add thread support

Fixes #129

lib/helpers/extensions/build_event_options.dart

@@ -26,6 +26,7 @@ extension BuildEventOptions on Event {
     required String roomId,
     required String userId,
     required void Function(int, RelationType) onRelation,
+    void Function(String threadRoot)? onStartThread,
   }) {
     final theme = Theme.of(context);
     final danger = theme.colorScheme.error;
@@ -34,11 +35,15 @@ extension BuildEventOptions on Event {
     final notifier = RoomChatController.provider((
       roomId: roomId,
       contextualEvent: null,
+      threadRoot: null,
     )).notifier;
 
     final isPinned = ref
         .read(PinnedIdsController.provider(roomId))
         .contains(eventId);
+    final canSend = ref.read(
+      PowerLevelController.provider(.new(eventType: .message, roomId: roomId)),
+    );
 
     void showReasonSheet({
       required String title,
@@ -170,11 +175,7 @@ extension BuildEventOptions on Event {
           ),
         ),
 
-      if (ref.read(
-        PowerLevelController.provider(
-          .new(eventType: .message, roomId: roomId),
-        ),
-      ))
+      if (canSend)
         PopupMenuItem(
           onTap: () => onRelation(rowId, .reply),
           child: const ListTile(
@@ -183,6 +184,18 @@ extension BuildEventOptions on Event {
           ),
         ),
 
+      if (onStartThread != null &&
+          threadCount == 0 &&
+          canSend &&
+          relatesTo == null)
+        PopupMenuItem(
+          onTap: () => onStartThread(eventId),
+          child: const ListTile(
+            leading: Icon(Icons.forum),
+            title: Text("Start Thread"),
+          ),
+        ),
+
       if (sender == userId &&
           switch (content) {
             LocationMessageContent() ||

lib/helpers/extensions/open_link_info.dart

@@ -32,7 +32,7 @@ extension OpenLinkInfo on WidgetRef {
         : await read(
             EventController.provider(
               .new(roomId: summary.roomId, eventId: linkInfo.eventId!),
-            ).selectAsync((data) => data?.rowId),
+            ).future,
           ).onError((_, _) => null);
 
     if (await focusRoom(summary.roomId, eventRowId) || !context.mounted) return;

lib/helpers/extensions/thread_events.dart

@@ -0,0 +1,50 @@
+import "package:collection/collection.dart";
+import "package:fast_immutable_collections/fast_immutable_collections.dart";
+import "package:nexus/helpers/extensions/event_id_is_fake.dart";
+import "package:nexus/models/event.dart";
+import "package:nexus/models/room.dart";
+
+typedef ThreadInfo = ({int count, Event? latest});
+typedef Thread = ({Event root, ThreadInfo info});
+
+extension ThreadEvents on Room {
+  /// The threads in the loaded events, most recently active first.
+  IList<Thread> get threads {
+    DateTime lastActive(Thread thread) =>
+        thread.info.latest?.timestamp ?? thread.root.timestamp;
+
+    return events.values
+        .where((event) => event.threadCount > 0)
+        .map((root) => (root: root, info: thread(root)))
+        .sorted((a, b) => lastActive(b).compareTo(lastActive(a)))
+        .toIList();
+  }
+
+  /// The events in the thread from [threadRoot], oldest first, without the
+  /// root itself.
+  IList<Event> threadEvents(String threadRoot) =>
+      (relations[threadRoot] ?? const .empty())
+          .map((rowId) => events[rowId])
+          .nonNulls
+          .where(
+            (event) =>
+                event.threadRoot == threadRoot &&
+                (!event.eventId.isFake || clientSticky.contains(event.rowId)),
+          )
+          .sorted((a, b) => a.timestamp.compareTo(b.timestamp))
+          .toIList();
+
+  /// How many replies the thread from [root] has, and its latest event, from
+  /// gomuks' aggregate on it
+  ThreadInfo thread(Event root) =>
+      (count: root.threadCount, latest: events[root.threadLatestRowId]);
+
+  /// The latest event in the thread from [threadRoot], if it's loaded.
+  Event? latestThreadEvent(String threadRoot) => switch (eventIds[threadRoot]) {
+    final rowId? => switch (events[rowId]) {
+      final root? => thread(root).latest,
+      null => null,
+    },
+    null => null,
+  };
+}

