groupMessagesByApiRound function

List<List<CompactMessage>> groupMessagesByApiRound(List<CompactMessage> messages)

Group messages by API round. The preamble (all messages up to and including the first assistant message) forms group 0. Each subsequent assistant message starts a new group (the assistant + all following user/attachment messages until the next assistant).

Implementation

List<List<CompactMessage>> groupMessagesByApiRound(
  List<CompactMessage> messages,
) {
  if (messages.isEmpty) return [];

  final groups = <List<CompactMessage>>[];
  var currentGroup = <CompactMessage>[];
  bool seenFirstAssistant = false;

  for (final msg in messages) {
    if (msg.type == MessageRole.assistant) {
      if (!seenFirstAssistant) {
        // Include this assistant in the preamble group
        currentGroup.add(msg);
        groups.add(currentGroup);
        currentGroup = <CompactMessage>[];
        seenFirstAssistant = true;
      } else {
        // Start a new group with this assistant
        if (currentGroup.isNotEmpty) {
          groups.add(currentGroup);
        }
        currentGroup = [msg];
      }
    } else {
      currentGroup.add(msg);
    }
  }

  if (currentGroup.isNotEmpty) {
    groups.add(currentGroup);
  }

  return groups;
}