chanora/apps/chanora_flutter/lib/widgets/bbcode_text.dart

import 'package:flutter/material.dart';
import 'package:url_launcher/url_launcher.dart';

import '../services/link_trust_service.dart';

final _tagRe = RegExp(
  r'\[(\/?(?:b|i|u|s'
  r'|color(?:=[^\]]*)?'
  r'|size(?:=\d+)?'
  r'|url(?:=[^\]]*)?'
  r'|img(?:=[^\]]*)?'
  r'|list|\*|quote|code|center|left|right'
  r'))\]',
  caseSensitive: false,
);
final _colorRe = RegExp(r'color=([#\w]+)');
final _sizeRe = RegExp(r'size=(\d+)');
final _urlRe = RegExp(r'url=(.+)');
final _imgRe = RegExp(r'img=(.+)');
final _urlAutoRe = RegExp(r'(?:\[url\])?(https?://[^\s\[\]]+)(?:\[/url\])?', caseSensitive: false);
final _closeUrlRe = RegExp(r'\[/url\]', caseSensitive: false);

int? _findCloseUrl(String src, int from) {
  final m = _closeUrlRe.matchAsPrefix(src, from);
  if (m != null) return from;
  final idx = src.indexOf('[/url]', from);
  if (idx >= 0) return idx;
  final idxu = src.indexOf('[/URL]', from);
  if (idxu >= 0) return idxu;
  return null;
}

Color? _parseColor(String hex) {
  try {
    var h = hex.replaceFirst('#', '');
    if (h.length == 6) h = 'FF$h';
    if (h.length == 8) {
      return Color(int.parse(h, radix: 16));
    }
  } catch (_) {}
  return null;
}

class BbCodeText extends StatelessWidget {
  const BbCodeText(this.text, {super.key, required this.linkTrust});

  final String text;
  final LinkTrustService linkTrust;

  @override
  Widget build(BuildContext context) {
    if (!text.contains('[') || !text.contains(']')) {
      return _plainWithAutoLinks(context, text);
    }
    return _render(context, text);
  }

  Widget _plainWithAutoLinks(BuildContext context, String src) {
    final parts = <InlineSpan>[];
    int last = 0;
    for (final m in _urlAutoRe.allMatches(src)) {
      if (m.start > last) {
        parts.add(TextSpan(text: src.substring(last, m.start)));
      }
      final url = m.group(1)!;
      parts.add(WidgetSpan(
        alignment: PlaceholderAlignment.middle,
        child: _LinkTap(
          url: url,
          linkTrust: linkTrust,
          child: Text(
            url,
            style: const TextStyle(
              color: Colors.blue,
              decoration: TextDecoration.underline,
            ),
          ),
        ),
      ));
      last = m.end;
    }
    if (last < src.length) {
      parts.add(TextSpan(text: src.substring(last)));
    }
    if (parts.isEmpty) return Text(src);
    return Text.rich(TextSpan(children: parts));
  }

  Widget _render(BuildContext context, String src) {
    final spans = <InlineSpan>[];
    final tags = <String>[];

    void flush(StringBuffer buf) {
      if (buf.isEmpty) return;
      var t = buf.toString();
      buf.clear();

      bool bold = false;
      bool italic = false;
      bool underline = false;
      bool strikethrough = false;
      Color? color;
      double? size;

      for (final tag in tags) {
        if (tag == 'b') {
          bold = true;
        } else if (tag == 'i') {
          italic = true;
        } else if (tag == 'u') {
          underline = true;
        } else if (tag == 's') {
          strikethrough = true;
        } else if (tag.startsWith('color=')) {
          color = _parseColor(tag.substring(6));
        } else if (tag.startsWith('size=')) {
          size = double.tryParse(tag.substring(5));
        }
      }

      spans.add(TextSpan(
        text: t,
        style: TextStyle(
          fontWeight: bold ? FontWeight.bold : null,
          fontStyle: italic ? FontStyle.italic : null,
          decoration: TextDecoration.combine([
            if (underline) TextDecoration.underline,
            if (strikethrough) TextDecoration.lineThrough,
          ]),
          color: color,
          fontSize: size,
        ),
      ));
    }

    final buf = StringBuffer();
    int i = 0;

