Read receipt support

Fixes #93

lib/controllers/client.dart

@@ -8,6 +8,7 @@ import "package:fast_immutable_collections/fast_immutable_collections.dart";
 import "package:ffi/ffi.dart";
 import "package:flutter/cupertino.dart";
 import "package:intl/intl.dart";
+import "package:nexus/controllers/settings.dart";
 import "package:nexus/helpers/extensions/gomuks_buffer.dart";
 import "package:nexus/models/capabilities.dart";
 import "package:nexus/models/content/message.dart";
@@ -344,9 +345,14 @@ class ClientController extends AsyncNotifier<int> {
 
     if (event == null) return;
 
+    // Private until settings have loaded, in case the user turned sending off
+    final sendPublic =
+        ref.read(SettingsController.provider).value?.readReceipts ==
+        .showAndSend;
+
     await _sendCommand("mark_read", {
       "room_id": room.metadata!.id,
-      "receipt_type": "m.read",
+      "receipt_type": sendPublic ? "m.read" : "m.read.private",
       "event_id": event.eventId,
     });
   }

lib/controllers/read_receipts.dart

@@ -0,0 +1,90 @@
+import "package:collection/collection.dart";
+import "package:fast_immutable_collections/fast_immutable_collections.dart";
+import "package:flutter_riverpod/flutter_riverpod.dart";
+import "package:nexus/controllers/client_state.dart";
+import "package:nexus/controllers/room_chat.dart";
+import "package:nexus/controllers/rooms.dart";
+import "package:nexus/controllers/settings.dart";
+import "package:nexus/helpers/extensions/is_shown_as_message.dart";
+import "package:nexus/models/read_receipt.dart";
+
+/// Other users' read receipts in a chat, by the event ID of the message to
+/// show them under: the nearest message at or before what they've read.
+class ReadReceiptsController(final ChatParams chat)
+    extends Notifier<IMap<String, IList<ReadReceipt>>> {
+  @override
+  IMap<String, IList<ReadReceipt>> build() {
+    final shouldShow = ref.watch(
+      SettingsController.provider.select(
+        (settings) => settings.value?.readReceipts != .neither,
+      ),
+    );
+    if (!shouldShow) return const .empty();
+
+    final userId = ref.watch(
+      ClientStateController.provider.select((state) => state?.userId),
+    );
+    // The chat's own timeline, so receipts follow what's actually shown
+    final timeline = ref.watch(
+      RoomChatController.provider(chat)
+          .select((roomChat) => roomChat.value?.timeline),
+    );
+    final room = ref.watch(
+      RoomsController.provider.select(
+        (rooms) => switch (rooms[chat.roomId]) {
+          final room? => (events: room.events, receipts: room.receipts),
+          null => null,
+        },
+      ),
+    );
+    if (userId == null || timeline == null || room == null) {
+      return const .empty();
+    }
+
+    final events = timeline.map((rowId) => room.events[rowId]).nonNulls;
+    final indexes = IMap.fromEntries(
+      events.indexed.map((entry) => MapEntry(entry.$2.eventId, entry.$1)),
+    );
+    final messages = events.indexed
+        .where((entry) => entry.$2.isShownAsMessage)
+        .toIList();
+    final messageIndexes = messages.map((entry) => entry.$1).toList();
+
+    return room.receipts.values.flattened
+        .where(
+          (receipt) =>
+              receipt.userId != userId &&
+              // Receipts in threads are for the thread, not the timeline
+              receipt.thread == "main",
+        )
+        .map(
+          (receipt) => switch (indexes[receipt.eventId]) {
+            final index? => (
+              receipt: receipt,
+              message: lowerBound(messageIndexes, index + 1) - 1,
+            ),
+            null => null,
+          },
+        )
+        .nonNulls
+        .where((entry) => entry.message >= 0)
+        .groupListsBy((entry) => messages[entry.message].$2.eventId)
+        .map(
+          (eventId, entries) => MapEntry(
+            eventId,
+            entries
+                .map((entry) => entry.receipt)
+                .sorted((a, b) => b.timestamp.compareTo(a.timestamp))
+                .toIList(),
+          ),
+        )
+        .toIMap();
+  }
+
+  static final provider = NotifierProvider.family
+      .autoDispose<
+        ReadReceiptsController,
+        IMap<String, IList<ReadReceipt>>,
+        ChatParams
+      >(ReadReceiptsController.new);
+}

lib/controllers/room_chat.dart

@@ -156,6 +156,7 @@ class RoomChatController(final ChatParams info)
                   valueMapper: (event) => event,
                 ),
                 hasMore: response.hasMore,
+                receipts: response.receipts,
                 timeline: IMap.fromIterable(
                   response.events,
                   keyMapper: (event) => event.timelineRowId,

lib/controllers/rooms.dart

@@ -2,6 +2,7 @@ import "package:collection/collection.dart";
 import "package:fast_immutable_collections/fast_immutable_collections.dart";
 import "package:flutter_riverpod/flutter_riverpod.dart";
 import "package:nexus/models/event.dart";
+import "package:nexus/models/read_receipt.dart";
 import "package:nexus/models/room.dart";
 
 class RoomsController extends Notifier<IMap<String, Room>> {
@@ -33,6 +34,26 @@ class RoomsController extends Notifier<IMap<String, Room>> {
     .new(),
   );
 
