/// Parsed page of Talk's `talk-message-current` search provider.
class SearchChatMessagesResponse {
  final List<SearchChatMessagesEntry> entries;

  /// Opaque pagination cursor; `null` when the provider has no further page.
  final Object? cursor;

  const SearchChatMessagesResponse({required this.entries, this.cursor});

  factory SearchChatMessagesResponse.fromJson(
    Map<String, dynamic> json, {
    required String term,
  }) {
    final rawEntries = json['entries'];
    final entries = rawEntries is List
        ? rawEntries
              .whereType<Map<String, dynamic>>()
              .map((e) => SearchChatMessagesEntry.fromJson(e, term: term))
              .whereType<SearchChatMessagesEntry>()
              .toList()
        : const <SearchChatMessagesEntry>[];
    final paginated = json['isPaginated'] == true;
    final cursor = json['cursor'];
    return SearchChatMessagesResponse(
      entries: entries,
      cursor: paginated && entries.isNotEmpty && cursor != null ? cursor : null,
    );
  }
}

class SearchChatMessagesEntry {
  final int messageId;
  final String? actorId;
  final String? actorDisplayName;

  /// Server-built excerpt of the message, placeholders already resolved.
  final String excerpt;
  final DateTime? sentAt;

  const SearchChatMessagesEntry({
    required this.messageId,
    required this.excerpt,
    this.actorId,
    this.actorDisplayName,
    this.sentAt,
  });

  /// Returns `null` for entries without a recognisable message id.
  static SearchChatMessagesEntry? fromJson(
    Map<String, dynamic> json, {
    required String term,
  }) {
    final attributes = json['attributes'];
    final attrs = attributes is Map ? attributes : const {};
    final messageId =
        _parseInt(attrs['messageId']) ??
        _parseInt(
          RegExp(
            r'#message_(\d+)',
          ).firstMatch(json['resourceUrl']?.toString() ?? '')?.group(1),
        );
    if (messageId == null) return null;

    // Title and subline have swapped roles across Talk versions (author vs.
    // excerpt); the one containing the search term is the excerpt.
    final title = json['title']?.toString() ?? '';
    final subline = json['subline']?.toString() ?? '';
    final q = term.trim().toLowerCase();
    final titleIsExcerpt =
        q.isNotEmpty &&
        title.toLowerCase().contains(q) &&
        !subline.toLowerCase().contains(q);
    final excerpt = titleIsExcerpt ? title : subline;
    final author = titleIsExcerpt ? subline : title;

    final timestamp = _parseInt(attrs['timestamp']);
    final actorId = attrs['actorId']?.toString();
    return SearchChatMessagesEntry(
      messageId: messageId,
      excerpt: excerpt,
      actorId: actorId == null || actorId.isEmpty ? null : actorId,
      actorDisplayName: author.isEmpty ? null : author,
      sentAt: timestamp == null
          ? null
          : DateTime.fromMillisecondsSinceEpoch(timestamp * 1000),
    );
  }

  static int? _parseInt(Object? raw) => switch (raw) {
    final int v => v,
    final String v => int.tryParse(v),
    _ => null,
  };
}