woocommerce-paypal-payments/modules/ppcp-wc-subscriptions/src/Endpoint/SubscriptionChangePaymentMethod.php

<?php
/**
 * The Create Payment Token endpoint.
 *
 * @package WooCommerce\PayPalCommerce\WcSubscriptions\Endpoint
 */

declare(strict_types=1);

namespace WooCommerce\PayPalCommerce\WcSubscriptions\Endpoint;

use Exception;
use WC_Order;
use WC_Payment_Tokens;
use WooCommerce\PayPalCommerce\Button\Endpoint\EndpointInterface;
use WooCommerce\PayPalCommerce\Button\Endpoint\RequestData;

/**
 * Class SubscriptionChangePaymentMethod
 */
class SubscriptionChangePaymentMethod implements EndpointInterface {

	const ENDPOINT = 'ppc-subscription-change-payment-method';

	/**
	 * The request data.
	 *
	 * @var RequestData
	 */
	private $request_data;

	/**
	 * SubscriptionChangePaymentMethod constructor.
	 *
	 * @param RequestData $request_data $request_data The request data.
	 */
	public function __construct( RequestData $request_data ) {
		$this->request_data = $request_data;
	}

	/**
	 * Returns the nonce.
	 *
	 * @return string
	 */
	public static function nonce(): string {
		return self::ENDPOINT;
	}

	/**
	 * Handles the request.
	 *
	 * @return bool
	 * @throws Exception On Error.
	 */
	public function handle_request(): bool {
		try {
			$data = $this->request_data->read_request( $this->nonce() );

			$subscription = wcs_get_subscription( $data['subscription_id'] );
			if ( $subscription instanceof WC_Order ) {
				$subscription->set_payment_method( $data['payment_method'] );

				$wc_payment_token = WC_Payment_Tokens::get( $data['wc_payment_token_id'] );
				if ( $wc_payment_token ) {
					$subscription->add_payment_token( $wc_payment_token );
					$subscription->save();
				}

				wp_send_json_success();
				return true;
			}

			wp_send_json_error();
			return false;
		} catch ( Exception $exception ) {
			wp_send_json_error();
			return false;
		}
	}
}