feat(bluetooth-low-energy): auto-attempt to recover scanning states

src/integrations/bluetooth/bluetooth.service.spec.ts

@@ -255,7 +255,7 @@ Requesting information ...
     it('should only setup noble listeners once', () => {
       service.onLowEnergyDiscovery(() => undefined);
       service.onLowEnergyDiscovery(() => undefined);
-      expect(mockNoble.on).toHaveBeenCalledTimes(4);
+      expect(mockNoble.on).toHaveBeenCalledTimes(5);
     });
 
     it('should enable scanning when the adapter is inactive', () => {
@@ -420,6 +420,29 @@ Requesting information ...
 
       expect(peripheral.disconnectAsync).toHaveBeenCalled();
     });
+
+    it('should restart scanning if nothing has been detected for a while', async () => {
+      jest.useFakeTimers('modern');
+
+      // eslint-disable-next-line @typescript-eslint/no-empty-function
+      service.onLowEnergyDiscovery(() => {});
+      const stateCallback = mockNoble.on.mock.calls.find(
+        (call) => call[0] === 'stateChange'
+      )[1];
+      const discoveryCallback = mockNoble.on.mock.calls.find(
+        (call) => call[0] === 'discover'
+      )[1];
+      await stateCallback('poweredOn');
+      jest.resetAllMocks();
+
+      discoveryCallback();
+      jest.setSystemTime(Date.now() + 31 * 1000);
+
+      await service.verifyLowEnergyScanner();
+
+      expect(mockNoble.stopScanning).toHaveBeenCalledTimes(1);
+      expect(mockNoble.startScanningAsync).toHaveBeenCalledTimes(1);
+    });
   });
 
   it('should reset adapters that have been locked for too long', () => {

src/integrations/bluetooth/bluetooth.service.ts

@@ -11,6 +11,7 @@ import { Interval } from '@nestjs/schedule';
 
 const RSSI_REGEX = new RegExp(/-?[0-9]+/);
 const INQUIRY_LOCK_TIMEOUT = 30 * 1000;
+const SCAN_NO_PERIPHERAL_TIMEOUT = 30 * 1000;
 
 const execPromise = util.promisify(exec);
 
@@ -38,6 +39,7 @@ export class BluetoothService {
   private readonly classicConfig: BluetoothClassicConfig;
   private readonly adapters = new BluetoothAdapterMap();
   private lowEnergyAdapterId: number;
+  private lastLowEnergyDiscovery: Date;
 
   constructor(
     private readonly configService: ConfigService,
@@ -294,13 +296,34 @@ export class BluetoothService {
     });
   }
 
+  /**
+   * Restarts the scanning process if nothing has been detected for a while.
+   */
+  @Interval(5 * 1000)
+  async verifyLowEnergyScanner(): Promise<void> {
+    if (
+      this.lowEnergyAdapterId != undefined &&
+      this.adapters.getState(this.lowEnergyAdapterId) == 'scan' &&
+      this.lastLowEnergyDiscovery != undefined &&
+      this.lastLowEnergyDiscovery.getTime() <
+        Date.now() - SCAN_NO_PERIPHERAL_TIMEOUT
+    ) {
+      this.logger.warn(
+        'Did not detect any low energy advertisements in a while, restarting scanner'
+      );
+      await this.handleAdapterStateChange('poweredOff');
+      await this.handleAdapterStateChange('poweredOn');
+    }
+  }
+
   /**
    * Sets up Noble hooks.
    */
   private setupNoble(): void {
     this.lowEnergyAdapterId = parseInt(process.env.NOBLE_HCI_DEVICE_ID) || 0;
 
     noble.on('stateChange', this.handleAdapterStateChange.bind(this));
+    noble.on('discover', () => (this.lastLowEnergyDiscovery = new Date()));
     noble.on('warning', (message) => {
       if (message == 'unknown peripheral undefined RSSI update!') {
         return;