calculateChatMessages function

List<Object> calculateChatMessages(List<Message> messages, User user, { String customDateHeaderText(DateTime)?, DateFormat? dateFormat, required int dateHeaderThreshold, String? dateLocale, required int groupMessagesThreshold, required bool showUserNames, DateFormat? timeFormat, })

Parses provided messages to chat messages (with headers and spacers) and returns them with a gallery

Implementation

List<Object> calculateChatMessages(
  List<types.Message> messages,
  types.User user, {
  String Function(DateTime)? customDateHeaderText,
  DateFormat? dateFormat,
  required int dateHeaderThreshold,
  String? dateLocale,
  required int groupMessagesThreshold,
  required bool showUserNames,
  DateFormat? timeFormat,
}) {
  final chatMessages = <Object>[];
  final gallery = <PreviewImage>[];

  var shouldShowName = false;

  for (var i = messages.length - 1; i >= 0; i--) {
    final isFirst = i == messages.length - 1;
    final isLast = i == 0;
    final message = messages[i];
    final messageHasCreatedAt = message.createdAt != null;
    final nextMessage = isLast ? null : messages[i - 1];
    final nextMessageHasCreatedAt = nextMessage?.createdAt != null;
    final nextMessageSameAuthor = message.author.id == nextMessage?.author.id;
    final notMyMessage = message.author.id != user.id;

    var nextMessageDateThreshold = false;
    var nextMessageDifferentDay = false;
    var nextMessageInGroup = false;
    var showName = false;

    if (showUserNames) {
      final previousMessage = isFirst ? null : messages[i + 1];

      final isFirstInGroup = notMyMessage &&
          ((message.author.id != previousMessage?.author.id) ||
              (messageHasCreatedAt &&
                  previousMessage?.createdAt != null &&
                  message.createdAt! - previousMessage!.createdAt! >
                      groupMessagesThreshold));

      if (isFirstInGroup) {
        shouldShowName = false;
        if (message.type == types.MessageType.text) {
          showName = true;
        } else {
          shouldShowName = true;
        }
      }

      if (message.type == types.MessageType.text && shouldShowName) {
        showName = true;
        shouldShowName = false;
      }
    }

    if (messageHasCreatedAt && nextMessageHasCreatedAt) {
      nextMessageDateThreshold =
          nextMessage!.createdAt! - message.createdAt! >= dateHeaderThreshold;

      nextMessageDifferentDay =
          DateTime.fromMillisecondsSinceEpoch(message.createdAt!).day !=
              DateTime.fromMillisecondsSinceEpoch(nextMessage.createdAt!).day;

      nextMessageInGroup = nextMessageSameAuthor &&
          nextMessage.createdAt! - message.createdAt! <= groupMessagesThreshold;
    }

    if (isFirst && messageHasCreatedAt) {
      chatMessages.insert(
        0,
        DateHeader(
          dateTime: DateTime.fromMillisecondsSinceEpoch(message.createdAt!),
          text: customDateHeaderText != null
              ? customDateHeaderText(
                  DateTime.fromMillisecondsSinceEpoch(message.createdAt!),
                )
              : getVerboseDateTimeRepresentation(
                  DateTime.fromMillisecondsSinceEpoch(message.createdAt!),
                  dateFormat: dateFormat,
                  dateLocale: dateLocale,
                  timeFormat: timeFormat,
                ),
        ),
      );
    }

    chatMessages.insert(0, {
      'message': message,
      'nextMessageInGroup': nextMessageInGroup,
      'showName': notMyMessage && showUserNames && showName,
      'showStatus': message.showStatus ?? true,
    });

    if (!nextMessageInGroup) {
      chatMessages.insert(
        0,
        MessageSpacer(
          height: 12,
          id: message.id,
        ),
      );
    }

    if (nextMessageDifferentDay || nextMessageDateThreshold) {
      chatMessages.insert(
        0,
        DateHeader(
          dateTime:
              DateTime.fromMillisecondsSinceEpoch(nextMessage!.createdAt!),
          text: customDateHeaderText != null
              ? customDateHeaderText(
                  DateTime.fromMillisecondsSinceEpoch(nextMessage.createdAt!),
                )
              : getVerboseDateTimeRepresentation(
                  DateTime.fromMillisecondsSinceEpoch(nextMessage.createdAt!),
                  dateFormat: dateFormat,
                  dateLocale: dateLocale,
                  timeFormat: timeFormat,
                ),
        ),
      );
    }

    if (message is types.ImageMessage) {
      if (kIsWeb) {
        if (message.uri.startsWith('http') || message.uri.startsWith('blob')) {
          gallery.add(PreviewImage(id: message.id, uri: message.uri));
        }
      } else {
        gallery.add(PreviewImage(id: message.id, uri: message.uri));
      }
    }
  }

  return [chatMessages, gallery];
}