/**
 * Copyright (C) 2009 Scalable Solutions.
 */

package se.scalablesolutions.akka.kernel

import java.util.concurrent.atomic.AtomicLong
import scala.collection.mutable.{HashSet, HashMap}
sealed abstract class TransactionStatus
object TransactionStatus {
  case object New extends TransactionStatus
  case object Active extends TransactionStatus
  case object Aborted extends TransactionStatus
  case object Completed extends TransactionStatus
}

/**
 * Represents a snapshot of the current invocation.
 *
 * @author <a href="http://jonasboner.com">Jonas Bon&#233;r</a>
 */
object TransactionIdFactory {
  // FIXME: will not work in distributed env
  private val currentId = new AtomicLong(0L)
  def newId = currentId.getAndIncrement
}

/**
 * Represents a snapshot of the current invocation.
 *
 * @author <a href="http://jonasboner.com">Jonas Bon&#233;r</a>
 */
class Transaction extends Logging {
  val id = TransactionIdFactory.newId

  log.debug("Creating a new transaction with id [%s]", id)

  // FIXME: add support for nested transactions
  private[this] var parent: Option[Transaction] = None
  private[this] val participants = new HashSet[GenericServerContainer]
  private[this] val precommitted = new HashSet[GenericServerContainer]
  @volatile private[this] var status: TransactionStatus = TransactionStatus.New

  def begin(server: GenericServerContainer) = synchronized {
    ensureIsActiveOrNew
    if (status == TransactionStatus.New) log.info("Server [%s] is starting NEW transaction [%s]", server.id, this)
    else log.info("Server [%s] is participating in transaction", server)
    server.transactionalItems.foreach(_.begin)
    participants + server
    status = TransactionStatus.Active
  }

  def precommit(server: GenericServerContainer) = synchronized {
    if (status == TransactionStatus.Active) {
      log.info("Pre-committing transaction [%s] for server [%s]", this, server.id)
      precommitted + server
    }
  }

  def commit(server: GenericServerContainer) = synchronized {
    if (status == TransactionStatus.Active) {
      log.info("Committing transaction [%s] for server [%s]", this, server.id)
      val haveAllPreCommitted =
        if (participants.size == precommitted.size) {{
          for (server <- participants) yield {
            if (precommitted.exists(_.id == server.id)) true
            else false
          }}.exists(_ == true)
        } else false
      if (haveAllPreCommitted) {
        participants.foreach(_.transactionalItems.foreach(_.commit))
        status = TransactionStatus.Completed
      }
      else rollback(server)
    }
    participants.clear
    precommitted.clear
  }

  def rollback(server: GenericServerContainer) = synchronized {
    ensureIsActiveOrAborted
    log.info("Server [%s] has initiated transaction rollback for [%s], rolling back [%s]", server.id, this, participants)
    participants.foreach(_.transactionalItems.foreach(_.rollback))
    status = TransactionStatus.Aborted
  }

  def join(server: GenericServerContainer) = synchronized {
    ensureIsActive
    log.info("Server [%s] is joining transaction [%s]" , server.id, this)
    server.transactionalItems.foreach(_.begin)
    participants + server
  }

  private def ensureIsActive = if (status != TransactionStatus.Active)
    throw new IllegalStateException("Expected ACTIVE transaction - current status [" + status + "]")

  private def ensureIsActiveOrAborted = if (!(status == TransactionStatus.Active || status == TransactionStatus.Aborted))
    throw new IllegalStateException("Expected ACTIVE or ABORTED transaction - current status [" + status + "]")

  private def ensureIsActiveOrNew = if (!(status == TransactionStatus.Active || status == TransactionStatus.New))
    throw new IllegalStateException("Expected ACTIVE or NEW transaction - current status [" + status + "]")

  override def equals(that: Any): Boolean = synchronized {
    that != null && 
    that.isInstanceOf[Transaction] && 
    that.asInstanceOf[Transaction].id == this.id
  }
 
  override def hashCode(): Int = id.toInt
 
  override def toString(): String = synchronized { 
    "Transaction[" + id + ", " + status + "]"
  }
}