es.scala

sealed trait Content
case class One(value: String) extends Content
case class Two(value: Int) extends Content

sealed trait AbstractCommand
case class IndexCommand(c: String) extends AbstractCommand
case class UpdateCommand(c: Int) extends AbstractCommand

trait Indexer {
  def index(content: Content): Unit
  def index(contents: Iterable[Content]): Unit
}

trait Client {
  def execute(command: IndexCommand): Unit
  def execute(command: UpdateCommand): Unit
}

class IndexerImpl extends Indexer {
  val client = new Client {
    override def execute(command: IndexCommand): Unit = ???
    override def execute(command: UpdateCommand): Unit = ???
  }

  implicit class ClientExtra(client: Client) {
    def executeCommand(command: AbstractCommand): Unit = {
      command match {
        case c: IndexCommand => client.execute(c)
        case c: UpdateCommand => client.execute(c)
      }
    }
  }

  override def index(content: Content): Unit = client.executeCommand(createCommand(content))
  override def index(contents: Iterable[Content]): Unit = {
    contents.foreach(c => client.executeCommand(createCommand(c)))
  }

  private def createCommand(content: Content): AbstractCommand = {
    content match {
      case One(c) => new IndexCommand(c)
      case Two(c) => new UpdateCommand(c)
    }
  }
}