feat(M06-C): 完成设备协议适配与消息幂等

backend/src/mqtt/mqtt-service.ts

@@ -26,6 +26,7 @@ export interface MqttClientLike {
 }
 
 export type MqttClientFactory = (url: string, options: IClientOptions) => MqttClientLike;
+export type MqttMessageHandler = (topic: string, payload: Buffer) => Promise<void>;
 
 export interface MqttHealthSnapshot {
   configured: boolean;
@@ -39,7 +40,14 @@ export interface MqttHealthSnapshot {
   lastError: string | null;
 }
 
-export class MqttService {
+export interface MqttTransport {
+  start(): void;
+  stop(): Promise<void>;
+  publishDeviceCommand(deviceId: string, payload: Buffer | string): Promise<void>;
+  health(): MqttHealthSnapshot;
+}
+
+export class MqttService implements MqttTransport {
   private client: MqttClientLike | null = null;
   private subscriptionsReady = false;
   private reconnectCount = 0;
@@ -51,7 +59,8 @@ export class MqttService {
 
   constructor(
     private readonly config: AppConfig['mqtt'],
-    private readonly clientFactory: MqttClientFactory = connect as MqttClientFactory
+    private readonly clientFactory: MqttClientFactory = connect as MqttClientFactory,
+    private readonly messageHandler?: MqttMessageHandler
   ) {}
 
   start(): void {
@@ -89,7 +98,7 @@ export class MqttService {
     this.client.on('error', (error: Error) => {
       this.lastError = sanitizeError(error);
     });
-    this.client.on('message', (_topic: string, payload: Buffer) => {
+    this.client.on('message', (topic: string, payload: Buffer) => {
       if (payload.length > this.config.maxMessageBytes) {
         this.rejectedOversizeMessages += 1;
         this.lastError = `MQTT message exceeded ${this.config.maxMessageBytes} bytes`;
@@ -97,6 +106,11 @@ export class MqttService {
       }
       this.receivedMessages += 1;
       this.lastMessageAt = new Date().toISOString();
+      void this.messageHandler?.(topic, payload).catch((error: unknown) => {
+        this.lastError = sanitizeError(
+          error instanceof Error ? error : new Error('MQTT message handler failed')
+        );
+      });
     });
   }