buzz/mobile/lib/features/channels/message_content.dart

import 'message_reply_drag_target.dart';
import 'package:buzz/shared/widgets/feedback_snackbar.dart';
import 'dart:async';
import '../../shared/widgets/ios_media_carousel.dart';
import '../../shared/widgets/message_attachment_corners.dart';
import 'dart:io';
import 'dart:math' as math;

import 'package:flutter/gestures.dart';
import 'package:flutter/material.dart';
import 'package:flutter/foundation.dart';
import 'package:flutter/services.dart';
import 'package:flutter_hooks/flutter_hooks.dart';
import 'package:hooks_riverpod/hooks_riverpod.dart';
import 'package:gpt_markdown/gpt_markdown.dart';
import 'package:buzz/shared/theme/buzz_icons.dart';
import 'package:open_filex/open_filex.dart';
import 'package:path_provider/path_provider.dart';
import 'package:share_plus/share_plus.dart';
import 'package:url_launcher/url_launcher.dart';

import '../../shared/clipboard_utils.dart';
import '../../shared/widgets/media_loading_placeholder.dart';
import '../../shared/widgets/modal_presentation.dart';
import '../../shared/widgets/sheet_action_section.dart';
import '../../shared/mentions/mention_bindings.dart';
import '../../shared/mentions/mention_tags.dart';
import '../../shared/deeplink/deep_link.dart';
import '../../shared/deeplink/pending_deep_link_provider.dart';
import '../../shared/relay/relay.dart';
import '../../shared/syntax_highlight.dart';
import '../../shared/theme/theme.dart';
import '../../shared/custom_emoji/custom_emoji.dart';
import '../../shared/custom_emoji/custom_emoji_provider.dart';
import '../../shared/custom_emoji/custom_emoji_render.dart';
import '../../shared/emoji/emoji_data_provider.dart';
import '../../shared/emoji/emoji_only.dart';
import 'channel_ids_by_name_provider.dart';
import 'local_send_bubble_surface.dart';
import 'media_viewer_page.dart';
import 'message_content/link_normalizer.dart';
import 'message_content/markdown_escapes.dart';
import 'message_content/preview_text.dart';
import 'message_media.dart';
import 'message_content/bubble_segments.dart';
import 'message_content/buzz_link_label.dart';
import 'message_content/channel_token_pattern.dart';
import 'message_mention_pill.dart';
import 'message_gallery.dart';
import 'message_gallery_frame.dart';
import 'message_long_press_region.dart';
import 'message_media_avatar.dart';
import 'message_media_geometry.dart';
import 'voice_note_attachment.dart';

part 'message_content/media_carousel.dart';
part 'message_content/message_preview.dart';
part 'message_content/bubble_shape.dart';
part 'message_content/inline_components.dart';
part 'message_content/token_pill.dart';
part 'message_content/video_preview.dart';
part 'message_content/link_actions.dart';

typedef OpenDownloadedFile =
    Future<void> Function(
      String url,
      Map<String, String> headers,
      String filename,
    );

final openDownloadedFileProvider = Provider<OpenDownloadedFile>((ref) {
  final client = ref.watch(mediaHttpClientProvider);
  return (url, headers, filename) async {
    final response = await client.get(Uri.parse(url), headers: headers);
    if (response.statusCode < 200 || response.statusCode >= 300) {
      throw HttpException(
        'Attachment download failed (${response.statusCode})',
        uri: Uri.parse(url),
      );
    }

    final directory = await getTemporaryDirectory();
    final safeName = _safeDownloadedFilename(filename);
    final file = File(
      '${directory.path}${Platform.pathSeparator}'
      '${DateTime.now().microsecondsSinceEpoch}-$safeName',
    );
    await file.writeAsBytes(response.bodyBytes, flush: true);
    final result = await OpenFilex.open(file.path);
    if (result.type != ResultType.done) {
      throw FileSystemException(result.message, file.path);
    }
  };
});

String _safeDownloadedFilename(String filename) {
  final safe = filename
      .split(RegExp(r'[/\\]'))
      .last
      .replaceAll(RegExp(r'[\x00-\x1F\x7F]'), '')
      .trim();
  return safe.isEmpty ? 'attachment' : safe;
}

/// Renders message content with markdown formatting, @mentions, #channel links,
/// and media-aware markdown images/videos.
class MessageContent extends HookConsumerWidget {
  final String content;

  /// Paint conversation text bubbles while keeping attachments on the page.
  final bool bubble;

  /// Distinguishes messages authored by the signed-in identity.
  final bool ownMessage;

  /// Lets an adjacent day divider own spacing after the final text segment.
  final bool trimTrailingSpacing;

  /// Marks the final message in a sender run for rounded corners and dots.
  final bool bubbleEnd;

  /// Marks the first message in a sender run for rounded top corners.
  final bool bubbleStart;

  /// Reserves room above overlapping reactions.
  final bool hasReactions;

