Improve resume and navigation responsiveness by fixing log flush races, incremental catalog resolution, and coalesced Android package scans

android/app/src/main/kotlin/dev/zapstore/app/plugins/AndroidPackageManagerPlugin.kt

@@ -32,6 +32,8 @@ import java.security.MessageDigest
 import java.security.cert.CertificateFactory
 import java.util.concurrent.ConcurrentHashMap
 import java.util.concurrent.CountDownLatch
+import java.util.concurrent.ExecutorService
+import java.util.concurrent.Executors
 import java.util.concurrent.TimeUnit
 
 private const val TAG = "AndroidPackageManager"
@@ -110,6 +112,8 @@ class AndroidPackageManagerPlugin :
     private lateinit var eventChannel: EventChannel
     private lateinit var context: Context
     private val mainHandler = Handler(Looper.getMainLooper())
+    private var packageQueryExecutor: ExecutorService? = null
+    @Volatile private var isEngineAttached = false
 
     /** Per-app watchdog generation counters (cancels old scheduled callbacks) */
     private val watchdogGen = mutableMapOf<String, Int>()
@@ -337,6 +341,8 @@ class AndroidPackageManagerPlugin :
         context = binding.applicationContext
         appContext = context
         instance = this
+        isEngineAttached = true
+        packageQueryExecutor = Executors.newSingleThreadExecutor()
 
         methodChannel = MethodChannel(binding.binaryMessenger, "android_package_manager")
         methodChannel.setMethodCallHandler(this)
@@ -355,6 +361,9 @@ class AndroidPackageManagerPlugin :
     }
 
     override fun onDetachedFromEngine(binding: FlutterPlugin.FlutterPluginBinding) {
+        isEngineAttached = false
+        packageQueryExecutor?.shutdownNow()
+        packageQueryExecutor = null
         mainHandler.post { ProcessLifecycleOwner.get().lifecycle.removeObserver(this) }
         unregisterSessionCallback()
         methodChannel.setMethodCallHandler(null)
@@ -680,7 +689,31 @@ class AndroidPackageManagerPlugin :
             "requestInstallPermission" -> requestInstallPermission(result)
             "getInstalledApps" -> {
                 val includeSystem = call.argument<Boolean>("includeSystemApps") ?: false
-                result.success(getInstalledApps(includeSystem))
+                val executor = packageQueryExecutor
+                if (executor == null) {
+                    result.error("PLUGIN_DETACHED", "Package manager is unavailable", null)
+                    return
+                }
+                executor.execute {
+                    try {
+                        val installedApps = getInstalledApps(includeSystem)
+                        mainHandler.post {
+                            if (isEngineAttached) {
+                                result.success(installedApps)
+                            }
+                        }
+                    } catch (error: Throwable) {
+                        mainHandler.post {
+                            if (isEngineAttached) {
+                                result.error(
+                                        "PACKAGE_QUERY_FAILED",
+                                        error.message ?: "Could not query installed apps",
+                                        null
+                                )
+                            }
+                        }
+                    }
+                }
             }
             "uninstall" -> {
                 val packageName = call.argument<String>("packageName")

lib/router.dart

@@ -200,20 +200,11 @@ final routerProvider = Provider<GoRouter>((ref) {
     previousPath = currentPath;
 
     Future.microtask(() {
-      // Sync installed packages on every navigation to catch sideloads,
-      // external installs/uninstalls, and self-updating apps.
-      // This is a local-only platform channel call (~100-500ms, no network).
-      unawaited(
-        ref.read(packageManagerProvider.notifier).syncInstalledPackages(),
-      );
-
       // Re-derive catalog from local DB when arriving at updates tab so
       // data written by other screens or the background service is visible
       // without waiting for the next poll cycle.
       if (isUpdatesRoute && !wasUpdatesRoute) {
-        unawaited(
-          ref.read(updatePollerProvider.notifier).refreshFromLocal(),
-        );
+        unawaited(ref.read(updatePollerProvider.notifier).refreshFromLocal());
       }
 
