/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * license agreements; and to You under the Apache License, version 2.0:
 *
 *   https://www.apache.org/licenses/LICENSE-2.0
 *
 * This file is part of the Apache Pekko project, which was derived from Akka.
 */

/*
 * Copyright (C) 2009-2022 Lightbend Inc. <https://www.lightbend.com>
 */

package org.apache.pekko.cluster

import scala.runtime.AbstractFunction2

import scala.annotation.nowarn

import org.apache.pekko
import pekko.actor.Address
import pekko.annotation.InternalApi
import pekko.cluster.ClusterSettings.DataCenter
import pekko.cluster.MemberStatus._
import pekko.util.Version

/**
 * Represents the address, current status, and roles of a cluster member node.
 *
 * Note: `hashCode` and `equals` are solely based on the underlying `Address`, not its `MemberStatus`
 * and roles.
 */
@SerialVersionUID(1L)
class Member private[cluster] (
    val uniqueAddress: UniqueAddress,
    private[cluster] val upNumber: Int, // INTERNAL API
    val status: MemberStatus,
    val roles: Set[String],
    val appVersion: Version)
    extends Serializable {

  lazy val dataCenter: DataCenter = roles
    .find(_.startsWith(ClusterSettings.DcRolePrefix))
    .getOrElse(throw new IllegalStateException("DataCenter undefined, should not be possible"))
    .substring(ClusterSettings.DcRolePrefix.length)

  def address: Address = uniqueAddress.address

  override def hashCode: Int = uniqueAddress.##
  override def equals(other: Any): Boolean = other match {
    case m: Member => uniqueAddress == m.uniqueAddress
    case _         => false
  }
  override def toString: String = {
    s"Member($address, $status${if (dataCenter == ClusterSettings.DefaultDataCenter) ""
      else s", $dataCenter"}${if (appVersion == Version.Zero) ""
      else s", $appVersion"})"
  }

  def hasRole(role: String): Boolean = roles.contains(role)

  /**
   * Java API
   */
  @nowarn("msg=deprecated")
  def getRoles: java.util.Set[String] = {
    import pekko.util.ccompat.JavaConverters._
    roles.asJava
  }

  /**
   * Is this member older, has been part of cluster longer, than another
   * member. It is only correct when comparing two existing members in a
   * cluster. A member that joined after removal of another member may be
   * considered older than the removed member.
   *
   * Note that it only makes sense to compare with other members of
   * same data center (upNumber has a higher risk of being reused across data centers).
   * To avoid mistakes of comparing members of different data centers this
   * method will throw `IllegalArgumentException` if the members belong
   * to different data centers.
   */
  @throws[IllegalArgumentException]("if members from different data centers")
  def isOlderThan(other: Member): Boolean = {
    if (dataCenter != other.dataCenter)
      throw new IllegalArgumentException(
        "Comparing members of different data centers with isOlderThan is not allowed. " +
        s"[$this] vs. [$other]")
    if (upNumber == other.upNumber)
      Member.addressOrdering.compare(address, other.address) < 0
    else
      upNumber < other.upNumber
  }

  def copy(status: MemberStatus): Member = {
    val oldStatus = this.status
    if (status == oldStatus) this
    else {
      require(allowedTransitions(oldStatus)(status), s"Invalid member status transition [ $this -> $status]")
      new Member(uniqueAddress, upNumber, status, roles, appVersion)
    }
  }

  def copyUp(upNumber: Int): Member = {
    new Member(uniqueAddress, upNumber, status, roles, appVersion).copy(Up)
  }
}

/**
 * Module with factory and ordering methods for Member instances.
 */
object Member {

  val none = Set.empty[Member]

  /**
   * INTERNAL API
   * Create a new member with status Joining.
   */
  @InternalApi
  private[pekko] def apply(uniqueAddress: UniqueAddress, roles: Set[String], appVersion: Version): Member =
    new Member(uniqueAddress, Int.MaxValue, Joining, roles, appVersion)

  /**
   * INTERNAL API
   */
  private[cluster] def removed(node: UniqueAddress): Member =
    new Member(node, Int.MaxValue, Removed, Set(ClusterSettings.DcRolePrefix + "-N/A"), Version.Zero)

  /**
   * `Address` ordering type class, sorts addresses by host and port.
   */
  implicit val addressOrdering: Ordering[Address] = Ordering.fromLessThan[Address] { (a, b) =>
    // cluster node identifier is the host and port of the address; protocol and system is assumed to be the same
    if (a eq b) false
    else if (a.host != b.host) a.host.getOrElse("").compareTo(b.host.getOrElse("")) < 0
    else if (a.port != b.port) a.port.getOrElse(0) < b.port.getOrElse(0)
    else false
  }

