From 1ecaf78e466aa6df37379d5202c3f907aefd3775 Mon Sep 17 00:00:00 2001
From: Kseniya Tomskikh <ktomskih@datamonsters.co>
Date: Thu, 1 Mar 2018 18:24:01 +0700
Subject: TRIAL-287 Created ListResponse class and directive for pagination
 parsing

---
 src/main/scala/xyz/driver/core/rest/package.scala | 44 +++++++++++++++++++++--
 1 file changed, 42 insertions(+), 2 deletions(-)

diff --git a/src/main/scala/xyz/driver/core/rest/package.scala b/src/main/scala/xyz/driver/core/rest/package.scala
index 5fd9417..78d04f4 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.Try
+import scala.util.{Failure, Success, Try}
 import scalaz.{Functor, OptionT}
 import scalaz.Scalaz.{intInstance, stringInstance}
 import scalaz.syntax.equal._
@@ -36,10 +36,39 @@ trait ServiceTransport {
 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) {
-  def offset: Int = pageSize * pageNumber
+  def offset: Int = pageSize * (pageNumber - 1)
+}
+
+final case class ListResponse[+T](items: Seq[T], meta: ListResponse.Meta)
+
+object ListResponse {
+
+  final case class Meta(itemsCount: Int, pageNumber: Int, pageSize: Int)
+
+  object Meta {
+    def apply(itemsCount: Int, pagination: Pagination): Meta =
+      Meta(itemsCount, pagination.pageNumber, pagination.pageSize)
+  }
+
 }
 
 object `package` {
@@ -204,4 +233,15 @@ object `package` {
   val sanitizeRequestEntity: Directive0 = {
     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)))
+    }
+  }
+
+  def paginationQuery(pagination: Pagination) =
+    Seq("pageNumber" -> pagination.pageNumber.toString, "pageSize" -> pagination.pageSize.toString)
 }
-- 
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