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WIP model: Add Unreads model, for tracking unread-message counts
TODO: - Tests - Change Sets of message IDs to sorted Lists, like in zulip-mobile, for space efficiency (needs attention to make sure they stay sorted and that operations are as time-efficient as possible) - Open #api documentation thread for when (if ever) to expect update_message_flags with 'mentioned' and 'wildcard_mentioned' flags - Track docs-change requests; as those are completed, have the code point to the doc instead of restating what the doc should say: - https://chat.zulip.org/#narrow/stream/378-api-design/topic/.60all.60.20in.20update_message_flags.2Fremove/near/1639963 - https://chat.zulip.org/#narrow/stream/412-api-documentation/topic/mark-as-read.20events.20on.20stream.20unsubscribe/near/1639566 - Other TODOs as noted in comments (perhaps in later work though)
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‎lib/model/narrow.dart

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import '../api/model/events.dart';
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import '../api/model/initial_snapshot.dart';
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import '../api/model/model.dart';
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import '../api/model/narrow.dart';
@@ -161,6 +162,22 @@ class DmNarrow extends Narrow implements SendableNarrow {
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);
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}
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/// A [DmNarrow] from an [UnreadHuddleSnapshot].
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factory DmNarrow.ofUnreadHuddleSnapshot(UnreadHuddleSnapshot snapshot, {required int selfUserId}) {
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final userIds = snapshot.userIdsString.split(',').map((id) => int.parse(id));
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return DmNarrow(selfUserId: selfUserId,
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allRecipientIds: userIds.toList(growable: false)..sort());
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}
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factory DmNarrow.ofUpdateMessageFlagsMessageDetail(
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UpdateMessageFlagsMessageDetail detail, {
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required int selfUserId,
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}) {
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assert(detail.type == MessageType.private);
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return DmNarrow(selfUserId: selfUserId,
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allRecipientIds: [...detail.userIds!, selfUserId]..sort());
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}
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factory DmNarrow.withUser(int userId, {required int selfUserId}) {
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return DmNarrow(
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allRecipientIds: {userId, selfUserId}.toList()..sort(),

‎lib/model/store.dart

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@@ -179,6 +179,7 @@ class PerAccountStore extends ChangeNotifier {
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// Data attached to the self-account on the realm.
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final UserSettings? userSettings; // TODO(server-5)
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// final Unreads unreads;
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// Users and data about them.
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final Map<int, User> users;

