MS-SQL Store Procedure to Postgresql Function

hi , how i can convert this store procedure to PostgreSQL function, especially I really dont know how to set type to readonly in PostgreSQL.
thanks

ALTERPROCEDURE [dbo].[sp_DeleteUserData]
      @ACDetailsID dbo.ACdetailsID_type READONLY
     
AS
 
DECLARE(at)ID int
begintry
begintransaction
 
 DECLARE c_ACDetailsID CURSOR FOR SELECT id FROM @ACDetailsID
 OPEN c_ACDetailsID
 FETCH NEXT FROM c_ACDetailsID INTO @ID
 WHILE (@@FETCH_STATUS = 0) BEGIN
 
      delete from UserAccountDetails  where UserDataAcountId=(at)ID
      delete from UserAC where UserDataAcountId=(at)ID
     
 FETCH NEXT FROM c_ACDetailsID INTO @ID
End--end of while loop      
 
committransaction     
CLOSEc_ACDetailsID
DEALLOCATEc_ACDetailsID
endtry
 
begincatch
      rollback transaction;
      print error_message(