bsf_registration_page_url( string $append = '', int $product_id = '' )

	function bsf_registration_page_url( $append = '', $product_id = '' ) {

		$bsf_updater_options       = get_option( 'bsf_updater_options', array() );
		$option                    = false;
		$constant                  = false;
		$skip_brainstorm_menu      = get_site_option( 'bsf_skip_braisntorm_menu', false );
		$product_registration_link = apply_filters( "bsf_registration_page_url_{$product_id}", '' );

		// If Brainstorm meu is not registered.
		if ( ( defined( 'BSF_UNREG_MENU' ) && ( BSF_UNREG_MENU === true || BSF_UNREG_MENU === 'true' ) ) ||
			true === $skip_brainstorm_menu
		) {

			if ( '&author' === $append ) {

				return admin_url( 'options.php?page=bsf-registration' . $append );
			}
		}

		if ( isset( $bsf_updater_options['brainstorm_menu'] ) && '1' === $bsf_updater_options['brainstorm_menu'] ) {
			$option = true;
		}

		if ( defined( 'BSF_REG_MENU_TO_SETTINGS' ) && 'BSF_REG_MENU_TO_SETTINGS' === true || 'BSF_REG_MENU_TO_SETTINGS' === 'true' ) {
			$constant = true;
		}

		if ( '' !== $product_registration_link ) {

			return $product_registration_link . '' . $append;
		} else {

			if ( true === $option || true === $constant ) {
				// bsf menu in settings.
				if ( is_multisite() ) {
					return network_admin_url( 'settings.php?page=bsf-registration' . $append );
				} else {
					return admin_url( 'options-general.php?page=bsf-registration' . $append );
				}
			} else {
				if ( is_multisite() ) {
					return network_admin_url( 'admin.php?page=bsf-registration' . $append );
				} else {
					return admin_url( 'index.php?page=bsf-registration' . $append );
				}
			}
		}

	}