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.api.core.graph;
  
  import com.datastax.dse.driver.internal.core.graph.GraphExecutionInfoConverter;
  import com.datastax.oss.driver.api.core.cql.ExecutionInfo;
  import edu.umd.cs.findbugs.annotations.NonNull;
  import edu.umd.cs.findbugs.annotations.Nullable;
  import java.util.Iterator;
  import java.util.concurrent.CompletionStage;
  
  /**
   * The result of an asynchronous graph query.
   *
   * <p>The default implementation returned by the driver is <b>not</b> thread-safe: the iterable
   * returned by {@link #currentPage()} should only be iterated by a single thread. However, if
   * subsequent pages are requested via {@link #fetchNextPage()}, it's safe to process those new
   * instances in other threads (as long as each individual page of results is not accessed
   * concurrently).
   *
   * @see GraphResultSet
   */
  public interface AsyncGraphResultSet {
  
    /** The execution information for this page of results. */
    @NonNull
    default ExecutionInfo getRequestExecutionInfo() {
      return GraphExecutionInfoConverter.convert(getExecutionInfo());
    }
  
    /**
     * The execution information for this page of results.
     *
     * @deprecated Use {@link #getRequestExecutionInfo()} instead.
     */
    @Deprecated
    @NonNull
    com.datastax.dse.driver.api.core.graph.GraphExecutionInfo getExecutionInfo();
  
    /** How many rows are left before the current page is exhausted. */
    int remaining();
  
    /**
     * The nodes in the current page. To keep iterating beyond that, use {@link #hasMorePages()} and
     * {@link #fetchNextPage()}.
     *
     * <p>Note that this method always returns the same object, and that that object can only be
     * iterated once: nodes are "consumed" as they are read.
     */
    @NonNull
    Iterable<GraphNode> currentPage();
  
    /**
     * Returns the next node, or {@code null} if the result set is exhausted.
     *
     * <p>This is convenient for queries that are known to return exactly one node.
     */
    @Nullable
    default GraphNode one() {
      Iterator<GraphNode> iterator = currentPage().iterator();
      return iterator.hasNext() ? iterator.next() : null;
    }
  
    /**
     * Whether there are more pages of results. If so, call {@link #fetchNextPage()} to fetch the next
     * one asynchronously.
     */
    boolean hasMorePages();
  
    /**
     * Fetch the next page of results asynchronously.
     *
     * @throws IllegalStateException if there are no more pages. Use {@link #hasMorePages()} to check
     *     if you can call this method.
     */
    @NonNull
    CompletionStage<AsyncGraphResultSet> fetchNextPage() throws IllegalStateException;
  
    /**
     * Cancels the query and asks the server to stop sending results.
     *
     * <p>At this time, graph queries are not paginated and the server sends all the results at once;
     * therefore this method has no effect.
     */
    void cancel();
  }
  