TransformerPipelineSupport.scala

/*
 * Copyright © 2011-2015 the spray project <http://spray.io>
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package spray.httpx

import scala.concurrent.{ ExecutionContext, Future }
import akka.event.{ Logging, LoggingAdapter }

trait TransformerPipelineSupport {

  def logValue[T](log: LoggingAdapter, level: Logging.LogLevel = Logging.DebugLevel): T ⇒ T =
    logValue { value ⇒ log.log(level, value.toString) }

  def logValue[T](logFun: T ⇒ Unit): T ⇒ T = { response ⇒
    logFun(response)
    response
  }

  implicit class WithTransformation[A](value: A) {
    def ~>[B](f: A ⇒ B): B = f(value)
  }

  implicit class WithTransformerConcatenation[A, B](f: A ⇒ B) extends (A ⇒ B) {
    def apply(input: A) = f(input)
    def ~>[AA, BB, R](g: AA ⇒ BB)(implicit aux: TransformerAux[A, B, AA, BB, R]) =
      new WithTransformerConcatenation[A, R](aux(f, g))
  }
}

object TransformerPipelineSupport extends TransformerPipelineSupport

trait TransformerAux[A, B, AA, BB, R] {
  def apply(f: A ⇒ B, g: AA ⇒ BB): A ⇒ R
}

object TransformerAux {
  implicit def aux1[A, B, C] = new TransformerAux[A, B, B, C, C] {
    def apply(f: A ⇒ B, g: B ⇒ C): A ⇒ C = f andThen g
  }
  implicit def aux2[A, B, C](implicit ec: ExecutionContext) =
    new TransformerAux[A, Future[B], B, C, Future[C]] {
      def apply(f: A ⇒ Future[B], g: B ⇒ C): A ⇒ Future[C] = f(_).map(g)
    }
  implicit def aux3[A, B, C](implicit ec: ExecutionContext) =
    new TransformerAux[A, Future[B], B, Future[C], Future[C]] {
      def apply(f: A ⇒ Future[B], g: B ⇒ Future[C]): A ⇒ Future[C] = f(_).flatMap(g)
    }
}