;;;;

(module current-nanoseconds

(;export
  ;special
  current-flnanoseconds
  ;
  current-nanoseconds)

(import scheme
  (chicken base)
  (chicken type)
  (chicken foreign))

(: current-flnanoseconds (-> float))

(: current-nanoseconds (-> integer))

;NOTE platforms have different epochs (macOS & Unix: ~311 days)
;however these timings are not treated as a calendar time

(: get-nanosecs (-> integer))
(cond-expand
  (macosx
    (include "macosx") )
  (unix
    (include "unix") )
  (windows
    (include "windows") )
  (else
    (error "unsupported platform") ) )

(cond-expand
  (reliable-time
    (define-syntax current-flnanoseconds
      (syntax-rules ()
        ((_) (exact->inexact (current-nanoseconds))) ) ) )

  (eventual-time
    (define-syntax current-flnanoseconds
      (syntax-rules ()
        ((_)
          (let loop ((ns (current-nanoseconds)))
            (unless (positive? ns) (loop (current-nanoseconds)))
            (exact->inexact ns) ) ) ) ) )

  (else ;warning-time
    (import (chicken module))
    (export $warn-unreliable-time)

    (: $warn-unreliable-time (integer -> void))
    (define ($warn-unreliable-time ns)
      (warning 'current-nanoseconds "cannot retrieve time reliably" ns) )

    (define-syntax current-flnanoseconds
      (syntax-rules ()
        ((_)
          (let ((ns (current-nanoseconds)))
            (unless (positive? ns) ($warn-unreliable-time ns))
            (exact->inexact ns) ) ) ) ) ) )

(define current-nanoseconds get-nanosecs)

) ;module current-nanoseconds