/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements. See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You under the Apache License, Version 2.0
 * (the "License"); you may not use this file except in compliance with
 * the License. You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package org.apache.hadoop.ozone.s3;

import java.util.List;
import java.util.concurrent.atomic.AtomicInteger;

/**
 * Round Robin load balancing strategy.
 * Distributes requests evenly across all available endpoints in a circular manner.
 */
public class RoundRobinStrategy implements LoadBalanceStrategy {

  private final AtomicInteger counter = new AtomicInteger(0);

  @Override
  public String selectEndpoint(List<String> endpoints) {
    if (endpoints == null || endpoints.isEmpty()) {
      throw new IllegalArgumentException("Endpoints list cannot be null or empty");
    }

    int idx = counter.getAndUpdate(i -> (i + 1) % endpoints.size());
    return endpoints.get(idx);
  }

}
