protected function process_customer( $data ) {
		$customer_id = apply_filters( 'woocommerce_checkout_customer_id', get_current_user_id() );

		if ( ! is_user_logged_in() && ( $this->is_registration_required() || ! empty( $data['createaccount'] ) ) ) {
			$username    = ! empty( $data['account_username'] ) ? $data['account_username'] : '';
			$password    = ! empty( $data['account_password'] ) ? $data['account_password'] : '';
			$customer_id = wc_create_new_customer(
				$data['billing_email'],
				$username,
				$password,
				array(
					'first_name' => ! empty( $data['billing_first_name'] ) ? $data['billing_first_name'] : '',
					'last_name'  => ! empty( $data['billing_last_name'] ) ? $data['billing_last_name'] : '',
				)
			);

			if ( is_wp_error( $customer_id ) ) {
				throw new Exception( $customer_id->get_error_message() );
			}

			wc_set_customer_auth_cookie( $customer_id );

			// As we are now logged in, checkout will need to refresh to show logged in data.
			WC()->session->set( 'reload_checkout', true );

			// Also, recalculate cart totals to reveal any role-based discounts that were unavailable before registering.
			WC()->cart->calculate_totals();
		}

		// On multisite, ensure user exists on current site, if not add them before allowing login.
		if ( $customer_id && is_multisite() && is_user_logged_in() && ! is_user_member_of_blog() ) {
			add_user_to_blog( get_current_blog_id(), $customer_id, 'customer' );
		}

		// Add customer info from other fields.
		if ( $customer_id && apply_filters( 'woocommerce_checkout_update_customer_data', true, $this ) ) {
			$customer = new WC_Customer( $customer_id );

			if ( ! empty( $data['billing_first_name'] ) && '' === $customer->get_first_name() ) {
				$customer->set_first_name( $data['billing_first_name'] );
			}

			if ( ! empty( $data['billing_last_name'] ) && '' === $customer->get_last_name() ) {
				$customer->set_last_name( $data['billing_last_name'] );
			}

			// If the display name is an email, update to the user's full name.
			if ( is_email( $customer->get_display_name() ) ) {
				$customer->set_display_name( $customer->get_first_name() . ' ' . $customer->get_last_name() );
			}

			foreach ( $data as $key => $value ) {
				// Use setters where available.
				if ( is_callable( array( $customer, "set_{$key}" ) ) ) {
					$customer->{"set_{$key}"}( $value );

					// Store custom fields prefixed with wither shipping_ or billing_.
				} elseif ( 0 === stripos( $key, 'billing_' ) || 0 === stripos( $key, 'shipping_' ) ) {
					$customer->update_meta_data( $key, $value );
				}
			}

			/**
			 * Action hook to adjust customer before save.
			 *
			 * @since 3.0.0
			 */
			do_action( 'woocommerce_checkout_update_customer', $customer, $data );

			$customer->save();
		}

		do_action( 'woocommerce_checkout_update_user_meta', $customer_id, $data );
	}