‎lib/model/unreads.dart

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import 'dart:core';
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import 'package:flutter/foundation.dart';
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import '../api/model/initial_snapshot.dart';
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import '../api/model/model.dart';
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import '../api/model/events.dart';
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import '../log.dart';
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import 'narrow.dart';
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/// A view-model for unread messages.
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///
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/// If a message ID is not represented, then its status is either:
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/// - read, or
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/// - unknown, because we're missing data on old unread messages
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/// (see [oldUnreadsMissing]).
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///
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/// Messages in unsubscribed streams are generally considered unread by the
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/// server and should not be expected to appear here. They may still appear
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/// temporarily when the server hasn't finished processing the transition to the
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/// unsubscribed-stream state; the marking-as-read may be done asynchronously:
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/// https://chat.zulip.org/#narrow/stream/378-api-design/topic/mark-as-read.20events.20with.20message.20moves.3F/near/1639926
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/// For that reason, consumers of this model may wish to filter out messages in
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/// unsubscribed streams.
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class Unreads extends ChangeNotifier {
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factory Unreads({required UnreadMessagesSnapshot initial, required selfUserId}) {
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final streams = <int, Map<String, Set<int>>>{};
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final dms = <DmNarrow, Set<int>>{};
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final mentions = Set.of(initial.mentions);
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for (final unreadStreamSnapshot in initial.streams) {
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final streamId = unreadStreamSnapshot.streamId;
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final topic = unreadStreamSnapshot.topic;
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(streams[streamId] ??= {})[topic] = Set.of(unreadStreamSnapshot.unreadMessageIds);
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}
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for (final unreadDmSnapshot in initial.dms) {
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final otherUserId = unreadDmSnapshot.otherUserId;
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final narrow = DmNarrow.withUser(otherUserId, selfUserId: selfUserId);
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dms[narrow] = Set.of(unreadDmSnapshot.unreadMessageIds);
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}
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for (final unreadHuddleSnapshot in initial.huddles) {
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final narrow = DmNarrow.ofUnreadHuddleSnapshot(selfUserId: selfUserId,
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unreadHuddleSnapshot);
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dms[narrow] = Set.of(unreadHuddleSnapshot.unreadMessageIds);
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}
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return Unreads._(
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streams: streams,
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dms: dms,
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mentions: mentions,
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oldUnreadsMissing: initial.oldUnreadsMissing,
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selfUserId: selfUserId,
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);
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}
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Unreads._({
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required this.streams,
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required this.dms,
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required this.mentions,
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required this.oldUnreadsMissing,
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required this.selfUserId,
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});
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/// Unread stream messages, as: stream ID → topic → message ID.
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final Map<int, Map<String, Set<int>>> streams;
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/// Unread DM messages, as: DM narrow → message ID.
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final Map<DmNarrow, Set<int>> dms;
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/// Unread messages with the self-user @-mentioned, as a set of message IDs.
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///
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/// Includes messages with
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/// [MessageFlag.mentioned] or [MessageFlag.wildcardMentioned] or both.
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final Set<int> mentions;
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/// Whether the model might be missing data on old unread messages.
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///
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/// Initialized to the value of [UnreadMessagesSnapshot.oldUnreadsMissing].
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/// Is set to false when the user clears out all unreads at once
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/// (signaled by a [UpdateMessageFlagsAddEvent] with [MessageFlag.read] and
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/// `true` for [UpdateMessageFlagsAddEvent.all]).
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bool oldUnreadsMissing;
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final int selfUserId;
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// TODO replace with efficient alternative
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bool _slowIsPresentInStreams(int messageId) {
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return streams.values.any(
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(topics) => topics.values.any(
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(ids) => ids.contains(messageId),
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),
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);
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}
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// TODO replace with efficient alternative
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bool _slowIsPresentInDms(int messageId) {
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return dms.values.any((ids) => ids.contains(messageId));
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}
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// TODO replace with efficient alternative
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void _slowRemoveInStreams(Iterable<int> messageIds) {
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for (final messageId in messageIds) {
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for (final stream in streams.values) {
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for (final topic in stream.values) {
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topic.remove(messageId);
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}
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}
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}
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}
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// TODO replace with efficient alternative
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void _slowRemoveInDms(Iterable<int> messageIds) {
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for (final messageId in messageIds) {
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for (final dm in dms.values) {
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dm.remove(messageId);
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}
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}
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}
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void _addToStreams(int messageId, int streamId, String topic) {
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((streams[streamId] ??= {})[topic] ??= {}).add(messageId);
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}
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void _addToDms(int messageId, DmNarrow narrow) {
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(dms[narrow] ??= {}).add(messageId);
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}
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void handleUpdateMessageEvent(UpdateMessageEvent event) {
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final messageId = event.messageId;
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final bool isMentioned = event.flags.any(
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(f) => f == MessageFlag.mentioned || f == MessageFlag.wildcardMentioned,
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);
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// We assume this event can't signal a change in a message's 'read' flag.
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// TODO can it actually though, when it's about messages being moved into an
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// unsubscribed stream?
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// https://chat.zulip.org/#narrow/stream/378-api-design/topic/mark-as-read.20events.20with.20message.20moves.3F/near/1639957
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final bool isRead = event.flags.contains(MessageFlag.read);
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assert(() {
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if (!oldUnreadsMissing && !event.messageIds.every((messageId) {
