private static function order_pay( $order_id ) {

		do_action( 'before_woocommerce_pay' );

		$order_id = absint( $order_id );

		// Pay for existing order.
		if ( isset( $_GET['pay_for_order'], $_GET['key'] ) && $order_id ) { // WPCS: input var ok, CSRF ok.
			try {
				$order_key = isset( $_GET['key'] ) ? wc_clean( wp_unslash( $_GET['key'] ) ) : ''; // WPCS: input var ok, CSRF ok.
				$order     = wc_get_order( $order_id );

				// Order or payment link is invalid.
				if ( ! $order || $order->get_id() !== $order_id || ! hash_equals( $order->get_order_key(), $order_key ) ) {
					throw new Exception( __( 'Sorry, this order is invalid and cannot be paid for.', 'woocommerce' ) );
				}

				// Logged out customer does not have permission to pay for this order.
				if ( ! current_user_can( 'pay_for_order', $order_id ) && ! is_user_logged_in() ) {
					echo '<div class="woocommerce-info">' . esc_html__( 'Please log in to your account below to continue to the payment form.', 'woocommerce' ) . '</div>';
					woocommerce_login_form(
						array(
							'redirect' => $order->get_checkout_payment_url(),
						)
					);
					return;
				}

				// Add notice if logged in customer is trying to pay for guest order.
				if ( ! $order->get_user_id() && is_user_logged_in() ) {
					// If order has does not have same billing email then current logged in user then show warning.
					if ( $order->get_billing_email() !== wp_get_current_user()->user_email ) {
						wc_print_notice( __( 'You are paying for a guest order. Please continue with payment only if you recognize this order.', 'woocommerce' ), 'error' );
					}
				}

				// Logged in customer trying to pay for someone else's order.
				if ( ! current_user_can( 'pay_for_order', $order_id ) ) {
					throw new Exception( __( 'This order cannot be paid for. Please contact us if you need assistance.', 'woocommerce' ) );
				}

				// Does not need payment.
				if ( ! $order->needs_payment() ) {
					/* translators: %s: order status */
					throw new Exception( sprintf( __( 'This order&rsquo;s status is &ldquo;%s&rdquo;&mdash;it cannot be paid for. Please contact us if you need assistance.', 'woocommerce' ), wc_get_order_status_name( $order->get_status() ) ) );
				}

				// Ensure order items are still stocked if paying for a failed order. Pending orders do not need this check because stock is held.
				if ( ! $order->has_status( wc_get_is_pending_statuses() ) ) {
					$quantities = array();

					foreach ( $order->get_items() as $item_key => $item ) {
						if ( $item && is_callable( array( $item, 'get_product' ) ) ) {
							$product = $item->get_product();

							if ( ! $product ) {
								continue;
							}

							$quantities[ $product->get_stock_managed_by_id() ] = isset( $quantities[ $product->get_stock_managed_by_id() ] ) ? $quantities[ $product->get_stock_managed_by_id() ] + $item->get_quantity() : $item->get_quantity();
						}
					}

					foreach ( $order->get_items() as $item_key => $item ) {
						if ( $item && is_callable( array( $item, 'get_product' ) ) ) {
							$product = $item->get_product();

							if ( ! $product ) {
								continue;
							}

							if ( ! apply_filters( 'woocommerce_pay_order_product_in_stock', $product->is_in_stock(), $product, $order ) ) {
								/* translators: %s: product name */
								throw new Exception( sprintf( __( 'Sorry, "%s" is no longer in stock so this order cannot be paid for. We apologize for any inconvenience caused.', 'woocommerce' ), $product->get_name() ) );
							}

							// We only need to check products managing stock, with a limited stock qty.
							if ( ! $product->managing_stock() || $product->backorders_allowed() ) {
								continue;
							}

							// Check stock based on all items in the cart and consider any held stock within pending orders.
							$held_stock     = wc_get_held_stock_quantity( $product, $order->get_id() );
							$required_stock = $quantities[ $product->get_stock_managed_by_id() ];

							if ( ! apply_filters( 'woocommerce_pay_order_product_has_enough_stock', ( $product->get_stock_quantity() >= ( $held_stock + $required_stock ) ), $product, $order ) ) {
								/* translators: 1: product name 2: quantity in stock */
								throw new Exception( sprintf( __( 'Sorry, we do not have enough "%1$s" in stock to fulfill your order (%2$s available). We apologize for any inconvenience caused.', 'woocommerce' ), $product->get_name(), wc_format_stock_quantity_for_display( $product->get_stock_quantity() - $held_stock, $product ) ) );
							}
						}
					}
				}

				WC()->customer->set_props(
					array(
						'billing_country'  => $order->get_billing_country() ? $order->get_billing_country() : null,
						'billing_state'    => $order->get_billing_state() ? $order->get_billing_state() : null,
						'billing_postcode' => $order->get_billing_postcode() ? $order->get_billing_postcode() : null,
					)
				);
				WC()->customer->save();

				$available_gateways = WC()->payment_gateways->get_available_payment_gateways();

				if ( count( $available_gateways ) ) {
					current( $available_gateways )->set_current();
				}

				wc_get_template(
					'checkout/form-pay.php',
					array(
						'order'              => $order,
						'available_gateways' => $available_gateways,
						'order_button_text'  => apply_filters( 'woocommerce_pay_order_button_text', __( 'Pay for order', 'woocommerce' ) ),
					)
				);

			} catch ( Exception $e ) {
				wc_print_notice( $e->getMessage(), 'error' );
			}
		} elseif ( $order_id ) {

			// Pay for order after checkout step.
			$order_key = isset( $_GET['key'] ) ? wc_clean( wp_unslash( $_GET['key'] ) ) : ''; // WPCS: input var ok, CSRF ok.
			$order     = wc_get_order( $order_id );

			if ( $order && $order->get_id() === $order_id && hash_equals( $order->get_order_key(), $order_key ) ) {

				if ( $order->needs_payment() ) {

					wc_get_template( 'checkout/order-receipt.php', array( 'order' => $order ) );

				} else {
					/* translators: %s: order status */
					wc_print_notice( sprintf( __( 'This order&rsquo;s status is &ldquo;%s&rdquo;&mdash;it cannot be paid for. Please contact us if you need assistance.', 'woocommerce' ), wc_get_order_status_name( $order->get_status() ) ), 'error' );
				}
			} else {
				wc_print_notice( __( 'Sorry, this order is invalid and cannot be paid for.', 'woocommerce' ), 'error' );
			}
		} else {
			wc_print_notice( __( 'Invalid order.', 'woocommerce' ), 'error' );
		}

		do_action( 'after_woocommerce_pay' );
	}