hrows RouteException On error.
	 */
	private function create_or_update_draft_order() {
		$this->order = $this->get_draft_order_id() ? wc_get_order( $this->get_draft_order_id() ) : null;

		if ( ! $this->is_valid_draft_order( $this->order ) ) {
			$this->order = $this->order_controller->create_order_from_cart();
		} else {
			$this->order_controller->update_order_from_cart( $this->order );
		}

		/**
		 * WooCommerce Blocks Checkout Update Order Meta (experimental).
		 *
		 * This hook gives extensions the chance to add or update meta data on the $order.
		 *
		 * This is similar to existing core hook woocommerce_checkout_update_order_meta.
		 * We're using a new action:
		 * - To keep the interface focused (only pass $order, not passing request data).
		 * - This also explicitly indicates these orders are from checkout block/StoreAPI.
		 *
		 * @see https://github.com/woocommerce/woocommerce-gutenberg-products-block/pull/3686
		 * @internal This Hook is experimental and may change or be removed.
		 *
		 * @param WC_Order $order Order object.
		 */
		do_action( '__experimental_woocommerce_blocks_checkout_update_order_meta', $this->order );

		// Confirm order is valid before proceeding further.
		if ( ! $this->order instanceof WC_Order ) {
			throw new RouteException(
				'woocommerce_rest_checkout_missing_order',
				__( 'Unable to create order', 'woocommerce' ),
				500
			);
		}

		// Store order ID to session.
		$this->set_draft_order_id( $this->order->get_id() );

		// Try to reserve stock for 10 mins, if available.
		try {
			$reserve_stock = new ReserveStock();
			$reserve_stock->reserve_stock_for_order( $this->order, 10 );
		} catch ( ReserveStockException $e ) {
			$error_data = $e->getErrorData();
			throw new RouteException(
				$e->getErrorCode(),
				$e->getMessage(),
				$e->getCode()
			);
		}
	}

	/**
	 * Updates the current customer session using data from the request (e.g. address data).
	 *
	 * Address session data is synced to the order itself later on by OrderController::update_order_from_cart()
	 *
	 * @param WP_REST_Request $request Full details about the request.
	 */
	private function update_customer_from_request( WP_REST_Request $request ) {
		$customer = wc()->customer;

		if ( isset( $request['billing_address'] ) ) {
			foreach ( $request['billing_address'] as $key => $value ) {
				if ( is_callable( [ $customer, "set_billing_$key" ] ) ) {
					$customer->{"set_billing_$key"}( $value );
				}
			}
		}

		if ( isset( $request['shipping_address'] ) ) {
			foreach ( $request['shipping_address'] as $key => $value ) {
				if ( is_callable( [ $customer, "set_shipping_$key" ] ) ) {
					$customer->{"set_shipping_$key"}( $value );
				}
			}
		}

		$customer->save();
	}

	/**
	 * Update the current order using the posted values from the request.
	 *
	 * @param WP_REST_Request $request Full details about the request.
	 */
	private function update_order_from_request( WP_REST_Request $request ) {
		if ( isset( $request['customer_note'] ) ) {
			$this->order->set_customer_note( $request['customer_note'] );
		}
		$this->order->set_payment_method( $this->order->needs_payment() ? $this->get_request_payment_method( $request ) : '' );
		$this->order->save();
	}

	/**
	 * For orders which do not require payment, just update status.
	 *
	 * @param WP_REST_Request $request Request object.
	 * @return PaymentResult
	 */
	private function process_without_payment( WP_REST_Request $request ) {
		$this->order->payment_complete();

		$result = new PaymentResult( 'success' );
		$result->set_redirect_url( $this->order->get_checkout_order_received_url() );

		return $result;
	}

	/**
	 * Fires an action hook instructing active payment gateways to process the payment for an order and provide a result.
	 *
	 * @throws RouteException On error.
	 * @param WP_REST_Request $request Request object.
	 * @return PaymentResult
	 */
	private function process_payment( WP_REST_Request $request ) {
		try {
			$result  = new PaymentResult();
			$context = new PaymentContext();
			$context->set_payment_method( $this->get_request_payment_method_id( $request ) );
			$context->set_payment_data( $this->get_request_payment_data( $request ) );

			// Orders are made pending before attempting payment.
			$this->order->update_status( 'pending' );
			$context->set_order( $this->order );

