fix: treat reply-to-bot as implicit mention across channels

extensions/msteams/src/sent-message-cache.ts

@@ -0,0 +1,41 @@
+const TTL_MS = 24 * 60 * 60 * 1000; // 24 hours
+
+type CacheEntry = {
+  messageIds: Set<string>;
+  timestamps: Map<string, number>;
+};
+
+const sentMessages = new Map<string, CacheEntry>();
+
+function cleanupExpired(entry: CacheEntry): void {
+  const now = Date.now();
+  for (const [msgId, timestamp] of entry.timestamps) {
+    if (now - timestamp > TTL_MS) {
+      entry.messageIds.delete(msgId);
+      entry.timestamps.delete(msgId);
+    }
+  }
+}
+
+export function recordMSTeamsSentMessage(conversationId: string, messageId: string): void {
+  if (!conversationId || !messageId) return;
+  let entry = sentMessages.get(conversationId);
+  if (!entry) {
+    entry = { messageIds: new Set(), timestamps: new Map() };
+    sentMessages.set(conversationId, entry);
+  }
+  entry.messageIds.add(messageId);
+  entry.timestamps.set(messageId, Date.now());
+  if (entry.messageIds.size > 200) cleanupExpired(entry);
+}
+
+export function wasMSTeamsMessageSent(conversationId: string, messageId: string): boolean {
+  const entry = sentMessages.get(conversationId);
+  if (!entry) return false;
+  cleanupExpired(entry);
+  return entry.messageIds.has(messageId);
+}
+
+export function clearMSTeamsSentMessageCache(): void {
+  sentMessages.clear();
+}