subscribe email

    /**
     * Subscribe an email address to a AWeber list
     *
     * @since       1.0
     * @return      bool
     */
    public function subscribe_email( $subscriber = array(), $list_id = '' ) {

        $defaults = array ( 'consumer_key' => false, 'consumer_secret' => false, 'access_key' => false, 'access_secret' => false );
        $options = get_option( 'ninja_forms_aweber_options', $defaults );
        $options = wp_parse_args( (array) $options, $defaults );

        try {
            $aweber = new AWeberAPI( $options['consumer_key'], $options['consumer_secret'] );
            $account = $aweber->getAccount( $options['access_key'], $options['access_secret'] );

            // direct API URL
            $account_id = $account->id;
            $url = "/accounts/{$account_id}/lists/{$list_id}/subscribers";

            $name = isset( $subscriber['first_name'] ) ? $subscriber['first_name'] : '';

            // add space between first and last names if both exist
            if( isset( $subscriber['first_name'] ) && isset( $subscriber['last_name'] ) ){
                $name .= ' ' . $subscriber['last_name'];
            } else if ( isset( $subscriber['last_name'] ) ){
                $name .= $subscriber['last_name'];
            }

            // get custom fields
            $custom_fields = isset( $subscriber['custom_fields'] ) ? (array) $subscriber['custom_fields'] : array();

            // get IP address
            $ip_address = isset( $subscriber['ip_address'] ) ? $subscriber['ip_address'] : '';

            # create a subscriber
            $params = array(
                'ws.op' => 'create',
                'email' => $subscriber['email'],
                'name' => $name,
                'ip_address' => $ip_address,
                'ad_tracking' => sprintf( __( 'Ninja Forms Form #%s', 'ninja-forms-aweber' ), $subscriber['form_id'] )
            );

            if( ! empty( $custom_fields ) ){
                $params['custom_fields'] = $custom_fields;
            }

            // single POST to API
            $data = $aweber->adapter->request( 'POST', $url, $params, array('return' => 'headers') );

        } catch( AWeberException $e ) {

            $error_message = $e->getMessage() ? $e->getMessage() : '';
            $error_code = null; // AWeber doesn't have codes yet, but this holds a place for when they do

            // process the AWeber message and return something i18n-ready and somewhat more friendly
            $new_message = $this->error_message( $error_message, $error_code, $subscriber, $list_id );

            // if we get an exception, generally the user can't be added to the list
            if( $new_message && apply_filters( 'ninja_forms_aweber_show_errors', true, $error_message, $error_code, $subscriber, $list_id ) ){
                global $ninja_forms_processing;
                $ninja_forms_processing->add_error( 'aweber_error', $new_message );
            }

        }

    }



/************* truncated *****************/


    /**
     * Create better error messages for AWeber
     *
     * @param       $error_message Message from AWeber
     * @param       $error_code placeholder, does not exist yet in AWeber
     * @param       $subscriber array of form data submission
     * @param       $list_id string AWeber list id
     * @return      string
     * @since       1.3.1
     */
    public function error_message( $error_message = '', $error_code = '', $subscriber = array(), $list_id = '' ) {

        // if in debug mode, return the error from AWeber without modification
        if( ! defined( 'NF_AWEBER_DEBUG' ) || ! NF_AWEBER_DEBUG ){

            switch( $error_message ){
                case strpos( $error_message, 'Consumer key is invalid' ) !== false :
                    $new_message = __( 'The form could not be submitted because this form is not connected to AWeber. Please enter your authorization code in the plugin settings.', 'ninja-forms-aweber' );
                    break;
                case strpos( $error_message, 'Subscriber already subscribed' ) !== false :
                    $new_message = __( 'The form could not be submitted because you have already subscribed to this mailing list.', 'ninja-forms-aweber' );
                    break;
                case strpos( $error_message, 'Email address blocked' ) !== false :
                    $new_message = __( 'The form could not be submitted because you are using an unsupported email address. Please try another.', 'ninja-forms-aweber' );
                    break;
                default:
                    $new_message = __( 'We\'re sorry, but there has been an error in submitting your form. Please try again later.', 'ninja-forms-aweber' );

            }
            $error_message = apply_filters( 'ninja_forms_aweber_subscribe_error_message', $new_message, $error_code, $error_message, $subscriber, $list_id );
        }
        return $error_message;
    }