fix: prevent same-name BLE discovery starvation

Author: enaboapps

src/transport/ReactNativeBleTransport.test.ts

@@ -588,7 +588,7 @@ describe('ReactNativeBleTransport', () => {
     expect(found).not.toHaveBeenCalled();
   });
 
-  it('deduplicates rotating addresses for the same named PC while a probe is in flight', async () => {
+  it('probes a distinct same-name address while another probe is in flight', async () => {
     let scanCallback!: (error: Error | null, value: Device | null) => void;
     let releaseConnect!: (value: Device) => void;
     const connected = device();
@@ -602,15 +602,15 @@ describe('ReactNativeBleTransport', () => {
     scanCallback(null, first);
     await waitFor(() => (first.connect as jest.Mock).mock.calls.length === 1);
     scanCallback(null, rotated);
-    expect(rotated.isConnected).not.toHaveBeenCalled();
+    expect(rotated.isConnected).toHaveBeenCalledTimes(1);
 
     stop();
     releaseConnect(connected);
     await waitFor(() => (connected.cancelConnection as jest.Mock).mock.calls.length === 1);
     expect(found).not.toHaveBeenCalled();
   });
 
-  it('deduplicates a rotated Windows address after the first probe completes', async () => {
+  it('deduplicates a known Windows address but probes a new same-name address', async () => {
     let scanCallback!: (error: Error | null, value: Device | null) => void;
     const firstConnected = device({
       readCharacteristicForService: jest.fn(async () => ({ value: fromByteArray(new TextEncoder().encode('{"protocolVersion":1,"desktopId":"pc-1","displayName":"A9_MAX","platform":"windows"}')) } as Characteristic)),
@@ -624,14 +624,16 @@ describe('ReactNativeBleTransport', () => {
 
     scanCallback(null, first);
     await waitFor(() => found.mock.calls.some(([desktop]) => desktop.desktopId === 'pc-1'));
+    scanCallback(null, first);
     scanCallback(null, rotated);
     await Promise.resolve();
 
-    expect(rotated.isConnected).not.toHaveBeenCalled();
+    expect(first.connect).toHaveBeenCalledTimes(1);
+    expect(rotated.isConnected).toHaveBeenCalledTimes(1);
     stop();
   });
 
-  it('discovers multiple Macs that share the Switchify PC Bluetooth name', async () => {
+  it.each(['android', 'ios'] as const)('discovers overlapping same-name PCs on %s', async (platform) => {
     let scanCallback!: (error: Error | null, value: Device | null) => void;
     const makeMac = (id: string, desktopId: string, displayName: string) => {
       const connected = device({
@@ -642,21 +644,38 @@ describe('ReactNativeBleTransport', () => {
     const first = makeMac('mac-1', 'pc-1', 'First Mac');
     const second = makeMac('mac-2', 'pc-2', 'Second Mac');
     const native = manager({ startDeviceScan: jest.fn((_uuids, _options, callback) => { scanCallback = callback; }) });
-    const transport = new ReactNativeBleTransport(native, 'ios');
+    const transport = new ReactNativeBleTransport(native, platform);
     const found = jest.fn();
     const stop = transport.scan(found, jest.fn());
 
     scanCallback(null, first);
-    await waitFor(() => found.mock.calls.some(([desktop]) => desktop.desktopId === 'pc-1'));
     scanCallback(null, second);
+    await waitFor(() => found.mock.calls.some(([desktop]) => desktop.desktopId === 'pc-1'));
     await waitFor(() => found.mock.calls.some(([desktop]) => desktop.desktopId === 'pc-2'));
 
     expect(first.connect).toHaveBeenCalledTimes(1);
     expect(second.connect).toHaveBeenCalledTimes(1);
     stop();
   });
 
