PerfStatFilter.scala

object MetaDataFilter extends EssentialFilter{
  def apply(next: EssentialAction) = new EssentialAction {
    def apply(rh: RequestHeader): Iteratee[Array[Byte], Result] = {
      val timeStart = System.currentTimeMillis
      def bodyToStr: Enumeratee[Any, String] = Enumeratee.map(s => s.toString)

      def addMetadata(result: PlainResult): Result = {
        val timeElapsed = System.currentTimeMillis - timeStart

        result match {
          case SimpleResult(header, content) => {
            val metaDataId = rh.headers.get("MetaData-Id").getOrElse("-1")
            val urls = MetaData.findUrlsById(metaDataId)        
            
            //convert body to a string
            val contentStr = content.through(bodyToStr)

            //consume body, if it's a JsArray, ignore, otherwise add the metadata
            val body: String = Await.result(Iteratee.flatten(contentStr(Iteratee.consume[String]())).run, Duration.Inf)

            //add metadata if this is a JsObject
            val newBody = Try(Json.parse(body)).map {
              case js:JsObject => (js ++ Json.obj("TIME" -> timeElapsed, "METADATA" -> urls)).toString()
              case _ => body
            }.recover{
              case _ => body
            }.get

            SimpleResult(result.header, Enumerator(newBody))
          }
          case _ => Logger.info("NO MATCH");  result
        }
      }

      val iteratee: Iteratee[Array[Byte], Result] = next(rh).map {
        case plain: PlainResult if (plain.header.headers.getOrElse("Content-Type", "").contains("json") && !rh.uri.contains("api-docs")) => addMetadata(plain)
        case async: AsyncResult => async.transform(addMetadata)
        case r: Result => r
      }

      iteratee
    }
  }
}