- fixes frontent nr. 89 - delete plang

src/ClientServer/Controllers/Core/Exercises/PLangController.cs

@@ -86,17 +86,20 @@ namespace ClientServer.Controllers.Core.Exercises
                 DisplayName = p.DisplayName,
                 EditorHighlightModeName = p.EditorHighlightModeName,
                 FileExtensionsWithDot = p.FileExtensionsWithDot,
-                CanBeDeleted = false
+                CanBeDeleted = false,
             }).ToList();
 
             foreach (var pLangForFrontend in forFrontend)
             {
-                pLangForFrontend.CanBeDeleted = await this._GetCanPLangBeDeleted(pLangForFrontend.Id);
+                var reasonCannotBeDeleted = await this._GetCanPLangBeDeleted(pLangForFrontend.Id);
+                pLangForFrontend.CanBeDeleted = reasonCannotBeDeleted == null;
+                pLangForFrontend.CannotBeDeletedReason = reasonCannotBeDeleted;
             }
-            
+
 
             await
-                Response.WriteAsync(Jc.Serialize(new BasicResponseWithData<List<PLangWithExtrasFromBackend>>(ResponseCode.Ok,
+                Response.WriteAsync(Jc.Serialize(new BasicResponseWithData<List<PLangWithExtrasFromBackend>>(
+                    ResponseCode.Ok,
                     "", forFrontend)));
         }
 
@@ -111,7 +114,7 @@ namespace ClientServer.Controllers.Core.Exercises
             if (await this._CheckPermission() == false) return;
 
             if (await this.ValidatePLang(pLang) == false) return;
-            
+
 
             var newPLang = new PLang()
             {
@@ -161,7 +164,7 @@ namespace ClientServer.Controllers.Core.Exercises
                         Jc.Serialize(new BasicResponse(ResponseCode.NotFound, "no old plang found")));
                 return;
             }
-            
+
             if (await this.ValidatePLang(pLang) == false) return;
 
             oldPLang.DisplayName = pLang.DisplayName;
@@ -179,6 +182,8 @@ namespace ClientServer.Controllers.Core.Exercises
                 return;
             }
 
+            var reasonCannotBeDeleted = await _GetCanPLangBeDeleted(oldPLang.Id);
+
             var forFrontend = new PLangWithExtrasFromBackend()
             {
                 Id = oldPLang.Id,
@@ -186,15 +191,16 @@ namespace ClientServer.Controllers.Core.Exercises
                 InternalName = oldPLang.InternalName,
                 EditorHighlightModeName = oldPLang.EditorHighlightModeName,
                 FileExtensionsWithDot = oldPLang.FileExtensionsWithDot,
-                CanBeDeleted = await _GetCanPLangBeDeleted(oldPLang.Id)
+                CanBeDeleted = reasonCannotBeDeleted == null,
+                CannotBeDeletedReason = reasonCannotBeDeleted,
             };
-            
+
             await
                 Response.WriteAsync(Jc.Serialize(new BasicResponseWithData<PLangWithExtrasFromBackend>(ResponseCode.Ok,
                     "", forFrontend)));
         }
 
-        
+
         /// <summary>
         /// deletes the given plang by id
         /// </summary>
@@ -219,13 +225,13 @@ namespace ClientServer.Controllers.Core.Exercises
 
             //check if we can delete plang... only if we have no release with this plang & no code template
 
-            var canBeDeleted = await this._GetCanPLangBeDeleted(oldPLang.Id);
+            var reason = await this._GetCanPLangBeDeleted(oldPLang.Id);
 
-            if (canBeDeleted == false)
+            if (reason != null)
             {
                 await
                     Response.WriteAsync(
-                        Jc.Serialize(new BasicResponse(ResponseCode.InvalidRequest, "cannot be deleted")));
+                        Jc.Serialize(new BasicResponse(ResponseCode.InvalidRequest, reason)));
                 return;
             }
 
@@ -254,7 +260,7 @@ namespace ClientServer.Controllers.Core.Exercises
                         Jc.Serialize(new BasicResponse(ResponseCode.NotFound, "display name was empty")));
                 return false;
             }
-            
+
             if (string.IsNullOrEmpty(pLang.InternalName))
             {
                 await
@@ -266,10 +272,53 @@ namespace ClientServer.Controllers.Core.Exercises
             return true;
         }
 
-        protected async Task<bool> _GetCanPLangBeDeleted(int pLangId)
+        /// <summary>
+        /// 
+        /// </summary>
+        /// <param name="pLangId"></param>
+        /// <returns>null: all ok, other the reason why the plang cannot be deleted</returns>
+        protected async Task<string> _GetCanPLangBeDeleted(int pLangId)
         {
-            //TODO
-            return false;
+            var releaseCount = await _context.ExerciseReleases
+                    .CountAsync(p => p.PLangId == pLangId)
+                ;
+
+            if (releaseCount > 0)
+            {
+                return "there are still releases with this plang";
+            }
+
+
+            var exerciseInGroupCount = await _context.Exercises
+                    .Where(p => p.IsOnlyVisibleToOwner == false &&
+                                p.CodeTemplates.Any(k => k.PLangId == pLangId))
+                    .ToListAsync()
+                ;
+
+            if (exerciseInGroupCount.Count > 0)
+            {
+                return
+                    $"there are {exerciseInGroupCount.Count} exercises with code templates that use the given plang." +
+                    $" the first exercise is '{exerciseInGroupCount.First().DisplayName}'";
+            }
+
+            var exerciseFromUser = await _context.Exercises
+                    .Include(p => p.User)
+                    .Where(p => p.IsOnlyVisibleToOwner &&
+                                p.CodeTemplates.Any(k => k.PLangId == pLangId))
+                    .ToListAsync()
+                ;
+
+
+            if (exerciseFromUser.Count > 0)
+            {
+                var firstExercise = exerciseFromUser.First();
+                return
+                    $"there are {exerciseFromUser.Count} exercises (that are only visible to the owner) with code templates that use the given plang." +
+                    $" the first exercise is '{firstExercise.DisplayName}' from the user '{firstExercise.User.LastName}, {firstExercise.User.FirstName} (token: {firstExercise.User.Token})'";
+            }
+
+            return null;
         }
     }
 
@@ -287,12 +336,12 @@ namespace ClientServer.Controllers.Core.Exercises
         /// ALSO make sure it's a valid file path would be good to use no spaces... c++ -> cpp
         /// </summary>
         public string InternalName { get; set; }
-        
+
         /// <summary>
         /// a comma separated list of file extensions for this plang
         /// </summary>
         public string FileExtensionsWithDot { get; set; }
-        
+
         /// <summary>
         /// the highlight mode for the editor (currently ace)
         /// </summary>
@@ -307,5 +356,11 @@ namespace ClientServer.Controllers.Core.Exercises
         /// false: deleting plang would cascade and delete other data 
         /// </summary>
         public bool CanBeDeleted { get; set; }
+
+        /// <summary>
+        /// the reason why the plang cannot be deleted
+        /// can be null if CanBeDeleted is true
+        /// </summary>
+        public string CannotBeDeletedReason { get; set; }
     }
 }