From 633d098206f2967638ecba6f358008d16b358e84 Mon Sep 17 00:00:00 2001
From: Christian Mueller <christian@cynfo.com>
Date: Mon, 6 Apr 2026 20:40:56 +0200
Subject: [PATCH] fix: store last_payload during MQTT topic discovery

The discovery message handler was missing the payload parameter,
so topics were saved without their last value.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
---
 display/middleware/src/modules/mqtt/topic-discovery.ts | 9 ++++++++-
 1 file changed, 8 insertions(+), 1 deletion(-)

diff --git a/display/middleware/src/modules/mqtt/topic-discovery.ts b/display/middleware/src/modules/mqtt/topic-discovery.ts
index 7603374..b9c1d88 100644
--- a/display/middleware/src/modules/mqtt/topic-discovery.ts
+++ b/display/middleware/src/modules/mqtt/topic-discovery.ts
@@ -93,11 +93,18 @@ export function startDiscovery(brokerId: number, prefix?: string): Promise<MqttT
       resolve(getTopicsForBroker(brokerId));
     };
 
-    const onMessage = (topic: string): void => {
+    const onMessage = (topic: string, payload: Buffer): void => {
+      const payloadStr = payload.toString();
       if (!discoveredTopics.has(topic)) {
         discoveredTopics.add(topic);
         ensureTopicExists(brokerId, topic);
       }
+      // Always update last_payload so the user sees the latest value
+      const db = getDb();
+      db.run(
+        'UPDATE mqtt_topics SET last_payload = ? WHERE broker_id = ? AND topic = ?',
+        [payloadStr, brokerId, topic]
+      );
     };
 
     if (existingClient && existingClient.connected) {