  /// Display names for mentioned pubkeys, extracted from event p-tags.
  /// Keys are lowercase pubkeys, values are display names.
  final Map<String, String> mentionNames;

  /// Contextual display labels for mentioned pubkeys (lowercase keys).
  ///
  /// Presentation only: text still binds through [mentionNames], so a
  /// disambiguated label never changes which signed text names whom.
  final Map<String, String> mentionLabels;

  /// Mentioned pubkeys that resolve to agents. Agent chips use the desktop
  /// robot treatment instead of an `@` prefix.
  final Set<String> agentMentionPubkeys;

  /// Known channel names for #channel links. Keys are lowercase channel
  /// names, values are channel IDs.
  final Map<String, String> channelNames;

  /// Raw event tags, used for `imeta` media metadata lookups.
  final List<List<String>> tags;

  /// Called when a #channel link is tapped.
  final void Function(String channelId)? onChannelTap;

  /// Called when an @mention of a known user is tapped, with the
  /// mentioned user's pubkey.
  final void Function(String pubkey)? onMentionTap;

  /// Opens the message's thread from the full-screen image viewer.
  final VoidCallback? onMediaReply;

  /// Opens message-specific actions for an image in the full-screen viewer.
  final MediaViewerMoreAction? onMediaMore;

  final TextStyle? baseStyle;

  /// Alignment applied to rendered markdown text.
  final TextAlign? textAlign;

  final int? maxLines;

  /// Render a body that is nothing but emoji at [kEmojiOnlyFontSize], the way
  /// desktop's `MessageRow` does. Off by default: previews, search hits, and
  /// notification rows want a message to occupy its usual line height whatever
  /// it contains.
  final bool scaleEmojiOnly;

  /// Allows a multi-image carousel to reclaim leading space reserved by the
  /// surrounding message layout, while keeping its image count aligned with
  /// the message body.
  final double mediaCarouselLeadingOverflow;

  /// Allows a multi-image carousel to continue through the trailing page
  /// gutter while keeping its first image and count aligned with the body.
  final double mediaCarouselTrailingOverflow;

  const MessageContent({
    super.key,
    required this.content,
    this.bubble = false,
    this.ownMessage = false,
    this.trimTrailingSpacing = false,
    this.bubbleEnd = true,
    this.bubbleStart = true,
    this.hasReactions = false,
    this.mentionNames = const {},
    this.mentionLabels = const {},
    this.agentMentionPubkeys = const {},
    this.channelNames = const {},
    this.tags = const [],
    this.onChannelTap,
    this.onMentionTap,
    this.onMediaReply,
    this.onMediaMore,
    this.baseStyle,
    this.textAlign,
    this.maxLines,
    this.scaleEmojiOnly = false,
    this.mediaCarouselLeadingOverflow = 0,
    this.mediaCarouselTrailingOverflow = 0,
  });

