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.oss.driver.internal.core.cql;
  
  import com.datastax.oss.driver.api.core.cql.AsyncResultSet;
  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.ResultSet;
  import com.datastax.oss.driver.api.core.cql.Row;
  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 edu.umd.cs.findbugs.annotations.NonNull;
  import java.util.ArrayList;
  import java.util.Iterator;
  import java.util.List;
  import net.jcip.annotations.NotThreadSafe;
  
  @NotThreadSafe
  public class MultiPageResultSet implements ResultSet {
  
    private final RowIterator iterator;
    private final List<ExecutionInfo> executionInfos = new ArrayList<>();
    private ColumnDefinitions columnDefinitions;
  
    public MultiPageResultSet(@NonNull AsyncResultSet firstPage) {
      assert firstPage.hasMorePages();
      this.iterator = new RowIterator(firstPage);
      this.executionInfos.add(firstPage.getExecutionInfo());
      this.columnDefinitions = firstPage.getColumnDefinitions();
    }
  
    @NonNull
    @Override
    public ColumnDefinitions getColumnDefinitions() {
      return columnDefinitions;
    }
  
    @NonNull
    @Override
    public List<ExecutionInfo> getExecutionInfos() {
      return executionInfos;
    }
  
    @Override
    public boolean isFullyFetched() {
      return iterator.isFullyFetched();
    }
  
    @Override
    public int getAvailableWithoutFetching() {
      return iterator.remaining();
    }
  
    @NonNull
    @Override
    public Iterator<Row> iterator() {
      return iterator;
    }
  
    @Override
    public boolean wasApplied() {
      return iterator.wasApplied();
    }
  
    private class RowIterator extends CountingIterator<Row> {
      private AsyncResultSet currentPage;
      private Iterator<Row> currentRows;
  
      private RowIterator(AsyncResultSet firstPage) {
        super(firstPage.remaining());
        this.currentPage = firstPage;
        this.currentRows = firstPage.currentPage().iterator();
      }
  
      @Override
      protected Row computeNext() {
        maybeMoveToNextPage();
        return currentRows.hasNext() ? currentRows.next() : endOfData();
      }
  
      private void maybeMoveToNextPage() {
        if (!currentRows.hasNext() && currentPage.hasMorePages()) {
          BlockingOperation.checkNotDriverThread();
          AsyncResultSet nextPage =
              CompletableFutures.getUninterruptibly(currentPage.fetchNextPage());
          currentPage = nextPage;
          remaining += nextPage.remaining();
          currentRows = nextPage.currentPage().iterator();
          executionInfos.add(nextPage.getExecutionInfo());
          // The definitions can change from page to page if this result set was built from a bound
          // 'SELECT *', and the schema was altered.
          columnDefinitions = nextPage.getColumnDefinitions();
        }
      }
  
      private boolean isFullyFetched() {
        return !currentPage.hasMorePages();
      }
  
      private boolean wasApplied() {
        return currentPage.wasApplied();
      }
    }
  }
  