Customer::get_group_id()

	public function get_group_id() {
		$customer_id = is_user_logged_in() ? get_user_option( self::CUSTOMER_ID_META, $this->wp_user_id ) : 0;
		if ( ! $customer_id ) {
			/**
			 * This filter is documented in src/BigCommerce/Accounts/Customer.php
			 */
			return apply_filters( 'bigcommerce/customer/group_id', null, $this );
		}
		$transient_key = sprintf( 'bccustomergroup%d', $customer_id );
		$group_id      = get_transient( $transient_key );

		if ( empty( $group_id ) ) {
			// Couldn't find in cache, retrieve from the API
			$profile    = $this->get_profile();
			$group_id   = isset( $profile['customer_group_id'] ) ? absint( $profile['customer_group_id'] ) : 0;
			$expiration = HOUR_IN_SECONDS; // TODO: a future webhook to flush this cache when the customer's group changes
			if ( $group_id === 0 ) {
				set_transient( $transient_key, 'zero', $expiration ); // workaround for storing empty values in cache
			} else {
				set_transient( $transient_key, $group_id, $expiration );
			}
		}

		if ( $group_id === 'zero' ) {
			$group_id = 0;
		}

		/**
		 * Filter the group ID associated with the customer
		 *
		 * @param int|null $group_id The customer's group ID. Null for guest users.
		 * @param Customer $customer The Customer object
		 */
		$group_id = apply_filters( 'bigcommerce/customer/group_id', $group_id, $this );

		return absint( $group_id );
	}