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package spray.json
package lenses

trait SeqLenses {
  /**
   * The lens which just converts another Lens into one of a
   * Seq value.
   */
  val asSeq: SeqLens = new LensImpl[Seq] {
    def updated(f: Operation)(parent: JsValue): SafeJsValue =
      f(Right(parent))

    def retr: JsValue ⇒ Validated[Seq[JsValue]] = x ⇒ Right(Seq(x))
  }

  /**
   * All the elements of a JsArray.
   */
  val elements: SeqLens = new LensImpl[Seq] {
    def updated(f: SafeJsValue ⇒ SafeJsValue)(parent: JsValue): SafeJsValue = parent match {
      case JsArray(elements) ⇒
        ops.allRight(elements.map(x ⇒ f(Right(x)))).map(JsArray(_: _*))
      case e @ _ ⇒ unexpected("Not a json array: " + e)
    }

    def retr: JsValue ⇒ Validated[Seq[JsValue]] = {
      case JsArray(elements) ⇒ Right(elements)
      case e @ _             ⇒ unexpected("Not a json array: " + e)
    }
  }

  /**
   * Like `elements` but filters elements where the `inner` lens doesn't apply
   */
  def allMatching[M[_]](inner: Lens[M]): SeqLens =
    filter(inner.retr(_).isRight) / inner.toSeq

  /**Alias for `elements`*/
  def * = elements

  /**
   * All the values of a JsArray which match the predicate.
   */
  def filter(pred: JsPred): SeqLens = new LensImpl[Seq] {
    def updated(f: SafeJsValue ⇒ SafeJsValue)(parent: JsValue): SafeJsValue = parent match {
      case JsArray(elements) ⇒
        ops.allRight(elements.map(x ⇒ if (pred(x)) f(Right(x)) else Right(x))).map(JsArray(_: _*))

      case e @ _ ⇒ unexpected("Not a json array: " + e)
    }

    def retr: JsValue ⇒ Validated[Seq[JsValue]] = {
      case JsArray(elements) ⇒
        Right(elements.filter(pred))
      case e @ _ ⇒ unexpected("Not a json array: " + e)
    }
  }
}

object SeqLenses extends SeqLenses