Мария обнови решението на 07.11.2011 13:39 (преди над 12 години)
+require 'bigdecimal'
+require 'bigdecimal/util'
+
+class Inventory
+ attr_reader :items, :coupons
+
+ def initialize
+ @items = []
+ @coupons = []
+ end
+
+ def register(name, price, promotion = nil)
+ price_num = BigDecimal(price)
+ if price_num < 0.01 or price_num > 999.99 or name.length > 40
+ raise "Invalid parameters passed."
+ elsif @items.select { |item| item.name == name }.size > 0
+ raise "Duplicate item registered."
+ else
+ @items << StockItem.new(name, price_num, promotion)
+ end
+ end
+
+ def register_coupon(coupon_name, coupon_details)
+ if registered_coupon(coupon_name)
+ raise "Duplicate coupon registration."
+ elsif coupon_details[:percent]
+ @coupons << PercentCoupon.new(coupon_name, coupon_details[:percent])
+ elsif coupon_details[:amount]
+ @coupons << AmountCoupon.new(coupon_name, coupon_details[:amount])
+ else
+ raise "Unsupported type of coupon."
+ end
+ end
+
+ def registered_coupon(coupon_name)
+ coupon = @coupons.select { |cupon| cupon.name == coupon_name }
+ if coupon.size == 0
+ nil
+ else
+ coupon[0]
+ end
+ end
+
+ def new_cart
+ Cart.new(self)
+ end
+
+ def get_item_with_name(name)
+ item = @items.select { |item| item.name == name }
+ if item == []
+ nil
+ else
+ item[0]
+ end
+ end
+end
+
+
+class Cart
+ attr_reader :items, :coupon
+
+ def initialize(inventory)
+ @items = {}
+ @inventory = inventory
+ @coupon = nil
+ end
+
+ # Adds an item/quantity to a cart
+ def add(name, quantity = 1)
+ item = @inventory.get_item_with_name(name)
+ if quantity < 0 or quantity > 99
+ raise "Too large or too small number of items requested."
+ elsif item and not @items[item]
+ @items[item] = quantity
+ elsif item and @items[item]
+ @items[item] += quantity
+ else
+ raise "The requested item is not in the inventory."
+ end
+ end
+
+ # Defines the usage of a coupon
+ def use(coupon_name)
+ coupon = @inventory.registered_coupon(coupon_name)
+ if coupon
+ @coupon ||= coupon
+ else
+ raise "Coupon not registered."
+ end
+ end
+
+
+ # Totals the price amount in the cart
+ def total
+ positive = @items.map { |item, qty| item.price * qty }.reduce(:+)
+ negative = @items.select { |item, qty| item.promotion }
+ .map { |item, qty| item.promotion.apply_for_n(qty, item.price) }
+ .reduce(:+)
+ negative = 0 if negative == nil
+ coupon = 0
+ coupon = @coupon.apply_to_total(positive + negative) if @coupon
+ positive + negative + coupon
+ end
+
+ def invoice
+ InvoiceFormatter.new(self, @inventory).invoice
+ end
+
+end
+
+
+class StockItem
+ attr_accessor :name, :price, :promotion
+
+ def initialize(name, price, promotion)
+ @price = price
+ @name = name
+ @promotion = StockItem.extract_promotion(promotion)
+ end
+
+ def self.extract_promotion(promotion)
+ if not promotion
+ nil
+ elsif promotion[:get_one_free]
+ @promotion = OneFreePromotion.new(promotion[:get_one_free])
+ elsif promotion[:package]
+ @promotion = NPacketPromotion.new(promotion[:package])
+ elsif promotion[:threshold]
+ @promotion = AfterNthPromotion.new(promotion[:threshold])
+ else
+ raise "Invalid promotion type."