  @override
  Widget build(BuildContext context, WidgetRef ref) {
    final markdownTheme = GptMarkdownTheme.of(context);
    final chatColors = ChatColors.of(context);
    final ownTextColor = chatColors.foreground;
    // Own-bubble links share the bubble ink; markdown marks them by underline.
    final linkColor = ownMessage ? ownTextColor : context.colors.tertiary;
    final bubbleInk = ownMessage ? ownTextColor : context.colors.onSurface;
    final onSurface = context.colors.onSurface;
    // GptMarkdownTheme notifies its dependents whenever the data object
    // changes (the data has no value equality), and each notification makes
    // every GptMarkdown below re-parse its text. Reuse one bubble theme while
    // its inputs are unchanged so an ordinary rebuild does not re-parse.
    final bubbleMarkdownTheme = useMemoized(
      () => markdownTheme.copyWith(
        linkColor: linkColor,
        // A neutral chip would put white ink on a light fill; tint the accent
        // instead.
        inlineCode: ownMessage
            ? markdownTheme.inlineCode.copyWith(
                color: ownTextColor,
                backgroundColor: chatCodeTint(ownTextColor, 0.18),
                borderColor: ownTextColor.withValues(alpha: 0.3),
              )
            : null,
        h1: markdownTheme.h1?.copyWith(color: bubbleInk),
        h2: markdownTheme.h2?.copyWith(color: bubbleInk),
        h3: markdownTheme.h3?.copyWith(color: bubbleInk),
        h4: markdownTheme.h4?.copyWith(color: bubbleInk),
        h5: markdownTheme.h5?.copyWith(color: bubbleInk),
        h6: markdownTheme.h6?.copyWith(color: bubbleInk),
      ),
      [markdownTheme, linkColor, ownMessage, ownTextColor, onSurface],
    );
    final baseTextStyle =
        (baseStyle ??
                context.textTheme.bodyMedium?.copyWith(
                  color: context.colors.onSurface,
                ))
            ?.copyWith(color: bubble && ownMessage ? ownTextColor : null);
    final resolvedMentionNames = mentionNames;
    final signedMentionPubkeys = mentionedPubkeysFromTags(tags);
    final mentionBindings = renderedMentionBindings(
      content,
      mentionNames,
      signedMentionPubkeys,
    );
    final resolvedAgentMentionPubkeys = {
      ...agentMentionPubkeys.map((pubkey) => pubkey.toLowerCase()),
    };
    final resolvedChannelNames = channelNames.isNotEmpty
        ? channelNames
        : ref.watch(channelIdsByNameProvider);
    final channelHandler = useRef(onChannelTap)..value = onChannelTap;
    final resolvedChannelTap = useMemoized(
      () => (String channelId) {
        final handler = channelHandler.value;
        if (handler != null) {
          handler(channelId);
        } else {
          ref
              .read(pendingDeepLinkProvider.notifier)
              .open(Uri(scheme: 'buzz', host: 'channel', path: channelId));
        }
      },
      const [],
    );
    final replyHandler = useRef(onMediaReply)..value = onMediaReply;
    final moreHandler = useRef(onMediaMore)..value = onMediaMore;
    final mediaReply = useMemoized(
      () =>
          () => replyHandler.value?.call(),
      const [],
    );
    final mediaMore = useMemoized(
      () =>
          (BuildContext context, String url) =>
              moreHandler.value?.call(context, url),
      const [],
    );
    final channelPresentationKey = [
      for (final entry
          in (resolvedChannelNames.entries.toList()
            ..sort((a, b) => a.key.compareTo(b.key))))
        '${entry.key}\u0000${entry.value}',
    ].join('\u0001');
    final imetaByUrl = {
      for (final entry in parseImetaTags(tags).entries)
        normalizeMarkdownDestination(entry.key): entry.value,
    };
    final normalizedContent = useMemoized(() => normalizeBareLinks(content), [
      content,
    ]);
    final trailingGallery = maxLines == null
        ? extractTrailingImageGallery(normalizedContent, imetaByUrl)
        : null;
    final galleryText = trailingGallery?.content ?? normalizedContent;
    // gpt_markdown has no backslash escapes, so hold escaped characters as
    // stand-ins that _MarkdownEscapeMd and the link builders restore.
    final markdownContent = useMemoized(
      () => shieldMarkdownProseEscapes(galleryText),
      [galleryText],
    );
    final customEmoji = _mergeCustomEmoji(
      customEmojiFromTags(tags),
      ref.watch(customEmojiListProvider),
    );
    final mentionPresentationKey = [
      for (final entry
          in (resolvedMentionNames.entries.toList()
            ..sort((a, b) => a.key.compareTo(b.key))))
        '${entry.key}\u0000${entry.value}',
      ...(resolvedAgentMentionPubkeys.toList()..sort()),
      ...(signedMentionPubkeys.toList()..sort()),
    ].join('\u0001');

    // Decided here rather than by the caller: this is where the event's own
    // emoji tags and the community palette have already been merged, and a
    // `:shortcode:` only counts as emoji if it resolves against that palette.
    final emojiOnly =
        scaleEmojiOnly &&
        isEmojiOnlyMessage(
          markdownContent,
          nativeEmoji: ref.watch(nativeEmojiGlyphsProvider),
          customEmoji: customEmoji,
        );
    final style = emojiOnly
        ? baseTextStyle?.copyWith(
            fontSize: kEmojiOnlyFontSize,
            height: kEmojiOnlyHeight,
          )
        : baseTextStyle;
    final inlineCustomEmojiSize = emojiOnly
        ? kEmojiOnlyCustomEmojiSize
        : kCustomEmojiInlineSize;

    final finalContent = useMemoized(() {
      // Replace spaces with non-breaking spaces inside known mention names
      // so the gpt_markdown combined regex can match multi-word names
      // even when caseSensitive is not preserved.
      // Skip content inside backticks to avoid altering inline code.
      final mentionParts = markdownContent.split('`');
      final mentionBuf = StringBuffer();
      for (var i = 0; i < mentionParts.length; i++) {
        if (i.isOdd) {
          mentionBuf.write('`${mentionParts[i]}`');
        } else {
          var segment = mentionParts[i];
          for (final range in mentionOccurrences(
            segment,
            mentionBindings.keys,
          ).reversed) {
            segment = segment.replaceRange(
              range.start,
              range.end,
              '@${_markdownMentionName(range.label)}',
            );
          }
          mentionBuf.write(segment);
        }
      }
      var result = mentionBuf.toString();

