#lang racket/base


(require racket/contract/base)


(provide
 (contract-out
  [now (-> timestamp?)]
  [clock? (-> any/c boolean?)]
  [clock-now (-> clock? timestamp?)]
  [system-clock clock?]
  [make-clock (-> (-> timestamp?) clock?)]
  [current-clock (parameter/c clock?)]))


(require thunderstorm/libraries/timestamp)


;@----------------------------------------------------------------------------------------------------


(struct clock (now-function) #:constructor-name make-clock)


(define (clock-now clock)
  ((clock-now-function clock)))


(define (system-now)
  (epoch-milliseconds->timestamp (current-inexact-milliseconds)))


(define system-clock (make-clock system-now))
(define current-clock (make-parameter system-clock))


(define (now)
  (clock-now (current-clock)))