autocomplete: Sort user-mention autocomplete results

Fixes: #228

Author: sm-sayedi

lib/model/autocomplete.dart

@@ -183,6 +183,7 @@ class MentionAutocompleteView extends ChangeNotifier {
   @override
   void dispose() {
     store.autocompleteViewManager.unregisterMentionAutocomplete(this);
+    _sortedUsers = null;
     // We cancel in-progress computations by checking [hasListeners] between tasks.
     // After [super.dispose] is called, [hasListeners] returns false.
     // TODO test that logic (may involve detecting an unhandled Future rejection; how?)
@@ -206,6 +207,7 @@ class MentionAutocompleteView extends ChangeNotifier {
   /// Called in particular when we get a [RealmUserEvent].
   void refreshStaleUserResults() {
     if (_query != null) {
+      _sortedUsers = null;
       _startSearch(_query!);
     }
   }
@@ -244,11 +246,108 @@ class MentionAutocompleteView extends ChangeNotifier {
     notifyListeners();
   }
 
+  List<User>? _sortedUsers;
+
+  int compareByDms(User userA, User userB) {
+    final countA = store.recentDmConversationsView.getRecipientCount(userA.userId);
+    final countB = store.recentDmConversationsView.getRecipientCount(userB.userId);
+
+    if (countA > countB) {
+      return -1;
+    } else if (countB > countA) {
+      return 1;
+    }
+
+    if (!userA.isBot && userB.isBot) {
+      return -1;
+    } else if (userA.isBot && !userB.isBot) {
+      return 1;
+    }
+
+    if (userA.fullName.toLowerCase().compareTo(
+      userB.fullName.toLowerCase()) < 0) {
+      return -1;
+    }
+    return 1;
+  }
+
+  int compareByRelevance({
+    required User userA,
+    required User userB,
+    required int Function(User, User) tertiaryCompare,
+  }) {
+    // TODO: give preference to "all", "everyone" or "stream".
+
+    // TODO: give preference to subscribed users first
+
+    // give preference to direct message partners if both (are)/(are not) subscribers
+    final aIsPartner = store.recentDmConversationsView.isPartner(userA.userId);
+    final bIsPartner = store.recentDmConversationsView.isPartner(userB.userId);
+
+    if (aIsPartner && !bIsPartner) {
+      return -1;
+    } else if (bIsPartner && !aIsPartner) {
+      return 1;
+    }
+
+    return tertiaryCompare(userA, userB);
+  }
+
+  List<User> sortByRelevance({
+    required List<User> users,
+    required int? currentStreamId,
+    required String? currentTopic,
+  }) {
+    // Sorting for DMs narrow
+    if (currentStreamId == null) {
+      users.sort((userA, userB) => compareByRelevance(
+        userA: userA,
+        userB: userB,
+        tertiaryCompare: compareByDms));
+    } else { // Sorting for stream/topic narrow
+      users.sort((userA, userB) => compareByRelevance(
+        userA: userA,
+        userB: userB,
+        tertiaryCompare: (userA, userB) => store.recentSenders.compareByRecency(
+          userA: userA,
+          userB: userB,
+          streamId: currentStreamId,
+          topic: currentTopic)));
+    }
+    return users;
+  }
+
+  void _sortUsers() {
+    final users = store.users.values.toList();
+    switch(narrow) {
+      case StreamNarrow():
+        _sortedUsers = sortByRelevance(
+            users: users,
+            currentStreamId: (narrow as StreamNarrow).streamId,
+            currentTopic: null);
+      case TopicNarrow():
+        _sortedUsers = sortByRelevance(
+            users: users,
+            currentStreamId: (narrow as TopicNarrow).streamId,
+            currentTopic: (narrow as TopicNarrow).topic);
+      case DmNarrow():
+        _sortedUsers = sortByRelevance(
+            users: users,
+            currentStreamId: null,
+            currentTopic: null);
+      case AllMessagesNarrow():
+        _sortedUsers = []; // TODO: sort (maybe in future)
+    }
+  }
+
   Future<List<MentionAutocompleteResult>?> _computeResults(MentionAutocompleteQuery query) async {
     final List<MentionAutocompleteResult> results = [];
-    final Iterable<User> users = store.users.values;
 
