1 files changed, 42 insertions, 0 deletions
diff --git a/util/findNthNeighbour.ts b/util/findNthNeighbour.ts
new file mode 100644
index 0000000..d48adbc
--- /dev/null
+++ b/util/findNthNeighbour.ts
@@ -0,0 +1,42 @@
+import { LinksByNodeId } from '../pages'
+import { normalizeLinkEnds } from './normalizeLinkEnds'
+
+export const findNthNeighbors = ({
+  ids,
+  excludedIds,
+  n,
+  linksByNodeId,
+}: {
+  ids: string[]
+  excludedIds: string[]
+  n: number
+  linksByNodeId: LinksByNodeId
+}) => {
+  let queue = [ids[0]]
+  let todo: string[] = []
+  const completed = [ids[0]]
+  Array.from({ length: n }, () => {
+    queue.forEach((node) => {
+      const links = linksByNodeId[node as string] ?? []
+      links.forEach((link) => {
+        const [sourceId, targetId] = normalizeLinkEnds(link)
+        if (excludedIds.some((id) => [sourceId, targetId].includes(id))) {
+          return
+        }
+        if (!completed.includes(sourceId)) {
+          todo.push(sourceId)
+          return
+        }
+        if (!completed.includes(targetId)) {
+          todo.push(targetId)
+          return
+        }
+        return
+      })
+    })
+    queue = todo
+    todo.forEach((neighbor) => neighbor && completed.push(neighbor))
+    todo = []
+  })
+  return completed
+}