#|
  This file is a part of stoe project.
  Copyright (c) 2014 Renaud Casenave-Péré (renaud@casenave-pere.fr)
|#

(uiop:define-package :stoe/core/time
    (:use :cl)
  (:export #:clock #:make-clock #:update-clock #:clock-delta))
(in-package :stoe/core/time)

(defun get-current-time ()
  "Return the current time in seconds and microseconds."
  #+sbcl
  (multiple-value-bind (sec usec) (sb-ext:get-time-of-day)
    (+ (* sec 1000000) usec))
  #-sbcl
  (let* ((time (get-internal-real-time))
         (sec (/ time internal-time-units-per-second))
         (usec (* time (/ 1000000 internal-time-units-per-second))))
    (+ (* sec 1000000) usec)))

(defclass clock ()
  ((current-time :initarg :time)
   (last-time :initarg :last-time)
   (delta-time :initform nil)
   (scale :initarg :scale)
   (pausep :initarg :pause)))

(defun make-clock (&optional (time 0 timep) (scale 1.0) pause)
  (unless timep
    (setf time (get-current-time)))
  (make-instance 'clock :time time :last-time time :scale scale :pause pause))

(defun update-clock (clock &optional (delta 0 deltap))
  (with-slots (current-time last-time delta-time scale pausep) clock
    (setf delta-time nil)
    (unless pausep
      (setf last-time current-time)
      (if deltap
          (incf current-time (* delta scale))
          (setf current-time (get-current-time))))))

(defun clock-delta (clock)
  (with-slots (current-time last-time delta-time) clock
    (or delta-time
        (setf delta-time (- current-time last-time)))))