Topic link autocomplete

lib/model/compose.dart

@@ -188,7 +188,7 @@ String userGroupMention(String userGroupName, {bool silent = false}) =>
 // Corresponds to `topic_link_util.escape_invalid_stream_topic_characters`
 // in Zulip web:
 //   https://github.com/zulip/zulip/blob/b42d3e77e/web/src/topic_link_util.ts#L15-L34
-const _channelAvoidedCharsReplacements = {
+const _channelTopicAvoidedCharsReplacements = {
   '`': '`',
   '>': '>',
   '*': '*',
@@ -198,41 +198,78 @@ const _channelAvoidedCharsReplacements = {
   r'$$': '$$',
 };
 
-final _channelAvoidedCharsRegex = RegExp(r'[`>*&[\]]|\$\$');
+final _channelTopicAvoidedCharsRegex = RegExp(r'[`>*&[\]]|\$\$');
+final _channelTopicAvoidedCharsReplacementsRegex =
+  RegExp(_channelTopicAvoidedCharsReplacements.values.join('|'));
 
-/// Markdown link for channel when the channel name includes characters that
+String escapeChannelTopicAvoidedChars(String str) {
+  return str.replaceAllMapped(_channelTopicAvoidedCharsRegex,
+    (match) => _channelTopicAvoidedCharsReplacements[match[0]]!);
+}
+
+String unescapeChannelTopicAvoidedChars(String str) {
+  return str.replaceAllMapped(_channelTopicAvoidedCharsReplacementsRegex,
+    (match) => _channelTopicAvoidedCharsReplacements.map((k, v) => MapEntry(v, k))[match[0]]!);
+}
+
+/// Markdown link for channel or topic whose name includes characters that
 /// will break normal markdown rendering.
 ///
-/// Refer to [_channelAvoidedCharsReplacements] for a complete list of
+/// Refer to [_channelTopicAvoidedCharsReplacements] for a complete list of
 /// these characters.
 // Adopted from `topic_link_util.get_fallback_markdown_link` in Zulip web;
 //   https://github.com/zulip/zulip/blob/b42d3e77e/web/src/topic_link_util.ts#L96-L108
-String _channelFallbackMarkdownLink(ZulipStream channel, {
-  required PerAccountStore store,
+String _channelTopicFallbackMarkdownLink(ZulipStream channel, PerAccountStore store, {
+  TopicName? topic,
 }) {
+  final text = StringBuffer('#${escapeChannelTopicAvoidedChars(channel.name)}');
+  if (topic != null) {
+    text.write(' > ${escapeChannelTopicAvoidedChars(topic.displayName ?? store.realmEmptyTopicDisplayName)}');
+  }
+
+  final narrow = topic == null
+    ? ChannelNarrow(channel.streamId) : TopicNarrow(channel.streamId, topic);
   // Like Zulip web, we use a relative URL here, unlike [quoteAndReply] which
   // uses an absolute URL.  There'd be little benefit to an absolute URL here
   // because this isn't a likely flow when a user wants something to copy-paste
-  // elsewhere: this flow normally produces `#**…**` syntax, which wouldn't work
-  // for that at all.  And conversely, it's nice to keep reasonably short the
-  // markup that we put into the text box and which the user sees.  Discussion:
+  // elsewhere: this flow normally produces `#**…**` or `#**…>…**` syntax,
+  // which wouldn't work for that at all.  And conversely, it's nice to keep
+  // reasonably short the markup that we put into the text box and which the
+  // user sees.  Discussion:
   //   https://chat.zulip.org/#narrow/channel/101-design/topic/.22quote.20message.22.20uses.20absolute.20URL.20instead.20of.20realm-relative/near/2325588
-  final relativeLink = '#${narrowLinkFragment(store, ChannelNarrow(channel.streamId))}';
+  final relativeLink = '#${narrowLinkFragment(store, narrow)}';
 
-  final text = '#${channel.name.replaceAllMapped(_channelAvoidedCharsRegex,
-    (match) => _channelAvoidedCharsReplacements[match[0]]!)}';
   return inlineLink(text.toString(), relativeLink);
 }
 
