;; timestamp: models a timestamp made by a timestamp clock
;;   hour: number
;;   minute: number
(define-struct timestamp (hour minute))

;; clock: models a timestamp clock for an employee
;;   employee: symbol
;;     - name of the employee
;;   timestamps: (listof timestamp)
;;     - a list of timestamps that the employee made with this clock
(define-struct clock (employee timestamps))

;; a list of clocks, one clock for every employee.
(define the-clocks
  (list (make-clock 'Anette
            (list (make-timestamp  5 11) (make-timestamp 15 59)
                  (make-timestamp  6 12) (make-timestamp 17 30) ))

        (make-clock 'Berta
            (list (make-timestamp  9 21) (make-timestamp 15 34)
                  (make-timestamp  8 35) (make-timestamp 13 56) ))

        (make-clock 'Carlo
            (list (make-timestamp 13 23) (make-timestamp 22 21)
                  (make-timestamp 12 52) (make-timestamp 23 54) ))

        (make-clock 'Dennis
            (list (make-timestamp 15 23) (make-timestamp 20 31)
                  (make-timestamp 16 43) (make-timestamp 21 23) ))

        (make-clock 'Elisabeth
            (list (make-timestamp 22 25) (make-timestamp  3 31)
                  (make-timestamp  7 76) (make-timestamp 10 52)
                  (make-timestamp  5 12) (make-timestamp  7 12)))

        (make-clock 'Guiseppe
            (list (make-timestamp  6  0) (make-timestamp  9  0)
                  (make-timestamp  7 20) (make-timestamp 10 11) )) ))

;; a shorter list of the clocks for testing purposes
(define test-clocks
  (list (make-clock 'Burnout
            (list (make-timestamp  1  0) (make-timestamp 23 50)
                  (make-timestamp  6 10) (make-timestamp  2 30) ))

        (make-clock 'JaneDoe
            (list (make-timestamp  8 21) (make-timestamp 14 21)
                  (make-timestamp  9 35) (make-timestamp 15  2) ))

        (make-clock 'SoonToBeFired empty) ))


; (1)

;; average: (listof number) number -> number
;; finds the average value of a list of numbers
;; if the list is empty, return the alternative
;; example: (average '(1 3 5)) returns 3
;;          (average '() returns ?


;; average = sum / length
(define (average a-list alternative)
  (cond
    [(empty? a-list) alternative]
    [else (/ (foldl + 0 a-list) (length a-list))]
  )
)


;; Tests

(check-expect (average '(1 3 5) 42) 3)
(check-expect (average '() 42) 42)

; (2)

;; in-minutes: timestamp -> number
;; calculates the minutes since midnight for a given timestamp
;; example: (in-minutes (make-timestamp 2 31)) = 151
(define (in-minutes stamp)
  (+ (* (timestamp-hour stamp) 60)
     (timestamp-minute stamp)))

(check-expect (in-minutes (make-timestamp 1 2)) 62)
(check-expect (in-minutes (make-timestamp 23 59)) 1439)

;; time-delta :: timestamp timestamp -> number
;; if end > start we can simply subtract start from end and return the difference in hours.
;; if start > end (start before midnight and end after midnight) we find the difference between 24 and the start (left side of the clock), 0 and the end ( right side of the clock), add those together and
;; return the result in hours

;; examples: (time-delta 8 0 16 0) returns 8
;;           (time-delta 15 0 15 0) returns 0
;;           (time-delta 23 0 2 0) returns 3


(define (time-delta start end)
  (local (define (time-dif start end)
           (cond
             [(empty? start) false]
             [(empty? end) false]
             [(< (in-minutes start) (in-minutes end)) (/ (- (in-minutes end) (in-minutes start)) 60)]
             [(> (in-minutes end) (in-minutes start)) (/(+ (- (in-minutes 24) start) (in-minutes end))60 )]
             [else 0]
           )
         )
    )
  )


;; Tests
(check-expect (time-delta 8 0 16 0) 8)
(check-expect (time-delta 15 0 15 0) 0)
(check-expect (time-delta 23 0 2 0 ) 3)

; (3)

;; group-into-pairs: ...
(define (group-into-pairs long-list)
  ; ...
  )

;; Tests

; (4)

;; work-time-sum: ...
(define (work-time-sum a-clock)
  ...)

;; Tests

; (5)

;; fire-and-raise: ...
(define (fire-and-raise clocks)
  ...)

;; Tests

; ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
; TEMPLATE TESTS

(check-expect (average '(458 382 219) 10000) 353)
(check-within (average '(1 2 3 4) -0) 2.5  0.1)

(check-expect (in-minutes (make-timestamp 11 22)) 682)
(check-expect (in-minutes (make-timestamp 1 0)) 60)

(check-expect (time-delta (make-timestamp  2 0)
                          (make-timestamp 23 0)) 1260)
(check-expect (time-delta (make-timestamp 12 0)
                          (make-timestamp 24 0)) 720)

(check-expect (group-into-pairs empty) empty)
(check-expect (group-into-pairs '(1 2 3 4 5 6 7 8))
              '((1 2) (3 4) (5 6) (7 8)))

(check-expect
 (work-time-sum
  (make-clock 'Berta
              (list (make-timestamp 0 0) (make-timestamp 0 1)
                    (make-timestamp 3 10) (make-timestamp 13 10))))
 '(Berta 601))

(check-expect (fire-and-raise the-clocks) '((Guiseppe) (Anette Carlo)))