/// `type` of the visible Connect push for a parent letter. Its data carries
/// the letter under [parentLetterIdKey].
const String parentLetterPushType = 'parent-letter';
const String parentLetterIdKey = 'parentLetterId';

/// Where a tapped notification leads.
sealed class PushTarget {
  const PushTarget();
}

class ParentLetterTarget extends PushTarget {
  final String letterId;
  const ParentLetterTarget(this.letterId);
}

class NewsletterTarget extends PushTarget {
  final String newsletterId;
  const NewsletterTarget(this.newsletterId);
}

class ChatTarget extends PushTarget {
  final String chatToken;
  const ChatTarget(this.chatToken);
}

/// Resolves the data of a tapped notification — the payload of a locally
/// rendered one as well as the data of an FCM message. Null when it names no
/// known target.
PushTarget? resolvePushTarget(Map<String, dynamic> data) {
  String? value(String key) {
    final value = data[key];
    return value is String && value.isNotEmpty ? value : null;
  }

  if (value(parentLetterIdKey) case final letterId?) {
    return ParentLetterTarget(letterId);
  }
  if (value('newsletterId') case final newsletterId?) {
    return NewsletterTarget(newsletterId);
  }
  for (final key in const ['chatToken', 'token', 'roomToken']) {
    if (value(key) case final chatToken?) return ChatTarget(chatToken);
  }
  return null;
}