Dummy client to use in specs for apps using waterdrop gem to produce kafka messages

kafka_producer_client.rb

# Spec producer client used to buffer messages that we send out in specs
class KafkaProducerClient < WaterDrop::Producer::DummyClient
  attr_accessor :messages

  # Sync fake response for the message delivery to Kafka, since we do not dispatch anything
  class SyncResponse
    # @param _args Handler wait arguments (irrelevant as waiting is fake here)
    def wait(*_args)
      false
    end
  end

  def initialize
    super()
    @messages = []
    @topics = Hash.new { |k, v| k[v] = [] }
  end

  # "Produces" message to Kafka. That is, it acknowledges it locally, adds it to the internal buffer
  # @param message [Hash] `WaterDrop::Producer#produce_sync` message hash
  def produce(message)
    topic = message.fetch(:topic) { raise ArgumentError, ':topic is missing' }
    @topics[topic] << message
    @messages << message
    SyncResponse.new
  end

  # Returns messages produced to a given topic
  # @param topic [String]
  def messages_for_topic(topic)
    @topics[topic]
  end

  # Clears internal buffer
  # Used in between specs so messages do not leak out
  def reset
    @messages.clear
    @topics.each_value(&:clear)
  end
end