public static function add_coupon_discount() {
		check_ajax_referer( 'order-item', 'security' );

		if ( ! current_user_can( 'edit_shop_orders' ) ) {
			wp_die( -1 );
		}

		$response = array();

		try {
			$order_id           = isset( $_POST['order_id'] ) ? absint( $_POST['order_id'] ) : 0;
			$order              = wc_get_order( $order_id );
			$calculate_tax_args = array(
				'country'  => isset( $_POST['country'] ) ? wc_strtoupper( wc_clean( wp_unslash( $_POST['country'] ) ) ) : '',
				'state'    => isset( $_POST['state'] ) ? wc_strtoupper( wc_clean( wp_unslash( $_POST['state'] ) ) ) : '',
				'postcode' => isset( $_POST['postcode'] ) ? wc_strtoupper( wc_clean( wp_unslash( $_POST['postcode'] ) ) ) : '',
				'city'     => isset( $_POST['city'] ) ? wc_strtoupper( wc_clean( wp_unslash( $_POST['city'] ) ) ) : '',
			);

			if ( ! $order ) {
				throw new Exception( __( 'Invalid order', 'woocommerce' ) );
			}

			if ( empty( $_POST['coupon'] ) ) {
				throw new Exception( __( 'Invalid coupon', 'woocommerce' ) );
			}

			// Add user ID and/or email so validation for coupon limits works.
			$user_id_arg    = isset( $_POST['user_id'] ) ? absint( $_POST['user_id'] ) : 0;
			$user_email_arg = isset( $_POST['user_email'] ) ? sanitize_email( wp_unslash( $_POST['user_email'] ) ) : '';

			if ( $user_id_arg ) {
				$order->set_customer_id( $user_id_arg );
			}
			if ( $user_email_arg ) {
				$order->set_billing_email( $user_email_arg );
			}

			$result = $order->apply_coupon( wc_format_coupon_code( wp_unslash( $_POST['coupon'] ) ) ); // phpcs:ignore WordPress.Security.NonceVerification.Missing, WordPress.Security.ValidatedSanitizedInput.InputNotSanitized

			if ( is_wp_error( $result ) ) {
				throw new Exception( html_entity_decode( wp_strip_all_tags( $result->get_error_message() ) ) );
			}

			$order->calculate_taxes( $calculate_tax_args );
			$order->calculate_totals( false );

			ob_start();
			include 'admin/meta-boxes/views/html-order-items.php';
			$response['html'] = ob_get_clean();
		} catch ( Exception $e ) {
			wp_send_json_error( array( 'error' => $e->getMessage() ) );
		}

		// wp_send_json_success must be outside the try block not to break phpunit tests.
		wp_send_json_success( $response );
	}