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.Predicate;
  import javax.annotation.Nullable;
  
  import org.apache.cassandra.service.ClientState;
  
  /**
   * A guardrail that enables the use of a particular feature.
   *
   * <p>Note that this guardrail only aborts operations (if the feature is not enabled) so is only meant for query-based
   * guardrails (we're happy to reject queries deemed dangerous, but we don't want to create a guardrail that breaks
   * compaction for instance).
   */
  public class EnableFlag extends Guardrail
  {
      private final Predicate<ClientState> warned;
      private final Predicate<ClientState> enabled;
      private final String featureName;
  
      /**
       * Creates a new {@link EnableFlag} guardrail.
       *
       * @param name        the identifying name of the guardrail
       * @param reason      the optional description of the reason for guarding the operation
       * @param enabled     a {@link ClientState}-based supplier of boolean indicating whether the feature guarded by this
       *                    guardrail is enabled.
       * @param featureName The feature that is guarded by this guardrail (for reporting in error messages), {@link
       *                    EnableFlag#ensureEnabled(String, ClientState)} can specify a different {@code featureName}.
       */
      public EnableFlag(String name, @Nullable String reason, Predicate<ClientState> enabled, String featureName)
      {
          this(name, reason, (state) -> false, enabled, featureName);
      }
  
      /**
       * Creates a new {@link EnableFlag} guardrail.
       *
       * @param name        the identifying name of the guardrail
       * @param reason      the optional description of the reason for guarding the operation
       * @param warned      a {@link ClientState}-based supplier of boolean indicating whether warning should be
       *                    emitted even guardrail as such has passed. If guardrail fails, the warning will not be
       *                    emitted. This might be used for cases when we want to warn a user regardless of successful
       *                    guardrail execution.
       * @param enabled     a {@link ClientState}-based supplier of boolean indicating whether the feature guarded by this
       *                    guardrail is enabled.
       * @param featureName The feature that is guarded by this guardrail (for reporting in error messages), {@link
       *                    EnableFlag#ensureEnabled(String, ClientState)} can specify a different {@code featureName}.
       */
      public EnableFlag(String name,
                        @Nullable String reason,
                        Predicate<ClientState> warned,
                        Predicate<ClientState> enabled,
                        String featureName)
      {
          super(name, reason);
          this.warned = warned;
          this.enabled = enabled;
          this.featureName = featureName;
      }
  
      /**
       * Returns whether the guarded feature is enabled or not.
       *
       * @param state The client state, used to skip the check if the query is internal or is done by a superuser.
       *              A {@code null} value means that the check should be done regardless of the query.
       * @return {@code true} is the feature is enabled, {@code false} otherwise.
       */
      public boolean isEnabled(@Nullable ClientState state)
      {
          return !enabled(state) || enabled.test(state);
      }
  
      /**
       * Aborts the operation if this guardrail is not enabled.
       *
       * <p>This must be called when the feature guarded by this guardrail is used to ensure such use is in fact
       * allowed.
       *
       * @param state The client state, used to skip the check if the query is internal or is done by a superuser.
       *              A {@code null} value means that the check should be done regardless of the query.
       */
      public void ensureEnabled(@Nullable ClientState state)
      {
          ensureEnabled(featureName, state);
      }
  
      /**
       * Aborts the operation if this guardrail is not enabled.
       *
       * <p>This must be called when the feature guarded by this guardrail is used to ensure such use is in fact
       * allowed.
       *
       * @param featureName The feature that is guarded by this guardrail (for reporting in error messages).
       * @param state       The client state, used to skip the check if the query is internal or is done by a superuser. A
       *                    {@code null} value means that the check should be done regardless of the query, although it
       *                    won't throw any exception if the failure threshold is exceeded. This is so because checks
       *                    without an associated client come from asynchronous processes such as compaction, and we don't
       *                    want to interrupt such processes.
       */
      public void ensureEnabled(String featureName, @Nullable ClientState state)
      {
          if (!enabled(state))
              return;
  
          if (!enabled.test(state))
          {
              fail(featureName + " is not allowed", state);
              return;
          }
  
          if (warned.test(state))
              warn(featureName + " is not recommended");
      }
  }
  