//MBRPopLPush : Multiple Blocking Right Pop + L Push
//Returns the source queue, data, and (optionally) an error
func MBRPopLPush(cli *redis.Client, queues ...string) (sourceQ string, val string, err error) {
	eg, ctx := errgroup.WithContext(cli.Context())
	cli = cli.WithContext(ctx)
	semaphore := make(chan interface{}, 1)
	for _, iq := range queues {
		q := iq
		eg.Go(func() error {
			cmd, err := cli.BRPopLPush(q, q+":acked", 0).Result()
			if err != nil {
				return err
			}
			_, semAquired := <-semaphore
			if !semAquired {
				tx := cli.TxPipeline()
				tx.RPush(q, cmd)
				tx.LRem(q+":acked", 1, cmd)
				_, err := tx.Exec()
				if err != nil {
					return err
				}
			}
			sourceQ = q
			val = cmd
			return context.Canceled
		})
	}
	semaphore <- true
	err = eg.Wait()
	if err == context.Canceled {
		err = nil
	}
	return
}