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.graph;
  
  import com.datastax.dse.driver.api.core.graph.AsyncGraphResultSet;
  import com.datastax.dse.driver.api.core.graph.GraphNode;
  import com.datastax.dse.driver.api.core.graph.GraphResultSet;
  import com.datastax.oss.driver.api.core.cql.ExecutionInfo;
  import com.datastax.oss.driver.internal.core.util.CountingIterator;
  import com.datastax.oss.driver.internal.core.util.concurrent.BlockingOperation;
  import com.datastax.oss.driver.internal.core.util.concurrent.CompletableFutures;
  import com.datastax.oss.driver.shaded.guava.common.collect.Lists;
  import edu.umd.cs.findbugs.annotations.NonNull;
  import java.util.ArrayList;
  import java.util.Iterator;
  import java.util.List;
  
  public class MultiPageGraphResultSet implements GraphResultSet {
    private final RowIterator iterator;
    private final List<ExecutionInfo> executionInfos = new ArrayList<>();
  
    public MultiPageGraphResultSet(AsyncGraphResultSet firstPage) {
      iterator = new RowIterator(firstPage);
      executionInfos.add(firstPage.getRequestExecutionInfo());
    }
  
    @Override
    public void cancel() {
      iterator.cancel();
    }
  
    @NonNull
    @Override
    public ExecutionInfo getRequestExecutionInfo() {
      return executionInfos.get(executionInfos.size() - 1);
    }
  
    @NonNull
    @Override
    @Deprecated
    public com.datastax.dse.driver.api.core.graph.GraphExecutionInfo getExecutionInfo() {
      return GraphExecutionInfoConverter.convert(getRequestExecutionInfo());
    }
  
    /**
     * The execution information for all the queries that have been performed so far to assemble this
     * iterable.
     *
     * <p>This will have multiple elements if the query is paged, since the driver performs blocking
     * background queries to fetch additional pages transparently as the result set is being iterated.
     */
    @NonNull
    public List<ExecutionInfo> getRequestExecutionInfos() {
      return executionInfos;
    }
  
    /** @deprecated use {@link #getRequestExecutionInfos()} instead. */
    @NonNull
    @Deprecated
    public List<com.datastax.dse.driver.api.core.graph.GraphExecutionInfo> getExecutionInfos() {
      return Lists.transform(executionInfos, GraphExecutionInfoConverter::convert);
    }
  
    @NonNull
    @Override
    public Iterator<GraphNode> iterator() {
      return iterator;
    }
  
    public class RowIterator extends CountingIterator<GraphNode> {
      private AsyncGraphResultSet currentPage;
      private Iterator<GraphNode> currentRows;
      private boolean cancelled = false;
  
      private RowIterator(AsyncGraphResultSet firstPage) {
        super(firstPage.remaining());
        currentPage = firstPage;
        currentRows = firstPage.currentPage().iterator();
      }
  
      @Override
      protected GraphNode computeNext() {
        maybeMoveToNextPage();
        return currentRows.hasNext() ? currentRows.next() : endOfData();
      }
  
      private void maybeMoveToNextPage() {
        if (!cancelled && !currentRows.hasNext() && currentPage.hasMorePages()) {
          BlockingOperation.checkNotDriverThread();
          AsyncGraphResultSet nextPage =
              CompletableFutures.getUninterruptibly(currentPage.fetchNextPage());
          currentPage = nextPage;
          remaining += currentPage.remaining();
          currentRows = nextPage.currentPage().iterator();
          executionInfos.add(nextPage.getRequestExecutionInfo());
        }
      }
  
      private void cancel() {
        currentPage.cancel();
        cancelled = true;
      }
  
      public boolean isCancelled() {
        return cancelled;
      }
    }
  }
  