 /// A #channel link syntax of a channel, like #**announce**.
 ///
 /// A plain Markdown link will be used if the channel name includes some
 /// characters that would break normal #**channel** rendering.
-String channelLink(ZulipStream channel, {required PerAccountStore store}) {
-  if (_channelAvoidedCharsRegex.hasMatch(channel.name)) {
-    return _channelFallbackMarkdownLink(channel, store: store);
+///
+/// Set [isComplete] to `false` for an incomplete syntax such as "#**…>""
+/// or "[#…](#…)>"; the one that will trigger a topic autocomplete
+/// interaction for the channel.
+String channelLink(ZulipStream channel, {
+  bool isComplete = true,
+  required PerAccountStore store,
+}) {
+  if (_channelTopicAvoidedCharsRegex.hasMatch(channel.name)) {
+    return '${_channelTopicFallbackMarkdownLink(channel, store)}${isComplete ? '' : '>'}';
+  }
+  return '#**${channel.name}${isComplete ? '**' : '>'}';
+}
+
+/// A #channel>topic link syntax of a topic, like #**announce>GSoC**.
+///
+/// A plain Markdown link will be used if the channel or topic name includes
+/// some characters that would break normal #**channel>topic** rendering.
+String topicLink(ZulipStream channel, TopicName topic, {required PerAccountStore store}) {
+  if (_channelTopicAvoidedCharsRegex.hasMatch(channel.name)
+      || _channelTopicAvoidedCharsRegex.hasMatch(topic.apiName)) {
+    return _channelTopicFallbackMarkdownLink(channel, topic: topic, store);
   }
-  return '#**${channel.name}**';
+  return '#**${channel.name}>${topic.apiName}**';
 }
 
 /// https://spec.commonmark.org/0.30/#inline-link

lib/model/store.dart

@@ -999,6 +999,7 @@ class PerAccountStore extends PerAccountStoreBase with
         _messages.handleUpdateMessageEvent(event);
         unreads.handleUpdateMessageEvent(event);
         topics.handleUpdateMessageEvent(event);
+        autocompleteViewManager.handleUpdateMessageEvent(event, store: this);
 
       case DeleteMessageEvent():
         assert(debugLog("server event: delete_message ${event.messageIds}"));

lib/widgets/autocomplete.dart

@@ -46,7 +46,8 @@ class _AutocompleteFieldState<QueryT extends AutocompleteQuery, ResultT extends
   }
 
   void _handleControllerChange() {
-    final newQuery = widget.autocompleteIntent()?.query;
+    var newQuery = widget.autocompleteIntent()?.query;
+    if (newQuery is TopicLinkAutocompleteQuery) newQuery = null; // TODO(#124)
     final oldQuery = _viewModel?.query;
     // First, tear down the old view-model if necessary.
     if (_viewModel != null
@@ -241,6 +242,9 @@ class ComposeAutocomplete extends AutocompleteField<ComposeAutocompleteQuery, Co
           return;
         }
         replacementString = '${channelLink(channel, store: store)} ';
+      case TopicLinkAutocompleteChannelResult():
+      case TopicLinkAutocompleteTopicResult():
+        throw UnimplementedError(); // TODO(#124)
     }
 
     controller.value = intent.textEditingValue.replaced(
@@ -259,6 +263,7 @@ class ComposeAutocomplete extends AutocompleteField<ComposeAutocompleteQuery, Co
       MentionAutocompleteResult() => MentionAutocompleteItem(
         option: option, narrow: narrow),
       ChannelLinkAutocompleteResult() => _ChannelLinkAutocompleteItem(option: option),
+      TopicLinkAutocompleteResult() => throw UnimplementedError(), // TODO(#124)
       EmojiAutocompleteResult() => EmojiAutocompleteItem(option: option),
     };
     return InkWell(

lib/widgets/compose_box.dart

@@ -237,11 +237,14 @@ class ComposeContentController extends ComposeController<ContentValidationError>
   ComposeContentController({
     super.text,
     required super.store,
+    required this.narrow,
     this.requireNotEmpty = true,
   }) {
     _update();
   }
 
+  final Narrow narrow;
+
   /// Whether to produce [ContentValidationError.empty].
   final bool requireNotEmpty;
 
