public function loginWithAmazonSignIn() {
        global $wpdb;

        $token = isset($_GET['buyerToken']) ? $_GET['buyerToken'] : '';
        if (empty($token)) {
            return __('Oops! An unknown error occured.', 'wcexaap');
        }

        $result = (new GetBuyer($this->module))->get($token);
        if ($result instanceof GenericError) {
            return $result->message;
        }

        if (empty($result)) {
            return __('Oops! An unknown error occured.', 'wcexaap');
        }

        $buyerInfo = json_decode($result['response'], true);
        $email = $buyerInfo['email'];
        $member_table = $wpdb->prefix . 'usces_member';
        $query = $wpdb->prepare("SELECT ID FROM $member_table WHERE mem_email = %s", $email);
        $id = $wpdb->get_var($query);
        if (!$id) {
            return __('<b>Error:</b> E-mail address is not correct.', 'usces');
        }

        $mmeta = new MemberMeta((int)$id);
        if ($mmeta->getAllowAmazonToWelcartLogin() === false) {
            return __('Cannot login to this account with Amazon.', 'wcexaap');
        }

        $this->executeLogin($email);
        /**
         * Mirrored Welcart action hook
         *
         * @ignore
         */
        do_action('usces_action_after_login');
    }