module Gitlab
  module BackgroundMigration
    # Begins stealing jobs from the background migrations queue, blocking the
    # caller until all jobs have been completed.
    #
    # steal_class - The name of the class for which to steal jobs.
    def self.steal(steal_class)
      queue = Sidekiq::Queue.
        new(BackgroundMigrationWorker.sidekiq_options['queue'])

      queue.each do |job|
        migration_class, migration_args = job.args

        next unless migration_class == steal_class

        perform(migration_class, migration_args)

        job.delete
      end
    end

    # class_name - The name of the background migration class as defined in the
    #              Gitlab::BackgroundMigration namespace.
    #
    # arguments - The arguments to pass to the background migration's "perform"
    #             method.
    def self.perform(class_name, arguments)
      const_get(class_name).new.perform(*arguments)
    end
  end
end