ChatRoom.scala

case class Administrators(userId: Long, userIds: Seq[Long])

case class Member(userId: Long, byAdministratorId: Option[Long] = None)

case class Memebers(userIds: Seq[Member])

case class Message(id: Long, value: String, senderId: Long)

case class Messages(values: Seq[Message])

case class ChatRoom(id: Long,
                    administrators: Administrators,
                    members: Members = Members.empty,
                    messsages: Messages = Messages.empty) {

  def isAddedMessage(id: Long, message: String, bySenderId: Long): ChatRoom =
    copy(messages = messages append Message(id, messages, senderId)
         
  def latestMessages: Messages = messages.withLatest
         
  def addAdministrator(userId: Long, by: Long): (ChatRoom, ) = {
    require(containsAdministrator(by))
    val newAdminisrator = Administrator(userId, Some(by))
    val newChatRoom = copy(administrators = administrators append newAdminisrator)
    (newChatRoom, newAdminisrator)
  }
         
  def removeAdministrator(userId: Long, by: Long): ChatRoom = {
    require(containsAdministrator(by))
    val newAdminisrator = Administrator(userId, Some(by))
    val newChatRoom = copy(administrators = administrators append Administrator(userId, Some(by))
    (newChatRoom, newAdminisrator)
  }
    
  def isAddedMember(userId: Long, by: Long): (ChatRoom, Member) = {
    require(containsMember(by))
    val newMember = Member(userId, Some(by))
    val newChatRoom = copy(members = members append Member(userId, Some(by)))
    (newChatRoom, newMember)
  }

  def removeMember(userId: Long, by: Long): ChatRoom = {
    require(containsInAdministrator(by))
    copy(members = members removeBy userId)
  }
  
  def isJoinedBy(userId: Long): ChatRoom = {
    require(roomType.isPublicType)
    copy(members = members append Member(userId))
  }
         
  def isLeavedBy(userId: Long): ChatRoom = {
    require(containsMembers(userId))
    copy(members = members removeBy userId)
  }
         
}
         
val room = ChatRoom(1L, Administrator(userId1))
  .isAddedMember(userId2, by = userId1)
val updatedRoom = room.isAddedMessage(1L, "Hi!", bySenderId = userId2)
val messageOnTimeLine = updatedRoom.latestMessages

usage.scala

val (updatedRoom1, member1) = room isAdded Member(userId1, by = admin1)
val (updatedRoom2, message1) = updatedRoom1 isAdded Message("Hi!", by = member1)
val latestMessages = updatedRoom2.latestMessages