fix: queue waiting BLE probes and rotate completed cache

Author: enaboapps

src/transport/ReactNativeBleTransport.test.ts

@@ -702,6 +702,49 @@ describe('ReactNativeBleTransport', () => {
     expect(secondConnected.cancelConnection).not.toHaveBeenCalled();
   });
 
+  it.each(['android', 'ios'] as const)('queues a target behind four active probes on %s', async (platform) => {
+    let callback!: (error: Error | null, value: Device | null) => void;
+    const releases: (() => void)[] = [];
+    const blockers = Array.from({ length: 4 }, (_, index) => device({
+      id: `other-${index}`, name: 'Switchify PC',
+      discoverAllServicesAndCharacteristics: jest.fn(() => new Promise<Device>((resolve) => {
+        releases.push(() => resolve(device()));
+      })),
+    }));
+    const target = device({ id: 'target', name: 'Switchify PC', readCharacteristicForService: jest.fn(async () => ({
+      value: fromByteArray(new TextEncoder().encode('{"protocolVersion":1,"desktopId":"wanted"}')),
+    } as Characteristic)) });
+    const transport = new ReactNativeBleTransport(manager({ startDeviceScan: jest.fn((_u, _o, cb) => { callback = cb; }) }), platform);
+    const resolving = transport.resolveAndConnect('wanted');
+    await waitFor(() => !!callback);
+    blockers.forEach((peer) => callback(null, peer));
+    await waitFor(() => releases.length === 4);
+    callback(null, target);
+    expect(target.isConnected).not.toHaveBeenCalled();
+    releases.forEach((release) => release());
+    await expect(resolving).resolves.toMatchObject({ desktopId: 'wanted' });
+    expect(target.isConnected).toHaveBeenCalledTimes(1);
+    await transport.disconnect();
+  });
+
+  it('retains the newest Windows address by evicting the oldest at capacity', async () => {
+    let callback!: (error: Error | null, value: Device | null) => void;
+    const found = jest.fn();
+    const transport = new ReactNativeBleTransport(manager({ startDeviceScan: jest.fn((_u, _o, cb) => { callback = cb; }) }), 'android');
+    const stop = transport.scan(found, jest.fn());
+    const peers = Array.from({ length: 257 }, (_, index) => device({ id: `windows-${index}` }));
+    for (const [index, peer] of peers.entries()) {
+      callback(null, peer);
+      await waitFor(() => found.mock.calls.length === index + 1);
+    }
+    callback(null, peers[256]!);
+    expect(peers[256]!.isConnected).toHaveBeenCalledTimes(1);
+    callback(null, peers[0]!);
+    expect(peers[0]!.isConnected).toHaveBeenCalledTimes(2);
+    stop();
+    await transport.disconnect();
+  });
+
   it('waits for cancelled discovery probe cleanup before a real connection', async () => {
     let scanCallback!: (error: Error | null, value: Device | null) => void;
     let releaseDiscovery!: (value: Device) => void;

