Spray multimap for form fields and parameters

spray-multimap.scala

type MultiMap = Map[String, List[String]]

def formFieldMultiMap: Directive1[MultiMap] = {
  requestInstance.flatMap[MultiMap :: HNil] { request =>
    import spray.httpx.unmarshalling._

    val result: Deserialized[MultiMap] =
      request.as[HttpForm].right.flatMap {
        case FormData(fields) =>
          val collected = fields.groupBy { case (k, _) => k }
          val valuesOnly = collected.mapValues(_.map { case (_, v) => v } toList)
          Right(valuesOnly)
        case _ =>
          Left(MalformedContent(s"Unable to construct form multi map"))
      }

    result match {
      case Right(value)                       ⇒ provide(value)
      case Left(ContentExpected)              ⇒ reject(MissingFormFieldRejection("form"))
      case Left(MalformedContent(msg, cause)) ⇒ reject(MalformedFormFieldRejection("form", msg, cause))
      case Left(UnsupportedContentType(msg))  ⇒ reject(UnsupportedRequestContentTypeRejection(msg))
    }
  }
}

def anyMultiMap: Directive1[MultiMap] =
  for {
    params <- parameterMultiMap
    fields <- formFieldMultiMap
  } yield fields.foldLeft(params) {
    case (map, (fk, fv)) if map.contains(fk) =>
      map.updated(fk, map(fk) ++ fv)
    case (map, field) =>
      map + field
  }