class ItemQueue
  BATCH_SIZE = 25

  def initialize(items = [])
    @mutex = Mutex.new
    @queue = items
  end

  def push(item)
    @mutex.synchronize {
      @queue << item
    }
  end

  def pop_batch
    @mutex.synchronize {
      batch = @queue[0...BATCH_SIZE]
      @queue = @queue[BATCH_SIZE..-1] || []
      batch
    }
  end

  def length
    @mutex.synchronize {
      @queue.length
    }
  end
end