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   * 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
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   */
  package org.apache.beam.sdk.nexmark.queries;
  
  import org.apache.beam.sdk.nexmark.NexmarkConfiguration;
  import org.apache.beam.sdk.nexmark.model.Bid;
  import org.apache.beam.sdk.nexmark.model.Event;
  import org.apache.beam.sdk.transforms.DoFn;
  import org.apache.beam.sdk.transforms.Max;
  import org.apache.beam.sdk.transforms.ParDo;
  import org.apache.beam.sdk.transforms.windowing.FixedWindows;
  import org.apache.beam.sdk.transforms.windowing.Window;
  import org.apache.beam.sdk.values.PCollection;
  import org.apache.beam.sdk.values.PCollectionView;
  import org.joda.time.Duration;
  
  /**
   * Query 7, 'Highest Bid'. Select the bids with the highest bid price in the last minute. In CQL
   * syntax:
   *
   * <pre>
   * SELECT Rstream(B.auction, B.price, B.bidder)
   * FROM Bid [RANGE 1 MINUTE SLIDE 1 MINUTE] B
   * WHERE B.price = (SELECT MAX(B1.price)
   *                  FROM BID [RANGE 1 MINUTE SLIDE 1 MINUTE] B1);
   * </pre>
   *
   * <p>We will use a shorter window to help make testing easier. We'll also implement this using a
   * side-input in order to exercise that functionality. (A combiner, as used in Query 5, is a more
   * efficient approach.).
   */
  public class Query7 extends NexmarkQueryTransform<Bid> {
    private final NexmarkConfiguration configuration;
  
    public Query7(NexmarkConfiguration configuration) {
      super("Query7");
      this.configuration = configuration;
    }
  
    @Override
    public PCollection<Bid> expand(PCollection<Event> events) {
      // Window the bids.
      PCollection<Bid> slidingBids =
          events
              .apply(NexmarkQueryUtil.JUST_BIDS)
              .apply(
                  Window.into(
                      FixedWindows.of(Duration.standardSeconds(configuration.windowSizeSec))));
  
      // Find the largest price in all bids.
      // NOTE: It would be more efficient to write this query much as we did for Query5, using
      // a binary combiner to accumulate the bids with maximal price. As written this query
      // requires an additional scan per window, with the associated cost of snapshotted state and
      // its I/O. We'll keep this implementation since it illustrates the use of side inputs.
      final PCollectionView<Long> maxPriceView =
          slidingBids
              .apply("BidToPrice", NexmarkQueryUtil.BID_TO_PRICE)
              .apply(Max.longsGlobally().withFanout(configuration.fanout).asSingletonView());
  
      return slidingBids
          // Select all bids which have that maximum price (there may be more than one).
          .apply(
          name + ".Select",
          ParDo.of(
                  new DoFn<Bid, Bid>() {
                    @ProcessElement
                    public void processElement(ProcessContext c) {
                      long maxPrice = c.sideInput(maxPriceView);
                      Bid bid = c.element();
                      if (bid.price == maxPrice) {
                        c.output(bid);
                      }
                    }
                  })
              .withSideInputs(maxPriceView));
    }
  }
  