Optics for Http request

HttpOptics.scala

package monocle.example

import monocle.Prism
import monocle.macros.Lenses
import monocle.function._
import monocle.std.map._
import monocle.std.string._

import scalaz.Equal

object HttpRequestExample extends App {

  sealed trait Method
  object Method {
    case object GET  extends Method
    case object POST extends Method

    implicit val eq: Equal[Method] = Equal.equalA[Method]
  }


  @Lenses case class URI(hostname: String, port: Int, path: String, query: Map[String, String])
  @Lenses case class Request(method: Method, uri: URI, headers: Map[String, String], body: String)

  import monocle.example.HttpRequestExample.{URI => U, Request => R}
  import Method._

  val _GET  = Prism.only[Method](GET)
  val _POST = Prism.only[Method](POST)

  val r = Request(
    method  = GET,
    uri     = URI("localhost", 8080, "/ping", Map("age" -> "15")),
    headers = Map.empty,
    body    = ""
  )

  R.method.get(r) // GET

  (R.method composePrism _GET).isMatching(r) // true

  (R.uri composeLens U.query composeOptional index("age")).modify(_ + 1)(r)

  (R.headers composeLens at("Content-Length")).set(Some("0"))(r)

  val r2 = Request(
    method  = POST,
    uri     = URI("localhost", 8080, "/pong", Map.empty),
    headers = Map("x-custom1" -> "5", "x-custom2" -> "10"),
    body    = "some body"
  )

  (R.headers composeTraversal filterIndex((_: String).startsWith("x-")) composePrism stringToInt).modify(_ * 2)(r2)
}