private function create_authors_for_mapping( $author_data ) {

		$author_mapping = array();
		foreach ( $author_data as $author ) {

			if ( isset( $author->user_email ) ) {
				$user = get_user_by( 'email', $author->user_email );
				if ( $user instanceof WP_User ) {
					$author_mapping[] = array(
						'old_user_login' => $author->user_login,
						'new_user_login' => $user->user_login,
					);
					continue;
				}
			}

			$user = get_user_by( 'login', $author->user_login );
			if ( $user instanceof WP_User ) {
				$author_mapping[] = array(
					'old_user_login' => $author->user_login,
					'new_user_login' => $user->user_login,
				);
				continue;
			}

			$user = array(
				'user_login' => '',
				'user_email' => '',
				'user_pass'  => wp_generate_password(),
			);
			$user = array_merge( $user, (array) $author );

			$user_id = wp_insert_user( $user );
			if ( is_wp_error( $user_id ) ) {
				return $user_id;
			}

			$user             = get_user_by( 'id', $user_id );
			$author_mapping[] = array(
				'old_user_login' => $author->user_login,
				'new_user_login' => $user->user_login,
			);
		}
		return $author_mapping;

	}