Add instance for QueryParamDecoder[FUUID]

build.sbt

@@ -51,6 +51,7 @@ lazy val http4s = project.in(file("modules/http4s"))
   .settings(
     name := "fuuid-http4s",
     libraryDependencies ++= Seq(
+      "org.http4s" %% "http4s-core" % http4sV,
       "org.http4s" %% "http4s-dsl" % http4sV % Test
     )
   )

modules/http4s/src/main/scala/io/chrisdavenport/fuuid/http4s/implicits.scala

@@ -0,0 +1,23 @@
+package io.chrisdavenport.fuuid.http4s
+
+import io.chrisdavenport.fuuid.FUUID
+import cats.data.ValidatedNel
+import cats.syntax.either._
+import org.http4s.QueryParamDecoder
+import org.http4s.QueryParameterValue
+import org.http4s.ParseFailure
+
+object implicits {
+  implicit val fuuidQueryParamDecoder: QueryParamDecoder[FUUID] =
+    new QueryParamDecoder[FUUID] {
+      def decode(value: QueryParameterValue): ValidatedNel[ParseFailure, FUUID] =
+        FUUID
+          .fromString(value.value)
+          .leftMap(
+            _ =>
+              ParseFailure(
+                "Failed to parse FUUID query parameter",
+                s"Could not parse ${value.value} as a FUUID"))
+          .toValidatedNel
+    }
+}

modules/http4s/src/test/scala/io/chrisdavenport/fuuid/http4s/FUUIDQueryParamDecoder.scala

@@ -0,0 +1,24 @@
+package io.chrisdavenport.fuuid.http4s
+
+import io.chrisdavenport.fuuid.{FUUID, FUUIDArbitraries}
+import io.chrisdavenport.fuuid.http4s.implicits._
+import org.http4s.dsl.io._
+import org.scalacheck._
+import org.specs2.ScalaCheck
+import org.specs2.mutable.Specification
+
+class FUUIDQueryParamDecoder extends Specification with ScalaCheck with FUUIDArbitraries {
+
+  object IdQueryParamMatcher extends QueryParamDecoderMatcher[FUUID]("id")
+
+  "FUUID QueryParamDecoder" should {
+
+    "work properly given a valid UUID" in prop { validFuuid: FUUID =>
+      IdQueryParamMatcher.unapply(Map("id" -> List(validFuuid.show))) must beSome(validFuuid)
+    }
+
+    "fail given an invalid UUID" in prop { invalidUuid: String =>
+      IdQueryParamMatcher.unapply(Map("id" -> List(invalidUuid))) must beNone
+    }.setArbitrary(Arbitrary(Gen.alphaStr))
+  }
+}