters
+
+
+trait WorkflowContext {
+
+  type State
+  type Event
+
+  // operation that transforms In into Out, while guaranteeing the output is a substate os State
+  sealed trait WIO[Err, In, Out <: State]
+  object WIO {
+
+    // example variant where IO is guarded with an event, IO is not run during recovery.
+    // event is guaranteed to be subtype of Event
+    case class HandleIO[Err, In, Out <: State, Evt <: Event](runIO: In => IO[Evt], handleEvent: Evt => Either[Err, Out]) 
+      extends WIO[Err, In, Out]
+  }
+
+}
+
+
+object WithdrawalContext {
+  type Event = WithdrawalEvent
+  type State = WithdrawalState
+}
+
+class WihdrawalWorkflow(service: WithdrawalService) {
+
+  // output type is specific to WithdrawalContext
+  // runing this workflow requires persistance for WithdrawalEvent
+  // at any point of time, we can get a state of the workflow which will be of type WitdrawalState
+  def workflow: WidrawalContext.WIO[Nothing, Unit, WithdrawalState.Complete] = 
+    WIO.RunIO(
+      _ => service.doSth().as(WithdrawalEvent.SthDone),
+      sthDone => WiithdrawalState.Completed()
+    )
+
+
+}
+
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