db.ex

def handle_events(transformations, _from, state) do
  Repo.transaction(fn ->
    case process_db_transformations(transformations) do
      { :error, cs } ->
        Repo.rollback(cs)

      resp -> resp
    end
  end)

  { :noreply, [], state }
end

def process_db_transformations([]), do: :ok
def process_db_transformations([ transformation | transformations ]) do
  perform_transformation(transformation)
  process_db_transformations(transformations)
end
  
def perform_transformation(%DBTransformation{ action: :insert } = transformation) do
  case Repo.insert(transformation.changeset) do
    { :error, changeset } = error ->
      Logger.error "Unable to insert #{to_string(transformation.changeset.data.__struct__)} record: #{inspect(validation_errors(changeset))}"
      error
    { :ok, record } = success ->
      success
  end
end