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Merged
hjiangsu merged 2 commits into from
Jan 14, 2026
Merged

Improve link handling for Lemmy & PieFed #2038

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63b1709
feat: improve link handling for lemmy/piefed links
hjiangsu Jan 14, 2026
e59cdf8
fix: fix piefed link handling with slugs
hjiangsu Jan 14, 2026
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177 changes: 48 additions & 129 deletions lib/src/shared/utils/instance.dart
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Original file line number Diff line number Diff line change
Expand Up @@ -11,6 +11,7 @@ import 'package:thunder/src/core/models/models.dart';
import 'package:thunder/src/features/instance/instance.dart';
import 'package:thunder/src/features/search/search.dart';
import 'package:thunder/src/shared/pages/loading_page.dart';
import 'package:thunder/src/shared/utils/link_utils.dart';

String? fetchInstanceNameFromUrl(String? url) {
if (url == null) {
Expand All @@ -21,160 +22,78 @@ String? fetchInstanceNameFromUrl(String? url) {
return uri.host;
}

/// Matches instance.tld/c/community@otherinstance.tld
/// Puts community in group 3 and otherinstance.tld in group 4
/// https://regex101.com/r/sE8SmL/1
final RegExp fullCommunityUrl = RegExp(r'^!?(https?:\/\/)?(.*)\/c\/(.*)@(.*)$');

/// Matches instance.tld/c/community
/// Puts community in group 3 and instance.tld in group 2
/// https://regex101.com/r/AW2qTr/1
final RegExp shortCommunityUrl = RegExp(r'^!?(https?:\/\/)?(.*)\/c\/([^@\n]*)$');

/// Matches community@instance.tld
/// Puts community in group 2 and instance.tld in group 3
/// https://regex101.com/r/1VrXgX/1
final RegExp instanceName = RegExp(r'^!?(https?:\/\/)?((?:(?!\/c\/c).)*)@(.*)$');

/// Checks if the given text references a community on a valid Lemmy server.
/// Checks if the given text references a community on a valid Lemmy/PieFed server.
/// If so, returns the community name in the format community@instance.tld.
/// Otherwise, returns null.
Future<String?> getLemmyCommunity(String text) async {
// Do an initial check for usernames in the format /u/user@instance.tld or @user@instance.tld.
// These can accidentally trip our community name detection.
if (text.toLowerCase().startsWith('/u/') || text.toLowerCase().startsWith('@')) {
return null;
}

final RegExpMatch? fullCommunityUrlMatch = fullCommunityUrl.firstMatch(text);
if (fullCommunityUrlMatch != null && fullCommunityUrlMatch.groupCount >= 4) {
return '${fullCommunityUrlMatch.group(3)}@${fullCommunityUrlMatch.group(4)}';
}

final RegExpMatch? shortCommunityUrlMatch = shortCommunityUrl.firstMatch(text);
if (shortCommunityUrlMatch != null && shortCommunityUrlMatch.groupCount >= 3) {
return '${shortCommunityUrlMatch.group(3)}@${shortCommunityUrlMatch.group(2)}';
}

final RegExpMatch? instanceNameMatch = instanceName.firstMatch(text);
if (instanceNameMatch != null && instanceNameMatch.groupCount >= 3) {
return '${instanceNameMatch.group(2)}@${instanceNameMatch.group(3)}';
}

return null;
final result = parseCommunity(text);
return result?.qualified;
}

/// Matches instance.tld/u/username@otherinstance.tld
/// Puts username in group 3 and otherinstance.tld in group 4
final RegExp fullUsernameUrl = RegExp(r'^@?(https?:\/\/)?(.*)\/u\/(.*)@(.*)$');

/// Matches instance.tld/u/username
/// Puts username in group 3 and instance.tld in group 2
final RegExp shortUsernameUrl = RegExp(r'^@?(https?:\/\/)?(.*)\/u\/([^@\n]*)$');

/// Matches username@instance.tld
/// Puts username in group 2 and instance.tld in group 3
final RegExp username = RegExp(r'^@?(https?:\/\/)?((?:(?!\/u\/u).)*)@(.*)$');