      // Ensure channel links at the very start of content don't get
      // swallowed by markdown processing.
      if (RegExp(r'^#[A-Za-z0-9_]').hasMatch(result)) {
        result = '\u200B$result';
      }
      return result;
    }, [markdownContent, mentionPresentationKey]);

    final inlineComponents = _useMessageInlineComponents(
      content: content,
      finalContent: finalContent,
      mentionNames: resolvedMentionNames,
      mentionLabels: mentionLabels,
      bindings: mentionBindings,
      agentPubkeys: resolvedAgentMentionPubkeys,
      channelNames: resolvedChannelNames,
      customEmoji: customEmoji,
      emojiSize: inlineCustomEmojiSize,
      tags: tags,
      hasMediaReply: onMediaReply != null,
      hasMediaMore: onMediaMore != null,
      onMentionTap: onMentionTap,
      onChannelTap: resolvedChannelTap,
    );

    Widget renderMarkdown(String text) => KeyedSubtree(
      key: ValueKey(
        '$text\u0000$mentionPresentationKey\u0000$channelPresentationKey',
      ),
      child: GptMarkdown(
        text,
        style: style,
        styleSheet: bubble
            ? GptMarkdownStyleSheet(
                blockQuote: BlockQuoteStyle(barColor: bubbleInk),
                hr: HrStyle(color: bubbleInk.withValues(alpha: 0.3)),
                table: TableStyle(
                  borderColor: bubbleInk.withValues(alpha: 0.3),
                  headerBackground: Colors.transparent,
                  headerTextStyle: TextStyle(color: bubbleInk),
                ),
              )
            : null,
        followLinkColor: false,
        // normalizeBareLinks() already turns bare URLs into Markdown links;
        // gpt_markdown 1.2.0 autolinks by default, so both would run.
        autolink: false,
        codeBuilder: (context, name, code, closed) => _MessageCodeBlock(
          name: name,
          code: code,
          bubble: bubble,
          ink: bubble && ownMessage ? ownTextColor : null,
        ),
        linkBuilder: (context, linkText, shieldedUrl, linkStyle) {
          final url = unshieldMarkdownEscapes(shieldedUrl);
          return _buildLink(
            context,
            ref,
            linkText,
            url,
            imetaByUrl[url],
            linkStyle,
            style,
            resolvedChannelTap,
            resolvedChannelNames,
          );
        },
        imageBuilder: (context, shieldedUrl, _, _) {
          final imageUrl = unshieldMarkdownEscapes(shieldedUrl);
          return _buildMedia(
            context,
            imageUrl,
            imetaByUrl[imageUrl],
            onReply: onMediaReply == null ? null : mediaReply,
            onMore: onMediaMore == null ? null : mediaMore,
          );
        },
        textAlign: textAlign ?? (bubble ? TextAlign.start : null),
        maxLines: maxLines,
        inlineComponents: inlineComponents,
      ),
    );
    final segments = bubble
        ? messageBubbleSegments(finalContent, imetaByUrl)
        : const <({String text, bool attachment})>[];
    final markdown = bubble
        ? Column(
            crossAxisAlignment: ownMessage
                ? CrossAxisAlignment.end
                : CrossAxisAlignment.start,
            mainAxisSize: MainAxisSize.min,
            children: [
              for (final (index, segment) in segments.indexed)
                if (segment.attachment)
                  MessageReplyDragTarget(
                    child: MessageAttachmentCorners(
                      borderRadius: _attachmentCorners(
                        start: bubbleStart && index == 0,
                        end:
                            bubbleEnd &&
                            trailingGallery == null &&
                            index == segments.length - 1,
                      ),
                      child: renderMarkdown(segment.text),
                    ),
                  )
                else
                  Padding(
                    key: ValueKey('message-text-bubble-$index'),
                    padding: EdgeInsets.only(
                      bottom:
                          trimTrailingSpacing &&
                              trailingGallery == null &&
                              index == segments.length - 1
                          ? 0
                          : Grid.quarter,
                    ),
                    child: ConstrainedBox(
                      constraints: BoxConstraints(
                        maxWidth:
                            MediaQuery.sizeOf(context).width *
                            messageTextMaxWidthFraction,
                      ),
                      child: MessageReplyDragTarget(
                        child: LocalSendBubbleSurface(
                          color: ownMessage
                              ? chatColors.outgoing
                              : receivedMessageSurface(
                                  context.colors.brightness,
                                ),
                          shape: const _MessageBubbleShape(),
                          child: Padding(
                            padding: EdgeInsets.fromLTRB(
                              Grid.xs,
                              Grid.xxs,
                              Grid.xs,
                              hasReactions && index == segments.length - 1
                                  ? Grid.xs
                                  : Grid.xxs,
                            ),
                            child: Theme(
                              data: Theme.of(context).copyWith(
                                colorScheme: context.colors.copyWith(
                                  primary: linkColor,
                                ),
                              ),
                              child: GptMarkdownTheme(
                                gptThemeData: bubbleMarkdownTheme,
                                child: renderMarkdown(segment.text),
                              ),
                            ),
                          ),
                        ),
                      ),
                    ),
                  ),
            ],
          )
        : renderMarkdown(finalContent);
    if (trailingGallery == null) return markdown;

