Clear Subtasks and fix indexing only when non subtask is deleted

backend/src/main/java/core/api/controller/TaskController.java

@@ -196,4 +196,15 @@ public class TaskController {
         Collection<Task> subtasks = taskPermissionResult.getResult().getSubtasks();
         return ResponseEntity.ok(subtasks.stream().map(TaskEntityInfo::new).toList());
     }
+
+    @DeleteMapping("/tasks/{taskID}/subtasks")
+    public ResponseEntity<?> onClearSubtasks(@PathVariable long taskID) {
+        var taskPermissionResult = taskService.getTaskPermissions(taskID, SecurityContextHolder.getContext().getAuthentication().getName());
+        if(taskPermissionResult.hasIssue()) {
+            return taskPermissionResult.mapToResponseEntity();
+        }
+
+        ServiceExitCode result = taskService.clearSubTasks(taskPermissionResult.getResult());
+        return result.mapToResponseEntity();
+    }
 }

backend/src/main/java/core/repositories/timemanager/TaskRepository.java

@@ -44,4 +44,9 @@ public interface TaskRepository extends CrudRepository<Task, Long> {
     @Transactional
     @Query(value = "UPDATE Task t SET t.parent = null WHERE t.taskgroup = ?1")
     void deleteTaskHierarchyWhereTaskgroup(Taskgroup taskgroup);
+
+    @Modifying
+    @Transactional
+    @Query(value = "DELETE Task t WHERE t.parent = ?1")
+    void deleteTasksByParent(Task parentTask);
 }

backend/src/main/java/core/services/TaskSeriesService.java

@@ -140,7 +140,7 @@ public class TaskSeriesService {
             }
             taskSerie.getTasks().clear();
             taskSeriesRepository.delete(taskSerie);
-        } else {
+        } else if(task.getParent() == null){
             repearIndexing(taskSerie, item.getSeriesIndex());
         }
     }

backend/src/main/java/core/services/TaskService.java

@@ -159,4 +159,9 @@ public class TaskService {
         }
 
     }
+
+    public ServiceExitCode clearSubTasks(Task parentTask) {
+        taskRepository.deleteTasksByParent(parentTask);
+        return ServiceExitCode.OK;
+    }
 }

openapi.yaml

@@ -1349,7 +1349,38 @@ paths:
             application/json:
               schema:
                 $ref: '#/components/schemas/SimpleStatusResponse'
-
+    delete:
+      security:
+        - API_TOKEN: []
+      tags:
+        - task
+      parameters:
+        - name: taskID
+          in: path
+          description: internal id of task
+          required: true
+          schema:
+            type: number
+            example: 1
+      responses:
+        200:
+          description: Operation successfull
+          content:
+            application/json:
+              schema:
+                $ref: '#/components/schemas/SimpleStatusResponse'
+        403:
+          description: No permission
+          content:
+            application/json:
+              schema:
+                $ref: '#/components/schemas/SimpleStatusResponse'
+        404:
+          description: Task not found
+          content:
+            application/json:
+              schema:
+                $ref: '#/components/schemas/SimpleStatusResponse'
 
       
   /schedules: