fix(client): ensure sidebar remains visible on shared subpages (#1887)

* fix(client): ensure sidebar remains visible on shared subpages

* Apply suggestions from code review

Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com>

---------

Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com>

apps/client/src/features/share/utils.ts

@@ -66,3 +66,20 @@ export function buildSharedPageTree(
 
   return sortTree(tree);
 }
+
+
+// Recursively checks if a page exists in the shared page tree.
+export function isPageInTree(
+  tree: SharedPageTreeNode[],
+  pageSlugId: string,
+): boolean {
+  for (const node of tree) {
+    if (node.slugId === pageSlugId) {
+      return true;
+    }
+    if (isPageInTree(node.children, pageSlugId)) {
+      return true;
+    }
+  }
+  return false;
+}

apps/client/src/pages/share/shared-page.tsx

@@ -8,6 +8,9 @@ import ReadonlyPageEditor from "@/features/editor/readonly-page-editor.tsx";
 import { extractPageSlugId } from "@/lib";
 import { Error404 } from "@/components/ui/error-404.tsx";
 import ShareBranding from "@/features/share/components/share-branding.tsx";
+import { useAtomValue } from "jotai";
+import { sharedTreeDataAtom } from "@/features/share/atoms/shared-page-atom.ts";
+import { isPageInTree } from "@/features/share/utils.ts";
 
 export default function SharedPage() {
   const { t } = useTranslation();
@@ -19,13 +22,22 @@ export default function SharedPage() {
     pageId: extractPageSlugId(pageSlug),
   });
 
+  const sharedTreeData = useAtomValue(sharedTreeDataAtom);
+
   useEffect(() => {
     if (shareId && data) {
       if (data.share.key !== shareId) {
-        navigate(`/share/${data.share.key}/p/${pageSlug}`, { replace: true });
+
+        // Check if the current page is part of the active sharing tree (sidebar) - If we are part of it, we will not redirect, keeping the sidebar visible.
+        const isPartOfTree =
+          sharedTreeData && isPageInTree(sharedTreeData, data.page.slugId);
+
+        if (!isPartOfTree) {
+          navigate(`/share/${data.share.key}/p/${pageSlug}`, { replace: true });
+        }
       }
     }
-  }, [shareId, data]);
+  }, [shareId, data, sharedTreeData]);
 
   if (isLoading) {
     return <></>;