limit students per class

app/controllers/Clas.scala

@@ -211,27 +211,28 @@ final class Clas(
       Ok(_)
     } else
       WithClassAndStudents(me, id) { (clas, students) =>
-        ctx.req.flash.get("created").map(_ split ' ').?? {
+        for {
+          created <- ctx.req.flash.get("created").map(_ split ' ').?? {
             case Array(userId, password) =>
               env.clas.api.student
                 .get(clas, userId)
                 .map2(lila.clas.Student.WithPassword(_, lila.user.User.ClearPassword(password)))
             case _ => fuccess(none)
-        } flatMap { created =>
-          env.clas.forms.student.generate map { createForm =>
-            Ok(
+          }
+          nbStudents <- env.clas.api.student.count(clas.id)
+          createForm <- env.clas.forms.student.generate
+        } yield Ok(
           html.clas.student.form(
             clas,
             students,
             env.clas.forms.student.invite(clas),
             createForm,
+            nbStudents,
             created
           )
         )
       }
   }
-      }
-  }
 
   def studentCreate(id: String) = SecureBody(_.Teacher) { implicit ctx => me =>
     NoTor {
@@ -241,14 +242,17 @@ final class Clas(
             .bindFromRequest()(ctx.body)
             .fold(
               err =>
+                env.clas.api.student.count(clas.id) map { nbStudents =>
                   BadRequest(
                     html.clas.student.form(
                       clas,
                       students,
                       env.clas.forms.student.invite(clas),
-                    err
+                      err,
+                      nbStudents
                     )
-                ).fuccess,
+                  )
+                },
               data =>
                 env.clas.api.student.create(clas, data, me) map {
                   case (user, password) =>
@@ -268,14 +272,17 @@ final class Clas(
         .bindFromRequest()(ctx.body)
         .fold(
           err =>
+            env.clas.api.student.count(clas.id) map { nbStudents =>
               BadRequest(
                 html.clas.student.form(
                   clas,
                   students,
                   err,
-                env.clas.forms.student.create
+                  env.clas.forms.student.create,
+                  nbStudents
                 )
-            ).fuccess,
+              )
+            },
           data =>
             env.user.repo named data.username flatMap {
               _ ?? { user =>

app/views/clas/student.scala

@@ -113,11 +113,21 @@ object student {
       students: List[Student],
       invite: Form[_],
       create: Form[_],
+      nbStudents: Int,
       created: Option[lila.clas.Student.WithPassword] = none
   )(implicit ctx: Context) =
     bits.layout(trans.clas.addStudent.txt(), Left(c withStudents students))(
       cls := "box-pad student-add",
-      h1(trans.clas.addStudent()),
+      h1(
+        trans.clas.addStudent(),
+        s" ($nbStudents/${lila.clas.Clas.maxStudents})"
+      ),
+      nbStudents > (lila.clas.Clas.maxStudents / 2) option p(dataIcon := "", cls := "text")(
+        s"Note that a class can have up to ${lila.clas.Clas.maxStudents} students.",
+        "To manage more students, ",
+        a(href := routes.Clas.studentForm(c.id.value))("create more classes"),
+        "."
+      ),
       created map {
         case Student.WithPassword(student, password) =>
           flashMessage(cls := "student-add__created")(
@@ -134,6 +144,7 @@ object student {
           )
       },
       standardFlash(),
+      (nbStudents <= lila.clas.Clas.maxStudents) option frag(
         div(cls := "student-add__choice")(
           div(cls := "info")(
             h2(trans.clas.inviteALichessAccount()),
@@ -158,14 +169,8 @@ object student {
           div(cls := "info")(
             h2(trans.clas.createANewLichessAccount()),
             p(trans.clas.createDesc1()),
-          p(
-            trans.clas.createDesc2()
-          ),
-          p(
-            strong(trans.clas.createDesc3()),
-            br,
-            trans.clas.createDesc4()
-          )
+            p(trans.clas.createDesc2()),
+            p(strong(trans.clas.createDesc3()), br, trans.clas.createDesc4())
           ),
           postForm(cls := "form3", action := routes.Clas.studentCreate(c.id.value))(
             form3.group(
@@ -182,6 +187,7 @@ object student {
           )
         )
       )
+    )
 
   def edit(clas: Clas, students: List[Student], s: Student.WithUser, form: Form[_])(implicit ctx: Context) =
     bits.layout(s.user.username, Left(clas withStudents students), s.student.some)(

modules/clas/src/main/Clas.scala

@@ -26,6 +26,8 @@ case class Clas(
 
 object Clas {
 
+  val maxStudents = 100
+
   def make(teacher: User, name: String, desc: String) = Clas(
     _id = Id(scala.util.Random.alphanumeric take 8 mkString),
     name = name,

modules/clas/src/main/ClasApi.scala

@@ -122,6 +122,8 @@ final class ClasApi(
         }
       }
 
+    def count(clasId: Clas.Id): Fu[Int] = coll.countSel($doc("clasId" -> clasId))
+
     def isManaged(user: User): Fu[Boolean] =
       coll.exists($doc("userId" -> user.id, "managed" -> true))