src/transport/ReactNativeBleTransport.ts

@@ -46,10 +46,16 @@ export class ReactNativeBleTransport implements BleTransport {
   scan(onDesktop: (desktop: DiscoveredDesktop) => void, onError: (error: Error) => void): Unsubscribe {
     const operation = ++this.#operation;
     let active = true;
-    this.#managerOrCreate().startDeviceScan([BLE_UUIDS.service], null, (error, device) => {
+    const waiting = new Map<string, Device>();
+    const onAdvertisement = (error: Error | null, device: Device | null) => {
       if (!active || operation !== this.#operation) return;
       if (error) { onError(error); return; }
-      if (!device || this.#scanDevices.has(device.id) || this.#scanKeys.has(this.#scanKey(device)) || this.#scanDevices.size >= 4) return;
+      if (!device || this.#scanDevices.has(device.id) || this.#scanKeys.has(this.#scanKey(device))) return;
+      if (this.#scanDevices.size >= 4) {
+        if (waiting.size < 32) waiting.set(device.id, device);
+        return;
+      }
+      waiting.delete(device.id);
       const scanKey = this.#scanKey(device);
       let retainCompletedKey = false;
       this.#scanDevices.set(device.id, device);
@@ -58,20 +64,28 @@ export class ReactNativeBleTransport implements BleTransport {
         // 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;
+        retainCompletedKey = desktop?.platform === 'windows';
+        if (active && operation === this.#operation && retainCompletedKey && this.#scanKeys.size > 256) {
+          const oldest = [...this.#scanKeys].find((key) => ![...this.#scanDevices.values()].some((peer) => this.#scanKey(peer) === key));
+          if (oldest) this.#scanKeys.delete(oldest);
+        }
         if (active && operation === this.#operation && desktop) onDesktop(desktop);
       }).catch(() => undefined).finally(() => {
         if (operation === this.#operation) {
           this.#scanDevices.delete(device.id);
           if (!retainCompletedKey) this.#scanKeys.delete(scanKey);
+          const next = waiting.values().next().value;
+          if (next) onAdvertisement(null, next);
         }
       });
       this.#scanTasks.add(task);
       void task.finally(() => this.#scanTasks.delete(task));
-    });
+    };
+    this.#managerOrCreate().startDeviceScan([BLE_UUIDS.service], null, onAdvertisement);
     return () => {
       if (!active) return;
       active = false;
+      waiting.clear();
       if (operation === this.#operation) this.#operation += 1;
       this.#managerOrCreate().stopDeviceScan();
       this.#cancelNativeOperations();
@@ -98,10 +112,12 @@ export class ReactNativeBleTransport implements BleTransport {
       let active = true;
       let claimedDeviceId: string | null = null;
       let cancellation: Promise<void> | null = null;
+      const waiting = new Map<string, Device>();
       const succeed = (desktop: DiscoveredDesktop) => {
         if (!active) return;
         this.#recordStage('resolution', 'succeeded', operation);
         active = false;
+        waiting.clear();
         clearTimeout(timer);
         this.#managerOrCreate().stopDeviceScan();
         this.#scanKeys.clear();
@@ -112,6 +128,7 @@ export class ReactNativeBleTransport implements BleTransport {
         if (!active) return cancellation ?? Promise.resolve();
         this.#recordStage('resolution', outcome, operation);
         active = false;
+        waiting.clear();
         clearTimeout(timer);
         this.#managerOrCreate().stopDeviceScan();
         const probes = [...this.#scanDevices.values()];
@@ -135,7 +152,12 @@ export class ReactNativeBleTransport implements BleTransport {
       const onAdvertisement = (error: Error | null, device: Device | null) => {
         if (!active || operation !== this.#operation) return;
         if (error) { void cancel(new Error('Saved PC discovery failed.')); return; }
-        if (!device || this.#scanDevices.has(device.id) || this.#scanKeys.has(this.#scanKey(device)) || this.#scanDevices.size >= 4) return;
+        if (!device || this.#scanDevices.has(device.id) || this.#scanKeys.has(this.#scanKey(device))) return;
+        if (this.#scanDevices.size >= 4) {
+          if (waiting.size < 32) waiting.set(device.id, device);
+          return;
+        }
+        waiting.delete(device.id);
         this.#scanDevices.set(device.id, device);
         this.#scanKeys.add(this.#scanKey(device));
         const task = this.#readStatus(device, (desktop) => {
@@ -174,6 +196,8 @@ export class ReactNativeBleTransport implements BleTransport {
           if (operation === this.#operation) {
             this.#scanDevices.delete(device.id);
             this.#scanKeys.delete(this.#scanKey(device));
+            const next = waiting.values().next().value;
+            if (next) onAdvertisement(null, next);
           }
         });
         this.#scanTasks.add(task);