;; ****************************************
;; *  Csu 211 : 1/30/2008
;; *  Lecture #9.1 Code
;; *  Structures and More Conditionals
;; ****************************************

;; A Clock is (make-clock H M S) where H, M, and S are Numbers
;;   representing the current time
(define-struct clock (h m s))

;; incr-clock: Clock -> Clock
;; Increment the seconds of the given clock and update minutes
;;   and hours accordingly
(define (incr-clock clk)
  (incr-min (clock-h clk) (clock-m clk) (+ (clock-s clk) 1)))

;; incr-min: Number Number Number -> Clock
;; If seconds is over 59, increment minutes and set sec. to 0
(define (incr-min h m s)
  (cond [(> s 59) (incr-hour h (+ m 1) 0)]
        [else (make-clock h m s)]))

;; incr-hour: Number Number Number -> Clock
;; If minutes is over 59, increment hours and set min. to 0
(define (incr-hour h m s)
  (cond [(> m 59) (fix-hour (+ h 1) 0 s)]
        [else (make-clock h m s)]))

;; fix-hour: Number Number Number -> Clock
;; If hours is > 23 then set hours to 0
(define (fix-hour h m s)
  (cond [(> h 23) (make-clock 0 m s)]
        [else (make-clock h m s)]))

;; two-digit: Number -> String
;; Convert the given number to a two digit String; if it is
;;   only one digit then we add another "0" to the front
(define (two-digit n)
  (string-append (cond [(< n 10) "0"]
                       [else ""])
                 (number->string n)))

;; Test Normal Time
(equal? (incr-clock (make-clock 5 6 7))
        (make-clock 5 6 8))
;; Test Minute update
(equal? (incr-clock (make-clock 5 6 59))
        (make-clock 5 7 0))
;; Test Hour update
(equal? (incr-clock (make-clock 5 59 59))
        (make-clock 6 0 0))
;; Test Hour wrapping
(equal? (incr-clock (make-clock 23 59 59))
        (make-clock 0 0 0))

;; clock->scene: Clock -> Scene
;; Draw an image of the clock into an empty scene
(define (clock->scene clk)
  (place-image (text (clock->string (clock-h clk) (clock-m clk)
                                    (clock-s clk)) 36 'black)
               0 0 (empty-scene 320 55)))

;; clock->string: Number Number Number -> String
;; Create a String representation of the given clock
(define (clock->string h m s)
  (string-append 
   (am/pm-hour h) ":" (two-digit m) "." (two-digit s) (am/pm h)))


;; am/pm-hour: Number -> String
;; Convert 24-hour into 12-hour (am/pm)
;; 0 or 12 -> "12"
;; h>12 -> "n-12"
;; else -> "n"
(define (am/pm-hour h)
  (two-digit (cond [(or (= h 0) (= h 12)) 12]
                   [(> h 12) (- h 12)]
                   [else h])))

;; am/pm: Number -> String
;; return "am" if h < 12, "pm" otherwise
(define (am/pm h)
  (cond [(< h 12) " am"]
        [else " pm"]))

;; Setup the Drawing/Ticking for the Clock display
(big-bang 320 55 1 (make-clock 0 59 55))
(on-redraw clock->scene)
(on-tick-event incr-clock)