implemented a lot of features

lib/nntp/group.ts

@@ -0,0 +1,23 @@
+export interface GroupInfo {
+  count: bigint
+  first: bigint
+  last: bigint
+  name: string
+}
+
+/**
+ * Parses a `211 count first last name` GROUP reply (RFC 3977 §6.1.1).
+ *
+ * nntp-js's own `group()` destructures this reply without skipping the status
+ * code, so its `first`/`last` are off by one field. Pass it `result.resp`.
+ */
+export function parseGroupResponse(resp: string): GroupInfo {
+  const match = /^211\s+(\d+)\s+(\d+)\s+(\d+)\s+(\S+)/.exec(resp.trim())
+  if (!match) throw new Error(`Unexpected GROUP response: ${resp}`)
+  return {
+    count: BigInt(match[1]),
+    first: BigInt(match[2]),
+    last: BigInt(match[3]),
+    name: match[4],
+  }
+}

lib/nntp/xref.ts

@@ -0,0 +1,13 @@
+/**
+ * Returns the group names from an Xref header,
+ * e.g. `news.eweka.nl alt.binaries.test:123 alt.binaries.x:456`.
+ */
+export function parseXrefGroups(xref: string | undefined): string[] {
+  if (!xref) return []
+  return xref
+    .trim()
+    .split(/\s+/)
+    .slice(1)
+    .map((entry) => entry.slice(0, entry.lastIndexOf(':')))
+    .filter(Boolean)
+}