Add Endpoint.mapK

finagle · Sep 18, 2019 · 849ac41 · 849ac41
1 parent 42c4a2d
commit 849ac41
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Showing 2 changed files with 31 additions and 2 deletions.
diff --git a/core/src/main/scala/io/finch/Endpoint.scala b/core/src/main/scala/io/finch/Endpoint.scala
@@ -1,6 +1,6 @@
 package io.finch
 
-import cats.{Alternative, Applicative, ApplicativeError, Id, Monad, MonadError}
+import cats.{~>, Alternative, Applicative, ApplicativeError, Id, Monad, MonadError}
 import cats.data._
 import cats.effect._
 import cats.syntax.all._
@@ -170,6 +170,21 @@ trait Endpoint[F[_], A] { self =>
       final override def toString: String = self.toString
     }
 
+  /**
+    * Transform effect of endpoint given natural transformation `F ~> G`
+    */
+  final def mapK[G[_]](nat: F ~> G): Endpoint[G, A] =
+    new Endpoint[G, A] {
+      def apply(input: Input): Endpoint.Result[G, A] =
+        self(input) match {
+          case EndpointResult.Matched(rem, trc, out) => EndpointResult.Matched(rem, trc, nat(out))
+          case skipped: EndpointResult.NotMatched[F] => skipped.asInstanceOf[EndpointResult[G, A]]
+        }
+
+      final override def item = self.item
+      final override def toString: String = self.toString
+    }
+
   /**
     * Returns a product of this and `other` endpoint. The resulting endpoint returns a tuple
     * of both values.

diff --git a/core/src/test/scala/io/finch/EndpointSpec.scala b/core/src/test/scala/io/finch/EndpointSpec.scala
@@ -3,12 +3,13 @@ package io.finch
 import java.util.UUID
 import java.util.concurrent.TimeUnit
 
-import cats.data.NonEmptyList
+import cats.data.{NonEmptyList, WriterT}
 import cats.effect.{IO, Resource}
 import cats.laws._
 import cats.laws.discipline._
 import cats.laws.discipline.AlternativeTests
 import cats.laws.discipline.SemigroupalTests.Isomorphisms
+import cats.~>
 import com.twitter.finagle.http.{Cookie, Method, Request}
 import com.twitter.io.Buf
 import io.finch.data.Foo
@@ -411,4 +412,17 @@ class EndpointSpec extends FinchSpec {
       asFunction.apply(p).attempt.unsafeRunSync() === Left(e)
     }}
   }
+
+  it should "transform F[_] to G[_] effect" in {
+    type W[A] = WriterT[IO, List[String], A]
+
+    check { (ep: Endpoint[IO, Int], input: Input) => {
+      val nat = new (IO ~> W) {
+        def apply[A](fa: IO[A]): WriterT[IO, List[String], A] = WriterT.liftF(fa)
+      }
+
+      ep.mapK(nat)(input).awaitOutput() === ep(input).awaitOutput()
+    }
+    }
+  }
 }