add bidirectional id type mappers

2 files changed, 8 insertions, 3 deletions

diff --git a/src/main/scala/xyz/driver/core/core.scala b/src/main/scala/xyz/driver/core/core.scala
index 8c13aeb..cbc5ce9 100644
--- a/src/main/scala/xyz/driver/core/core.scala
+++ b/src/main/scala/xyz/driver/core/core.scala
@@ -38,9 +38,16 @@ package core {
     implicit def idEqual[T]: Equal[Id[T]]       = Equal.equal[Id[T]](_ == _)
     implicit def idOrdering[T]: Ordering[Id[T]] = Ordering.by[Id[T], String](_.value)
 
+    sealed trait Mapper[Entity, Row]
     object Mapper {
-      def apply[A, B]: (Id[A] => Id[B]) = (id: Id[A]) => Id[B](id.value)
+      def apply[Entity, Row] = new Mapper[Entity, Row] {}
     }
+
+    implicit def to[Row, Entity](rowId: Id[Row])(implicit ev: Mapper[Entity, Row]): Id[Entity] =
+      Id[Entity](rowId.value)
+
+    implicit def from[Entity, Row](entityId: Id[Entity])(implicit ev: Mapper[Entity, Row]): Id[Row] =
+      Id[Row](entityId.value)
   }
 
   final case class Name[+Tag](value: String) extends AnyVal {
diff --git a/src/test/scala/xyz/driver/core/CoreTest.scala b/src/test/scala/xyz/driver/core/CoreTest.scala
index e210887..520fe8e 100644
--- a/src/test/scala/xyz/driver/core/CoreTest.scala
+++ b/src/test/scala/xyz/driver/core/CoreTest.scala
@@ -45,9 +45,7 @@ class CoreTest extends FlatSpec with Matchers with MockitoSugar {
     final case class Z(id: Id[Z])
 
     implicit val xy = Id.Mapper[X, Y]
-    implicit val yx = Id.Mapper[Y, X]
     implicit val yz = Id.Mapper[Y, Z]
-    implicit val zy = Id.Mapper[Z, Y]
 
     // The real test is that the following statements compile:
     val x  = X(Id("0"))