Allow motions to go a state back

client/src/app/shared/models/motions/workflow-state.ts

@@ -45,13 +45,15 @@ export class WorkflowState extends Deserializer {
      * Also adds the current state.
      */
     public getNextStates(workflow: Workflow): WorkflowState[] {
-        const nextStates = [];
-        workflow.states.forEach(state => {
-            if (this.next_states_id.includes(state.id)) {
-                nextStates.push(state as WorkflowState);
-            }
+        return workflow.states.filter(state => {
+            return this.next_states_id.includes(state.id);
+        });
+    }
+
+    public getPreviousStates(workflow: Workflow): WorkflowState[] {
+        return workflow.states.filter(state => {
+            return state.next_states_id.includes(this.id);
         });
-        return nextStates;
     }
 
     public toString = (): string => {

client/src/app/site/motions/components/motion-detail/motion-detail.component.html

@@ -223,6 +223,9 @@
                 </button>
                 <div *ngIf="perms.isAllowed('change_metadata', motion)">
                     <mat-divider *ngIf="motion.nextStates.length > 0"></mat-divider>
+                    <button *ngFor="let state of motion.previousStates" mat-menu-item (click)="setState(state.id)">
+                        <mat-icon>arrow_back</mat-icon> {{ state.name | translate }} <span *ngIf="state.show_state_extension_field">&nbsp;...</span>
+                    </button>
                     <button mat-menu-item (click)="setState(null)">
                         <mat-icon>replay</mat-icon> {{ 'Reset state' | translate }}
                     </button>

client/src/app/site/motions/components/motion-detail/motion-detail.component.ts

@@ -1035,7 +1035,7 @@ export class MotionDetailComponent extends BaseViewComponent implements OnInit {
      * @param id Motion state id
      */
     public setState(id: number): void {
-        this.repo.setState(this.motion, id);
+        this.repo.setState(this.motion, id).then(null, this.raiseError);
     }
 
     /**

client/src/app/site/motions/models/view-motion.ts

@@ -194,6 +194,10 @@ export class ViewMotion extends BaseAgendaViewModel implements Searchable {
         return this.state && this.workflow ? this.state.getNextStates(this.workflow.workflow) : [];
     }
 
+    public get previousStates(): WorkflowState[] {
+        return this.state && this.workflow ? this.state.getPreviousStates(this.workflow.workflow) : [];
+    }
+
     public get item(): ViewItem {
         return this._item;
     }

openslides/motions/models.py

@@ -1176,6 +1176,14 @@ class State(RESTModelMixin, models.Model):
                     f"{state} can not be next state of {self} because it does not belong to the same workflow."
                 )
 
+    def is_next_or_previous_state_id(self, state_id):
+        """ Returns true, if the given state id is a valid next or previous state """
+        next_state_ids = [item.id for item in self.next_states.all()]
+        previous_state_ids = [
+            item.id for item in State.objects.filter(next_states__in=[self.id])
+        ]
+        return state_id in next_state_ids or state_id in previous_state_ids
+
     def get_root_rest_element(self):
         """
         Returns the workflow to this instance which is the root REST element.

openslides/motions/views.py

@@ -552,6 +552,8 @@ class MotionViewSet(ModelViewSet):
 
         Send PUT {'state': <state_id>} to set and just PUT {} to reset the
         state. Only managers can use this view.
+
+        If a state is given, it must be a next or previous state.
         """
         # Retrieve motion and state.
         motion = self.get_object()
@@ -570,7 +572,7 @@ class MotionViewSet(ModelViewSet):
                 raise ValidationError(
                     {"detail": "Invalid data. State must be an integer."}
                 )
-            if state_id not in [item.id for item in motion.state.next_states.all()]:
+            if not motion.state.is_next_or_previous_state_id(state_id):
                 raise ValidationError(
                     {"detail": f"You can not set the state to {state_id}."}
                 )