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 java.util.function.Function;
  import java.util.function.Predicate;
  import javax.annotation.Nullable;
  
  import org.apache.cassandra.service.ClientState;
  
  /**
   * A guardrail based on two predicates.
   *
   * <p>A {@link Predicates} guardrail defines (up to) 2 predicates, one at which a warning is issued, and another one
   * at which a failure is triggered. If failure is triggered, warning is skipped.
   *
   * @param <T> the type of the values to be tested against predicates.
   */
  public class Predicates<T> extends Guardrail
  {
      private final Function<ClientState, Predicate<T>> warnPredicate;
      private final Function<ClientState, Predicate<T>> failurePredicate;
      private final MessageProvider<T> messageProvider;
  
      /**
       * A function used to build the warning or error message of a triggered {@link Predicates} guardrail.
       */
      public interface MessageProvider<T>
      {
          /**
           * Called when the guardrail is triggered to build the corresponding message.
           *
           * @param isWarning whether the trigger is a warning one; otherwise it is failure one.
           * @param value     the value that triggers guardrail.
           */
          String createMessage(boolean isWarning, T value);
      }
  
      /**
       * Creates a new {@link Predicates} guardrail.
       *
       * @param name             the identifying name of the guardrail
       * @param reason           the optional description of the reason for guarding the operation
       * @param warnPredicate    a {@link ClientState}-based predicate provider that is used to check if given value should trigger a warning.
       * @param failurePredicate a {@link ClientState}-based predicate provider that is used to check if given value should trigger a failure.
       * @param messageProvider  a function to generate the warning or error message if the guardrail is triggered
       */
      Predicates(String name,
                 @Nullable String reason,
                 Function<ClientState, Predicate<T>> warnPredicate,
                 Function<ClientState, Predicate<T>> failurePredicate,
                 MessageProvider<T> messageProvider)
      {
          super(name, reason);
          this.warnPredicate = warnPredicate;
          this.failurePredicate = failurePredicate;
          this.messageProvider = messageProvider;
      }
  
      /**
       * Apply the guardrail to the provided value, triggering a warning or failure if appropriate.
       *
       * @param value the value to check.
       */
      public void guard(T value, @Nullable ClientState state)
      {
          if (!enabled(state))
              return;
  
          if (failurePredicate.apply(state).test(value))
          {
              fail(messageProvider.createMessage(false, value), state);
          }
          else if (warnPredicate.apply(state).test(value))
          {
              warn(messageProvider.createMessage(true, value));
          }
      }
  }
  