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/**
 * Copyright (C) 2009-2012 Typesafe Inc. 
 */

package akka.serialization

import akka.AkkaException
import scala.util.DynamicVariable
import com.typesafe.config.Config
import akka.actor.{ Extension, ExtendedActorSystem, Address, DynamicAccess }
import akka.event.Logging
import java.util.concurrent.ConcurrentHashMap
import akka.util.NonFatal
import scala.collection.mutable.ArrayBuffer
import java.io.NotSerializableException

case class NoSerializerFoundException(m: String) extends AkkaException(m)

object Serialization {

  /**
   * Tuple that represents mapping from Class to Serializer
   */
  type ClassSerializer = (Class[_], Serializer)

  /**
   * This holds a reference to the current transport address to be inserted
   * into local actor refs during serialization.
   */
  val currentTransportAddress = new DynamicVariable[Address](null)

  class Settings(val config: Config) {

    import scala.collection.JavaConverters._
    import config._

    val Serializers: Map[String, String] = configToMap(getConfig("akka.actor.serializers"))

    val SerializationBindings: Map[String, String] = configToMap(getConfig("akka.actor.serialization-bindings"))

    private def configToMap(cfg: Config): Map[String, String] =
      cfg.root.unwrapped.asScala.toMap.map { case (k, v) ⇒ (k, v.toString) }

  }
}

/**
 * Serialization module. Contains methods for serialization and deserialization as well as
 * locating a Serializer for a particular class as defined in the mapping in the configuration.
 */
class Serialization(val system: ExtendedActorSystem) extends Extension {
  import Serialization._

  val settings = new Settings(system.settings.config)
  val log = Logging(system, getClass.getName)

  /**
   * Serializes the given AnyRef/java.lang.Object according to the Serialization configuration
   * to either an Array of Bytes or an Exception if one was thrown.
   */
  def serialize(o: AnyRef): Either[Throwable, Array[Byte]] =
    try Right(findSerializerFor(o).toBinary(o))
    catch { case NonFatal(e) ⇒ Left(e) }

  /**
   * Deserializes the given array of bytes using the specified serializer id,
   * using the optional type hint to the Serializer and the optional ClassLoader ot load it into.
   * Returns either the resulting object or an Exception if one was thrown.
   */
  def deserialize(bytes: Array[Byte],
                  serializerId: Int,
                  clazz: Option[Class[_]]): Either[Throwable, AnyRef] =
    try Right(serializerByIdentity(serializerId).fromBinary(bytes, clazz))
    catch { case NonFatal(e) ⇒ Left(e) }

  /**
   * Deserializes the given array of bytes using the specified type to look up what Serializer should be used.
   * You can specify an optional ClassLoader to load the object into.
   * Returns either the resulting object or an Exception if one was thrown.
   */
  def deserialize(bytes: Array[Byte], clazz: Class[_]): Either[Throwable, AnyRef] =
    try Right(serializerFor(clazz).fromBinary(bytes, Some(clazz)))
    catch { case NonFatal(e) ⇒ Left(e) }

  /**
   * Returns the Serializer configured for the given object, returns the NullSerializer if it's null.
   *
   * @throws akka.config.ConfigurationException if no `serialization-bindings` is configured for the
   *   class of the object
   */
  def findSerializerFor(o: AnyRef): Serializer = o match {
    case null  ⇒ NullSerializer
    case other ⇒ serializerFor(other.getClass)
  }

  /**
   * Returns the configured Serializer for the given Class. The configured Serializer
   * is used if the configured class `isAssignableFrom` from the `clazz`, i.e.
   * the configured class is a super class or implemented interface. In case of
   * ambiguity it is primarily using the most specific configured class,
   * and secondly the entry configured first.
   *
   * @throws java.io.NotSerializableException if no `serialization-bindings` is configured for the class
   */
  def serializerFor(clazz: Class[_]): Serializer =
    serializerMap.get(clazz) match {
      case null ⇒
        // bindings are ordered from most specific to least specific
        def unique(possibilities: Seq[(Class[_], Serializer)]): Boolean =
          possibilities.size == 1 ||
            (possibilities map (_._1) forall (_ isAssignableFrom possibilities(0)._1)) ||
            (possibilities map (_._2) forall (_ == possibilities(0)._2))

        val ser = bindings filter { _._1 isAssignableFrom clazz } match {
          case Seq() ⇒
            throw new NotSerializableException("No configured serialization-bindings for class [%s]" format clazz.getName)
          case possibilities ⇒
            if (!unique(possibilities))
              log.warning("Multiple serializers found for " + clazz + ", choosing first: " + possibilities)
            possibilities(0)._2
        }
        serializerMap.putIfAbsent(clazz, ser) match {
          case null ⇒
            log.debug("Using serializer[{}] for message [{}]", ser.getClass.getName, clazz.getName)
            ser
          case some ⇒ some
        }
      case ser ⇒ ser
    }

  /**
   * Tries to load the specified Serializer by the fully-qualified name; the actual
   * loading is performed by the system’s [[akka.actor.DynamicAccess]].
   */
  def serializerOf(serializerFQN: String): Either[Throwable, Serializer] =
    system.dynamicAccess.createInstanceFor[Serializer](serializerFQN, Seq(classOf[ExtendedActorSystem] -> system)).fold(_ ⇒
      system.dynamicAccess.createInstanceFor[Serializer](serializerFQN, Seq()), Right(_))

  /**
   * A Map of serializer from alias to implementation (class implementing akka.serialization.Serializer)
   * By default always contains the following mapping: "java" -> akka.serialization.JavaSerializer
   */
  private val serializers: Map[String, Serializer] = {
    for ((k: String, v: String) ← settings.Serializers)
      yield k -> serializerOf(v).fold(throw _, identity)
  }

  /**
   *  bindings is a Seq of tuple representing the mapping from Class to Serializer.
   *  It is primarily ordered by the most specific classes first, and secondly in the configured order.
   */
  private[akka] val bindings: Seq[ClassSerializer] = {
    val configuredBindings = for ((k: String, v: String) ← settings.SerializationBindings if v != "none") yield {
      val c = system.dynamicAccess.getClassFor(k).fold(throw _, identity[Class[_]])
      (c, serializers(v))
    }
    sort(configuredBindings)
  }

  /**
   * Sort so that subtypes always precede their supertypes, but without
   * obeying any order between unrelated subtypes (insert sort).
   */
  private def sort(in: Iterable[ClassSerializer]): Seq[ClassSerializer] =
    (new ArrayBuffer[ClassSerializer](in.size) /: in) { (buf, ca) ⇒
      buf.indexWhere(_._1 isAssignableFrom ca._1) match {
        case -1 ⇒ buf append ca
        case x  ⇒ buf insert (x, ca)
      }
      buf
    }

  /**
   * serializerMap is a Map whose keys is the class that is serializable and values is the serializer
   * to be used for that class.
   */
  private val serializerMap: ConcurrentHashMap[Class[_], Serializer] = {
    val serializerMap = new ConcurrentHashMap[Class[_], Serializer]
    for ((c, s) ← bindings) serializerMap.put(c, s)
    serializerMap
  }

  /**
   * Maps from a Serializer Identity (Int) to a Serializer instance (optimization)
   */
  val serializerByIdentity: Map[Int, Serializer] =
    Map(NullSerializer.identifier -> NullSerializer) ++ serializers map { case (_, v) ⇒ (v.identifier, v) }
}