feat: Factor out "multiple-waiting" into its own thing

packages/moxxmpp/lib/src/util/wait.dart

@@ -0,0 +1,67 @@
+import 'dart:async';
+import 'package:meta/meta.dart';
+import 'package:synchronized/synchronized.dart';
+
+/// This class allows for multiple asynchronous code places to wait on the
+/// same computation of type [V], indentified by a key of type [K].
+class WaitForTracker<K, V> {
+  /// The mapping of key -> Completer for the pending tasks.
+  final Map<K, List<Completer<V>>> _tracker = {};
+
+  /// The lock for accessing _tracker.
+  final Lock _lock = Lock();
+
+  /// Wait for a task with key [key]. If there was no such task already
+  /// present, returns null. If one or more tasks were already present, returns
+  /// a future that will resolve to the result of the first task.
+  Future<Future<V>?> waitFor(K key) async {
+    final result = await _lock.synchronized(() {
+      if (_tracker.containsKey(key)) {
+        // The task already exists. Just append outselves
+        final completer = Completer<V>();
+        _tracker[key]!.add(completer);
+        return completer;
+      }
+
+      // The task does not exist yet
+      _tracker[key] = List<Completer<V>>.empty(growable: true);
+      return null;
+    });
+
+    return result?.future;
+  }
+
+  /// Resolve a task with key [key] to [value].
+  Future<void> resolve(K key, V value) async {
+    await _lock.synchronized(() {
+      if (!_tracker.containsKey(key)) return;
+
+      for (final completer in _tracker[key]!) {
+        completer.complete(value);
+      }
+
+      _tracker.remove(key);
+    });
+  }
+
+  Future<void> resolveAll(V value) async {
+    await _lock.synchronized(() {
+      for (final key in _tracker.keys) {
+        for (final completer in _tracker[key]!) {
+          completer.complete(value);
+        }
+      }
+    });
+  }
+  
+  /// Remove all tasks from the tracker.
+  Future<void> clear() async {
+    await _lock.synchronized(_tracker.clear);
+  }
+
+  @visibleForTesting
+  bool hasTasksRunning() => _tracker.isNotEmpty;
+
+  @visibleForTesting
+  List<Completer<V>> getRunningTasks(K key) => _tracker[key]!;
+}

packages/moxxmpp/lib/src/xeps/xep_0030/cache.dart

@@ -0,0 +1,23 @@
+import 'package:meta/meta.dart';
+
+@internal
+@immutable
+class DiscoCacheKey {
+  const DiscoCacheKey(this.jid, this.node);
+  
+  /// The JID we're requesting disco data from.
+  final String jid;
+
+  /// Optionally the node we are requesting from.
+  final String? node;
+
+  @override
+  bool operator ==(Object other) {
+    return other is DiscoCacheKey &&
+           jid == other.jid &&
+           node == other.node;
+  }
+  
+  @override
+  int get hashCode => jid.hashCode ^ node.hashCode;
+}

packages/moxxmpp/lib/src/xeps/xep_0030/xep_0030.dart

@@ -1,5 +1,6 @@
 import 'dart:async';
 import 'package:meta/meta.dart';
+import 'package:moxxmpp/src/connection.dart';
 import 'package:moxxmpp/src/events.dart';
 import 'package:moxxmpp/src/jid.dart';
 import 'package:moxxmpp/src/managers/base.dart';
@@ -10,6 +11,8 @@ import 'package:moxxmpp/src/namespaces.dart';
 import 'package:moxxmpp/src/stanza.dart';
 import 'package:moxxmpp/src/stringxml.dart';
 import 'package:moxxmpp/src/types/result.dart';
+import 'package:moxxmpp/src/util/wait.dart';
+import 'package:moxxmpp/src/xeps/xep_0030/cache.dart';
 import 'package:moxxmpp/src/xeps/xep_0030/errors.dart';
 import 'package:moxxmpp/src/xeps/xep_0030/helpers.dart';
 import 'package:moxxmpp/src/xeps/xep_0030/types.dart';
@@ -22,21 +25,6 @@ typedef DiscoInfoRequestCallback = Future<DiscoInfo> Function();
 /// Callback that is called when a disco#items requests is received on a given node.
 typedef DiscoItemsRequestCallback = Future<List<DiscoItem>> Function();
 
-@immutable
-class DiscoCacheKey {
-  const DiscoCacheKey(this.jid, this.node);
-  final String jid;
-  final String? node;
-
-  @override
-  bool operator ==(Object other) {
-    return other is DiscoCacheKey && jid == other.jid && node == other.node;
-  }
-  
-  @override
-  int get hashCode => jid.hashCode ^ node.hashCode;
-}
-
 /// This manager implements XEP-0030 by providing a way of performing disco#info and
 /// disco#items requests and answering those requests.
 /// A caching mechanism is also provided.
@@ -62,8 +50,11 @@ class DiscoManager extends XmppManagerBase {
   /// Map full JID to Disco Info
   final Map<DiscoCacheKey, DiscoInfo> _discoInfoCache = {};
 
