Added PageComponents

src/lib/site/navigation.ts

@@ -30,3 +30,23 @@ export function trailOf(article: Article): Article[] {
   for (let node: Article | null = article; node; node = node.parent) trail.unshift(node)
   return trail
 }
+
+export type ContextGroup = {
+  heading: Article | null
+  entries: Article[]
+}
+
+export function contextOf(article: Article | null, roots: Article[]): ContextGroup[] {
+  if (!article) return [{ heading: null, entries: roots }]
+
+  const { parent } = article
+  const siblings = (parent ? parent.children : roots).filter((entry) => entry !== article)
+
+  const groups: ContextGroup[] = [
+    { heading: parent?.parent ?? null, entries: parent?.listed ? [parent] : [] },
+    { heading: parent, entries: siblings },
+    { heading: article, entries: article.children },
+  ]
+
+  return groups.filter((group) => group.entries.length > 0)
+}