/*
 * Copyright DataStax, Inc.
 *
 * Licensed 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 com.datastax.oss.driver.internal.core.loadbalancing.helper;

import com.datastax.oss.driver.api.core.loadbalancing.LoadBalancingPolicy;
import com.datastax.oss.driver.api.core.metadata.Node;
import edu.umd.cs.findbugs.annotations.NonNull;
import java.util.Map;
import java.util.Optional;
import java.util.UUID;
import net.jcip.annotations.ThreadSafe;

@FunctionalInterface
@ThreadSafe
public interface LocalDcHelper {

  
Returns the local datacenter, if it can be discovered, or returns empty otherwise. 
Implementors may choose to throw IllegalStateException instead of returning empty, if they require a local datacenter to be defined in order to operate properly. 
Params:
nodes – All the nodes that were known to exist in the cluster (regardless of their state) when the load balancing policy was initialized. This argument is provided in case implementors need to inspect the cluster topology to discover the local datacenter.
Throws:
IllegalStateException – if the local datacenter could not be discovered, and this policy
    cannot operate without it.
Returns:
The local datacenter, or empty if none found./**
   * Returns the local datacenter, if it can be discovered, or returns {@link Optional#empty empty}
   * otherwise.
   *
   * <p>Implementors may choose to throw {@link IllegalStateException} instead of returning {@link
   * Optional#empty empty}, if they require a local datacenter to be defined in order to operate
   * properly.
   *
   * @param nodes All the nodes that were known to exist in the cluster (regardless of their state)
   *     when the load balancing policy was {@linkplain LoadBalancingPolicy#init(Map,
   *     LoadBalancingPolicy.DistanceReporter) initialized}. This argument is provided in case
   *     implementors need to inspect the cluster topology to discover the local datacenter.
   * @return The local datacenter, or {@link Optional#empty empty} if none found.
   * @throws IllegalStateException if the local datacenter could not be discovered, and this policy
   *     cannot operate without it.
   */
  @NonNull
  Optional<String> discoverLocalDc(@NonNull Map<UUID, Node> nodes);
}