lib/helpers/hooks/chat_composer.dart

@@ -0,0 +1,40 @@
+import "package:flutter/services.dart";
+import "package:flutter_hooks/flutter_hooks.dart";
+import "package:material_ui/material_ui.dart";
+import "package:nexus/models/relation_type.dart";
+
+final class ChatComposer({
+  required final ValueNotifier<int?> relatedEvent,
+  required final ValueNotifier<RelationType> relationType,
+  required final FocusNode node,
+}) {
+  factory use() {
+    final relatedEvent = useState<int?>(null);
+    final relationType = useState(RelationType.reply);
+    final node = useFocusNode(
+      onKeyEvent: (_, event) {
+        if (event is KeyDownEvent && event.logicalKey == .escape) {
+          relatedEvent.value = null;
+          return .handled;
+        }
+
+        return .ignored;
+      },
+    );
+
+    return .new(
+      relatedEvent: relatedEvent,
+      relationType: relationType,
+      node: node,
+    );
+  }
+
+  int? get repliedEventRowId =>
+      relationType.value == .reply ? relatedEvent.value : null;
+
+  void relate(int rowId, RelationType type) {
+    relatedEvent.value = rowId;
+    relationType.value = type;
+    node.requestFocus();
+  }
+}

lib/helpers/hooks/chat_scroll.dart

@@ -15,6 +15,8 @@ final class ChatScroll({
   required final GlobalKey centerKey,
   required final ScrollController scrollController,
   required final bool atBottom,
+  required final int? highlightedEvent,
+
   required final JumpToEvent jumpToEvent,
   required final Future<void> Function() jumpToBottom,
   required final GlobalKey Function(int eventRowId) keyFor,
@@ -28,6 +30,8 @@ final class ChatScroll({
     final anchorId = useState<int?>(null);
     final atBottom = useState(true);
     final pendingJump = useState<int?>(null);
+    final highlightedEvent = useState<int?>(null);
+    final hookContext = useContext();
     final pendingJumpDone = useRef<Completer<void>?>(null);
     void finishPendingJump() {
       pendingJumpDone.value?.complete();
@@ -95,15 +99,14 @@ final class ChatScroll({
 
       final anchorIndex = items.indexOf(anchor);
 
-      if (anchorIndex == -1) return (history: const .empty(), live: items);
-
+      final historyLength = anchorIndex == -1 ? items.length : anchorIndex + 1;
       return (
-        history: items.take(anchorIndex).toIList().reversed.toIList(),
-        live: items.skip(anchorIndex).toIList(),
+        history: items.take(historyLength).toIList().reversed.toIList(),
+        live: items.skip(historyLength).toIList(),
       );
     }, [controllerData, anchorId.value]);
 
-    final lastRowId = split.live.lastOrNull;
+    final lastRowId = controllerData.value?.timeline.lastOrNull;
     final previousLastRowId = useRef<int?>(null);
 
     useEffect(() {
@@ -118,7 +121,8 @@ final class ChatScroll({
       WidgetsBinding.instance.addPostFrameCallback((_) {
         if (!scrollController.hasClients) return;
 
-        scrollController.jumpTo(scrollController.position.minScrollExtent);
+        anchorId.value = lastRowId;
+        scrollController.position.correctPixels(0);
       });
 
       return null;
@@ -173,37 +177,49 @@ final class ChatScroll({
       ],
     );
 
+    Future<void> scrollToEvent(int rowId) async {
+      if (!scrollController.hasClients) return;
+
+      final context = keyFor(rowId).currentContext;
+      if (context != null) {
+        await Scrollable.ensureVisible(
+          context,
+          alignment: 0.5,
+          duration: Durations.extralong1,
+          curve: Curves.easeInOut,
+        );
+        return;
+      }
+
+      finishPendingJump();
+      final done = pendingJumpDone.value = Completer();
+      pendingJump.value = rowId;
+      if (controllerData.value?.timeline.contains(rowId) ?? false) {
+        anchorId.value = rowId;
+      } else {
+        anchorId.value = null;
+        contextualEvent.value = rowId;
+      }
+      await done.future;
+    }
+
     return .new(
       historyRows: split.history,
       liveRows: split.live,
       centerKey: centerKey,
       scrollController: scrollController,
       atBottom: atBottom.value,
+      highlightedEvent: highlightedEvent.value,
       keyFor: keyFor,
       jumpToEvent: (int rowId) async {
-        if (!scrollController.hasClients) return;
+        highlightedEvent.value = rowId;
 
-        final context = keyFor(rowId).currentContext;
-        if (context != null) {
-          await Scrollable.ensureVisible(
-            context,
-            alignment: 0.5,
-            duration: Durations.extralong1,
-            curve: Curves.easeInOut,
-          );
-          return;
-        }
-
-        finishPendingJump();
-        final done = pendingJumpDone.value = Completer();
-        pendingJump.value = rowId;
-        if (controllerData.value?.timeline.contains(rowId) ?? false) {
-          anchorId.value = rowId;
-        } else {
-          anchorId.value = null;
-          contextualEvent.value = rowId;
-        }
-        await done.future;
+        await scrollToEvent(rowId);
+        await Future.delayed(Durations.extralong1, () {
+          if (hookContext.mounted && highlightedEvent.value == rowId) {
+            highlightedEvent.value = null;
+          }
+        });
       },
       jumpToBottom: () async {
         finishPendingJump();