# frozen_string_literal: true

module Karafka
  # Module used to provide a persistent cache layer for Karafka components that need to be
  # shared inside of a same thread
  module Persistence
    # Module used to provide a persistent cache across batch requests for a given
    # topic and partition to store some additional details when the persistent mode
    # for a given topic is turned on
    class Controller
      # Used to build (if block given) and/or fetch a current controller instance that will be used
      #   to process messages from a given topic and partition
      # @return [Karafka::BaseController] base controller descendant
      # @param topic [Karafka::Routing::Topic] topic instance for which we might cache
      # @param partition [Integer] number of partition for which we want to cache
      def self.fetch(topic, partition)
        return yield unless topic.persistent
        Thread.current[topic.id] ||= {}
        Thread.current[topic.id][partition] ||= yield
      end
    end
  end
end