       // Clear completed operations when navigating away from updates

lib/services/log_service.dart

@@ -375,11 +375,9 @@ class LogService {
         await f;
         continue;
       }
-      if (_pending.isEmpty) return;
-      // No flush in flight but entries pending — kick one off and
-      // record it as the active future so concurrent callers join.
-      _flushFuture = _runFlush();
-      await _flushFuture;
+      if (_pending.isEmpty || _diskDisabled) return;
+      // No flush in flight but entries pending — kick one off.
+      await _startFlush();
     }
   }
 
@@ -449,21 +447,47 @@ class LogService {
       _flushScheduled = false;
       // Another caller (e.g. `flush()`) may have started the flush
       // already; if so, do nothing — entries added after that will
-      // re-schedule in the `_runFlush` finally block.
+      // re-schedule when the in-flight flush completes.
       if (_flushFuture != null) return;
-      _flushFuture = _runFlush();
+      _startFlush();
     });
   }
 
+  /// Sole owner of [_flushFuture]: assigned exactly once here and cleared
+  /// exactly once on completion. `_runFlush` must never touch it — it used
+  /// to null it synchronously on an early return, after which the caller's
+  /// `_flushFuture = _runFlush()` assignment resurrected the already
+  /// completed future. That stale non-null future made `flush()` spin its
+  /// `await`-loop on the microtask queue forever, permanently starving the
+  /// UI event loop (app frozen on resume, kill required).
+  ///
+  /// `whenComplete` on an async function's future always fires in a later
+  /// microtask, so the clear below is guaranteed to run after the
+  /// assignment — even when `_runFlush` returns without suspending.
+  Future<void> _startFlush() {
+    late final Future<void> future;
+    future = _runFlush().whenComplete(() {
+      if (identical(_flushFuture, future)) {
+        _flushFuture = null;
+      }
+      // If new entries arrived while we were flushing, schedule again.
+      if (_pending.isNotEmpty && !_diskDisabled) _scheduleFlush();
+    });
+    _flushFuture = future;
+    return future;
+  }
+
   Future<void> _runFlush() async {
-    if (_pending.isEmpty || _diskDisabled) {
-      _flushFuture = null;
+    if (_diskDisabled) {
+      // Entries can never reach disk this session; drop them so callers
+      // of flush() terminate. The ring buffer still holds them.
+      _pending.clear();
       return;
     }
+    if (_pending.isEmpty) return;
     final file = _activeFile;
     if (file == null) {
       _pending.clear();
-      _flushFuture = null;
       return;
     }
     final batch = List<LogEntry>.from(_pending);
@@ -475,10 +499,6 @@ class LogService {
       _onDiskWriteFailure(e);
     } catch (_) {
       // Swallow — logging must never crash the app.
-    } finally {
-      _flushFuture = null;
-      // If new entries arrived while we were flushing, schedule again.
-      if (_pending.isNotEmpty) _scheduleFlush();
     }
   }
 

lib/services/package_manager/android_package_manager.dart

@@ -1,6 +1,7 @@
 import 'dart:async';
 import 'dart:io';
 
+import 'package:flutter/foundation.dart';
 import 'package:flutter/services.dart';
 import 'package:models/models.dart';
 import 'package:zapstore/services/c1_proof_verification.dart';
@@ -75,6 +76,7 @@ final class AndroidPackageManager extends PackageManager {
   static const _eventChannel = EventChannel('android_package_manager/events');
   bool _supportsSilentInstall = false;
   int _syncGeneration = 0;
+  Future<void>? _syncInFlight;
   StreamSubscription<dynamic>? _eventSubscription;
 
   /// Tracks appIds where we've already attempted to abort orphaned sessions.
@@ -713,7 +715,21 @@ final class AndroidPackageManager extends PackageManager {
   // ═══════════════════════════════════════════════════════════════════════════
 
   @override
-  Future<void> syncInstalledPackages() async {
+  Future<void> syncInstalledPackages() {
+    final inFlight = _syncInFlight;
+    if (inFlight != null) return inFlight;
+
+    late final Future<void> operation;
+    operation = _performInstalledPackagesSync().whenComplete(() {
+      if (identical(_syncInFlight, operation)) {
+        _syncInFlight = null;
+      }
+    });
+    _syncInFlight = operation;
+    return operation;
+  }
+
+  Future<void> _performInstalledPackagesSync() async {
     final syncGen = ++_syncGeneration;
     state = state.copyWith(isScanning: true);
     try {
@@ -729,7 +745,7 @@ final class AndroidPackageManager extends PackageManager {
               ) ??
           [];
 