+ end
+ end
+end
+
+
+class PercentCoupon
+ attr_reader :name, :percent, :value
+
+ def initialize(name, percent)
+ @name = name
+ @percent = percent
+ @value
+ end
+
+ def to_s
+ @name + " - " + @percent.to_s + "% off"
+ end
+
+ def apply_to_total(total)
+ @value = - @percent * total / 100
+ @value
+ end
+end
+
+
+class AmountCoupon
+ attr_reader :name, :amount, :value
+
+ def initialize(name, amount)
+ @name = name
+ @amount = amount
+ @value = 0
+ end
+
+ def to_s
+ @name + " - " + InvoiceFormatter.format_big_d(@amount) + " off"
+ end
+
+ def apply_to_total(total)
+ if (total < @amount)
+ @value = - total
+ else
+ @value = - @amount
+ end
+ @value
+ end
+end
+
+
+class OneFreePromotion
+ def initialize(n)
+ @n = n
+ end
+
+ def to_s
+ "(buy " + (@n - 1).to_s + ", get 1 free)"
+ end
+
+ def apply_for_n(number_of_items, price)
+ -price * (number_of_items / @n)
+ end
+end
+
+
+class NPacketPromotion
+ def initialize(parameters)
+ @n = parameters.keys[0]
+ @percent = parameters[@n]
+ end
+
+ def to_s
+ "(get " + @percent.to_s + "% off for every " + @n.to_s + ")"
+ end
+
+ def apply_for_n(number_of_items, price)
+ items_in_promotion = (number_of_items / @n) * @n
+ -price * @percent * items_in_promotion / 100
+ end
+end
+
+
+class AfterNthPromotion
+ def initialize(parameters)
+ @n = parameters.keys[0]
+ @percent = parameters[@n]
+ end
+
+ def to_s
+ "(" + @percent.to_s + "% off of every after the " + format_num(@n) + ")"
+ end
+
+ def apply_for_n(number_of_items, price)
+ if (number_of_items < @n)
+ 0
+ else
+ -price * @percent * (number_of_items - @n) / 100
+ end
+ end
+
+ def format_num(n)
+ if n % 10 == 1
+ n.to_s + "st"
+ elsif n % 10 == 2
+ n.to_s + "nd"
+ elsif n % 100 == 3
+ n.to_s + "rd"
+ else
+ n.to_s + "th"
+ end
+ end
+end
+
+class InvoiceFormatter
+ @@line_length = 50
+ @@line2_length = 10
+
+ def initialize(cart, inventory)
+ @cart = cart
+ @inventory = inventory
+ end
+
+ def invoice
+ limit = "+" << "-" * (@@line_length - 2) << "+" << "-" * @@line2_length << "+" << "\n"
+ invoice_header = limit + format_header() + limit
+ invoice_items = @cart.items.map { |item, qty| format_lines(item, qty) }.join("")
+ total = format_total InvoiceFormatter.format_big_d(@cart.total)
+ invoice_coupon = ""
+ invoice_coupon = format_coupon(@cart.coupon) if @cart.coupon
+
+ invoice_total = limit + total + limit
+ invoice_header + invoice_items + invoice_coupon + invoice_total
+ end
+
+ def self.format_big_d(big_decimal)
+ "%5.2f" % big_decimal.to_f
+ end
+
+ private
+ def format_lines(item, qty)
+ line = format_item item.name, qty.to_s,InvoiceFormatter.format_big_d(item.price * qty)
+ if item.promotion
+ line << format_promotion(item.promotion, item.promotion.apply_for_n(qty,item.price))
+ end
+ line
+ end
+
+ def format_header
+ format_item "Name", "qty", "price"
+ end
+
+ def format_total(total)
+ format_item "TOTAL", "", total.to_s
+ end
+
+ def format_item(left, right, rightest)
+ left_ws = @@line_length - 4 - left.length - right.length
+ rightest_ws = @@line2_length - 1 - rightest.length
+ "| " + left + " " * left_ws + right + " |" + " " * rightest_ws + rightest + " |\n"
+ end
+
+ def format_coupon(coupon)
+ amount = InvoiceFormatter.format_big_d coupon.value
+ format_item "Coupon " + coupon.to_s, "", amount
+ end
+
+ def format_promotion(promotion, value)
+ format_item " " + promotion.to_s, "", InvoiceFormatter.format_big_d(value)
+ end
+end