/// Checks if the given text references a user on a valid Lemmy server.
/// If so, returns the username name in the format username@instance.tld.
/// Checks if the given text references a user on a valid Lemmy/PieFed server.
/// If so, returns the username in the format username@instance.tld.
/// Otherwise, returns null.
Future<String?> getLemmyUser(String text) async {
// Do an initial check for communities in the format /c/community@instance.tld or !community@instance.tld.
// These can accidentally trip our user name detection.
if (text.toLowerCase().startsWith('/c/') || text.toLowerCase().startsWith('!')) {
return null;
}
final result = parseUser(text);
return result?.qualified;
}

final RegExpMatch? fullUsernameUrlMatch = fullUsernameUrl.firstMatch(text);
if (fullUsernameUrlMatch != null && fullUsernameUrlMatch.groupCount >= 4) {
return '${fullUsernameUrlMatch.group(3)}@${fullUsernameUrlMatch.group(4)}';
/// Gets the post ID from a Lemmy/PieFed URL.
/// If the URL is from a different instance, it will attempt to resolve it.
Future<int?> getLemmyPostId(BuildContext context, String text) async {
final parsed = parsePostId(text);
if (parsed == null) {
return null;
}

final RegExpMatch? shortUsernameUrlMatch = shortUsernameUrl.firstMatch(text);
if (shortUsernameUrlMatch != null && shortUsernameUrlMatch.groupCount >= 3) {
return '${shortUsernameUrlMatch.group(3)}@${shortUsernameUrlMatch.group(2)}';
}
final account = context.read<ProfileBloc>().state.account;
final postId = int.tryParse(parsed.value);

final RegExpMatch? usernameMatch = username.firstMatch(text);
if (usernameMatch != null && usernameMatch.groupCount >= 3) {
return '${usernameMatch.group(2)}@${usernameMatch.group(3)}';
if (postId == null) {
return null;
}

return null;
}

final RegExp _post = RegExp(r'^(https?:\/\/)(.*)\/post\/([0-9]*).*$');
Future<int?> getLemmyPostId(BuildContext context, String text) async {
final account = context.read<ProfileBloc>().state.account;

final RegExpMatch? postMatch = _post.firstMatch(text);
if (postMatch != null) {
final String? instance = postMatch.group(2);
final int? postId = int.tryParse(postMatch.group(3)!);
if (postId != null) {
if (instance == account.instance) {
return postId;
} else {
// This is a post on another instance. Try to resolve it
try {
// Show the loading page while we resolve the post
showLoadingPage(context);

final response = await SearchRepositoryImpl(account: account).resolve(query: text);
return response['post']?.id;
} catch (e) {
return null;
}
}
if (parsed.instance == account.instance) {
return postId;
} else {
// This is a post on another instance. Try to resolve it
try {
showLoadingPage(context);
final response = await SearchRepositoryImpl(account: account).resolve(query: text);
return response['post']?.id;
} catch (e) {
return null;
}
}

return null;
}

final RegExp _comment = RegExp(r'^(https?:\/\/)(.*)\/comment\/([0-9]*).*$');
final RegExp _commentAlternate = RegExp(r'^(https?:\/\/)(.*)\/post\/([0-9]*)\/([0-9]*).*$');
/// Gets the comment ID from a Lemmy/PieFed URL.
/// If the URL is from a different instance, it will attempt to resolve it.
Future<int?> getLemmyCommentId(BuildContext context, String text) async {
String? instance;
int? commentId;
final parsed = parseCommentId(text);
if (parsed == null) {
return null;
}

final account = context.read<ProfileBloc>().state.account;
final commentId = int.tryParse(parsed.value);

// Try legacy comment link format
RegExpMatch? commentMatch = _comment.firstMatch(text);
if (commentMatch != null) {
// It's a match!
instance = commentMatch.group(2);
commentId = int.tryParse(commentMatch.group(3)!);
} else {
// Otherwise, try the new format
commentMatch = _commentAlternate.firstMatch(text);
if (commentMatch != null) {
// It's a match!
instance = commentMatch.group(2);
commentId = int.tryParse(commentMatch.group(4)!);
}
if (commentId == null) {
return null;
}

if (commentId != null) {
if (instance == account.instance) {
return commentId;
} else {
// This is a comment on another instance. Try to resolve it
try {
// Show the loading page while we resolve the post
showLoadingPage(context);

final response = await SearchRepositoryImpl(account: account).resolve(query: text);
return response['comment']?.id;
} catch (e) {
return null;
}
if (parsed.instance == account.instance) {
return commentId;
} else {
// This is a comment on another instance. Try to resolve it
try {
showLoadingPage(context);
final response = await SearchRepositoryImpl(account: account).resolve(query: text);
return response['comment']?.id;
} catch (e) {
return null;
}
}

return null;
}

/// Fetches the instance info for a given URL.
Expand Down
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