  /**
   * INTERNAL API
   * Orders the members by their address except that members with status
   * Joining, Exiting and Down are ordered last (in that order).
   */
  private[cluster] val leaderStatusOrdering: Ordering[Member] = Ordering.fromLessThan[Member] { (a, b) =>
    (a.status, b.status) match {
      case (as, bs) if as == bs => ordering.compare(a, b) <= 0
      case (Down, _)            => false
      case (_, Down)            => true
      case (Exiting, _)         => false
      case (_, Exiting)         => true
      case (Joining, _)         => false
      case (_, Joining)         => true
      case (WeaklyUp, _)        => false
      case (_, WeaklyUp)        => true
      case _                    => ordering.compare(a, b) <= 0
    }
  }

  /**
   * `Member` ordering type class, sorts members by host and port.
   */
  implicit val ordering: Ordering[Member] = new Ordering[Member] {
    def compare(a: Member, b: Member): Int = {
      a.uniqueAddress.compare(b.uniqueAddress)
    }
  }

  /**
   * Sort members by age, i.e. using [[Member#isOlderThan]].
   *
   * Note that it only makes sense to compare with other members of
   * same data center. To avoid mistakes of comparing members of different
   * data centers it will throw `IllegalArgumentException` if the
   * members belong to different data centers.
   */
  val ageOrdering: Ordering[Member] = Ordering.fromLessThan[Member] { (a, b) =>
    a.isOlderThan(b)
  }

  @deprecated("Was accidentally made a public API, internal", since = "Akka 2.5.4")
  def pickHighestPriority(a: Set[Member], b: Set[Member]): Set[Member] =
    pickHighestPriority(a, b, Map.empty)

  /**
   * INTERNAL API.
   */
  @InternalApi
  private[pekko] def pickHighestPriority(
      a: Set[Member],
      b: Set[Member],
      tombstones: Map[UniqueAddress, Long]): Set[Member] = {
    // group all members by Address => Seq[Member]
    val groupedByAddress = (a.toSeq ++ b.toSeq).groupBy(_.uniqueAddress)
    // pick highest MemberStatus
    groupedByAddress.foldLeft(Member.none) {
      case (acc, (_, members)) =>
        if (members.size == 2) acc + members.reduceLeft(highestPriorityOf)
        else {
          val m = members.head
          if (tombstones.contains(m.uniqueAddress) || MembershipState.removeUnreachableWithMemberStatus(m.status))
            acc // removed
          else acc + m
        }
    }
  }

  /**
   * Picks the Member with the highest "priority" MemberStatus.
   * Where highest priority is furthest along the membership state machine
   */
  def highestPriorityOf(m1: Member, m2: Member): Member = {
    if (m1.status == m2.status)
      // preserve the oldest in case of different upNumber
      if (m1.isOlderThan(m2)) m1 else m2
    else
      (m1.status, m2.status) match {
        case (Removed, _)              => m1
        case (_, Removed)              => m2
        case (ReadyForShutdown, _)     => m1
        case (_, ReadyForShutdown)     => m2
        case (Down, _)                 => m1
        case (_, Down)                 => m2
        case (Exiting, _)              => m1
        case (_, Exiting)              => m2
        case (Leaving, _)              => m1
        case (_, Leaving)              => m2
        case (Joining, _)              => m2
        case (_, Joining)              => m1
        case (WeaklyUp, _)             => m2
        case (_, WeaklyUp)             => m1
        case (PreparingForShutdown, _) => m1
        case (_, PreparingForShutdown) => m2
        case (Up, Up)                  => m1
      }
  }

}

/**
 * Defines the current status of a cluster member node
 *
 * Can be one of: Joining, WeaklyUp, Up, Leaving, Exiting and Down and Removed.
 */
sealed abstract class MemberStatus

object MemberStatus {
  @SerialVersionUID(1L) case object Joining extends MemberStatus
  @SerialVersionUID(1L) case object WeaklyUp extends MemberStatus
  @SerialVersionUID(1L) case object Up extends MemberStatus
  @SerialVersionUID(1L) case object Leaving extends MemberStatus
  @SerialVersionUID(1L) case object Exiting extends MemberStatus
  @SerialVersionUID(1L) case object Down extends MemberStatus
  @SerialVersionUID(1L) case object Removed extends MemberStatus
  @SerialVersionUID(1L) case object PreparingForShutdown extends MemberStatus
  @SerialVersionUID(1L) case object ReadyForShutdown extends MemberStatus

