Hi.scala

import scala.concurrent.duration._

object Hi extends App {

  case class A[K](k: K)

  /**
   * Settings for producers. See `akka.kafka.producer` section in
   * reference.conf. Note that the [[ProducerSettings companion]] object provides
   * `apply` and `create` functions for convenient construction of the settings, together with
   * the `with` methods.
   */
  final class ProducerSettings[K, V](
    val properties: Map[String, String],
    val keySerializerOpt: Option[A[K]],
    val valueSerializerOpt: Option[A[V]],
    val closeTimeout: FiniteDuration,
    val parallelism: Int,
    val dispatcher: String
  ) {

    /**
     * The raw properties of the kafka-clients driver, see constants in
     * `org.apache.kafka.clients.producer.ProducerConfig`.
     */
    def withProperty(key: String, value: String): ProducerSettings[K, V] =
      copy(properties = properties.updated(key, value))

    def withCloseTimeout(closeTimeout: FiniteDuration): ProducerSettings[K, V] =
      copy(closeTimeout = closeTimeout)

    def withParallelism(parallelism: Int): ProducerSettings[K, V] =
      copy(parallelism = parallelism)

    def withDispatcher(dispatcher: String): ProducerSettings[K, V] =
      copy(dispatcher = dispatcher)

    private def copy(
      properties: Map[String, String] = properties,
      keySerializer: Option[A[K]] = keySerializerOpt,
      valueSerializer: Option[A[V]] = valueSerializerOpt,
      closeTimeout: FiniteDuration = closeTimeout,
      parallelism: Int = parallelism,
      dispatcher: String = dispatcher
    ): ProducerSettings[K, V] =
      new ProducerSettings[K, V](properties, keySerializer, valueSerializer, closeTimeout, parallelism, dispatcher)

  }

  def getConnectionString(username: String, password: String): String =
    raw"""org.apache.kafka.common.security.plain.PlainLoginModule required username="$username" password="$password";"""

  def getGenericSettings(): Map[String, String] =
    Map("request.timeout.ms" -> "20000", "retry.backoff.ms" -> "500")

  def getConfluentSettings(listener: String,
    username: String,
    password: String): Map[String, String] =
    Map(
      "listeners" -> listener,
      "security.protocol" -> "SASL_SSL",
      "sasl.mechanism" -> "PLAIN",
      "sasl.jaas.config" -> getConnectionString(username, password)
    )

  def connect[K, V](settings: ProducerSettings[K, V],
    listener: String,
    username: Option[String],
    password: Option[String],
    other: Option[Map[String, String]]): ProducerSettings[K, V] = {
    val m1 = getGenericSettings() ++ other.getOrElse(Map())
    val result = (for {
      u <- username
      p <- password
    } yield getConfluentSettings(listener, u, p)).getOrElse(Map()) ++ m1
    result.foldLeft(settings)((a, b) => a.withProperty(b._1, b._2))
  }

  val producer = new ProducerSettings[String, String](Map(), None, None, 5 seconds, 2, "hi")

  print(connect(producer, "hi", Some("kappa"), Some("keepo"), None).properties)
}