+  static IMap<String, IList<ReadReceipt>> mergeReceipts(
+    IMap<String, IList<ReadReceipt>> existing,
+    IMap<String, IList<ReadReceipt>> incoming,
+  ) => incoming.isEmpty
+      ? existing
+      : existing.values.flattened
+            .followedBy(incoming.values.flattened)
+            .groupListsBy((receipt) => (receipt.userId, receipt.thread))
+            .values
+            .map(
+              (receipts) => receipts.reduce(
+                (newest, receipt) => newest.timestamp.isAfter(receipt.timestamp)
+                    ? newest
+                    : receipt,
+              ),
+            )
+            .groupListsBy((receipt) => receipt.eventId)
+            .map((eventId, receipts) => MapEntry(eventId, receipts.toIList()))
+            .toIMap();
+
   /// Adds events to their rooms, without changing the rooms' timelines.
   void storeEvents(Iterable<Event> events) => update(
     .new(
@@ -96,15 +117,11 @@ class RoomsController extends Notifier<IMap<String, Room>> {
               timeline: incoming.reset
                   ? incoming.timeline
                   : existing.timeline.addAll(incoming.timeline),
-              receipts: incoming.receipts.entries.fold(
-                existing.receipts,
-                (receiptAcc, event) => receiptAcc.add(
-                  event.key,
-                  (receiptAcc[event.key] ?? .new()).addAll(event.value),
-                ),
-              ),
+              receipts: mergeReceipts(existing.receipts, incoming.receipts),
             ) ??
-            incoming,
+            incoming.copyWith(
+              receipts: mergeReceipts(const .empty(), incoming.receipts),
+            ),
       );
     });
 

lib/controllers/settings_sections.dart

@@ -19,8 +19,9 @@ import "package:nexus/controllers/unified_push_distributors.dart";
 import "package:nexus/helpers/extensions/distributor_name.dart";
 import "package:nexus/models/account_data.dart";
 import "package:nexus/models/room_order.dart";
+import "package:nexus/models/settings.dart";
 import "package:nexus/models/settings_category.dart";
-import "package:nexus/models/typing_indicators.dart";
+import "package:nexus/models/show_and_send.dart";
 import "package:nexus/main.dart";
 import "package:nexus/widgets/settings/dialog_list_tile.dart";
 import "package:nexus/widgets/reset_encryption_sheet.dart";
@@ -32,6 +33,30 @@ class SettingsSectionsController
   Future<IMap<String, IList<SettingsCategory>>> build() async {
     final settings = await ref.watch(SettingsController.provider.future);
 
+    /// A tile for a [ShowAndSend] setting, saving the settings from [update].
+    Widget showAndSendTile(
+      String title,
+      String description,
+      IconData icon, {
+      required ShowAndSend value,
+      required Settings Function(ShowAndSend value) update,
+    }) => DialogListTile<ShowAndSend>(
+      icon: Icon(icon),
+      title: title,
+      subtitle: Text(description),
+      value: value,
+      options: ShowAndSend.values,
+      getName: (option) => switch (option) {
+        .showAndSend => "Show and send",
+        .show => "Only show",
+        .neither => "Neither",
+      },
+      onChanged: (value) => ref
+          .read(SettingsController.provider.notifier)
+          .set(update(value))
+          .onError(showError),
+    );
+
     return .new({
       "General": .new([
         .new(
@@ -192,23 +217,25 @@ class SettingsSectionsController
               title: "Typing Indicators",
               description: "Show when others are typing, and let others see when you're typing.",
               icon: Icons.keyboard,
-              builder: (title, description, icon) =>
-                  DialogListTile<TypingIndicators>(
-                    icon: Icon(icon),
-                    title: title,
-                    subtitle: Text(description),
-                    value: settings.typingIndicators,
-                    options: TypingIndicators.values,
-                    getName: (option) => switch (option) {
-                      .showAndSend => "Show and send",
-                      .show => "Only show",
-                      .neither => "Neither",
-                    },
-                    onChanged: (value) => ref
-                        .read(SettingsController.provider.notifier)
-                        .set(settings.copyWith(typingIndicators: value))
-                        .onError(showError),
-                  ),
+              builder: (title, description, icon) => showAndSendTile(
+                title,
+                description,
+                icon,
+                value: settings.typingIndicators,
+                update: (value) => settings.copyWith(typingIndicators: value),
+              ),
+            ),
+            .new(
+              title: "Read Receipts",
+              description: "Show how far others have read, and let others see what you've read. When not sent, read receipts are still sent privately, so your other devices know what you've read.",
+              icon: Icons.done_all,
+              builder: (title, description, icon) => showAndSendTile(
+                title,
+                description,
+                icon,
+                value: settings.readReceipts,
+                update: (value) => settings.copyWith(readReceipts: value),
+              ),
             ),
           ]),
         ),