    while (i < src.length) {
      if (src[i] != '[') {
        buf.write(src[i]);
        i++;
        continue;
      }
      final m = _tagRe.matchAsPrefix(src, i);
      if (m == null) {
        buf.write(src[i]);
        i++;
        continue;
      }

      flush(buf);
      final raw = m.group(1)!.toLowerCase();
      i = m.end;

      if (raw.startsWith('/')) {
        final closeTag = raw.substring(1);
        if (closeTag == 'url' || closeTag == 'img') {
          continue;
        }
        tags.remove(closeTag);
        continue;
      }

      switch (raw) {
        case 'b':
        case 'i':
        case 'u':
        case 's':
        case 'list':
        case 'quote':
        case 'code':
        case 'center':
        case 'left':
        case 'right':
          tags.add(raw);
          break;

        case '*':
          spans.add(const TextSpan(text: '\n \u2022 '));
          break;

        default:
          if (raw.startsWith('color=') || raw.startsWith('size=')) {
            tags.add(raw);
          } else if (raw.startsWith('url=')) {
            final url = _urlRe.firstMatch(raw)?.group(1) ?? '';
            final closeIdx = _findCloseUrl(src, i);
            String inner;
            if (closeIdx != null) {
              inner = src.substring(i, closeIdx);
              i = closeIdx + 6;
            } else {
              inner = url;
            }
            spans.add(WidgetSpan(
              alignment: PlaceholderAlignment.middle,
              child: _LinkTap(
                url: url.isNotEmpty ? url : inner,
                linkTrust: linkTrust,
                child: Text(
                  inner,
                  style: const TextStyle(
                    color: Colors.blue,
                    decoration: TextDecoration.underline,
                  ),
                ),
              ),
            ));
          } else if (raw.startsWith('img=')) {
            final src2 = _imgRe.firstMatch(raw)?.group(1) ?? '';
            if (src2.isNotEmpty) {
              spans.add(WidgetSpan(
                child: ClipRRect(
                  borderRadius: BorderRadius.circular(8),
                  child: Image.network(
                    Uri.tryParse(src2)?.toString() ?? src2,
                    fit: BoxFit.scaleDown,
                    errorBuilder: (_, __, ___) => const SizedBox.shrink(),
                  ),
                ),
              ));
            }
          } else if (raw == 'url') {
            final closeIdx = _findCloseUrl(src, i);
            if (closeIdx != null) {
              final url = src.substring(i, closeIdx).trim();
              i = closeIdx + 6;
              spans.add(WidgetSpan(
                alignment: PlaceholderAlignment.middle,
                child: _LinkTap(
                  url: url,
                  linkTrust: linkTrust,
                  child: Text(
                    url,
                    style: const TextStyle(
                      color: Colors.blue,
                      decoration: TextDecoration.underline,
                    ),
                  ),
                ),
              ));
            }
          }
          break;
      }
    }

    flush(buf);

    if (spans.isEmpty) return Text(src);
    return Text.rich(TextSpan(children: spans));
  }
}

class _LinkTap extends StatefulWidget {
  const _LinkTap({
    required this.url,
    required this.child,
    required this.linkTrust,
  });

  final String url;
  final Widget child;
  final LinkTrustService linkTrust;

  @override
  State<_LinkTap> createState() => _LinkTapState();
}

class _LinkTapState extends State<_LinkTap> {
  @override
  void initState() {
    super.initState();
    widget.linkTrust.addListener(_onChanged);
  }

  @override
  void dispose() {
    widget.linkTrust.removeListener(_onChanged);
    super.dispose();
  }

  void _onChanged() => mounted ? setState(() {}) : null;

  Future<void> _open() async {
    final uri = Uri.tryParse(widget.url);
    if (uri == null) return;
    final host = uri.host;
    if (host.isEmpty) return;

    if (widget.linkTrust.isTrusted(host)) {
      await launchUrl(uri, mode: LaunchMode.externalApplication);
      return;
    }

    if (!mounted) return;
    final trust = await showLinkTrustDialog(context, host);
    if (trust == null) return;
    if (trust) {
      await widget.linkTrust.addTrustedDomain(host);
    }
    await launchUrl(uri, mode: LaunchMode.externalApplication);
  }

  @override
  Widget build(BuildContext context) {
    return GestureDetector(
      onTap: _open,
      child: widget.child,
    );
  }
}