make NameGenerator check availability

app/controllers/Clas.scala

@@ -95,16 +95,18 @@ final class Clas(
             .get(clas, userId)
             .map2(lila.clas.Student.WithPassword(_, lila.user.User.ClearPassword(password)))
         case _ => fuccess(none)
-      } map { created =>
+      } flatMap { created =>
-        Ok(
+        env.clas.forms.student.generate map { createForm =>
-          html.clas.student.form(
+          Ok(
-            clas,
+            html.clas.student.form(
-            students,
+              clas,
-            env.clas.forms.student.invite,
+              students,
-            env.clas.forms.student.create,
+              env.clas.forms.student.invite,
-            created
+              createForm,
+              created
+            )
           )
-        )
+        }
       }
     }
   }

modules/clas/src/main/ClasForm.scala

@@ -6,8 +6,9 @@ import scala.concurrent.duration._
 
 final class ClasForm(
     lightUserAsync: lila.common.LightUser.Getter,
-    securityForms: lila.security.DataForm
+    securityForms: lila.security.DataForm,
-) {
+    nameGenerator: NameGenerator
+)(implicit ec: scala.concurrent.ExecutionContext) {
 
   import ClasForm._
 
@@ -27,13 +28,21 @@ final class ClasForm(
 
   object student {
 
-    def create =
+    def create: Form[NewStudent] =
       Form(
         mapping(
           "username" -> securityForms.signup.username,
-          "realName" -> nonEmptyText
+          "realName" -> nonEmptyText(maxLength = 100)
         )(NewStudent.apply)(NewStudent.unapply)
-      ) fill generateStudent
+      )
+
+    def generate: Fu[Form[NewStudent]] = nameGenerator() map { username =>
+      create fill
+        NewStudent(
+          username = ~username,
+          realName = ""
+        )
+    }
 
     def invite =
       Form(
@@ -75,11 +84,6 @@ object ClasForm {
       realName: String
   )
 
-  def generateStudent = NewStudent(
-    username = ~NameGenerator(),
-    realName = ""
-  )
-
   case class StudentData(
       realName: String,
       notes: String

modules/clas/src/main/Env.scala

@@ -1,6 +1,5 @@
 package lila.clas
 
-import play.api.Configuration
 import com.softwaremill.macwire._
 
 import lila.common.config._
@@ -16,6 +15,8 @@ final class Env(
     baseUrl: BaseUrl
 )(implicit ec: scala.concurrent.ExecutionContext) {
 
+  lazy val nameGenerator = wire[NameGenerator]
+
   lazy val forms = wire[ClasForm]
 
   private val colls = wire[ClasColls]

modules/clas/src/main/NameGenerator.scala

@@ -1,14 +1,18 @@
 package lila.clas
 
 import scala.util.Random
+import scala.concurrent.ExecutionContext
 
-private object NameGenerator {
+final class NameGenerator(userRepo: lila.user.UserRepo)(implicit ec: ExecutionContext) {
 
-  def apply(maxSize: Int = 16, triesLeft: Int = 100): Option[String] = {
+  def apply(maxSize: Int = 16, triesLeft: Int = 100): Fu[Option[String]] = {
     val name = anyOf(combinations).map(anyOf).mkString
-    if (name.size <= maxSize) name.some
+    if (name.size <= maxSize) userRepo.nameExists(name) flatMap {
+      case true => apply(maxSize, triesLeft - 1)
+      case _    => fuccess(name.some)
+    }
     else if (triesLeft > 0) apply(maxSize, triesLeft - 1)
-    else none
+    else fuccess(none)
   }
 
   private def anyOf[A](vec: Vector[A]): A =