Payum\Paypal\Rest\PaypalRestGatewayFactory::populateConfig PHP Method

    protected function populateConfig(ArrayObject $config)
    {
        if (false == class_exists(ApiContext::class)) {
            throw new \LogicException('You must install "paypal/rest-api-sdk-php" library.');
        }
        $config->defaults(['payum.factory_name' => 'paypal_rest', 'payum.factory_title' => 'PayPal Rest', 'payum.action.capture' => new CaptureAction(), 'payum.action.sync' => new SyncAction(), 'payum.action.status' => new StatusAction()]);
        if (false == $config['payum.api']) {
            $config['payum.default_options'] = ['client_id' => '', 'client_secret' => '', 'config_path' => ''];
            $config->defaults($config['payum.default_options']);
            $config['payum.required_options'] = ['client_id', 'client_secret', 'config_path'];
            $config['payum.api'] = function (ArrayObject $config) {
                $config->validateNotEmpty($config['payum.required_options']);
                if (false == defined('PP_CONFIG_PATH')) {
                    define('PP_CONFIG_PATH', $config['config_path']);
                } elseif (PP_CONFIG_PATH !== $config['config_path']) {
                    throw new InvalidArgumentException(sprintf('Given "config_path" is invalid. Should be equal to the defined "PP_CONFIG_PATH": %s.', PP_CONFIG_PATH));
                }
                $credential = new OAuthTokenCredential($config['client_id'], $config['client_secret']);
                return new ApiContext($credential);
            };
        }
    }