Refactoring for clarity.

        Gets or creates a default history and associates it with the current

        session.

        """

        # Just return the current history if one exists and is not deleted.

        history = self.galaxy_session.current_history

        if history and not history.deleted:

            return history

        # Look for an existing history that has the default name, is not

        # deleted, and is empty. If this exists, we associate it with the

        # current session and return it.

        user = self.galaxy_session.user

        if user:

            # Look for default history that (a) has default name + is not deleted and

            # (b) has no datasets. If suitable history found, use it; otherwise, create

            # new history.

            stmt = select(self.app.model.History).filter_by(

                user=user, name=self.app.model.History.default_name, deleted=False

            )

            unnamed_histories = self.sa_session.scalars(stmt)

            default_history = None

            for history in unnamed_histories:

                if history.empty:

                    # Found suitable default history.

                    default_history = history

                    break

            # Set or create history.

            if default_history:

                history = default_history

                    self.set_history(history)

            else:

                history = self.new_history()

        else:

            history = self.new_history()

                    return history

        # No suitable history found, create a new one.

        return self.new_history()

    def get_most_recent_history(self):

        """

        Gets the most recently updated history.