/*
 * Copyright (C) 2009-2021 Lightbend Inc. <https://www.lightbend.com>
 */

package akka.io

import akka.actor.Props
import akka.io.Udp._

/**
 * INTERNAL API
 *
 * UdpManager is a facade for simple fire-and-forget style UDP operations
 *
 * UdpManager is obtainable by calling {{{ IO(Udp) }}} (see [[akka.io.IO]] and [[akka.io.Udp]])
 *
 * *Warning!* Udp uses [[java.nio.channels.DatagramChannel#send]] to deliver datagrams, and as a consequence if a
 * security manager  has been installed then for each datagram it will verify if the target address and port number are
 * permitted. If this performance overhead is undesirable use the connection style Udp extension.
 *
 * == Bind and send ==
 *
 * To bind and listen to a local address, a [[akka.io.Udp..Bind]] command must be sent to this actor. If the binding
 * was successful, the sender of the [[akka.io.Udp.Bind]] will be notified with a [[akka.io.Udp.Bound]]
 * message. The sender of the [[akka.io.Udp.Bound]] message is the Listener actor (an internal actor responsible for
 * listening to server events). To unbind the port an [[akka.io.Tcp.Unbind]] message must be sent to the Listener actor.
 *
 * If the bind request is rejected because the Udp system is not able to register more channels (see the nr-of-selectors
 * and max-channels configuration options in the akka.io.udp section of the configuration) the sender will be notified
 * with a [[akka.io.Udp.CommandFailed]] message. This message contains the original command for reference.
 *
 * The handler provided in the [[akka.io.Udp.Bind]] message will receive inbound datagrams to the bound port
 * wrapped in [[akka.io.Udp.Received]] messages which contain the payload of the datagram and the sender address.
 *
 * UDP datagrams can be sent by sending [[akka.io.Udp.Send]] messages to the Listener actor. The sender port of the
 * outbound datagram will be the port to which the Listener is bound.
 *
 * == Simple send ==
 *
 * Udp provides a simple method of sending UDP datagrams if no reply is expected. To acquire the Sender actor
 * a SimpleSend message has to be sent to the manager. The sender of the command will be notified by a SimpleSenderReady
 * message that the service is available. UDP datagrams can be sent by sending [[akka.io.Udp.Send]] messages to the
 * sender of SimpleSenderReady. All the datagrams will contain an ephemeral local port as sender and answers will be
 * discarded.
 *
 */
private[io] class UdpManager(udp: UdpExt)
    extends SelectionHandler.SelectorBasedManager(udp.settings, udp.settings.NrOfSelectors) {

  def receive = workerForCommandHandler {
    case b: Bind =>
      val commander = sender() // cache because we create a function that will run asynchly
      (registry => Props(classOf[UdpListener], udp, registry, commander, b))

    case SimpleSender(options) =>
      val commander = sender() // cache because we create a function that will run asynchly
      (registry => Props(classOf[UdpSender], udp, registry, commander, options))
  }

}