  /**
   * Java API: retrieve the `Joining` status singleton
   */
  def joining: MemberStatus = Joining

  /**
   * Java API: retrieve the `WeaklyUp` status singleton.
   */
  def weaklyUp: MemberStatus = WeaklyUp

  /**
   * Java API: retrieve the `Up` status singleton
   */
  def up: MemberStatus = Up

  /**
   * Java API: retrieve the `Leaving` status singleton
   */
  def leaving: MemberStatus = Leaving

  /**
   * Java API: retrieve the `Exiting` status singleton
   */
  def exiting: MemberStatus = Exiting

  /**
   * Java API: retrieve the `Down` status singleton
   */
  def down: MemberStatus = Down

  /**
   * Java API: retrieve the `Removed` status singleton
   */
  def removed: MemberStatus = Removed

  /**
   * Java API: retrieve the `ShuttingDown` status singleton
   */
  def shuttingDown: MemberStatus = PreparingForShutdown

  /**
   * Java API: retrieve the `ShutDown` status singleton
   */
  def shutDown: MemberStatus = ReadyForShutdown

  /**
   * INTERNAL API
   */
  private[cluster] val allowedTransitions: Map[MemberStatus, Set[MemberStatus]] =
    Map(
      Joining -> Set(WeaklyUp, Up, Leaving, Down, Removed),
      WeaklyUp -> Set(Up, Leaving, Down, Removed),
      Up -> Set(Leaving, Down, Removed, PreparingForShutdown),
      Leaving -> Set(Exiting, Down, Removed),
      Down -> Set(Removed),
      Exiting -> Set(Removed, Down),
      PreparingForShutdown -> Set(ReadyForShutdown, Removed, Leaving, Down),
      ReadyForShutdown -> Set(Removed, Leaving, Down),
      Removed -> Set.empty[MemberStatus])
}

object UniqueAddress extends AbstractFunction2[Address, Int, UniqueAddress] {
  // for binary compatibility
  @deprecated("Use Long UID apply instead", since = "Akka 2.4.11")
  def apply(address: Address, uid: Int) = new UniqueAddress(address, uid.toLong)

  def apply(remoteUniqueAddress: pekko.remote.UniqueAddress): UniqueAddress =
    new UniqueAddress(remoteUniqueAddress.address, remoteUniqueAddress.uid)

  def apply(address: Address, longUid: Long) = new UniqueAddress(address, longUid)

  def unapply(address: UniqueAddress): Option[(Address, Long)] = Some((address.address, address.longUid))
}

/**
 * Member identifier consisting of address and random `uid`.
 * The `uid` is needed to be able to distinguish different
 * incarnations of a member with same hostname and port.
 */
@SerialVersionUID(1L)
final class UniqueAddress(val address: Address, val longUid: Long)
    extends Product
    with Serializable
    with Ordered[UniqueAddress] {

  override def hashCode = java.lang.Long.hashCode(longUid)

  override def productArity: Int = 2
  override def productElement(n: Int): Any = n match {
    case 0 => address
    case 1 => longUid
  }
  override def canEqual(that: Any): Boolean = that.isInstanceOf[UniqueAddress]

  override def equals(obj: Any): Boolean =
    obj match {
      case ua: UniqueAddress => this.address.equals(ua.address) && this.longUid.equals(ua.longUid)
      case _                 => false
    }

  override def toString = s"UniqueAddress($address,$longUid)"

  def compare(that: UniqueAddress): Int = {
    val result = Member.addressOrdering.compare(this.address, that.address)
    if (result == 0) if (this.longUid < that.longUid) -1 else if (this.longUid == that.longUid) 0 else 1
    else result
  }

  // for binary compatibility

  @deprecated("Use Long UID constructor instead", since = "Akka 2.4.11")
  def this(address: Address, uid: Int) = this(address, uid.toLong)

  @deprecated("Use longUid instead", since = "Akka 2.4.11")
  def uid = longUid.toInt

  /**
   * For binary compatibility
   * Stops `copy(Address, Long)` copy from being generated, use `apply` instead.
   */
  @deprecated("Use Long UID constructor instead", since = "Akka 2.4.11")
  @nowarn("msg=deprecated")
  def copy(address: Address = address, uid: Int = uid) = new UniqueAddress(address, uid.toLong)

}