-      if (syncGen != _syncGeneration) return;
+      if (!mounted || syncGen != _syncGeneration) return;
 
       final packages = <String, PackageInfo>{};
       var anyCanInstallSilently = false;
@@ -762,7 +778,7 @@ final class AndroidPackageManager extends PackageManager {
         }
       }
 
-      if (syncGen != _syncGeneration) return;
+      if (!mounted || syncGen != _syncGeneration) return;
 
       // Derive general silent install capability from per-app data
       _supportsSilentInstall = anyCanInstallSilently;
@@ -770,8 +786,10 @@ final class AndroidPackageManager extends PackageManager {
       // Trust the native source as the single source of truth.
       // Android's SUCCESS broadcast only fires after the package is committed,
       // so there's no race condition with queryable state.
-      state = state.copyWith(installed: packages);
-      await InstalledPackagesSnapshot.save(state.installed);
+      if (!mapEquals(state.installed, packages)) {
+        state = state.copyWith(installed: packages);
+        await InstalledPackagesSnapshot.save(packages);
+      }
 
       // Clear operations for apps where the installed version matches the target version
       // This catches installs that succeeded but we missed the event
@@ -827,7 +845,9 @@ final class AndroidPackageManager extends PackageManager {
     } catch (_) {
       // Don't clobber state on transient errors
     } finally {
-      state = state.copyWith(isScanning: false);
+      if (mounted) {
+        state = state.copyWith(isScanning: false);
+      }
     }
   }
 }

lib/services/updates_service.dart

@@ -152,11 +152,11 @@ class UpdatePollerNotifier extends StateNotifier<UpdatePollerState> {
     // Fire-and-forget: a remote check blocks for tens of seconds offline,
     // but must not delay the local-first UI render that [refreshFromLocal]
     // already produced.
-    unawaited(checkNow());
+    unawaited(checkNow(refreshInstalledPackages: false));
   }
 
   /// Trigger an update check. Called by timer and pull-to-refresh.
-  Future<void> checkNow() async {
+  Future<void> checkNow({bool refreshInstalledPackages = true}) async {
     if (state.isChecking) return;
 
     if (state.lastCheckTime != null) {
@@ -167,7 +167,9 @@ class UpdatePollerNotifier extends StateNotifier<UpdatePollerState> {
     state = state.copyWith(isChecking: true);
 
     try {
-      await ref.read(packageManagerProvider.notifier).syncInstalledPackages();
+      if (refreshInstalledPackages) {
+        await ref.read(packageManagerProvider.notifier).syncInstalledPackages();
+      }
       await _fetchCatalog();
       state = state.copyWith(
         isChecking: false,

lib/widgets/latest_releases_container.dart

@@ -134,7 +134,11 @@ class LatestReleasesNotifier extends StateNotifier<LatestReleasesState> {
 
     final keepAssets = [...assets, ...filteredOlder];
 
-    final appsByAssetId = _resolveAppsFromLocal(storage, keepAssets);
+    final appsByAssetId = _resolveAppsFromLocal(
+      storage,
+      keepAssets,
+      existing: state.appsByAssetId,
+    );
 
     state = state.copyWith(
       firstPage: assets,
@@ -224,9 +228,17 @@ class LatestReleasesNotifier extends StateNotifier<LatestReleasesState> {
 
       state = state.copyWith(
         olderPages: [...state.olderPages, ...unique],
-        appsByAssetId: _resolveAppsFromLocal(storage, keepAssets),
+        appsByAssetId: _resolveAppsFromLocal(
+          storage,
+          keepAssets,
+          existing: state.appsByAssetId,
+        ),
         isLoadingMore: false,
-        hasMore: assets.length >= _kPageSize,
+        // A page that yields no NEW assets is end-of-list. Mirrors the
+        // shared PagedSubscriptionNotifier contract — without the
+        // `unique.isNotEmpty` half, a page of all-duplicates keeps
+        // `hasMore` true and spins the viewport auto-fill loop.
+        hasMore: unique.isNotEmpty && assets.length >= _kPageSize,
       );
     } catch (_) {
       state = state.copyWith(isLoadingMore: false);
@@ -235,13 +247,30 @@ class LatestReleasesNotifier extends StateNotifier<LatestReleasesState> {
 