-  /// Mapping the full JID to a list of running requests
-  final Map<DiscoCacheKey, List<Completer<Result<DiscoError, DiscoInfo>>>> _runningInfoQueries = {};
+  /// The tracker for tracking disco#info queries that are in flight.
+  final WaitForTracker<DiscoCacheKey, Result<DiscoError, DiscoInfo>> _discoInfoTracker = WaitForTracker();
+
+  /// The tracker for tracking disco#info queries that are in flight.
+  final WaitForTracker<DiscoCacheKey, Result<DiscoError, List<DiscoItem>>> _discoItemsTracker = WaitForTracker();
 
   /// Cache lock
   final Lock _cacheLock = Lock();
@@ -79,12 +70,9 @@ class DiscoManager extends XmppManagerBase {
 
   /// The list of disco features that are registered.
   List<String> get features => _features;
-  
-  @visibleForTesting
-  bool hasInfoQueriesRunning() => _runningInfoQueries.isNotEmpty;
 
   @visibleForTesting
-  List<Completer<Result<DiscoError, DiscoInfo>>> getRunningInfoQueries(DiscoCacheKey key) => _runningInfoQueries[key]!;
+  WaitForTracker<DiscoCacheKey, Result<DiscoError, DiscoInfo>> get infoTracker => _discoInfoTracker;
   
   @override
   List<StanzaHandler> getIncomingStanzaHandlers() => [
@@ -118,7 +106,21 @@ class DiscoManager extends XmppManagerBase {
   Future<void> onXmppEvent(XmppEvent event) async {
     if (event is PresenceReceivedEvent) {
       await _onPresence(event.jid, event.presence);
-    } else if (event is StreamResumeFailedEvent) {
+    } else if (event is ConnectionStateChangedEvent) {
+      // TODO(Unknown): This handling is stupid. We should have an event that is
+      //                triggered when we cannot guarantee that everything is as
+      //                it was before.
+      if (event.state != XmppConnectionState.connected) return;
+      if (event.resumed) return;
+
+      // Cancel all waiting requests
+      await _discoInfoTracker.resolveAll(
+        Result<DiscoError, DiscoInfo>(UnknownDiscoError()),
+      );
+      await _discoItemsTracker.resolveAll(
+        Result<DiscoError, List<DiscoItem>>(UnknownDiscoError()),
+      );
+      
       await _cacheLock.synchronized(() async {
         // Clear the cache
         _discoInfoCache.clear();
@@ -259,46 +261,37 @@ class DiscoManager extends XmppManagerBase {
   }
 
   Future<void> _exitDiscoInfoCriticalSection(DiscoCacheKey key, Result<DiscoError, DiscoInfo> result) async {
-    return _cacheLock.synchronized(() async {
-      // Complete all futures
-      for (final completer in _runningInfoQueries[key]!) {
-        completer.complete(result);
-      }
-
+    await _cacheLock.synchronized(() async {
       // Add to cache if it is a result
       if (result.isType<DiscoInfo>()) {
         _discoInfoCache[key] = result.get<DiscoInfo>();
       }
-      
-      // Remove from the request cache
-      _runningInfoQueries.remove(key);
     });
+
+    await _discoInfoTracker.resolve(key, result);
   }
   
   /// Sends a disco info query to the (full) jid [entity], optionally with node=[node].
   Future<Result<DiscoError, DiscoInfo>> discoInfoQuery(String entity, { String? node, bool shouldEncrypt = true }) async {
     final cacheKey = DiscoCacheKey(entity, node);
     DiscoInfo? info;
-    Completer<Result<DiscoError, DiscoInfo>>? completer;
-    await _cacheLock.synchronized(() async {
+    final ffuture = await _cacheLock.synchronized<Future<Future<Result<DiscoError, DiscoInfo>>?>?>(() async {
       // Check if we already know what the JID supports
       if (_discoInfoCache.containsKey(cacheKey)) {
         info = _discoInfoCache[cacheKey];
+        return null;
       } else {
-        // Is a request running?
-        if (_runningInfoQueries.containsKey(cacheKey)) {
-          completer = Completer();
-          _runningInfoQueries[cacheKey]!.add(completer!);
-        } else {
-          _runningInfoQueries[cacheKey] = List.from(<Completer<DiscoInfo?>>[]);
-        }
+        return _discoInfoTracker.waitFor(cacheKey);
       }
     });
 
     if (info != null) {
       return Result<DiscoError, DiscoInfo>(info);
-    } else if (completer != null) {
-      return completer!.future;
+    } else {
+      final future = await ffuture;
+      if (future != null) {
+        return future;
+      }
     }
 
     final stanza = await getAttributes().sendStanza(
@@ -331,6 +324,12 @@ class DiscoManager extends XmppManagerBase {
 
