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package examples.actors
import java.util.Date
import scala.actors._
import scala.actors.Actor._
/** A simple demonstrator program implementing an online auction service
* The example uses the actor abstraction defined in the API of
* package scala.actors.
*/
trait AuctionMessage
case class Offer(bid: Int, client: Actor) extends AuctionMessage // make a bid
case class Inquire(client: Actor) extends AuctionMessage // inquire status
trait AuctionReply
case class Status(asked: Int, expiration: Date) // asked sum, expiration date
extends AuctionReply
case object BestOffer extends AuctionReply // yours is the best offer
case class BeatenOffer(maxBid: Int) extends AuctionReply // offer beaten by maxBid
case class AuctionConcluded(seller: Actor, client: Actor) // auction concluded
extends AuctionReply
case object AuctionFailed extends AuctionReply // failed with no bids
case object AuctionOver extends AuctionReply // bidding is closed
class AuctionActor(seller: Actor, minBid: Int, closing: Date) extends Actor {
val timeToShutdown = 3000 // msec
val bidIncrement = 10
def act() {
var maxBid = minBid - bidIncrement
var maxBidder: Actor = null
loop {
reactWithin (closing.getTime() - new Date().getTime()) {
case Offer(bid, client) =>
if (bid >= maxBid + bidIncrement) {
if (maxBid >= minBid)
maxBidder ! BeatenOffer(bid)
maxBid = bid
maxBidder = client
client ! BestOffer
}
else
client ! BeatenOffer(maxBid)
case Inquire(client) =>
client ! Status(maxBid, closing)
case TIMEOUT =>
if (maxBid >= minBid) {
val reply = AuctionConcluded(seller, maxBidder)
maxBidder ! reply
seller ! reply
} else {
seller ! AuctionFailed
}
reactWithin(timeToShutdown) {
case Offer(_, client) => client ! AuctionOver
case TIMEOUT => exit()
}
}
}
}
}
object auction {
val random = new scala.util.Random
val minBid = 100
val closing = new Date(new Date().getTime() + 4000)
val seller = Actor.actor { }
val auction = new AuctionActor(seller, minBid, closing)
def client(i: Int, increment: Int, top: Int) = new Actor {
val name = "Client " + i
def log(msg: String) = Console.println(name + ": " + msg)
var max: Int = _
var current: Int = 0
def act() {
log("started")
auction ! Inquire(this)
receive {
case Status(maxBid, _) =>
log("status(" + maxBid + ")")
max = maxBid
}
loop {
if (max >= top) {
log("too high for me")
}
else if (current < max) {
current = max + increment
Thread.sleep(1 + random.nextInt(1000))
auction ! Offer(current, this)
}
reactWithin(3000) {
case BestOffer =>
log("bestOffer(" + current + ")")
case BeatenOffer(maxBid) =>
log("beatenOffer(" + maxBid + ")")
max = maxBid
case AuctionConcluded(seller, maxBidder) =>
log("auctionConcluded"); exit()
case AuctionOver =>
log("auctionOver"); exit()
case TIMEOUT =>
exit()
}
}
}
}
def main(args: Array[String]) {
seller.start()
auction.start()
client(1, 20, 200).start()
client(2, 10, 300).start()
}
}
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