    return Column(
      crossAxisAlignment: ownMessage
          ? CrossAxisAlignment.end
          : CrossAxisAlignment.start,
      mainAxisSize: MainAxisSize.min,
      children: [
        if (trailingGallery.content.trim().isNotEmpty) markdown,
        MessageReplyDragTarget(
          child: MessageAttachmentCorners(
            borderRadius: _attachmentCorners(
              start: bubbleStart && trailingGallery.content.trim().isEmpty,
              end: bubbleEnd,
            ),
            child: _MessageImageCarousel(
              key: ValueKey(
                trailingGallery.items.map((item) => item.url).join('\u0000'),
              ),
              items: trailingGallery.items,
              mirrored: ownMessage,
              leadingOverflow: mediaCarouselLeadingOverflow,
              trailingOverflow: mediaCarouselTrailingOverflow,
              onReply: onMediaReply,
              onMore: onMediaMore,
            ),
          ),
        ),
      ],
    );
  }

  Widget _buildMedia(
    BuildContext context,
    String imageUrl,
    ImetaEntry? imeta, {
    VoidCallback? onReply,
    MediaViewerMoreAction? onMore,
  }) {
    final mediaKind = classifyMediaUrl(imageUrl, imeta: imeta);
    if (mediaKind == MessageMediaKind.audio) {
      return Padding(
        padding: const EdgeInsets.only(top: Grid.half),
        child: VoiceNoteAttachment.remote(
          url: imageUrl,
          duration: Duration(
            milliseconds: ((imeta?.duration ?? 0) * 1000).round(),
          ),
        ),
      );
    }
    if (mediaKind == MessageMediaKind.video) {
      return _MessageVideoPreview(
        url: imageUrl,
        imeta: imeta,
        onReply: onReply,
      );
    }
    return _MessageImagePreview(
      url: imageUrl,
      imeta: imeta,
      semanticLabel: imeta?.alt ?? 'Message image',
      onReply: onReply,
      onMore: onMore,
    );
  }

  Widget _buildLink(
    BuildContext context,
    WidgetRef ref,
    InlineSpan linkText,
    String url,
    ImetaEntry? imeta,
    TextStyle linkStyle,
    TextStyle? fallbackStyle,
    void Function(String channelId) resolvedChannelTap,
    Map<String, String> resolvedChannelNames,
  ) {
    String text = '';
    linkText.visitChildren((span) {
      if (span is TextSpan && span.text != null) {
        text += span.text!;
      }
      return true;
    });

    final baseStyle = fallbackStyle ?? linkStyle;
    if (imeta != null &&
        classifyMediaUrl(url, imeta: imeta) == MessageMediaKind.audio) {
      return _buildMedia(context, url, imeta);
    }
    final uri = Uri.tryParse(url);
    final buzzLink = uri?.scheme == 'buzz'
        ? parseBuzzDeepLink(uri!) ?? parseEntityDeepLink(uri)
        : null;
    final isBuzzLink =
        buzzLink is ChannelDeepLink ||
        buzzLink is MessageDeepLink ||
        buzzLink is EntityDeepLink;
    final isCanonicalBuzzLabel = isBuzzLink && text == url;
    String? channelName(String id) =>
        _channelNameForId(resolvedChannelNames, id);
    final buzzLabel = buzzLinkLabel(buzzLink, channelName);
    final buzzPresentation = switch (buzzLink) {
      ChannelDeepLink() => (
        icon: BuzzIcons.hash,
        label: buzzLabel!,
        semanticLabel: 'Open channel $buzzLabel',
        interactive: true,
      ),
      MessageDeepLink(:final channelId, :final messageId) => (
        icon: BuzzIcons.messageSquare,
        label: buzzLabel!,
        semanticLabel:
            'Open message ${shortBuzzId(messageId)} in channel ${buzzChannelLabel(channelId, channelName)}',
        interactive: true,
      ),
      EntityDeepLink(:final type, :final repository, :final eventId) => (
        icon: switch (type) {
          'repo' => BuzzIcons.folderGit2,
          'pr' => BuzzIcons.gitPullRequest,
          _ => BuzzIcons.circleDot,
        },
        label: buzzLabel!,
        semanticLabel: switch (type) {
          'repo' => 'Repository $repository',
          'pr' =>
            'Pull request ${shortBuzzId(eventId ?? '')} in repository $repository',
          _ => 'Issue ${shortBuzzId(eventId ?? '')} in repository $repository',
        },
        interactive: false,
      ),
      _ => null,
    };

    final authoredLinkStyle = baseStyle.copyWith(
      color: context.colors.primary,
      decoration: TextDecoration.underline,
      decorationColor: context.colors.primary,
    );
    final linkTextWidget = isCanonicalBuzzLabel
        ? Text(
            text,
            style: baseStyle.copyWith(
              color: context.colors.primary,
              fontWeight: FontWeight.w600,
            ),
          )
        : Text.rich(TextSpan(style: authoredLinkStyle, children: [linkText]));