@@ -1595,8 +1598,8 @@ class _EditMessageComposeBoxBody extends _ComposeBoxBody {
 }
 
 sealed class ComposeBoxController {
-  ComposeBoxController({required PerAccountStore store})
-    : content = ComposeContentController(store: store);
+  ComposeBoxController({required PerAccountStore store, required Narrow narrow})
+    : content = ComposeContentController(store: store, narrow: narrow);
 
   final ComposeContentController content;
   final contentFocusNode = FocusNode();
@@ -1691,7 +1694,7 @@ enum ComposeTopicInteractionStatus {
 }
 
 class StreamComposeBoxController extends ComposeBoxController {
-  StreamComposeBoxController({required super.store})
+  StreamComposeBoxController({required super.store, required super.narrow})
     : topic = ComposeTopicController(store: store);
 
   final ComposeTopicController topic;
@@ -1722,24 +1725,26 @@ class StreamComposeBoxController extends ComposeBoxController {
 }
 
 class FixedDestinationComposeBoxController extends ComposeBoxController {
-  FixedDestinationComposeBoxController({required super.store});
+  FixedDestinationComposeBoxController({required super.store, required super.narrow});
 }
 
 class EditMessageComposeBoxController extends ComposeBoxController {
   EditMessageComposeBoxController({
     required super.store,
+    required super.narrow,
     required this.messageId,
     required this.originalRawContent,
     required String? initialText,
   }) : _content = ComposeContentController(
                     text: initialText,
                     store: store,
+                    narrow: narrow,
                     // Editing to delete the content is a supported form of
                     // deletion: https://zulip.com/help/delete-a-message#delete-message-content
                     requireNotEmpty: false);
 
-  factory EditMessageComposeBoxController.empty(PerAccountStore store, int messageId) =>
-    EditMessageComposeBoxController(store: store, messageId: messageId,
+  factory EditMessageComposeBoxController.empty(PerAccountStore store, Narrow narrow, int messageId) =>
+    EditMessageComposeBoxController(store: store, narrow: narrow, messageId: messageId,
       originalRawContent: null, initialText: null);
 
   @override ComposeContentController get content => _content;
@@ -2121,6 +2126,7 @@ class _ComposeBoxState extends State<ComposeBox> with PerAccountStoreAwareStateM
       controller.dispose();
       _controller = EditMessageComposeBoxController(
         store: store,
+        narrow: widget.narrow,
         messageId: messageId,
         originalRawContent: failedEdit.originalRawContent,
         initialText: failedEdit.newContent,
@@ -2132,7 +2138,7 @@ class _ComposeBoxState extends State<ComposeBox> with PerAccountStoreAwareStateM
   void _editFromRawContentFetch(int messageId) async {
     final store = PerAccountStoreWidget.of(context);
     final zulipLocalizations = ZulipLocalizations.of(context);
-    final emptyEditController = EditMessageComposeBoxController.empty(store, messageId);
+    final emptyEditController = EditMessageComposeBoxController.empty(store, widget.narrow, messageId);
     setState(() {
       controller.dispose();
       _controller = emptyEditController;
@@ -2210,10 +2216,10 @@ class _ComposeBoxState extends State<ComposeBox> with PerAccountStoreAwareStateM
     _controller?.dispose(); // `?.` because this might be the first call
     switch (widget.narrow) {
       case ChannelNarrow():
-        _controller = StreamComposeBoxController(store: store);
+        _controller = StreamComposeBoxController(store: store, narrow: widget.narrow);
       case TopicNarrow():
       case DmNarrow():
-        _controller = FixedDestinationComposeBoxController(store: store);
+        _controller = FixedDestinationComposeBoxController(store: store, narrow: widget.narrow);
       case CombinedFeedNarrow():
       case MentionsNarrow():
       case StarredMessagesNarrow():

test/model/autocomplete_checks.dart

@@ -37,3 +37,13 @@ extension TopicAutocompleteResultChecks on Subject<TopicAutocompleteResult> {
 extension ChannelLinkAutocompleteResultChecks on Subject<ChannelLinkAutocompleteResult> {
   Subject<int> get channelId => has((r) => r.channelId, 'channelId');
 }
+
+extension TopicLinkAutocompleteChannelResultChecks on Subject<TopicLinkAutocompleteChannelResult> {
+  Subject<int> get channelId => has((r) => r.channelId, 'channelId');
+}
+
+extension TopicLinkAutocompleteTopicResultChecks on Subject<TopicLinkAutocompleteTopicResult> {
+  Subject<int> get channelId => has((r) => r.channelId, 'channelId');
+  Subject<TopicName> get topic => has((r) => r.topic, 'topic');
+  Subject<bool> get isNew => has((r) => r.isNew, 'isNew');
+}