rely/lib/features/share_intake/domain/signal_share_parser.dart

class SignalSharePayload {
  const SignalSharePayload({
    required this.messageText,
    this.sourceDisplayName,
    this.sourceUserId,
    this.sourceThreadId,
  });

  final String messageText;
  final String? sourceDisplayName;
  final String? sourceUserId;
  final String? sourceThreadId;
}

/// Parses raw shared text from Signal into normalized sender/message fields.
class SignalShareParser {
  const SignalShareParser._();

  static final RegExp _namePrefixPattern = RegExp(
    r'^([^:\n]{2,80}):\s*(.+)$',
    dotAll: true,
  );

  static SignalSharePayload parse(String raw) {
    final String input = raw.trim();
    if (input.isEmpty) {
      return const SignalSharePayload(messageText: '');
    }

    final RegExpMatch? match = _namePrefixPattern.firstMatch(input);
    if (match == null) {
      return SignalSharePayload(messageText: input);
    }

    final String? senderName = _cleanSender(match.group(1));
    final String messageText = match.group(2)?.trim() ?? input;
    return SignalSharePayload(
      messageText: messageText,
      sourceDisplayName: senderName,
      sourceUserId: _normalizedKey(senderName),
      sourceThreadId: null,
    );
  }

  static bool looksLikeSignalMessage(String raw) {
    final String input = raw.trim();
    if (input.isEmpty) {
      return false;
    }
    return _namePrefixPattern.hasMatch(input);
  }

  static String? _cleanSender(String? input) {
    if (input == null) {
      return null;
    }
    final String cleaned = input.trim();
    return cleaned.isEmpty ? null : cleaned;
  }

  static String? _normalizedKey(String? input) {
    if (input == null) {
      return null;
    }
    final String key = input
        .toLowerCase()
        .replaceAll(RegExp(r'[^a-z0-9]+'), ' ')
        .trim()
        .replaceAll(RegExp(r'\s+'), ' ');
    return key.isEmpty ? null : 'signal:$key';
  }
}