nth-weekday-of-month-p.el

;; * TODO receber salário no quinto dia útil do mês
;; DEADLINE: <%%(nth-weekday-of-month-p date 5)>
;;
;; requer configuração das variáveis calendar-holidays ou holiday-*

(defun nth-weekday-of-month-p (date &optional n)
  "Check if DATE is the Nth weekday of current month."
  (or n (setq n 1))
  (let* ((month (calendar-extract-month date))
         (year (calendar-extract-year date))
         (day (calendar-extract-day date))
         (month-days-to-n (mapcar
                           (lambda (day)
                              `(,month ,day ,year))
                           (number-sequence 1 day)))
         (business-days (seq-filter
                         (lambda (date)
                           (and (memq (calendar-day-of-week date)
                                      '(1 2 3 4 5))
                                (not (calendar-check-holidays date))))
                         month-days-to-n)))
    (and (eq n (length business-days))
         (eq day (calendar-extract-day (car (last business-days)))))))