   /// Sends a disco items query to the (full) jid [entity], optionally with node=[node].
   Future<Result<DiscoError, List<DiscoItem>>> discoItemsQuery(String entity, { String? node, bool shouldEncrypt = true }) async {
+    final key = DiscoCacheKey(entity, node);
+    final future = await _discoItemsTracker.waitFor(key);
+    if (future != null) {
+      return future;
+    }
+
     final stanza = await getAttributes()
       .sendStanza(
         buildDiscoItemsQueryStanza(entity, node: node),
@@ -338,12 +337,18 @@ class DiscoManager extends XmppManagerBase {
       ) as Stanza;
 
     final query = stanza.firstTag('query');
-    if (query == null) return Result(InvalidResponseDiscoError());
+    if (query == null) {
+      final result = Result<DiscoError, List<DiscoItem>>(InvalidResponseDiscoError());
+      await _discoItemsTracker.resolve(key, result);
+      return result;
+    }
 
     if (stanza.type == 'error') {
       //final error = stanza.firstTag('error');
       //print("Disco Items error: " + error.toXml());
-      return Result(ErrorResponseDiscoError());
+      final result = Result<DiscoError, List<DiscoItem>>(ErrorResponseDiscoError());
+      await _discoItemsTracker.resolve(key, result);
+      return result;
     }
 
     final items = query.findTags('item').map((node) => DiscoItem(
@@ -352,7 +357,9 @@ class DiscoManager extends XmppManagerBase {
       name: node.attributes['name'] as String?,
     ),).toList();
 
-    return Result(items);
+    final result = Result<DiscoError, List<DiscoItem>>(items);
+    await _discoItemsTracker.resolve(key, result);
+    return result;
   }
 
   /// Queries information about a jid based on its node and capability hash.

packages/moxxmpp/test/wait_test.dart

@@ -0,0 +1,40 @@
+import 'package:test/test.dart';
+import 'package:moxxmpp/src/util/wait.dart';
+
+void main() {
+  test('Test adding and resolving', () async {
+    // ID -> Milliseconds since epoch
+    final tracker = WaitForTracker<int, int>();
+
+    int r2 = 0;
+    int r3 = 0;
+    
+    // Queue some jobs
+    final r1 = await tracker.waitFor(0);
+    expect(r1, null);
+    
+    tracker
+      .waitFor(0)
+      .then((result) async {
+        expect(result != null, true);
+        r2 = await result!;
+      });
+    tracker
+      .waitFor(0)
+      .then((result) async {
+        expect(result != null, true);
+        r3 = await result!;
+      });
+
+    final c = await tracker.waitFor(1);
+    expect(c, null);
+
+    // Resolve jobs
+    await tracker.resolve(0, 42);
+    await tracker.resolve(1, 25);
+    await tracker.resolve(2, -1);
+
+    expect(r2, 42);
+    expect(r3, 42);
+  });
+}

packages/moxxmpp/test/xeps/xep_0030_test.dart

@@ -1,9 +1,12 @@
 import 'package:moxxmpp/moxxmpp.dart';
 import 'package:test/test.dart';
 
+import '../helpers/logging.dart';
 import '../helpers/xmpp.dart';
 
 void main() {
+  initLogger();
+
   test('Test having multiple disco requests for the same JID', () async {
     final fakeSocket = StubTCPSocket(
       play: [
@@ -102,7 +105,7 @@ void main() {
 
     await Future.delayed(const Duration(seconds: 1));
     expect(
-      disco.getRunningInfoQueries(DiscoCacheKey(jid.toString(), null)).length,
+      disco.infoTracker.getRunningTasks(DiscoCacheKey(jid.toString(), null)).length,
       1,
     );
     fakeSocket.injectRawXml("<iq type='result' id='${fakeSocket.lastId!}' from='romeo@montague.lit/orchard' to='polynomdivision@test.server/MU29eEZn' xmlns='jabber:client'><query xmlns='http://jabber.org/protocol/disco#info' /></iq>");
@@ -111,6 +114,6 @@ void main() {
     
     expect(fakeSocket.getState(), 6);
     expect(await result1, await result2);
-    expect(disco.hasInfoQueriesRunning(), false);
+    expect(disco.infoTracker.hasTasksRunning(), false);
   });
 }