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A driver for DataStax Enterprise (DSE) and Apache Cassandra 1.2+ clusters that works exclusively with the Cassandra Query Language version 3 (CQL3) and Cassandra's binary protocol, supporting DSE-specific features such as geospatial types, DSE Graph and DSE authentication.

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/*
 * Copyright DataStax, Inc.
 *
 * This software can be used solely with DataStax Enterprise. Please consult the license at
 * http://www.datastax.com/terms/datastax-dse-driver-license-terms
 */
package com.datastax.driver.core;

import com.google.common.collect.AbstractIterator;
import com.google.common.util.concurrent.ListenableFuture;
import com.google.common.util.concurrent.Uninterruptibles;
import java.util.Iterator;
import java.util.concurrent.ExecutionException;

class DefaultContinuousPagingResult implements ContinuousPagingResult {

  private final RowIterator iterator;
  private final ColumnDefinitions columnDefinitions;

  DefaultContinuousPagingResult(ListenableFuture firstPageFuture) {
    try {
      AsyncContinuousPagingResult result = Uninterruptibles.getUninterruptibly(firstPageFuture);
      this.iterator = new RowIterator(result);
      this.columnDefinitions = result.getColumnDefinitions();
    } catch (ExecutionException e) {
      throw DriverThrowables.propagateCause(e);
    }
  }

  @Override
  public Iterator iterator() {
    return iterator;
  }

  @Override
  public ColumnDefinitions getColumnDefinitions() {
    return columnDefinitions;
  }

  @Override
  public void cancel() {
    this.iterator.cancel();
  }

  @Override
  public ExecutionInfo getExecutionInfo() {
    return this.iterator.getExecutionInfo();
  }

  private static class RowIterator extends AbstractIterator {
    private AsyncContinuousPagingResult currentResult;
    private Iterator currentRows;
    private boolean cancelled;

    private RowIterator(AsyncContinuousPagingResult result) {
      this.currentResult = result;
      this.currentRows = result.currentPage().iterator();
    }

    @Override
    protected Row computeNext() {
      maybeFetchNextResult();
      return currentRows.hasNext() ? currentRows.next() : endOfData();
    }

    private void maybeFetchNextResult() {
      if (!currentRows.hasNext() && !cancelled && !currentResult.isLast()) {
        try {
          currentResult = Uninterruptibles.getUninterruptibly(currentResult.nextPage());
          currentRows = currentResult.currentPage().iterator();
        } catch (ExecutionException e) {
          throw DriverThrowables.propagateCause(e);
        }
      }
    }

    private ExecutionInfo getExecutionInfo() {
      return currentResult.getExecutionInfo();
    }

    private void cancel() {
      currentResult.cancel();
      cancelled = true;
    }
  }
}