def headSourceFile()

in app/services/FileMove/ImprovedLargeFileCopier.scala [332:381]
48 lines of code
7 McCabe index (conditional complexity)

  def headSourceFile(region:Regions, credentialsProvider: Option[AwsCredentialsProvider], sourceBucket: String, sourceKey:String, sourceVersion:Option[String])
                    (implicit poolClientFlow:HostConnectionPool[Any]) = {
    val req = createRequest(HttpMethods.HEAD, region, sourceBucket, sourceKey, sourceVersion)(ImprovedLargeFileCopier.NoRequestCustomisation)
    Source
      .single(req)
      .mapAsync(1)(reqparts=>doRequestSigning(reqparts._1, region, credentialsProvider).map(req=>(req, reqparts._2)))
      .map(reqparts=>{
        logger.info(s"Request to send has ${reqparts._1.headers.length} headers.  Signed request headers:")
        reqparts._1.headers.foreach(hdr=>logger.info(s"\t${hdr.name()}: ${hdr.value()}"))
        reqparts
      })
      .via(poolClientFlow)
      .runWith(Sink.head)
      .map({
        case (Success(result), _) =>
          (result.status: @switch) match {
            case StatusCodes.OK =>
              logger.info(s"HEAD success on $sourceBucket/$sourceKey@${sourceVersion.getOrElse("LATEST")}")
              result.headers.foreach(hdr => {
                logger.debug(s"\t${hdr.name()} => ${hdr.value()}")
              })
              result.discardEntityBytes()
              Some(ImprovedLargeFileCopier.HeadInfo(sourceBucket, sourceKey, sourceVersion,
                result.headers, result.entity.contentType, result.entity.contentLengthOption)
              )
            case StatusCodes.NotFound=>
              result.discardEntityBytes()
              logger.warn(s"No file found for $sourceBucket/$sourceKey@${sourceVersion.getOrElse("LATEST")}")
              None
            case StatusCodes.Forbidden=>
              val contentFut = result
                .entity
                .dataBytes
                .runWith(Sink.fold(ByteString.empty)(_ ++ _))
              //only for debugging!!
              val content = Await.result(contentFut, 10.seconds)

              logger.error(s"Access was forbidden to $sourceBucket/$sourceKey@${sourceVersion.getOrElse("LATEST")}: '${content.utf8String}'")
              throw new RuntimeException("Access forbidden")
            case _=>
              result.discardEntityBytes()
              logger.error(s"Unexpected response from S3 in HEAD operation: ${result.status.value}")
              throw new RuntimeException(s"Unexpected response from S3: ${result.status.value}")
          }
        case (Failure(err), _) =>
          logger.error(s"Could not retrieve metadata for s3://$sourceBucket/$sourceKey@${sourceVersion.getOrElse("LATEST")}:" +
            s" ${err.getMessage}", err)
          throw err //fail the future
      })
  }