previous day's count except on Monday, use Friday's counts - sql-server

Question

I have the below code. I am comparing counts from today's date to yesterday's date unless date falls on Monday then I want to use Friday's count.
select
cast(getdate() as date)run_dt,
'dx' as db,
'dbo' as [schema],
'tb_cust' as [table],
'completed status' as check_type,
a.curr_cnt,
a.prev_cnt,
abs(cast((a.prev_cnt - a.curr_cnt) / cast(a.curr_cnt as decimal(10,2)) as decimal(5,2))*100) as cal_prcnt_dff,
case
when abs(cast((a.prev_cnt - a.curr_cnt) / cast(a.curr_cnt as decimal(10,2)) * 100 as int) ) >= 100
then 'Y'
else 'N'
end email_trigger,
concat('count on',' ', #curr_dt,' ','[',datename(dw,#curr_dt),']',' ' ,'increased/decreased by 100% from',' ',#prev_dt,' ','[',datename(dw,#prev_dt),']') as 'comment'
from (select
sum(
case
when a.custstatus = 'completed'
and a.custdate = cast(getdate() -1 as date)
then 1
else 0
end) curr_cnt,
sum(
case
when a.custstatus = 'completed'
and a.custtdate = cast(getdate() -2 as date)
--and cast(getdate() as date) in ()
--and datepart(dw,getdate()) in (3,4,5,6)
--or
then 1
else 0
end) prev_cnt,
a.custstatus
from cte_apt a
where 1=1
and a.custstatus = 'completed'
group by
a.custstatus)a
How can I get prev_cnt to count Friday when the day lands on a Monday?
sum(
case
when a.custstatus = 'completed'
and a.custtdate = cast(getdate() -2 as date)
--and cast(getdate() as date) in ()
--and datepart(dw,getdate()) in (3,4,5,6)
--or
then 1
else 0
end) prev_cnt,