			/**
			 * Process payment with context.
			 *
			 * @hook woocommerce_rest_checkout_process_payment_with_context
			 *
			 * @throws Exception If there is an error taking payment, an Exception object can be thrown
			 *                                     with an error message.
			 *
			 * @param PaymentContext $context Holds context for the payment, including order ID and payment method.
			 * @param PaymentResult  $result Result object for the transaction.
			 */
			do_action_ref_array( 'woocommerce_rest_checkout_process_payment_with_context', [ $context, &$result ] );

			if ( ! $result instanceof PaymentResult ) {
				throw new RouteException( 'woocommerce_rest_checkout_invalid_payment_result', __( 'Invalid payment result received from payment method.', 'woocommerce' ), 500 );
			}

			return $result;
		} catch ( Exception $e ) {
			throw new RouteException( 'woocommerce_rest_checkout_process_payment_error', $e->getMessage(), 400 );
		}
	}

	/**
	 * Gets the chosen payment method ID from the request.
	 *
	 * @throws RouteException On error.
	 * @param WP_REST_Request $request Request object.
	 * @return string
	 */
	private function get_request_payment_method_id( WP_REST_Request $request ) {
		$payment_method_id = isset( $request['payment_method'] )
			? wc_clean( wp_unslash( $request['payment_method'] ) )
			: '';

		if ( empty( $payment_method_id ) ) {
			throw new RouteException(
				'woocommerce_rest_checkout_missing_payment_method',
				__( 'No payment method provided.', 'woocommerce' ),
				400
			);
		}

		return $payment_method_id;
	}

	/**
	 * Gets the chosen payment method from the request.
	 *
	 * @throws RouteException On error.
	 * @param WP_REST_Request $request Request object.
	 * @return \WC_Payment_Gateway
	 */
	private function get_request_payment_method( WP_REST_Request $request ) {
		$payment_method_id  = $this->get_request_payment_method_id( $request );
		$available_gateways = WC()->payment_gateways->get_available_payment_gateways();

		if ( ! isset( $available_gateways[ $payment_method_id ] ) ) {
			throw new RouteException(
				'woocommerce_rest_checkout_payment_method_disabled',
				__( 'This payment gateway is not available.', 'woocommerce' ),
				400
			);
		}

		return $available_gateways[ $payment_method_id ];
	}

	/**
	 * Gets and formats payment request data.
	 *
	 * @param WP_REST_Request $request Request object.
	 * @return array
	 */
	private function get_request_payment_data( WP_REST_Request $request ) {
		static $payment_data = [];
		if ( ! empty( $payment_data ) ) {
			return $payment_data;
		}
		if ( ! empty( $request['payment_data'] ) ) {
			foreach ( $request['payment_data'] as $data ) {
				$payment_data[ sanitize_key( $data['key'] ) ] = wc_clean( $data['value'] );
			}
		}

		return $payment_data;
	}

	/**
	 * Order processing relating to customer account.
	 *
	 * Creates a customer account as needed (based on request & store settings) and  updates the order with the new customer ID.
	 * Updates the order with user details (e.g. address).
	 *
	 * @internal CreateAccount class includes feature gating logic (i.e. this may not create an account depending on build).
	 * @internal Checkout signup is feature gated to WooCommerce 4.7 and newer; Because it requires updated my-account/lost-password screen in 4.7+ for setting initial password.
	 *
	 * @throws RouteException API error object with error details.
	 * @param WP_REST_Request $request Request object.
	 */
	private function process_customer( WP_REST_Request $request ) {
		if ( defined( 'WC_VERSION' ) && version_compare( WC_VERSION, '4.7', '>=' ) ) {
			try {
				$create_account = Package::container()->get( CreateAccount::class );
				$create_account->from_order_request( $request );
				$this->order->set_customer_id( get_current_user_id() );
				$this->order->save();
			} catch ( Exception $error ) {
				switch ( $error->getMessage() ) {
					case 'registration-error-invalid-email':
						throw new RouteException(
							'registration-error-invalid-email',
							__( 'Please provide a valid email address.', 'woocommerce' ),
							400
						);
					case 'registration-error-email-exists':
						throw new RouteException(
							'registration-error-email-exists',
							__( 'An account is already registered with your email address. Please log in before proceeding.', 'woocommerce' ),
							400
						);
				}
			}
		}

		// Persist customer address data to account.
		$this->order_controller->sync_customer_data_with_order( $this->order );
	}

}