   /// Synchronously map asset IDs -> parent App using local storage only.
   /// Never awaits network; returns an empty entry for ids not yet in cache.
+  ///
+  /// INCREMENTAL: reuses already-resolved entries from [existing] and only
+  /// runs a `querySync` for assets not yet resolved. This is critical for
+  /// UI responsiveness — this method runs on the UI isolate on EVERY
+  /// subscription emission, and emissions arrive in bursts on resume
+  /// (relay reconnect re-streams the catalog). Re-resolving the entire
+  /// accumulated asset list on every emission is O(loaded assets) of
+  /// synchronous DB work per emission, which pegs the isolate and freezes
+  /// the app. Resolving only new assets keeps steady-state emissions ~O(0).
   Map<String, App> _resolveAppsFromLocal(
     StorageNotifier storage,
-    List<SoftwareAsset> assets,
-  ) {
-    final result = <String, App>{};
+    List<SoftwareAsset> assets, {
+    Map<String, App> existing = const {},
+  }) {
+    final assetIds = assets.map((asset) => asset.id).toSet();
+    // Carry over previously resolved entries whose asset is still present;
+    // drop entries for assets no longer in the list.
+    final result = <String, App>{
+      for (final entry in existing.entries)
+        if (assetIds.contains(entry.key)) entry.key: entry.value,
+    };
     for (final asset in assets) {
       if (asset.appIdentifier.isEmpty) continue;
+      if (result.containsKey(asset.id)) continue; // already resolved
       final matches = storage.querySync(
         RequestFilter<App>(
           authors: {asset.event.pubkey},
@@ -339,6 +368,13 @@ class LatestReleasesContainer extends HookConsumerWidget {
 
     final combinedApps = [...pinnedApps, ...dedupedApps];
 
+    // Tracks the visible (deduped) app count the last time we auto-filled an
+    // underfilled viewport. Guards against an unbounded loop: when many
+    // SoftwareAssets collapse to few app cards, `maxScrollExtent` stays <= 0
+    // and the post-frame check would otherwise call `loadMore` every frame,
+    // walking the entire local asset history synchronously on the UI isolate.
+    final lastAutoFillLength = useRef<int?>(null);
+
     useEffect(() {
       if (state == null) return null;
       void onScroll() {
@@ -356,9 +392,23 @@ class LatestReleasesContainer extends HookConsumerWidget {
         final position = scrollController.position;
         final s = ref.read(latestReleasesProvider);
         if (s.isLoadingMore || !s.hasMore) return;
-        if (position.maxScrollExtent <= 0 ||
+
+        // User scrolled near the bottom of a scrollable list — normal
+        // infinite scroll. Only possible once content overflows the viewport.
+        if (position.maxScrollExtent > 0 &&
             position.pixels >= position.maxScrollExtent - 300) {
           ref.read(latestReleasesProvider.notifier).loadMore();
+          return;
+        }
+
+        // Viewport not filled yet — auto-fill so infinite scroll can engage.
+        // Only attempt again once the visible app count has actually grown;
+        // otherwise a page of assets that maps only to already-shown apps
+        // would keep this firing forever.
+        if (position.maxScrollExtent <= 0) {
+          if (lastAutoFillLength.value == combinedApps.length) return;
+          lastAutoFillLength.value = combinedApps.length;
+          ref.read(latestReleasesProvider.notifier).loadMore();
         }
       }
 

test/services/log_service_test.dart

@@ -1,4 +1,5 @@
 import 'dart:io';
+import 'dart:isolate';
 
 import 'package:flutter_test/flutter_test.dart';
 import 'package:path/path.dart' as p;
@@ -18,6 +19,18 @@ Future<({LogService log, Directory dir})> _newService(
 
 File _activeFile(Directory dir) => File(p.join(dir.path, 'zapstore.log'));
 
