automatically create a new study chapter when the last one is deleted

modules/study/src/main/ChapterMaker.scala

@@ -181,13 +181,13 @@ private[study] object ChapterMaker {
 
   case class Data(
       name: Chapter.Name,
-      game: Option[String],
-      variant: Option[String],
-      fen: Option[String],
-      pgn: Option[String],
-      orientation: String,
-      mode: String,
-      initial: Boolean
+      game: Option[String] = None,
+      variant: Option[String] = None,
+      fen: Option[String] = None,
+      pgn: Option[String] = None,
+      orientation: String = "white",
+      mode: String = ChapterMaker.Mode.Normal.key,
+      initial: Boolean = false
   ) extends ChapterData
 
   case class EditData(

modules/study/src/main/StudyApi.scala

@@ -553,14 +553,21 @@ final class StudyApi(
     Contribute(byUserId, study) {
       chapterRepo.byIdAndStudy(chapterId, studyId) flatMap {
         _ ?? { chapter =>
-          chapterRepo.orderedMetadataByStudy(studyId).flatMap {
-            case chaps if chaps.size > 1 => (study.position.chapterId == chapterId).?? {
+          chapterRepo.orderedMetadataByStudy(studyId).flatMap { chaps =>
+            // deleting the only chapter? Automatically create an empty one
+            if (chaps.size < 2) {
+              chapterMaker(study, ChapterMaker.Data(Chapter.Name("Chapter 1")), 1, byUserId) flatMap {
+                _ ?? { c =>
+                  doAddChapter(study, c, sticky = true, uid) >> doSetChapter(study, c.id, uid)
+                }
+              }
+            } // deleting the current chapter? Automatically move to another one
+            else (study.position.chapterId == chapterId).?? {
               chaps.find(_.id != chapterId) ?? { newChap =>
                 doSetChapter(study, newChap.id, uid)
               }
-            } >> chapterRepo.delete(chapter.id)
-            case _ => funit
-          } >>- reloadChapters(study)
+            }
+          } >> chapterRepo.delete(chapter.id) >>- reloadChapters(study)
         } >>- indexStudy(study)
       }
     }