make available selected date dependant on day of order

I'm working on an order form for my website. For the orders the requirement is 4 days clear notice(i.e. Monday for Friday, Tuesday for Saturday etc), but for orders made on a Saturday and Sunday the minimum day they can get is the following Thursday. They are also not allowed to select Sundays as a day for delivery.

This is my date field:

<p>What date is this required for?</p>
<p>Please note, we need 4 days clear notice(Monday-Friday)</p>
<input id="datefield" name="date" type='date' onkeydown="return false" min='2019-05-10' max='2000-13-13'></input>

This is the js I have so far for not letting them pick sundays and for making the earliest date selection 4 days in advance

<script>
var date = document.querySelector('[type=date]');

function noSundays(e){

    var day = new Date( e.target.value ).getUTCDay();

    // Days in JS range from 0-6 where 0 is Sunday and 6 is Saturday

    if( day == 0 ){

        e.target.setCustomValidity('Unfortunately we cannot deliver cakes on a Sunday, please select another day');

    } else {

        e.target.setCustomValidity('');

    }

}

date.addEventListener('input',noSundays);

</script>

<script>

var today = new Date();
var dd = today.getDate()+4;
var mm = today.getMonth()+1; //January is 0!
var yyyy = today.getFullYear();
 if(dd<10){
        dd='0'+dd
    } 
    if(mm<10){
        mm='0'+mm
    } 

today = yyyy+'-'+mm+'-'+dd;
document.getElementById("datefield").setAttribute("min", today);

</script>

So this is fine and works but how would I go about making a condition if the day they are ordering is a Saturday or Sunday that the minimum date they can select is the following Thursday?