    final renderedLink = isCanonicalBuzzLabel && buzzPresentation != null
        ? _TokenPill(
            key: ValueKey('buzz-link-chip:$url'),
            icon: buzzPresentation.icon,
            interactive: buzzPresentation.interactive,
            semanticLabel: buzzPresentation.semanticLabel,
            text: buzzPresentation.label,
            textStyle: baseStyle.copyWith(fontWeight: FontWeight.w600),
          )
        : linkTextWidget;

    final highlightColor = (baseStyle.color ?? context.colors.primary)
        .withValues(alpha: 0.2);

    // Mobile has no repo/PR/issue destination yet, so these chips have no tap
    // and no Open action, but a hold still copies or shares the link.
    if (buzzLink is EntityDeepLink) {
      return _LinkLongPress(
        url: url,
        onOpen: null,
        highlightColor: highlightColor,
        child: renderedLink,
      );
    }

    Future<void> openLink() async {
      final uri = Uri.tryParse(url);
      if (uri == null) return;

      // Rendered channel URLs must use the same callback as `#channel`
      // references so detail-page callers can suppress self-navigation.
      // Message and join links still need the top-level authenticated
      // dispatcher.
      if (uri.scheme == 'buzz') {
        final deepLink = parseBuzzDeepLink(uri);
        if (deepLink case ChannelDeepLink(:final channelId)) {
          resolvedChannelTap(channelId);
        } else if (deepLink is MessageDeepLink || deepLink is InviteDeepLink) {
          ref.read(pendingDeepLinkProvider.notifier).open(uri);
        }
        return;
      }
      if (uri.scheme != 'http' && uri.scheme != 'https') return;

      final auth = ref.read(mediaGetAuthServiceProvider);
      if (!auth.isRelayMediaUrl(url)) {
        await launchUrl(uri, mode: LaunchMode.externalApplication);
        return;
      }

      try {
        await ref.read(openDownloadedFileProvider)(
          url,
          auth.headersFor(url),
          text,
        );
      } catch (_) {
        if (!context.mounted) return;
        ScaffoldMessenger.maybeOf(context)?.showFeedbackSnackBar(
          const SnackBar(content: Text('Could not open attachment')),
          kind: ToastKind.error,
        );
      }
    }

    // openLink handles only these schemes; the sheet hides Open for others.
    final scheme = Uri.tryParse(url)?.scheme;
    final canOpen = scheme == 'buzz' || scheme == 'http' || scheme == 'https';
    return _LinkLongPress(
      url: url,
      onOpen: canOpen ? () => unawaited(openLink()) : null,
      highlightColor: highlightColor,
      child: GestureDetector(onTap: openLink, child: renderedLink),
    );
  }
}

List<CustomEmoji> _mergeCustomEmoji(
  List<CustomEmoji> eventEmoji,
  List<CustomEmoji> paletteEmoji,
) {
  if (eventEmoji.isEmpty) return paletteEmoji;
  if (paletteEmoji.isEmpty) return eventEmoji;
  final seen = <String>{};
  final merged = <CustomEmoji>[];
  for (final emoji in [...eventEmoji, ...paletteEmoji]) {
    if (seen.add(emoji.shortcode)) merged.add(emoji);
  }
  return merged;
}

class _MessageImagePreview extends HookConsumerWidget {
  final String url;
  final ImetaEntry? imeta;
  final String semanticLabel;
  final VoidCallback? onReply;
  final MediaViewerMoreAction? onMore;

  const _MessageImagePreview({
    required this.url,
    required this.imeta,
    required this.semanticLabel,
    required this.onReply,
    required this.onMore,
  });

  @override
  Widget build(BuildContext context, WidgetRef ref) {
    final heroTag = useMemoized(() => Object());
    final layout = _resolveImagePreviewLayout(context, imeta?.aspectRatio);
    final previewDecodeWidth = layout.width ?? messageMediaMaxWidth(context);

    return Padding(
      padding: const EdgeInsets.only(top: Grid.half),
      child: GestureDetector(
        onTap: () => openImageViewer(
          context,
          imageUrl: url,
          heroTag: heroTag,
          semanticLabel: semanticLabel,
          previewDecodeWidth: previewDecodeWidth,
          aspectRatio: imeta?.aspectRatio,
          onReply: onReply,
          onMore: onMore,
        ),
        child: _MessageMediaPreviewFrame(
          previewKey: ValueKey('message-media-image-preview:$url'),
          backgroundColor: context.colors.surfaceContainerHighest,
          width: layout.width,
          height: layout.height,
          child: MediaViewerHero(
            tag: heroTag,
            child: ClipRRect(
              borderRadius:
                  MessageAttachmentCorners.of(context) ??
                  BorderRadius.circular(Radii.md),
              child: MediaImage(
                url: url,
                decodeWidth: previewDecodeWidth,
                fit: layout.fit,
                semanticLabel: semanticLabel,
                frameBuilder: (context, child, frame, synchronous) =>
                    frame != null || synchronous
                    ? child
                    : const MediaLoadingPlaceholder(label: 'Loading image'),
                errorBuilder: (_, _, _) => _MediaPreviewFallback(
                  icon: BuzzIcons.imageOff,
                  label: 'Image unavailable',
                ),
              ),
            ),
          ),
        ),
      ),
    );
  }
}