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final isUnreadLocally = _slowIsPresentInDms(messageId) || _slowIsPresentInStreams(messageId);
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return isUnreadLocally == !isRead;
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})) {
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// If this happens, then either:
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// - the server and client have been out of sync about a message's
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// unread state since before this event, or
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// - this event was unexpectedly used to announce a change in a
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// message's 'read' flag.
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debugLog('Unreads warning: got surprising UpdateMessageEvent');
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}
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return true;
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}());
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switch ((isRead, isMentioned)) {
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case (true, false):
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mentions.remove(messageId);
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case (true, true ):
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// A mention (even if new with this event) makes no difference
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// for a message that's already read.
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break;
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case (false, false):
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mentions.remove(messageId);
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case (false, true ):
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mentions.add(messageId);
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}
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// TODO: Handle moved messages.
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notifyListeners();
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}
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void handleUpdateMessageFlagsEvent(UpdateMessageFlagsEvent event) {
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switch (event.flag) {
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case MessageFlag.starred:
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case MessageFlag.collapsed:
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case MessageFlag.hasAlertWord:
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case MessageFlag.historical:
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case MessageFlag.unknown:
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// These are irrelevant.
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return;
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case MessageFlag.mentioned:
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case MessageFlag.wildcardMentioned:
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// Empirically, we don't seem to get these events when a message is edited
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// to add/remove an @-mention, even though @-mention state is represented
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// as flags. Instead, we just get the [UpdateMessageEvent], and that
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// contains the new set of flags, which we'll use to update [mentions].
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// (See our handling of [UpdateMessageEvent].)
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//
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// Best to handle the event anyway, using the meaning on the tin.
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// It might be used in a valid case we haven't thought of yet.
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switch (event) {
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case UpdateMessageFlagsAddEvent():
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if (event.all) { // TODO(log)
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// Strange and unexpected for this flag.
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return;
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}
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mentions.addAll(
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event.messages.where(
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(messageId) => _slowIsPresentInStreams(messageId) || _slowIsPresentInDms(messageId),
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),
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);
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case UpdateMessageFlagsRemoveEvent():
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mentions.removeAll(event.messages);
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}
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case MessageFlag.read:
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switch (event) {
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case UpdateMessageFlagsAddEvent():
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if (event.all) {
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streams.clear();
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dms.clear();
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mentions.clear();
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oldUnreadsMissing = false;
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} else {
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// We get these mark-as-read events when the user's scrolling
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// causes messages to be marked as read, as you would expect.
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// We also get them when you unsubscribe from a stream that has
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// unreads in it:
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// https://chat.zulip.org/#narrow/stream/412-api-documentation/topic/mark-as-read.20events.20on.20stream.20unsubscribe/near/1639566
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mentions.removeAll(event.messages);
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_slowRemoveInStreams(event.messages);
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_slowRemoveInDms(event.messages);
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}
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case UpdateMessageFlagsRemoveEvent():
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for (final messageId in event.messages) {
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final detail = event.messageDetails![messageId];
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if (detail == null) { // TODO(log) if on Zulip 6.0+
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// Known to happen as a bug in some cases before Zulip 6.0:
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// https://chat.zulip.org/#narrow/stream/378-api-design/topic/unreads.20in.20unsubscribed.20streams/near/1458467
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// TODO(server-6) remove Zulip 6.0 comment
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return;
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}
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switch (detail.type) {
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case MessageType.stream:
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_addToStreams(messageId, detail.streamId!, detail.topic!);
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case MessageType.private:
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final narrow = DmNarrow.ofUpdateMessageFlagsMessageDetail(selfUserId: selfUserId,
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detail);
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_addToDms(messageId, narrow);
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}
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}
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}
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}
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notifyListeners();
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}
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void handleMessageEvent(MessageEvent event) {
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final message = event.message;
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if (message.flags.contains(MessageFlag.read)) {
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return;
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}
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switch (message) {
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case StreamMessage():
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_addToStreams(message.id, message.streamId, message.subject);
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case DmMessage():
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final narrow = DmNarrow.ofMessage(message, selfUserId: selfUserId);
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_addToDms(message.id, narrow);
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}
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if (message.flags.contains(MessageFlag.mentioned)
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|| message.flags.contains(MessageFlag.wildcardMentioned)) {
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mentions.add(message.id);
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}
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notifyListeners();
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}
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void handleDeleteMessageEvent(DeleteMessageEvent event) {
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mentions.removeAll(event.messageIds);
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switch (event.messageType) {
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case MessageType.stream:
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streams[event.streamId!]?[event.topic!]?.removeAll(event.messageIds);
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case MessageType.private:
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_slowRemoveInDms(event.messageIds);
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}
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notifyListeners();
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}
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}

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