;; Question 3

(define-struct checking (balance transactions))
;; checking is a structure: (make-checking balance transactions)
;; will create a checking account with a given balance and number of transactions

(define-struct savings (balance transactions rate))
;; savings is a structure: (make-savings balance transactions rate)
;; will create a savings account with a given balance, number of transactions and a
;; yearly interest rate

(define-struct credit (balance limit transactions rate))
;; credit is a structure: (make-credit balance limit transactions rate)
;; will create a credit account with a given balance, credit limit, number of transactions
;; and a yearly interest rate

(define (bank-of-canada-update acct newrate)
  (cond
    [(credit? acct) (make-credit (credit-balance acct) (credit-limit acct) (credit-transactions acct) (+ newrate 2))]
    [(savings? acct) (make-savings (savings-balance acct) (savings-transactions acct) 
                                    (cond
                                      [(>= (- newrate 1) 0) (- newrate 1)]
                                      [else 0]
                                    )
                      )
    ]
    [(checking? acct) (make-checking (checking-balance acct) (checking-transactions acct))]
    [else 'Error]
   )
) 

(define (withdrawal acct amt)
  (cond
    [(credit? acct) (make-credit 
                     (cond
                       [(<= (+ (credit-balance acct) amt) (credit-limit acct)) (+ (credit-balance acct) amt)]
                       [else 'Error]) ;; exceeded balance limit (throw in a defined constant)
                     (credit-limit acct) 
                     (cond
                       [(> (- (credit-transactions acct) 1) 0) (- (credit-transactions acct) 1)]
                       [else 'Error]) ;; exceed transaction limit (throw in a defined constant)
                     (credit-rate acct)
                    )
    ]
    [(savings? acct) (make-savings 
                      (cond
                        [(>= (- (savings-balance acct) amt) 0) (- (savings-balance acct) amt)]
                        [else 'Error]) ;; exceeded balance limit (throw in a defined constant)
                      (cond
                       [(> (- (savings-transactions acct) 1) 0) (- (savings-transactions acct) 1)]
                       [else 'Error]) ;; exceed transaction limit (throw in a defined constant) 
                      (savings-rate acct)
                     )
    ]
    [(checking? acct) (make-checking 
                       (cond
                        [(>= (- (checking-balance acct) amt) (- 1000)) (- (checking-balance acct) amt)]
                        [else 'Error]) ;; exceeded balance limit (throw in a defined constant)
                       (cond
                        [(> (- (checking-transactions acct) 1) 0) (- (checking-transactions acct) 1)]
                        [else 'Error]) ;; exceed transaction limit (throw in a defined constant)
                      ) 
    ]
    [else 'Error]
  )
)

(define (year-end-update acct)
  (cond
    [(checking? acct) (checking-balance acct)]
    [(credit? acct) (* (credit-balance acct) (+ 1 (* (credit-rate acct) 0.01)))]
    [(savings? acct) (* (savings-balance acct) (+ 1 (* (savings-rate acct) 0.01)))]
    [else 'Error]
  )
)