User should redirect to common login page after log out

[Gulfam]

Hi Experts

I have a requirement regarding portal routing that I need some help.

The requirement is as follows:

If a user belongs to Company "ABC," they should be routed to the Service Portal (SP).
If a user belongs to Company "XYZ," they should be routed to the Customer Service Management (CSM) Portal.
if user logged out then they should redirected to common login page

I have made changes to SPEntryPage script include where I set 'this.portal = "/sp/";' in initialize function. and write a following code in getFirstPageURL function.

if (user.hasRole("admin") && !redirectURL && !isServicePortalURL)
return;

var userId = gs.getUserID();

var userRec = new GlideRecord('sys_user');

userRec.addEncodedQuery('sys_class_name=customer_contact^ORsys_class_name=sys_user^company.nameINBoxeo,Cambrian,Shark Hotels^sys_id=' + userId);

userRec.query();

if (userRec.next()) {

            this.portal = "/csm/";

        } else {

            this.portal = "/sp/";

        }

To redirect them on common login page i have made changes to System Definition - Installation Exits - logout
i have set hard code value it is working fine with normal user but when a contact log out then they redirected to csm login page

gs.include("PrototypeServer");

var Logout = Class.create();

Logout.prototype = {

process: function() {

        var s = "https://dev231151.service-now.com/sp";

        // var s = request.getParameter('sysparm_goto_url');

        var localLoginMethod = request.getSession().getAttribute("glide.authenticate.local.login.method");

        if (localLoginMethod == "certificate") {

            if (s)

                response.sendRedirect("logout_certificate_complete.do?sysparm_goto_url=" + s);

            else

                response.sendRedirect("logout_certificate_complete.do");

            return true;

        }

        if (s && GlideSecurityUtils.isURLWhiteListedStrict(s))

            response.sendRedirect(s);

        else

            response.sendRedirect("logout_success.do");

        return true;

    }

}