feat: add contextual layer inspector

operations/document/layerActions.ts

@@ -143,6 +143,25 @@ export function addLayerMask(documentIndex: DocumentReadIndex, layerInfo: Indexe
   });
 }
 
+export function duplicateLayer(documentIndex: DocumentReadIndex, layerInfo: IndexedLayerInfo, dispatch: AppStore["dispatch"]) {
+  const ids = collectDuplicateIds(layerInfo.layer, layerInfo.siblings);
+  dispatch(commandIds.documentDuplicateLayer, {
+    layerId: layerInfo.layer.id,
+    idByLayerId: Object.fromEntries(ids.map((id) => [id, crypto.randomUUID()])),
+  });
+}
+
+function collectDuplicateIds(layer: Layer, siblings: readonly Layer[]): string[] {
+  const ids = collectTreeIds(layer);
+  const maskId = getLayerMask(layer)?.maskLayerId;
+  const mask = maskId ? siblings.find((candidate) => candidate.id === maskId) : undefined;
+  return mask ? [...collectTreeIds(mask), ...ids] : ids;
+}
+
+function collectTreeIds(layer: Layer): string[] {
+  return [layer.id, ...(layer.type === "group" ? layer.children.flatMap(collectTreeIds) : [])];
+}
+
 const emptyLayerIds = new Set<string>();
 
 function createGroup(name: string): Extract<Layer, { type: "group" }> {