public class BidGenerator {

  /**
   * Fraction of people/auctions which may be 'hot' sellers/bidders/auctions are 1
   * over these values.
   */
  private static final int HOT_AUCTION_RATIO = 100;
  private static final int HOT_BIDDER_RATIO = 100;


  /**
   * Generate and return a random bid with next available id.
   */
  public static Bid nextBid(
      long eventId, Random random, long timestamp, GeneratorConfig config) {

    long auction;
    // Here P(bid will be for a hot auction) = 1 - 1/hotAuctionRatio.
    if (random.nextInt(config.getHotAuctionRatio()) > 0) {
      // Choose the first auction in the batch of last HOT_AUCTION_RATIO auctions.
      auction = (lastBase0AuctionId(eventId) / HOT_AUCTION_RATIO) * HOT_AUCTION_RATIO;
    } else {
      auction = nextBase0AuctionId(eventId, random, config);
    }
    auction += GeneratorConfig.FIRST_AUCTION_ID;

    long bidder;
    // Here P(bid will be by a hot bidder) = 1 - 1/hotBiddersRatio
    if (random.nextInt(config.getHotBiddersRatio()) > 0) {
      // Choose the second person (so hot bidders and hot sellers don't collide) in the batch of
      // last HOT_BIDDER_RATIO people.
      bidder = (lastBase0PersonId(eventId) / HOT_BIDDER_RATIO) * HOT_BIDDER_RATIO + 1;
    } else {
      bidder = nextBase0PersonId(eventId, random, config);
    }
    bidder += GeneratorConfig.FIRST_PERSON_ID;

    long price = PriceGenerator.nextPrice(random);
    int currentSize = 8 + 8 + 8 + 8;
    String extra = nextExtra(random, currentSize, config.getAvgBidByteSize());
    return new Bid(auction, bidder, price, timestamp, extra);
  }
}