class Aws::EventEmitter

def emit(type, params)
  unless @stream
    raise Aws::Errors::SignalEventError.new(
      "Singaling events before making async request"\
      " is not allowed."
    )
  end
  if @validate_event && type != :end_stream
    Aws::ParamValidator.validate!(
      @encoder.rules.shape.member(type), params)
  end
  @stream.data(
    @encoder.encode(type, params),
    end_stream: type == :end_stream
  )
end

def initialize
  @listeners = {}
  @validate_event = true
  @signal_queue = Queue.new
end

def on(type, callback)
  (@listeners[type] ||= []) << callback
end

def signal(type, event)
  return unless @listeners[type]
  @listeners[type].each do |listener|
    listener.call(event) if event.event_type == type
  end
end