class _MessageMediaPreviewFrame extends StatelessWidget {
  final Key previewKey;
  final Color backgroundColor;
  final double? width;
  final double? height;
  final Widget child;

  const _MessageMediaPreviewFrame({
    required this.previewKey,
    required this.backgroundColor,
    this.width,
    this.height,
    required this.child,
  });

  @override
  Widget build(BuildContext context) {
    final resolvedWidth = width ?? messageMediaMaxWidth(context);

    return Container(
      key: previewKey,
      width: resolvedWidth,
      height: height,
      clipBehavior: Clip.antiAlias,
      decoration: BoxDecoration(
        color: backgroundColor,
        borderRadius:
            MessageAttachmentCorners.of(context) ??
            BorderRadius.circular(Radii.md),
        border: Border.all(color: context.colors.outlineVariant),
      ),
      child: child,
    );
  }
}

_ImagePreviewLayout _resolveImagePreviewLayout(
  BuildContext context,
  double? aspectRatio,
) {
  final previewSize = messageImagePreviewSize(context, aspectRatio);
  return _ImagePreviewLayout(
    width: previewSize.width,
    height: previewSize.height,
    fit: aspectRatio == null ? BoxFit.contain : BoxFit.cover,
  );
}

class _ImagePreviewLayout {
  final double? width;
  final double? height;
  final BoxFit fit;

  const _ImagePreviewLayout({this.width, this.height, required this.fit});
}

class _MediaPreviewFallback extends StatelessWidget {
  final IconData icon;
  final String label;

  const _MediaPreviewFallback({required this.icon, required this.label});

  @override
  Widget build(BuildContext context) {
    return ColoredBox(
      color: context.colors.surfaceContainerHighest,
      child: Center(
        child: Column(
          mainAxisSize: MainAxisSize.min,
          children: [
            Icon(icon, color: context.colors.onSurfaceVariant),
            const SizedBox(height: Grid.quarter),
            Text(
              label,
              style: context.textTheme.labelSmall?.copyWith(
                color: context.colors.onSurfaceVariant,
              ),
              textAlign: TextAlign.center,
            ),
          ],
        ),
      ),
    );
  }
}

class _MessageCodeBlock extends HookWidget {
  final String name;
  final String code;

  /// Whether the block sits inside a message bubble.
  final bool bubble;

  /// Text color on an accent bubble; null keeps the neutral highlighted card.
  final Color? ink;

  const _MessageCodeBlock({
    required this.name,
    required this.code,
    this.bubble = false,
    this.ink,
  });

  @override
  Widget build(BuildContext context) {
    final isCopied = useState(false);

    Future<void> handleCopy() async {
      await copyToClipboard(context, code, message: 'Code copied');
      if (!context.mounted) return;
      isCopied.value = true;
      Future.delayed(const Duration(seconds: 2), () {
        if (context.mounted) isCopied.value = false;
      });
    }