-    final iterator = users.iterator;
+    if (_sortedUsers == null) {
+      _sortUsers();
+    }
+
+    final iterator = _sortedUsers!.iterator;
     bool isDone = false;
     while (!isDone) {
       // CPU perf: End this task; enqueue a new one for resuming this work
@@ -270,7 +369,7 @@ class MentionAutocompleteView extends ChangeNotifier {
         }
       }
     }
-    return results; // TODO(#228) sort for most relevant first
+    return results;
   }
 }
 

lib/model/message_list.dart

@@ -317,6 +317,7 @@ class MessageListView with ChangeNotifier, _MessageSequence {
   @override
   void dispose() {
     store.unregisterMessageList(this);
+    store.recentDmConversationsView.clearRecipientCount(narrow);
     super.dispose();
   }
 
@@ -382,6 +383,8 @@ class MessageListView with ChangeNotifier, _MessageSequence {
       if (_messageVisible(message)) {
         _addMessage(message);
       }
+      store.recentSenders.processStreamMessage(message);
+      store.recentDmConversationsView.maybeIncrRecipientCount(message);
     }
     _fetched = true;
     _haveOldest = result.foundOldest;

lib/model/recent_dm_conversations.dart

@@ -40,6 +40,9 @@ class RecentDmConversationsView extends ChangeNotifier {
 
   final int selfUserId;
 
+  // Number of messages sent per user
+  final Map<int, int> _recipientCountMap = {};
+
   /// Insert the key at the proper place in [sorted].
   ///
   /// Optimized, taking O(1) time, for the case where that place is the start,
@@ -123,4 +126,42 @@ class RecentDmConversationsView extends ChangeNotifier {
   // TODO update from messages loaded in message lists. When doing so,
   //   review handleMessageEvent so it acknowledges the subtle races that can
   //   happen when taking data from outside the event system.
+
+  bool isPartner(int userId) {
+    return sorted.any((dmNarrow) =>  dmNarrow.otherRecipientIds.contains(userId));
+  }
+
+  int getRecipientCount(int userId) => _recipientCountMap[userId] ?? 0;
+
+  void incrRecipientCount(int userId) {
+    final oldCount = _recipientCountMap[userId] ?? 0;
+    _recipientCountMap[userId] = oldCount + 1;
+  }
+
+  void clearRecipientCount(Narrow narrow) {
+    if (narrow is! DmNarrow) {
+      return;
+    }
+
+    for (final userId in narrow.otherRecipientIds) {
+      _recipientCountMap[userId] = 0;
+    }
+  }
+
+  void maybeIncrRecipientCount(Message message) {
+    if (message is! DmMessage) {
+      return;
+    }
+
+    if (message.senderId != selfUserId) {
+      return;
+    }
+
+    for (final recipient in message.displayRecipient) {
+      if (recipient.id == selfUserId) {
+        continue;
+      }
+      incrRecipientCount(recipient.id);
+    }
+  }
 }

lib/model/store.dart

@@ -1,6 +1,7 @@
 import 'dart:async';
 import 'dart:convert';
 import 'dart:io';
+import 'dart:math' as math;
 
 import 'package:drift/native.dart';
 import 'package:flutter/foundation.dart';
@@ -287,6 +288,8 @@ class PerAccountStore extends ChangeNotifier with StreamStore {
 
   final Map<int, User> users;
 
+  final RecentSenders recentSenders = RecentSenders();
+
   ////////////////////////////////
   // Streams, topics, and stuff about them.
 
