fix(synology-chat): resolve Chat API user_id for reply delivery (#23709)

* fix(synology-chat): resolve Chat API user_id for reply delivery

Synology Chat outgoing webhooks use a per-integration user_id that
differs from the global Chat API user_id required by method=chatbot.
This caused reply messages to fail silently when the IDs diverged.

Changes:
- Add fetchChatUsers() and resolveChatUserId() to resolve the correct
  Chat API user_id via the user_list endpoint (cached 5min)
- Use resolved user_id for all sendMessage() calls in webhook handler
  and channel dispatcher
- Add Provider field to MsgContext so the agent runner correctly
  identifies the message channel (was "unknown", now "synology-chat")
- Log warnings when user_list API fails or when falling back to
  unresolved webhook user_id
- Add 5 tests for user_id resolution (nickname, username, case,
  not-found, URL rewrite)

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

* fix(synology-chat): use Readable stream in integration test for Windows compat

Replace EventEmitter + process.nextTick with Readable stream for
request body simulation. The process.nextTick approach caused the test
to hang on Windows CI (120s timeout) because events were not reliably
delivered to readBody() listeners.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

* fix: harden synology reply user resolution and cache scope (#23709) (thanks @druide67)

---------

Co-authored-by: Claude Opus 4.6 <noreply@anthropic.com>
Co-authored-by: Peter Steinberger <steipete@gmail.com>

extensions/synology-chat/src/client.ts

@@ -9,6 +9,28 @@ import * as https from "node:https";
 const MIN_SEND_INTERVAL_MS = 500;
 let lastSendTime = 0;
 
+// --- Chat user_id resolution ---
+// Synology Chat uses two different user_id spaces:
+//   - Outgoing webhook user_id: per-integration sequential ID (e.g. 1)
+//   - Chat API user_id: global internal ID (e.g. 4)
+// The chatbot API (method=chatbot) requires the Chat API user_id in the
+// user_ids array. We resolve via the user_list API and cache the result.
+
+interface ChatUser {
+  user_id: number;
+  username: string;
+  nickname: string;
+}
+
+type ChatUserCacheEntry = {
+  users: ChatUser[];
+  cachedAt: number;
+};
+
+// Cache user lists per bot endpoint to avoid cross-account bleed.
+const chatUserCache = new Map<string, ChatUserCacheEntry>();
+const CACHE_TTL_MS = 5 * 60 * 1000; // 5 minutes
+
 /**
  * Send a text message to Synology Chat via the incoming webhook.
  *
@@ -92,6 +114,107 @@ export async function sendFileUrl(
   }
 }
 
+/**
+ * Fetch the list of Chat users visible to this bot via the user_list API.
+ * Results are cached for CACHE_TTL_MS to avoid excessive API calls.
+ *
+ * The user_list endpoint uses the same base URL as the chatbot API but
+ * with method=user_list instead of method=chatbot.
+ */
+export async function fetchChatUsers(
+  incomingUrl: string,
+  allowInsecureSsl = true,
+  log?: { warn: (...args: unknown[]) => void },
+): Promise<ChatUser[]> {
+  const now = Date.now();
+  const listUrl = incomingUrl.replace(/method=\w+/, "method=user_list");
+  const cached = chatUserCache.get(listUrl);
+  if (cached && now - cached.cachedAt < CACHE_TTL_MS) {
+    return cached.users;
+  }
+
+  return new Promise((resolve) => {
+    let parsedUrl: URL;
+    try {
+      parsedUrl = new URL(listUrl);
+    } catch {
+      log?.warn("fetchChatUsers: invalid user_list URL, using cached data");
+      resolve(cached?.users ?? []);
+      return;
+    }
+    const transport = parsedUrl.protocol === "https:" ? https : http;
+
+    transport
+      .get(listUrl, { rejectUnauthorized: !allowInsecureSsl } as any, (res) => {
+        let data = "";
+        res.on("data", (c: Buffer) => {
+          data += c.toString();
+        });
+        res.on("end", () => {
+          try {
+            const result = JSON.parse(data);
+            if (result.success && result.data?.users) {
+              const users = result.data.users.map((u: any) => ({
+                user_id: u.user_id,
+                username: u.username || "",
+                nickname: u.nickname || "",
+              }));
+              chatUserCache.set(listUrl, {
+                users,
+                cachedAt: now,
+              });
+              resolve(users);
+            } else {
+              log?.warn(
+                `fetchChatUsers: API returned success=${result.success}, using cached data`,
+              );
+              resolve(cached?.users ?? []);
+            }
+          } catch {
+            log?.warn("fetchChatUsers: failed to parse user_list response");
+            resolve(cached?.users ?? []);
+          }
+        });
+      })
+      .on("error", (err) => {
+        log?.warn(`fetchChatUsers: HTTP error — ${err instanceof Error ? err.message : err}`);
+        resolve(cached?.users ?? []);
+      });
+  });
+}
+
+/**
+ * Resolve a webhook username to the correct Chat API user_id.
+ *
+ * Synology Chat outgoing webhooks send a user_id that may NOT match the
+ * Chat-internal user_id needed by the chatbot API (method=chatbot).
+ * The webhook's "username" field corresponds to the Chat user's "nickname".
+ *
+ * @param incomingUrl - Bot incoming webhook URL (used to derive user_list URL)
+ * @param webhookUsername - The username from the outgoing webhook payload
+ * @param allowInsecureSsl - Skip TLS verification
+ * @returns The correct Chat user_id, or undefined if not found
+ */
+export async function resolveChatUserId(
+  incomingUrl: string,
+  webhookUsername: string,
+  allowInsecureSsl = true,
+  log?: { warn: (...args: unknown[]) => void },
+): Promise<number | undefined> {
+  const users = await fetchChatUsers(incomingUrl, allowInsecureSsl, log);
+  const lower = webhookUsername.toLowerCase();
+
+  // Match by nickname first (webhook "username" field = Chat "nickname")
+  const byNickname = users.find((u) => u.nickname.toLowerCase() === lower);
+  if (byNickname) return byNickname.user_id;
+
+  // Then by username
+  const byUsername = users.find((u) => u.username.toLowerCase() === lower);
+  if (byUsername) return byUsername.user_id;
+
+  return undefined;
+}
+
 function doPost(url: string, body: string, allowInsecureSsl = true): Promise<boolean> {
   return new Promise((resolve, reject) => {
     let parsedUrl: URL;