content: /*
   * 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.cassandra.db.guardrails;
  
  import javax.annotation.Nullable;
  
  import org.apache.cassandra.config.DatabaseDescriptor;
  import org.apache.cassandra.service.ClientState;
  import org.apache.cassandra.utils.FBUtilities;
  
  import static org.apache.cassandra.config.CassandraRelevantProperties.CUSTOM_GUARDRAILS_CONFIG_PROVIDER_CLASS;
  
  /**
   * Provider of {@link GuardrailsConfig}s for a {@link ClientState}.
   * <p>
   * The {@link Default} implementation always retuns the {@link GuardrailsConfig} parsed from {@code cassandra.yaml},
   * but different implementations can return different configurations based on the specified {@link ClientState}.
   * <p>
   * Custom implementations can be specified at runtime with the system property {@link #CUSTOM_IMPLEMENTATION_PROPERTY}.
   * These configurations can be used to read the guardrails configuration from some other source, and provide different
   * configurations depending on the {@link ClientState} or some other factors. However, this mechanism for pluggability
   * and the related {@link GuardrailsConfig} interface are not officially supported and may change in a minor release.
   */
  public interface GuardrailsConfigProvider
  {
      /**
       * @deprecated CUSTOM_GUARDRAILS_CONFIG_PROVIDER_CLASS.getKey() must be used instead. See CASSANDRA-17797
       */
      @Deprecated(since = "5.0")
      public static final String CUSTOM_IMPLEMENTATION_PROPERTY = CUSTOM_GUARDRAILS_CONFIG_PROVIDER_CLASS.getKey();
  
      GuardrailsConfigProvider instance = CUSTOM_GUARDRAILS_CONFIG_PROVIDER_CLASS.getString() == null ?
                                          new Default() : build(CUSTOM_GUARDRAILS_CONFIG_PROVIDER_CLASS.getString());
  
      /**
       * Returns the {@link GuardrailsConfig} to be used for the specified {@link ClientState}.
       *
       * @param state a client state, maybe {@code null} if the guardrails check for which we are getting the config is
       *              for a background process that is not associated to a user query.
       * @return the configuration to be used for {@code state}
       */
      GuardrailsConfig getOrCreate(@Nullable ClientState state);
  
      /**
       * Creates an instance of the custom guardrails config provider of the given class.
       *
       * @param customImpl the fully qualified classname of the guardrails config provider to be instantiated
       * @return a new instance of the specified custom guardrails config provider of the given class.
       */
      static GuardrailsConfigProvider build(String customImpl)
      {
          return FBUtilities.construct(customImpl, "custom guardrails config provider");
      }
  
      /**
       * Default implementation of {@link GuardrailsConfigProvider} that always returns the {@link GuardrailsConfig}
       * parsed from {@code cassandra.yaml}, independently of the {@link ClientState}.
       */
      class Default implements GuardrailsConfigProvider
      {
          @Override
          public GuardrailsConfig getOrCreate(@Nullable ClientState state)
          {
              return DatabaseDescriptor.getGuardrailsConfig();
          }
      }
  }
  