initial commit on Federted servers

web/lib/page-order.ts

@@ -0,0 +1,25 @@
+import type { PageSummary } from '@/lib/pages'
+
+/**
+ * Reorder pages by moving sourceId beside targetId. Pinned and unpinned pages
+ * are separate groups (the server sorts pinned first), so a cross-group drop
+ * returns 'blocked' instead of silently landing at a different boundary.
+ * `after` places the source after the target; otherwise it goes before it.
+ */
+export function reorderPages(
+  pages: PageSummary[],
+  sourceId: string,
+  targetId: string,
+  after = false,
+): PageSummary[] | 'blocked' | null {
+  const from = pages.findIndex((p) => p.id === sourceId)
+  const to = pages.findIndex((p) => p.id === targetId)
+  if (from < 0 || to < 0 || sourceId === targetId) return null
+  if (pages[from].pinned !== pages[to].pinned) return 'blocked'
+  const next = [...pages]
+  const [moved] = next.splice(from, 1)
+  let insertAt = to + (after ? 1 : 0)
+  if (from < insertAt) insertAt--
+  next.splice(insertAt, 0, moved)
+  return next
+}