#lang racket

(define report-no-size-error
  (lambda (size)
    (error "We do not have size you ordered:" size)))

(define warning-coupon-not-suitable
  (lambda (coupon-code)
    (begin
      (display
       (string-append "Your order cannot use coupon '"
                      (symbol->string coupon-code)
                      "'."))
      (newline))))

(define pizza-size-price-table
  '([small  . 5]
    [medium . 7]
    [large  . 8.5]
    [xl     . 10]))

(define pizza-size-price
  (lambda (size)
    (cond
      [(assoc size pizza-size-price-table) => cdr]
      [else (report-no-size-error size)])))

(define pizza-standard-topping-price
  (lambda (amount)
    (* 0.75 amount)))

(define pizza-premium-topping-price
  (lambda (amount)
    (* 1.25 amount)))

(define regular-pizza-price
  (lambda (size ST-count PT-count)
    (+ (pizza-size-price size)
       (pizza-standard-topping-price ST-count)
       (pizza-premium-topping-price PT-count))))

(define pizza-size-down-casting-table
  '([medium . small]
    [large  . medium]
    [xl     . large]))

(define pizza-size-down-casting
  (lambda (size)
    (cond
      [(assoc size pizza-size-down-casting-table) => cdr]
      [else (report-no-size-error size)])))

(define pizza-price
  (lambda (size ST-count PT-count coupon-code)
    (cond
      [(eqv? coupon-code 'two-off)
       (- (regular-pizza-price size ST-count PT-count)
          2)]
      [(and (eqv? coupon-code 'upsize)
            (assoc size pizza-size-down-casting-table))
       (regular-pizza-price (pizza-size-down-casting size)
                            ST-count
                            PT-count)]
      [(eqv? coupon-code 'three-top)
       (regular-pizza-price size
                            (if (< ST-count 3)
                                0
                                (- ST-count 3))
                            PT-count)]
      [(eqv? coupon-code 'premium)
       (regular-pizza-price size (+ ST-count PT-count) 0)]
      [(and (eqv? coupon-code 'solo)
            (eqv? size 'small)
            (= ST-count 0)
            (= PT-count 2))
       6]
      [(and (eqv? coupon-code 'party)
            (eqv? size 'xl)
            (= ST-count 3)
            (= PT-count 0))
       11]
      [(and (eqv? coupon-code 'loaded)
            (eqv? size 'xl))
       15]
      [else
       (regular-pizza-price size ST-count PT-count)])))