restore original gamebook shapes on clear

ui/analyse/src/study/gamebook/gamebookPlayCtrl.ts

@@ -24,7 +24,10 @@ export default class GamebookPlayCtrl {
 
     // ensure all original nodes have a gamebook entry,
     // so we can differentiate original nodes from user-made ones
-    treeOps.updateAll(root.tree.root, n => n.gamebook = n.gamebook || {});
+    treeOps.updateAll(root.tree.root, n => {
+      n.gamebook = n.gamebook || {};
+      if (n.shapes) n.gamebook.shapes = n.shapes.slice(0);
+    });
   }
 
   private makeState(): void {
@@ -77,5 +80,11 @@ export default class GamebookPlayCtrl {
     this.makeState();
   };
 
-  private study = (): StudyCtrl => this.root.study!;
+  onShapeChange = shapes => {
+    const node = this.root.node;
+    if (node.gamebook && node.gamebook.shapes && !shapes.length) {
+      node.shapes = node.gamebook.shapes.slice(0);
+      this.root.jump(this.root.path);
+    }
+  };
 }

ui/analyse/src/study/studyCtrl.ts

@@ -217,6 +217,7 @@ export default function(data: StudyData, ctrl: AnalyseCtrl, tagTypes: TagTypes,
           shapes
         }));
       }
+      gamebookPlay && gamebookPlay.onShapeChange(shapes);
     };
   }
 

ui/types/lichess.d.ts

@@ -206,6 +206,7 @@ declare namespace Tree {
   export interface Gamebook {
     deviation?: string;
     hint?: string;
+    shapes?: Shape[]
   }
 
   export interface Opening {