pub trait Event {
  fn version() -> Int
  fn type_name() -> String
}

pub(all) suberror EventBusError {
  PublishError(String)
}

pub(all) enum EventApplier[S, E] {
  Single((S, E) -> S)
  Batch((S, Array[E]) -> S)
}

pub(all) struct EventBus[AggregateId, E] {
  publish : (EventBus[AggregateId, E], Array[EventMessage[AggregateId, E]]) -> Unit raise EventBusError
}

pub(all) struct EventMessage[AggregateId, E] {
  event : E
  event_id : String
  aggregate_id : AggregateId
  aggregate_version : Int
  correlation_id : String
  causation_id : String
  user_id : String?
  timestamp : Int64
  metadata : Json
  schema_version : Int
}

pub(all) enum EventStream[AggregateId, E] {
  Nil
  Cons(EventMessage[AggregateId, E], EventStream[AggregateId, E])
}