refactor(telegram): centralize target parsing

src/telegram/targets.ts

@@ -0,0 +1,43 @@
+export type TelegramTarget = {
+  chatId: string;
+  messageThreadId?: number;
+};
+
+export function stripTelegramInternalPrefixes(to: string): string {
+  let trimmed = to.trim();
+  while (true) {
+    const next = trimmed.replace(/^(telegram|tg|group):/i, "").trim();
+    if (next === trimmed) return trimmed;
+    trimmed = next;
+  }
+}
+
+/**
+ * Parse a Telegram delivery target into chatId and optional topic/thread ID.
+ *
+ * Supported formats:
+ * - `chatId` (plain chat ID, t.me link, @username, or internal prefixes like `telegram:...`)
+ * - `chatId:topicId` (numeric topic/thread ID)
+ * - `chatId:topic:topicId` (explicit topic marker; preferred)
+ */
+export function parseTelegramTarget(to: string): TelegramTarget {
+  const normalized = stripTelegramInternalPrefixes(to);
+
+  const topicMatch = /^(.+?):topic:(\d+)$/.exec(normalized);
+  if (topicMatch) {
+    return {
+      chatId: topicMatch[1],
+      messageThreadId: Number.parseInt(topicMatch[2], 10),
+    };
+  }
+
+  const colonMatch = /^(.+):(\d+)$/.exec(normalized);
+  if (colonMatch) {
+    return {
+      chatId: colonMatch[1],
+      messageThreadId: Number.parseInt(colonMatch[2], 10),
+    };
+  }
+
+  return { chatId: normalized };
+}