# This class is responsible for dispatching the messages to the appropriate handler.
# The handlers must be registered with the dispatcher.
# Tha handlers need to be modules that implement the process method.
# What handler to dispatch the message to is figured out from the subject of the message.
module DispatchRider
  class Dispatcher
    extend Forwardable

    attr_reader :handler_registrar

    def_delegators :handler_registrar, :register, :fetch, :unregister

    def initialize
      @handler_registrar = Registrars::Handler.new
      @error_handler = method(:default_error_handler)
    end

    def on_error(&block)
      @error_handler = block
    end

    def dispatch(message)
      handler_registrar.fetch(message.subject).process(message.body)
    rescue Exception => exception
      @error_handler.call(message, exception)
    end

    private

    def default_error_handler(message, exception)
      raise exception
    end
  end
end