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 com.datastax.dse.driver.internal.core.cql.reactive;
  
  import com.datastax.dse.driver.api.core.cql.reactive.ReactiveResultSet;
  import com.datastax.dse.driver.api.core.cql.reactive.ReactiveRow;
  import com.datastax.oss.driver.api.core.AsyncPagingIterable;
  import com.datastax.oss.driver.api.core.cql.ColumnDefinitions;
  import com.datastax.oss.driver.api.core.cql.ExecutionInfo;
  import com.datastax.oss.driver.api.core.cql.Row;
  import edu.umd.cs.findbugs.annotations.NonNull;
  import java.util.Objects;
  import java.util.concurrent.Callable;
  import java.util.concurrent.CompletionStage;
  import java.util.concurrent.atomic.AtomicBoolean;
  import net.jcip.annotations.ThreadSafe;
  import org.reactivestreams.Publisher;
  import org.reactivestreams.Subscriber;
  
  @ThreadSafe
  public abstract class ReactiveResultSetBase<ResultSetT extends AsyncPagingIterable<Row, ResultSetT>>
      implements ReactiveResultSet {
  
    private final Callable<CompletionStage<ResultSetT>> firstPage;
  
    private final AtomicBoolean alreadySubscribed = new AtomicBoolean(false);
  
    private final SimpleUnicastProcessor<ColumnDefinitions> columnDefinitionsPublisher =
        new SimpleUnicastProcessor<>();
  
    private final SimpleUnicastProcessor<ExecutionInfo> executionInfosPublisher =
        new SimpleUnicastProcessor<>();
  
    private final SimpleUnicastProcessor<Boolean> wasAppliedPublisher =
        new SimpleUnicastProcessor<>();
  
    protected ReactiveResultSetBase(Callable<CompletionStage<ResultSetT>> firstPage) {
      this.firstPage = firstPage;
    }
  
    @Override
    public void subscribe(@NonNull Subscriber<? super ReactiveRow> subscriber) {
      // As per rule 1.9, we need to throw an NPE if subscriber is null
      Objects.requireNonNull(subscriber, "Subscriber cannot be null");
      // As per rule 1.11, this publisher is allowed to support only one subscriber.
      if (alreadySubscribed.compareAndSet(false, true)) {
        ReactiveResultSetSubscription<ResultSetT> subscription =
            new ReactiveResultSetSubscription<>(
                subscriber, columnDefinitionsPublisher, executionInfosPublisher, wasAppliedPublisher);
        try {
          subscriber.onSubscribe(subscription);
          // must be done after onSubscribe
          subscription.start(firstPage);
        } catch (Throwable t) {
          // As per rule 2.13: In the case that this rule is violated,
          // any associated Subscription to the Subscriber MUST be considered as
          // cancelled, and the caller MUST raise this error condition in a fashion
          // that is adequate for the runtime environment.
          subscription.doOnError(
              new IllegalStateException(
                  subscriber
                      + " violated the Reactive Streams rule 2.13 by throwing an exception from onSubscribe.",
                  t));
        }
      } else {
        subscriber.onSubscribe(EmptySubscription.INSTANCE);
        subscriber.onError(
            new IllegalStateException("This publisher does not support multiple subscriptions"));
      }
      // As per 2.13, this method must return normally (i.e. not throw)
    }
  
    @NonNull
    @Override
    public Publisher<? extends ColumnDefinitions> getColumnDefinitions() {
      return columnDefinitionsPublisher;
    }
  
    @NonNull
    @Override
    public Publisher<? extends ExecutionInfo> getExecutionInfos() {
      return executionInfosPublisher;
    }
  
    @NonNull
    @Override
    public Publisher<Boolean> wasApplied() {
      return wasAppliedPublisher;
    }
  }
  