-  it('can resolve the second of two same-name PCs', async () => {
+  it('limits concurrent same-name probes to four and cancels them on stop', async () => {
+    let callback!: (error: Error | null, value: Device | null) => void;
+    const native = manager({ startDeviceScan: jest.fn((_u, _o, cb) => { callback = cb; }) });
+    const transport = new ReactNativeBleTransport(native, 'android');
+    const peers = Array.from({ length: 5 }, (_, index) => device({
+      id: `peer-${index}`, name: 'Switchify PC',
+      isConnected: jest.fn(() => new Promise<boolean>(() => undefined)),
+    }));
+    const stop = transport.scan(jest.fn(), jest.fn());
+    peers.forEach((peer) => callback(null, peer));
+    peers.slice(0, 4).forEach((peer) => expect(peer.isConnected).toHaveBeenCalledTimes(1));
+    expect(peers[4]!.isConnected).not.toHaveBeenCalled();
+    stop();
+    peers.slice(0, 4).forEach((peer) => expect(peer.cancelConnection).toHaveBeenCalled());
+    await transport.disconnect();
+  });
+
+  it.each(['android', 'ios'] as const)('resolves overlapping same-name PCs on %s without starving the target', async (platform) => {
     let scanCallback!: (error: Error | null, value: Device | null) => void;
     const firstConnected = device();
     const first = device({ id: 'mac-1', name: 'Switchify PC', isConnected: jest.fn(async () => false), connect: jest.fn(async () => firstConnected) });
@@ -668,12 +687,13 @@ describe('ReactNativeBleTransport', () => {
     });
     const second = device({ id: 'mac-2', name: 'Switchify PC', isConnected: jest.fn(async () => false), connect: jest.fn(async () => secondConnected) });
     const native = manager({ startDeviceScan: jest.fn((_uuids, _options, callback) => { scanCallback = callback; }) });
-    const transport = new ReactNativeBleTransport(native, 'ios');
+    const transport = new ReactNativeBleTransport(native, platform);
 
     const resolving = transport.resolveAndConnect('pc-2');
     await waitFor(() => typeof scanCallback === 'function');
     scanCallback(null, first);
-    await waitFor(() => (firstConnected.cancelConnection as jest.Mock).mock.calls.length === 1);
+    scanCallback(null, second);
+    scanCallback(null, first);
     scanCallback(null, second);
     await expect(resolving).resolves.toMatchObject({ desktopId: 'pc-2', peripheralId: 'mac-2' });
 

src/transport/ReactNativeBleTransport.ts

@@ -6,7 +6,7 @@ import { BLE_DESCRIPTORS, BLE_UUIDS } from '@/domain/protocol/constants';
 import { parseStatus } from '@/domain/protocol/responses';
 import type { ConnectionStage, ConnectionStageOutcome, DiagnosticLog } from '@/diagnostics/DiagnosticLog';
 import type { BleAvailability, BleTransport, DiscoveredDesktop, Unsubscribe } from './BleTransport';
-import { bluetoothDeviceDisplayName, desktopDisplayName } from './desktopDisplayName';
+import { desktopDisplayName } from './desktopDisplayName';
 import { ReadResponsePoller } from './ReadResponsePoller';
 
 export class ReactNativeBleTransport implements BleTransport {
@@ -55,12 +55,10 @@ export class ReactNativeBleTransport implements BleTransport {
       this.#scanDevices.set(device.id, device);
       this.#scanKeys.add(scanKey);
       const task = this.#readStatus(device).then((desktop) => {
-        // Windows commonly rotates its private BLE address while retaining the
-        // computer name. Keep that name claimed for this scan after a
-        // successful probe so one PC cannot repeatedly open GATT connections.
-        // macOS uses the shared name "Switchify PC", so its key must be
-        // released after each probe to allow multiple Macs to be discovered.
-        retainCompletedKey = desktop?.platform === 'windows' && scanKey.startsWith('name:');
+        // Suppress repeats only for this peripheral. A rotated address must be
+        // probed again: neither a shared nor a cached name establishes identity.
+        // Cap retained keys so long scans cannot accumulate unbounded state.
+        retainCompletedKey = desktop?.platform === 'windows' && this.#scanKeys.size <= 256;
         if (active && operation === this.#operation && desktop) onDesktop(desktop);
       }).catch(() => undefined).finally(() => {
         if (operation === this.#operation) {
@@ -474,8 +472,7 @@ export class ReactNativeBleTransport implements BleTransport {
   }
 
   #scanKey(device: Device): string {
-    const name = bluetoothDeviceDisplayName({ name: device.name, localName: device.localName }, this.platform);
-    return name ? `name:${name}` : `id:${device.id}`;
+    return `id:${device.id}`;
   }
 
   #bounded<T>(operation: Promise<T>, timeoutMs = this.nativeTimeoutMs): Promise<T> {