class BaseParticipant
  include Ruote::LocalParticipant

  def initialize(opts)
    @opts = []
  end

  def validate(workitem)
    (@opts[:present] || []).each { |field_name|
      raise ArgumentError.new(
        "missing field '#{field_name}'"
      ) if workitem.fields[field_name].nil?
    }
  end

  def consume(workitem)
    validate(workitem)
    do_consume(workitem)
  end
end

class FinalParticipant < BaseParticipant

  def do_consume(workitem)
    # do the work
  end
end