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 org.apache.beam.sdk.nexmark.queries;
  
  import java.util.ArrayList;
  import java.util.Iterator;
  import java.util.List;
  import java.util.Map;
  import java.util.Set;
  import java.util.TreeMap;
  import java.util.TreeSet;
  import org.apache.beam.sdk.nexmark.NexmarkConfiguration;
  import org.apache.beam.sdk.nexmark.NexmarkUtils;
  import org.apache.beam.sdk.nexmark.model.Auction;
  import org.apache.beam.sdk.nexmark.model.AuctionBid;
  import org.apache.beam.sdk.nexmark.model.Bid;
  import org.apache.beam.sdk.nexmark.model.Event;
  import org.apache.beam.sdk.transforms.windowing.BoundedWindow;
  import org.apache.beam.sdk.values.TimestampedValue;
  import org.checkerframework.checker.nullness.qual.Nullable;
  import org.joda.time.Instant;
  
  /** A simulator of the {@code WinningBids} query. */
  @SuppressWarnings({
    "nullness" // TODO(https://github.com/apache/beam/issues/20497)
  })
  public class WinningBidsSimulator extends AbstractSimulator<Event, AuctionBid> {
    /** Auctions currently still open, indexed by auction id. */
    private final Map<Long, Auction> openAuctions;
  
    /** The ids of auctions known to be closed. */
    private final Set<Long> closedAuctions;
  
    /** Current best valid bids for open auctions, indexed by auction id. */
    private final Map<Long, Bid> bestBids;
  
    /** Bids for auctions we havn't seen yet. */
    private final List<Bid> bidsWithoutAuctions;
  
    /** Timestamp of last new auction or bid event (ms since epoch). */
    private Instant lastTimestamp;
  
    public WinningBidsSimulator(NexmarkConfiguration configuration) {
      super(NexmarkUtils.standardEventIterator(configuration));
      openAuctions = new TreeMap<>();
      closedAuctions = new TreeSet<>();
      bestBids = new TreeMap<>();
      bidsWithoutAuctions = new ArrayList<>();
      lastTimestamp = BoundedWindow.TIMESTAMP_MIN_VALUE;
    }
  
    /**
     * Try to account for {@code bid} in state. Return true if bid has now been accounted for by
     * {@code bestBids}.
     */
    private boolean captureBestBid(Bid bid, boolean shouldLog) {
      if (closedAuctions.contains(bid.auction)) {
        // Ignore bids for known, closed auctions.
        if (shouldLog) {
          NexmarkUtils.info("closed auction: %s", bid);
        }
        return true;
      }
      Auction auction = openAuctions.get(bid.auction);
      if (auction == null) {
        // We don't have an auction for this bid yet, so can't determine if it is
        // winning or not.
        if (shouldLog) {
          NexmarkUtils.info("pending auction: %s", bid);
        }
        return false;
      }
      if (bid.price < auction.reserve) {
        // Bid price is too low.
        if (shouldLog) {
          NexmarkUtils.info("below reserve: %s", bid);
        }
        return true;
      }
      Bid existingBid = bestBids.get(bid.auction);
      if (existingBid == null || Bid.PRICE_THEN_DESCENDING_TIME.compare(existingBid, bid) < 0) {
        // We've found a (new) best bid for a known auction.
        bestBids.put(bid.auction, bid);
        if (shouldLog) {
          NexmarkUtils.info("new winning bid: %s", bid);
        }
      } else {
        if (shouldLog) {
          NexmarkUtils.info("ignoring low bid: %s", bid);
        }
      }
      return true;
    }
  
    /** Try to match bids without auctions to auctions. */
    private void flushBidsWithoutAuctions() {
      Iterator<Bid> itr = bidsWithoutAuctions.iterator();
      while (itr.hasNext()) {
        Bid bid = itr.next();
        if (captureBestBid(bid, false)) {
          NexmarkUtils.info("bid now accounted for: %s", bid);
          itr.remove();
        }
      }
    }
  
    /**
     * Return the next winning bid for an expired auction relative to {@code timestamp}. Return null
     * if no more winning bids, in which case all expired auctions will have been removed from our
     * state. Retire auctions in order of expire time.
     */
    private @Nullable TimestampedValue<AuctionBid> nextWinningBid(Instant timestamp) {
      Map<Instant, List<Long>> toBeRetired = new TreeMap<>();
      for (Map.Entry<Long, Auction> entry : openAuctions.entrySet()) {
        if (entry.getValue().expires.compareTo(timestamp) <= 0) {
          List<Long> idsAtTime =
              toBeRetired.computeIfAbsent(entry.getValue().expires, k -> new ArrayList<>());
          idsAtTime.add(entry.getKey());
        }
      }
      for (Map.Entry<Instant, List<Long>> entry : toBeRetired.entrySet()) {
        for (long id : entry.getValue()) {
          Auction auction = openAuctions.get(id);
          NexmarkUtils.info("retiring auction: %s", auction);
          openAuctions.remove(id);
          Bid bestBid = bestBids.get(id);
          if (bestBid != null) {
            TimestampedValue<AuctionBid> result =
                TimestampedValue.of(new AuctionBid(auction, bestBid), auction.expires);
            NexmarkUtils.info("winning: %s", result);
            return result;
          }
        }
      }
      return null;
    }
  
    @Override
    protected void run() {
      if (lastTimestamp.compareTo(BoundedWindow.TIMESTAMP_MIN_VALUE) > 0) {
        // We may have finally seen the auction a bid was intended for.
        flushBidsWithoutAuctions();
        TimestampedValue<AuctionBid> result = nextWinningBid(lastTimestamp);
        if (result != null) {
          addResult(result);
          return;
        }
      }
  
      TimestampedValue<Event> timestampedEvent = nextInput();
      if (timestampedEvent == null) {
        // No more events. Flush any still open auctions.
        TimestampedValue<AuctionBid> result = nextWinningBid(BoundedWindow.TIMESTAMP_MAX_VALUE);
        if (result == null) {
          // We are done.
          allDone();
          return;
        }
        addResult(result);
        return;
      }
  
      Event event = timestampedEvent.getValue();
      if (event.newPerson != null) {
        // Ignore new person events.
        return;
      }
  
      lastTimestamp = timestampedEvent.getTimestamp();
      if (event.newAuction != null) {
        // Add this new open auction to our state.
        openAuctions.put(event.newAuction.id, event.newAuction);
      } else {
        if (!captureBestBid(event.bid, true)) {
          // We don't know what to do with this bid yet.
          NexmarkUtils.info("bid not yet accounted for: %s", event.bid);
          bidsWithoutAuctions.add(event.bid);
        }
      }
      // Keep looking for winning bids.
    }
  }
  