;; make-shopper-card: name --> (command, any --> any)
;;
(define make-shopper-card
  (local [(define most-recently-bought #f)]
    (lambda (name)
      (lambda (command some-item)
        (cond [(eq? command 'show-name) name]
              [(eq? command 'buy) (set! most-recently-bought some-item)]
              [(eq? command 'show-fave) most-recently-bought])))))


"make-shopper-card tests:"
(define sw (make-shopper-card "sw"))
(define jg (make-shopper-card "jg"))

(sw 'show-name null)
(jg 'show-name null)

(sw 'show-fave null)
(jg 'show-fave null)

(sw 'buy "pizza")
(sw 'show-fave null)
(jg 'show-fave null)  ;; this is a problem


;; make-shopper-card2: name --> (command, any --> any)
;;
(define (make-shopper-card2 name)
  (local [(define most-recently-bought false)]
    (lambda (command some-item)
      (cond [(eq? command 'show-name) name]
            [(eq? command 'buy) (set! most-recently-bought some-item)]
            [(eq? command 'show-fave) most-recently-bought]))))

"make-shopper-card2 tests:"

(define sw2 (make-shopper-card2 "sw"))
(define jg2 (make-shopper-card2 "jg"))

(sw2 'show-name null)
(jg2 'show-name null)

(sw2 'show-fave null)
(jg2 'show-fave null)

(sw2 'buy "pizza")
(sw2 'show-fave null)
(jg2 'show-fave null)  ;; fixed!

;;-----------------  Alternative implementation ---------------------------

;;  A shopping card is a structure with that holds three functions (lambdas):
;;  getName returns the name associated with the card
;;  buy will set the most recently bought item to the given string
;;  getFave will return the most currently bought item
;; (make-shopcard
;;      (lambda: --> string)
;;      (lambda: string --> void)
;;      (lambda: --> string))
(define-struct ShopCard (getName buy getFave))


;; shopcardFac:  string --> ShopCard
;; Factory for ShopCard that takes the 
;; name string associated with the card 
;; as an input.
(define (shopcardFac name)
  (local
      [(define most-recently-bought false)]
    (make-ShopCard
     (lambda () name)
     (lambda (item)  (set! most-recently-bought item))
     (lambda () most-recently-bought))))


"ShopCard tests:"

(define sw3 (shopcardFac "sw"))
(define jg3 (shopcardFac "jg"))

((ShopCard-getName sw3))   ;; remember that getName returns a function,so it needs to be evaluated.
((ShopCard-getName jg3)) 

((ShopCard-getFave sw3)) 
((ShopCard-getFave jg3)) 

((ShopCard-buy sw3) "pizza") 
((ShopCard-getFave sw3)) 
((ShopCard-getFave jg3))