feat(bot): support tagged assistant replies in topics

apps/bot/src/telegram-mentions.ts

@@ -0,0 +1,42 @@
+import type { Context } from 'grammy'
+
+function escapeRegExp(value: string): string {
+  return value.replace(/[.*+?^${}()|[\]\\]/g, '\\$&')
+}
+
+function getMessageText(ctx: Pick<Context, 'msg'>): string | null {
+  const message = ctx.msg
+  if (!message || !('text' in message) || typeof message.text !== 'string') {
+    return null
+  }
+
+  return message.text
+}
+
+export function stripExplicitBotMention(ctx: Pick<Context, 'msg' | 'me'>): {
+  originalText: string
+  strippedText: string
+} | null {
+  const text = getMessageText(ctx)
+  const username = ctx.me.username
+
+  if (!text || !username) {
+    return null
+  }
+
+  const mentionPattern = new RegExp(`(^|\\s)@${escapeRegExp(username)}\\b`, 'giu')
+  if (!mentionPattern.test(text)) {
+    return null
+  }
+
+  mentionPattern.lastIndex = 0
+
+  return {
+    originalText: text,
+    strippedText: text.replace(mentionPattern, '$1').replace(/\s+/gu, ' ').trim()
+  }
+}
+
+export function hasExplicitBotMention(ctx: Pick<Context, 'msg' | 'me'>): boolean {
+  return stripExplicitBotMention(ctx) !== null
+}