(define-module (tk mcron)
  #:export (sec/min sec/hour sec/day sec/week
            sec/mins sec/hours sec/days sec/weeks
            step-from
            str->secs
            strf->secs
            )
  #:use-module (srfi srfi-19)
  #:duplicates (warn-override-core warn))

(define sec/min  60)
(define sec/hour (* 60 sec/min))
(define sec/day  (* 24 sec/hour))
(define sec/week (* 7 sec/day))

(define (sec/mins n)  (* n sec/min))
(define (sec/hours n) (* n sec/hour))
(define (sec/days n)  (* n sec/day))
(define (sec/weeks n) (* n sec/week))

;; Format here refers to the format found in srfi-19 (Ref: 7.5.16.6)
;; Literally just conversions out of (string->date)
(define (strf->secs str format)
  (time-second (date->time-utc (string->date str format))))

(define (str->secs str)
  (strf->secs str "~Y~m~d~H~M~S"))

;; Normalize the time tm to be the next step sized increment from base.
;; All time arguments are expected to be a time in seconds
(define (step-from base step tm)
  (let ((steps (euclidean-quotient (- tm base) step)))
    (+ base (* step (+ 1 steps)))))