+/// Isolate entry for the flushSync-race regression test. Reports 'ok'
+/// once flush() returns; if flush() spins forever the parent times out.
+Future<void> _flushAfterFlushSyncRace(SendPort report) async {
+  final dir = await Directory.systemTemp.createTemp('log_service_race_');
+  final svc = LogService.forTesting(directory: dir, isolate: 'race');
+  svc.info('entry'); // schedules the flush microtask
+  svc.flushSync(); // drains _pending before the microtask runs
+  await Future<void>.delayed(Duration.zero); // let the microtask fire
+  await svc.flush(); // must terminate
+  report.send('ok');
+}
+
 void main() {
   group('LogService basics', () {
     test('records to ring buffer and disk', () async {
@@ -288,6 +301,37 @@ void main() {
   });
 
   group('Concurrency', () {
+    // Regression: log() schedules a flush microtask; if flushSync() (the
+    // uncaught-error path) drains _pending before that microtask runs,
+    // the microtask used to leave a stale, already-completed
+    // _flushFuture behind. The next flush() — called on every app
+    // pause — then spun `await`ing that completed future forever,
+    // starving the UI event loop with microtasks (app frozen on
+    // resume, kill required).
+    //
+    // A regression cannot be caught by a plain `await flush()` here:
+    // the spin never yields to the event loop, so even a timeout timer
+    // would never fire in this isolate. Run the scenario in a separate
+    // isolate and time out from the outside.
+    test('flush completes after flushSync races a scheduled flush',
+        () async {
+      final done = ReceivePort();
+      final isolate = await Isolate.spawn(
+        _flushAfterFlushSyncRace,
+        done.sendPort,
+      );
+      try {
+        final result = await done.first.timeout(
+          const Duration(seconds: 10),
+          onTimeout: () => 'flush() never completed — microtask spin',
+        );
+        expect(result, 'ok');
+      } finally {
+        isolate.kill(priority: Isolate.immediate);
+        done.close();
+      }
+    });
+
     test('many overlapping flushes never corrupt a line', () async {
       final (:log, :dir) = await _newService();
 

test/services/package_manager/android_package_manager_test.dart

@@ -0,0 +1,54 @@
+import 'dart:async';
+
+import 'package:flutter/services.dart';
+import 'package:flutter_test/flutter_test.dart';
+import 'package:hooks_riverpod/hooks_riverpod.dart';
+import 'package:zapstore/services/package_manager/android_package_manager.dart';
+import 'package:zapstore/services/package_manager/package_manager.dart';
+
+void main() {
+  TestWidgetsFlutterBinding.ensureInitialized();
+
+  const methodChannel = MethodChannel('android_package_manager');
+  const eventChannel = MethodChannel('android_package_manager/events');
+
+  tearDown(() async {
+    final messenger =
+        TestDefaultBinaryMessengerBinding.instance.defaultBinaryMessenger;
+    messenger.setMockMethodCallHandler(methodChannel, null);
+    messenger.setMockMethodCallHandler(eventChannel, null);
+  });
+
+  test('coalesces overlapping installed-package scans', () async {
+    final scanResult = Completer<List<Object?>>();
+    var scanCalls = 0;
+    final messenger =
+        TestDefaultBinaryMessengerBinding.instance.defaultBinaryMessenger;
+
+    messenger.setMockMethodCallHandler(eventChannel, (_) async => null);
+    messenger.setMockMethodCallHandler(methodChannel, (call) async {
+      expect(call.method, 'getInstalledApps');
+      scanCalls++;
+      return scanResult.future;
+    });
+
+    final container = ProviderContainer(
+      overrides: [
+        packageManagerProvider.overrideWith(AndroidPackageManager.new),
+      ],
+    );
+    addTearDown(container.dispose);
+
+    final packageManager = container.read(packageManagerProvider.notifier);
+    final first = packageManager.syncInstalledPackages();
+    final second = packageManager.syncInstalledPackages();
+
+    expect(identical(first, second), isTrue);
+    expect(scanCalls, 1);
+
+    scanResult.complete(const []);
+    await Future.wait([first, second]);
+
+    expect(scanCalls, 1);
+  });
+}