@@ -347,6 +350,7 @@ class PerAccountStore extends ChangeNotifier with StreamStore {
   void dispose() {
     unreads.dispose();
     recentDmConversationsView.dispose();
+    recentSenders.clear();
     for (final view in _messageListViews.toList()) {
       view.dispose();
     }
@@ -436,7 +440,9 @@ class PerAccountStore extends ChangeNotifier with StreamStore {
       notifyListeners();
     } else if (event is MessageEvent) {
       assert(debugLog("server event: message ${jsonEncode(event.message.toJson())}"));
+      recentSenders.processStreamMessage(event.message);
       recentDmConversationsView.handleMessageEvent(event);
+      recentDmConversationsView.maybeIncrRecipientCount(event.message);
       for (final view in _messageListViews) {
         view.maybeAddMessage(event.message);
       }
@@ -767,3 +773,145 @@ class UpdateMachine {
   @override
   String toString() => '${objectRuntimeType(this, 'UpdateMachine')}#${shortHash(this)}';
 }
+
+extension Max<T extends num> on Iterable<T> {
+  /// Finds the maximum number in an [Iterable].
+  ///
+  /// Returns null if the [Iterable] is empty.
+  T? max() => isNotEmpty ? reduce(math.max) : null;
+}
+
+/// A data structure to keep track of message ids.
+class IdTracker {
+  final Set<int> _ids = {};
+
+  int _maxId = -1;
+
+  void add(int id) {
+    _ids.add(id);
+
+    if (id > _maxId) {
+      _maxId = id;
+    }
+  }
+
+  // TODO: remove
+
+  int maxId() {
+    if (_maxId == -1) {
+      _maxId = _ids.max() ?? -1;
+    }
+    return _maxId;
+  }
+
+  @override
+  String toString() {
+    return _ids.toString();
+  }
+}
+
+/// A data structure to keep track of stream and topic messages.
+class RecentSenders {
+  // streamSenders[streamId][senderId] = IdTracker
+  final Map<int, Map<int, IdTracker>> _streamSenders = {};
+
+  // topicSenders[streamId][topic][senderId] = IdTracker
+  final Map<int, Map<String, Map<int, IdTracker>>> _topicSenders = {};
+
+  // TODO: dmSenders (maybe)
+
+  void clear() {
+    _streamSenders.clear();
+    _topicSenders.clear();
+  }
+
+  int maxIdForStreamSender({required int streamId, required int senderId}) {
+    return _streamSenders[streamId]?[senderId]?.maxId() ?? -1;
+  }
+
+  int maxIdForStreamTopicSender({
+    required int streamId,
+    required String topic,
+    required int senderId,
+  }) {
+    topic = topic.toLowerCase();
+    return _topicSenders[streamId]?[topic]?[senderId]?.maxId() ?? -1;
+  }
+
+  void addStreamMessage({
+    required int streamId,
+    required int senderId,
+    required messageId,
+  }) {
+    final senderMap = _streamSenders[streamId] ?? {};
+    final idTracker = senderMap[senderId] ?? IdTracker();
+    _streamSenders[streamId] = senderMap;
+    senderMap[senderId] = idTracker;
+    idTracker.add(messageId);
+  }
+
+  void addTopicMessage({
+    required int streamId,
+    required String topic,
+    required int senderId,
+    required messageId,
+  }) {
+    topic = topic.toLowerCase();
+    final topicMap = _topicSenders[streamId] ?? {};
+    final senderMap = topicMap[topic] ?? {};
+    final idTracker = senderMap[senderId] ?? IdTracker();
+    _topicSenders[streamId] = topicMap;
+    topicMap[topic] = senderMap;
+    senderMap[senderId] = idTracker;
+    idTracker.add(messageId);
+  }
+
+  void processStreamMessage(Message message) {
+    if (message is! StreamMessage) {
+      return;
+    }
+
+    final streamId = message.streamId;
+    final topic = message.subject;
+    final senderId = message.senderId;
+    final messageId = message.id;
+
+    addStreamMessage(
+        streamId: streamId, senderId: senderId, messageId: messageId);
+    addTopicMessage(
+        streamId: streamId,
+        topic: topic,
+        senderId: senderId,
+        messageId: messageId);
+  }
+
+  // TODO: removeTopicMessage
+
+  int compareByRecency({
+    required User userA,
+    required User userB,
+    required int streamId,
+    // TODO: may turn this into a non-nullable string after (#493)
+    required String? topic,
+  }) {
+    int aMessageId, bMessageId;
+
+    if (topic != null) {
+      aMessageId = maxIdForStreamTopicSender(
+          streamId: streamId, topic: topic, senderId: userA.userId);
+      bMessageId = maxIdForStreamTopicSender(
+          streamId: streamId, topic: topic, senderId: userB.userId);
+
+      if (aMessageId != bMessageId) {
+        return bMessageId - aMessageId;
+      }
+    }
+
+    aMessageId =
+        maxIdForStreamSender(streamId: streamId, senderId: userA.userId);
+    bMessageId =
+        maxIdForStreamSender(streamId: streamId, senderId: userB.userId);
+
+    return bMessageId - aMessageId;
+  }
+}