[52] Change task creation in Gantt

Change task creation in Gantt from creating a sibling task to a child task.

Issue: #52

Author: ncouvert

CHANGELOG.adoc

@@ -1,5 +1,20 @@
 = Changelog
 
+== v2026.X.X
+
+=== Dependency update
+
+
+=== New features
+
+
+=== Improvements
+- https://github.com/ObeoNetwork/pepper/issues/52[#52] Change task creation in Gantt
+Change task creation in Gantt from creating a sibling task to a child task.
+
+=== Bug fixes
+
+
 == v2026.6.1
 
 === Dependency update
@@ -35,6 +50,7 @@
 - https://github.com/ObeoNetwork/pepper/issues/49[#49] Rework the detail views of Task and Workpackage
 - https://github.com/ObeoNetwork/pepper/issues/55[#55] Link detail view updates with Gantt view
 
+
 === Bug fixes
 
 - https://github.com/ObeoNetwork/pepper/issues/50[#50] Stop extending DefaultLabelService

backend/pepper-starter/src/main/java/pepper/starter/services/view/PepperMMJavaService.java

@@ -163,25 +163,35 @@ public void createTask(EObject context) {
         Task task = PepperFactory.eINSTANCE.createTask();
         task.setName(NEW_TASK);
         if (context instanceof AbstractTask abstractTask) {
-            // The new task follows the context task and has the same duration as the context task.
-            if (abstractTask.getEndTime() != null && abstractTask.getStartTime() != null) {
-                if (abstractTask.getEndTime().equals(abstractTask.getStartTime())) {
-                    // If the task is a Milestone
-                    task.setStartTime(abstractTask.getEndTime());
-                    task.setEndTime(Instant.ofEpochSecond(2 * abstractTask.getEndTime().getEpochSecond() - abstractTask.getStartTime().getEpochSecond()));
+            // The new task follows the last sub-task.
+            Optional<Task> optionalTask = abstractTask.getSubTasks().stream().reduce((first, second) -> second)
+                    .filter(filteredTask -> filteredTask.getEndTime() != null && filteredTask.getStartTime() != null);
+
+            if (optionalTask.isPresent()) {
+                Task lastTask = optionalTask.get();
+                if (lastTask.getEndTime().equals(lastTask.getStartTime())) {
+                    // If the last task is a Milestone
+                    task.setStartTime(lastTask.getEndTime());
+                    task.setEndTime(lastTask.getEndTime());
                 } else {
-                    task.setStartTime(abstractTask.getEndTime().plus(1, ChronoUnit.MINUTES));
-                    task.setEndTime(Instant.ofEpochSecond(2 * abstractTask.getEndTime().getEpochSecond() - abstractTask.getStartTime().getEpochSecond()).plus(1, ChronoUnit.MINUTES));
+                    task.setStartTime(lastTask.getEndTime().plus(1, ChronoUnit.MINUTES));
+                    task.setEndTime(Instant.ofEpochSecond(2 * lastTask.getEndTime().getEpochSecond() - lastTask.getStartTime().getEpochSecond()).plus(1, ChronoUnit.MINUTES));
+                }
+            } else {
+                if (abstractTask.getEndTime() != null && abstractTask.getStartTime() != null) {
+                    task.setStartTime(abstractTask.getStartTime());
+                    task.setEndTime(abstractTask.getEndTime());
                 }
             }
-
-            EObject parent = context.eContainer();
-            if (parent instanceof Workpackage workpackage) {
-                int index = workpackage.getOwnedTasks().indexOf(context);
-                workpackage.getOwnedTasks().add(index + 1, task);
-            } else if (parent instanceof AbstractTask parentTask) {
-                int index = parentTask.getSubTasks().indexOf(context);
-                parentTask.getSubTasks().add(index + 1, task);
+            abstractTask.getSubTasks().add(task);
+            int levelLayer = 1;
+            var parent = context.eContainer();
+            while (!(parent instanceof Workpackage)) {
+                levelLayer++;
+                parent = parent.eContainer();
+            }
+            if (levelLayer == 4) {
+                this.feedbackMessageService.addFeedbackMessage(new Message("This view does not display more than 4 levels of tasks.", MessageLevel.WARNING));
             }
         } else if (context instanceof Workpackage workpackage) {
             long epochSecondStartTime = Instant.now().getEpochSecond();

backend/pepper-starter/src/test/java/pepper/starter/configuration/view/PepperMMJavaServiceTests.java

@@ -313,14 +313,14 @@ public void createTask() {
         assertThat(workpackage.getOwnedTasks()).hasSize(2);
 
         service.createTask(task1);
-        assertThat(workpackage.getOwnedTasks()).hasSize(3);
-        assertThat(workpackage.getOwnedTasks().get(1).getStartTime()).isEqualTo(Instant.parse(DATE2024_01_02_T00_00_00));
-        assertThat(workpackage.getOwnedTasks().get(1).getEndTime()).isEqualTo(Instant.parse(DATE2024_01_02_T23_59_00));
-
-        service.createTask(task11);
         assertThat(task1.getSubTasks()).hasSize(2);
         assertThat(task1.getSubTasks().get(1).getStartTime()).isEqualTo(Instant.parse(DATE2024_01_02_T00_00_00));
         assertThat(task1.getSubTasks().get(1).getEndTime()).isEqualTo(Instant.parse(DATE2024_01_02_T23_59_00));
+
+        service.createTask(task11);
+        assertThat(task11.getSubTasks()).hasSize(1);
+        assertThat(task11.getSubTasks().get(0).getStartTime()).isEqualTo(task11.getStartTime());
+        assertThat(task11.getSubTasks().get(0).getEndTime()).isEqualTo(task11.getEndTime());
     }
 
     @Test