Toggle Parse Server public read ACL using cloud code

I am using Parse Server (on Node.js) and have to expand my application to give my users a new function.

I have a class class called 'Programme'. Previously I locked this programme down to user only ACL using a before save function:

Parse.Cloud.beforeSave("Programme", function(req, res) {
    user = req.object.get("user");
    var acl = new Parse.ACL();
    acl.setReadAccess(req.user, true);
    acl.setWriteAccess(req.user, true);
    req.object.setACL(acl);
    res.success();
});

However I now wish to give the users a button to toggle the public view of a Program.

I have coded the button to request the cloud code and have got the beginning of a working function.

However, I have issues with checking if the queried programme has already got public view ACL set, or if it needs setting.

Questions:

1. How can I toggle the setPublicReadAccess of an item in the Programme class.

2. How can I deconflict this with my beforeSave function, because I expect my function is going to change it and then the beforeSave function will change it straight back.

My function so far:

Parse.Cloud.define('toggleSharedProgramme', function(req, res) {
    var user = req.object;
    var programmeId = req.params.programmeId;

    var query = new Parse.Query("Programme");
    query.equalTo("objectId", programmeId);
    query.first({ sessionToken: req.user.getSessionToken()}).then(function(results) {

        var acl = new Parse.ACL();
        // acl.setReadAccess(req.user, true);
        // acl.setWriteAccess(req.user, true);
        acl.setPublicReadAccess(true);
        results.setACL(acl);
        results.save();

        res.success('Working - code needs to be added to set the programme's ACL');
    })

});