From fe589e384c950d72ad1065b58d7937b36df27b61 Mon Sep 17 00:00:00 2001
From: Jakob Odersky <jakob@driver.xyz>
Date: Thu, 1 Mar 2018 15:37:11 -0800
Subject: Use Akka's parameter directive to extract a pagination

---
 src/main/scala/xyz/driver/core/rest/package.scala  | 35 +++-------------
 src/test/scala/xyz/driver/core/rest/RestTest.scala | 49 ++++++++++++++++++----
 2 files changed, 48 insertions(+), 36 deletions(-)

diff --git a/src/main/scala/xyz/driver/core/rest/package.scala b/src/main/scala/xyz/driver/core/rest/package.scala
index 78d04f4..19752a1 100644
--- a/src/main/scala/xyz/driver/core/rest/package.scala
+++ b/src/main/scala/xyz/driver/core/rest/package.scala
@@ -14,7 +14,7 @@ import akka.util.ByteString
 import xyz.driver.tracing.TracingDirectives
 
 import scala.concurrent.Future
-import scala.util.{Failure, Success, Try}
+import scala.util.Try
 import scalaz.{Functor, OptionT}
 import scalaz.Scalaz.{intInstance, stringInstance}
 import scalaz.syntax.equal._
@@ -33,28 +33,10 @@ trait ServiceTransport {
       implicit mat: Materializer): Future[Unmarshal[ResponseEntity]]
 }
 
-object Pagination {
-
-  val Default = Pagination(pageSize = 100, pageNumber = 1)
-
-  def parse(query: Seq[(String, String)]): Try[Pagination] = {
-    val IntString = """(\d+)""".r
-    def validate(field: String, default: Int) = query.collectFirst { case (`field`, size) => size } match {
-      case Some(IntString(x)) if x.toInt > 0 => x.toInt
-      case Some(IntString(x))                => throw new Exception(s"$field must greater than zero (found $x)")
-      case Some(str)                         => throw new Exception(s"$field must be an integer (found $str)")
-      case None                              => default
-    }
-
-    Try {
-      Pagination(
-        validate("pageSize", Pagination.Default.pageSize),
-        validate("pageNumber", Pagination.Default.pageNumber))
-    }
-  }
-}
-
 final case class Pagination(pageSize: Int, pageNumber: Int) {
+  require(pageSize > 0, "Page size must be greater than zero")
+  require(pageNumber > 0, "Page number must be greater than zero")
+
   def offset: Int = pageSize * (pageNumber - 1)
 }
 
@@ -234,13 +216,8 @@ object `package` {
     mapRequest(request => request.mapEntity(entity => entity.transformDataBytes(Flow.fromFunction(escapeScriptTags))))
   }
 
-  val paginated: Directive1[Pagination] = parameterSeq.flatMap { params =>
-    Pagination.parse(params) match {
-      case Success(pagination) => provide(pagination)
-      case Failure(ex) =>
-        reject(ValidationRejection("invalid pagination parameter", Some(ex)))
-    }
-  }
+  val paginated: Directive1[Pagination] =
+    parameters(("pageSize".as[Int] ? 100, "pageNumber".as[Int] ? 1)).as(Pagination)
 
   def paginationQuery(pagination: Pagination) =
     Seq("pageNumber" -> pagination.pageNumber.toString, "pageSize" -> pagination.pageSize.toString)
diff --git a/src/test/scala/xyz/driver/core/rest/RestTest.scala b/src/test/scala/xyz/driver/core/rest/RestTest.scala
index 2c3fb7f..d36e04d 100644
--- a/src/test/scala/xyz/driver/core/rest/RestTest.scala
+++ b/src/test/scala/xyz/driver/core/rest/RestTest.scala
@@ -1,15 +1,50 @@
 package xyz.driver.core.rest
 
+import akka.http.scaladsl.model.StatusCodes
+import akka.http.scaladsl.server.{Directives, Route, ValidationRejection}
+import akka.http.scaladsl.testkit.ScalatestRouteTest
 import akka.util.ByteString
-import org.scalatest.{FlatSpec, Matchers}
+import org.scalatest.{Matchers, WordSpec}
+import xyz.driver.core.rest
 
-class RestTest extends FlatSpec with Matchers {
-  "`escapeScriptTags` function" should "escap script tags properly" in {
-    val dirtyString = "</sc----</sc----</sc"
-    val cleanString = "--------------------"
+class RestTest extends WordSpec with Matchers with ScalatestRouteTest with Directives {
+  "`escapeScriptTags` function" should {
+    "escape script tags properly" in {
+      val dirtyString = "</sc----</sc----</sc"
+      val cleanString = "--------------------"
 
-    (escapeScriptTags(ByteString(dirtyString)).utf8String) should be(dirtyString.replace("</sc", "< /sc"))
+      (escapeScriptTags(ByteString(dirtyString)).utf8String) should be(dirtyString.replace("</sc", "< /sc"))
 
-    (escapeScriptTags(ByteString(cleanString)).utf8String) should be(cleanString)
+      (escapeScriptTags(ByteString(cleanString)).utf8String) should be(cleanString)
+    }
+  }
+
+  "paginated directive" should {
+    val route: Route = rest.paginated { paginated =>
+      complete(StatusCodes.OK -> s"${paginated.pageNumber},${paginated.pageSize}")
+    }
+    "accept a pagination" in {
+      Get("/?pageNumber=2&pageSize=42") ~> route ~> check {
+        assert(status == StatusCodes.OK)
+        assert(entityAs[String] == "2,42")
+      }
+    }
+    "provide a default pagination" in {
+      Get("/") ~> route ~> check {
+        assert(status == StatusCodes.OK)
+        assert(entityAs[String] == "1,100")
+      }
+    }
+    "provide default values for a partial pagination" in {
+      Get("/?pageSize=2") ~> route ~> check {
+        assert(status == StatusCodes.OK)
+        assert(entityAs[String] == "1,2")
+      }
+    }
+    "reject an invalid pagination" in {
+      Get("/?pageNumber=-1") ~> route ~> check {
+        assert(rejection.isInstanceOf[ValidationRejection])
+      }
+    }
   }
 }
-- 
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