;;Edmund Horsch & Alex Russo
(require 2htdp/image)
(require 2htdp/universe)

; A MonthFormat is one of:
; - "long"
; - "short"

; A DateOrder is one of:
; - "MDY"
; - "DMY"

;;#3
; calendar : Year Month Day -> Image
; returns an image of a date on a background

(define (calendar y m d)
  (overlay (beside (text (number->string d) 20 "red") (text " " 20 "red") (text m 20 "red") (text " " 20 "red") (text (number->string y) 20 "red"))
           (rectangle 400 200 "outline" "white")))

; year-month-day->date : Year Month Day DateOrder MonthFormat -> String
; produces a date as a string
(define (year-month-day->date y m d o f)
  (cond [(string=? o "DMY") (beside (text (number->string d) 20 "red") (text " " 20 "red") (month-format m f) (text " " 20 "red") (text (number->string y) 20 "red"))]
        [(string=? o "MDY") (beside (month-format m f) (text " " 20 "red") (text (number->string d) 20 "red") (text " " 20 "red") (text (number->string y) 20 "red"))]))
;(check-expect (year-month-day->date 1936 "November" 12 "MDY" "long") "November 12, 1936")


; month-format : Month MonthFormat -> String
; abbreviates Month to three letters or not
(define (month-format m f)
  (cond [(string=? f "long") (text m 20 "red")]
        [(string=? f "short") (text (substring m 0 3) 20 "red")]))
;(check-expect (month-format "November" "long") "November")
;(check-expect (month-format "November" "short") "Nov")

;;#4
; days-between : Year Month Day Year Month Day -> Number
; Determines th enumber of days between two dates
(define (days-between y1 m1 d1 y2 m2 d2)
  (abs(- (year-month-day->days y1 m1 d1) (year-month-day->days y2 m2 d2))))

(check-expect (days-between 2010 "September" 28 2012 "September" 28) (* 365 2))
(check-expect (days-between 2010 "September" 28 2013 "September" 28) (* 365 3))

; year-month-day->days : Year Month Day -> Number
; returns the number of days elapsed since January 1, 0
(define (year-month-day->days y m d)
  (- (+ (* y 365) (month->day-in-year m) d) 1))
(check-expect (year-month-day->days 0 "January" 1) 0)
(check-expect (year-month-day->days 2017 "August" 28) 736444)

; month->day-in-year : Month -> Number
; returns the days elapsed in the year
(define (month->day-in-year m)
  (cond[(string=? m "January") 0]
       [(string=? m "February") 31]
       [(string=? m "March") 59]
       [(string=? m "April") 90]
       [(string=? m "May") 120]
       [(string=? m "June") 151]
       [(string=? m "July") 181]
       [(string=? m "August") 212]
       [(string=? m "September") 243]
       [(string=? m "October") 273]
       [(string=? m "November") 304]
       [(string=? m "December") 334]))
(check-expect (month->day-in-year "January") 0)
(check-expect (month->day-in-year "September") 243)

;;#5
; days->year : Number -> Year
; takes days since 1 Jan 0 and returns the year
(define (days->year d)
  (quotient d 365))
(check-expect (days->year 364) 0)

; days-in-year->month : DaysInYear -> Month
; takes days since the first of the year and returns the month
(define (days-in-year->month d)
  (cond[(and (>= d 0) (< d 32)) "January"]
       [(and (>= d 31) (< d 59)) "February"]
       [(and (> d 58) (< d 91)) "March"]
       [(and (>= d 90) (< d 121)) "April"]
       [(and (>= d 120) (< d 152)) "May"]
       [(and (>= d 151) (< d 182)) "June"]
       [(and (>= d 181) (< d 213)) "July"]
       [(and (>= d 212) (< d 244)) "August"]
       [(and (>= d 243) (< d 274)) "September"]
       [(and (>= d 273) (< d 305)) "October"]
       [(and (>= d 304) (< d 335)) "November"]
       [(and (>= d 334) (< d 366)) "December"]))
(check-expect (days-in-year->month 0) "January")

; days->month : Number -> Month
; takes days since 1 Jan 0 and returns the month
(define (days->month d)
  (days-in-year->month(- d (* (days->year d) 365))))
(check-expect (days->month 59) "March")

; days-in-year->days-in-month : DaysInYear -> DaysInMonth
; takes days since the first of the year
; and returns days since the first of the month
(define (days-in-year->days-in-month d)
  (- d (month->day-in-year(days-in-year->month d))))

; days->day : Number -> Day
; takes days since 1 Jan 0 and returns the day of the month
(define (days->day d)
  (days-in-year->days-in-month(+ 1 (- d (* (days->year d) 365)))))
(check-expect (days->day 0) 1)

;;init-year is the starting year
(define init-year 0)
;;init-month is the starting month
(define init-month "January")
;;init-day is the starting day
(define init-day 28)

; init-time : Number
; days since init-month init-day, init-year
(define init-time (year-month-day->days init-year init-month init-day))

; time-passing : Number -> Image
; takes days t since 1 Jan 0, advances t by init-time
; and returns a calendar image of the corresponding date
(define (time-passing t)
  (calendar (days->year t) (days->month t) (days->day t)))