    final ink = this.ink;
    // A fence's closing newline would otherwise render as a blank last line.
    final shownCode = code.trimRight();
    final codeBaseStyle = TextStyle(
      fontFamily: CodeStyle.fontFamily,
      fontSize: CodeStyle.fontSize,
      height: CodeStyle.lineHeight,
      color: ink ?? context.colors.onSurface,
    );
    final isDark = context.theme.brightness == Brightness.dark;
    final codeTheme = isDark ? highlightDarkTheme : highlightLightTheme;
    // Syntax colors are tuned for neutral cards and lose contrast on accents.
    final codeSpans = useMemoized(
      () => ink == null
          ? highlightCode(shownCode, name, codeTheme, codeBaseStyle)
          : [TextSpan(text: shownCode)],
      [code, name, isDark, ink],
    );
    return Container(
      // In a bubble, the vertical margin brings the bubble's 8px vertical
      // padding up to its 16px side padding, so the block is inset evenly and
      // its corners stay concentric with the bubble's.
      margin: bubble
          ? const EdgeInsets.symmetric(vertical: Grid.xs - Grid.xxs)
          : const EdgeInsets.only(top: Grid.half),
      decoration: BoxDecoration(
        color: ink == null
            ? CodeStyle.background(context.colors)
            : chatCodeTint(ink, 0.14),
        borderRadius: BorderRadius.circular(
          bubble ? Radii.container - Grid.xs : 12,
        ),
        border: Border.all(
          color:
              ink?.withValues(alpha: 0.24) ?? CodeStyle.border(context.colors),
        ),
      ),
      child: Stack(
        children: [
          // Even 12px insets; the right side also reserves the copy button.
          Padding(
            padding: const EdgeInsets.fromLTRB(
              Grid.twelve,
              Grid.twelve,
              Grid.twelve + 28,
              Grid.twelve,
            ),
            child: Column(
              crossAxisAlignment: CrossAxisAlignment.stretch,
              mainAxisSize: MainAxisSize.min,
              children: [
                if (name.isNotEmpty)
                  Padding(
                    padding: const EdgeInsets.only(bottom: Grid.half),
                    child: Text(
                      name,
                      style: context.textTheme.labelSmall?.copyWith(
                        color: ink ?? context.colors.onSurfaceVariant,
                      ),
                    ),
                  ),
                SingleChildScrollView(
                  scrollDirection: Axis.horizontal,
                  child: RichText(
                    softWrap: false,
                    text: TextSpan(style: codeBaseStyle, children: codeSpans),
                  ),
                ),
              ],
            ),
          ),
          Positioned(
            top: Grid.half + Grid.quarter,
            right: Grid.half + Grid.quarter,
            child: SizedBox(
              width: 28,
              height: 28,
              child: IconButton(
                onPressed: handleCopy,
                padding: EdgeInsets.zero,
                visualDensity: VisualDensity.compact,
                style: IconButton.styleFrom(
                  tapTargetSize: MaterialTapTargetSize.shrinkWrap,
                ),
                icon: Icon(
                  isCopied.value ? BuzzIcons.check : BuzzIcons.copy,
                  size: 14,
                  color:
                      ink ??
                      (isCopied.value
                          ? context.colors.primary
                          : context.colors.onSurfaceVariant),
                ),
              ),
            ),
          ),
        ],
      ),
    );
  }
}

class _MentionMd extends InlineMd {
  final Map<String, Set<String>> bindings;
  final Map<String, String> displayLabels;
  final Map<String, String> mentionNames;
  final Map<String, String> mentionLabels;
  final Set<String> agentMentionPubkeys;
  final void Function(String pubkey)? onMentionTap;
  late final RegExp _exp = _buildPrefixPattern(
    prefix: '@',
    knownNames: bindings.keys.map(_markdownMentionName),
    genericTokenPattern: r'[A-Za-z0-9_][A-Za-z0-9_\u00A0-]*',
  );

  _MentionMd({
    required this.bindings,
    required this.displayLabels,
    required this.mentionNames,
    required this.mentionLabels,
    required this.agentMentionPubkeys,
    this.onMentionTap,
  });

  /// Excluded from link labels: this component renders a [WidgetSpan], and a
  /// placeholder nested inside the link's own placeholder does not paint on
  /// iOS — an authored `[@mention](url)` renders as nothing. Link resolution
  /// wins over token detection inside a label.
  @override
  Set<MarkdownScope> get scopes => MarkdownComponent.allScopesExceptLinkLabel;

  @override
  RegExp get exp => _exp;

  @override
  InlineSpan span(
    BuildContext context,
    String text,
    final GptMarkdownConfig config,
  ) {
    final raw = exp.firstMatch(text.trim())?.group(0);
    if (raw == null) {
      return TextSpan(text: text, style: config.style);
    }

    final name = raw.substring(1).replaceAll('\u00A0', ' ').toLowerCase();
    final matches = bindings[name] ?? const <String>{};
    final pubkey = matches.length == 1 ? matches.single : null;
    if (bindings.containsKey(name) && matches.length != 1) {
      return TextSpan(text: text, style: config.style);
    }
    final displayName = name.contains(RegExp(r'\([0-9a-f]{64}\)'))
        ? displayLabels[name]
        : mentionLabels[pubkey] ?? mentionNames[pubkey];

    final isAgent =
        pubkey != null && agentMentionPubkeys.contains(pubkey.toLowerCase());
    final fullLabel = displayName ?? raw.substring(1);
    final visibleLabel = fullLabel.replaceAllMapped(
      RegExp(r'\(([0-9a-f]{64})\)'),
      (m) => '(${m[1]!.substring(0, 8)}…${m[1]!.substring(60)})',
    );
    final pill = MessageMentionPill(
      label: visibleLabel,
      semanticsLabel: fullLabel,
      isAgent: isAgent,
      textStyle: config.style,
    );

    return WidgetSpan(
      alignment: PlaceholderAlignment.baseline,
      baseline: TextBaseline.alphabetic,
      child: pubkey != null && onMentionTap != null
          ? GestureDetector(onTap: () => onMentionTap!(pubkey), child: pill)
          : pill,
    );
  }
}

String _markdownMentionName(String name) => name.replaceAll(' ', '\u00A0');