Мартин обнови решението на 07.11.2011 00:11 (преди около 14 години)
+require 'bigdecimal'
+require 'bigdecimal/util'
+
+class Product
+ attr_reader :name, :price, :promo
+
+ def initialize(name, price, promo)
+ @name, @price, @promo = name, price, promo
+ end
+end
+
+
+class Coupon
+ attr_reader :name, :discount_type, :discount
+
+ def initialize(name, type)
+ @name = name
+ @discount_type = type.first.first
+ @discount = @discount_type == :percent ? type.first.last :
+ type.first.last.to_d
+ end
+end
+
+
+class Invoice
+ def initialize(cart)
+ @cart = cart
+ end
+
+ def to_s
+ invoice = header
+ invoice << body
+ invoice << coupon_line if @cart.coupon
+ invoice << footer
+ end
+
+ def header
+ <<-eos.gsub(/^\s+/, "")
+ +------------------------------------------------+----------+
+ | Name qty | price |
+ +------------------------------------------------+----------+
+ eos
+ end
+
+ def body
+ body_invoice = ""
+ @cart.each do | product, count |
+ digits = count.to_s.length
+ price = sprintf("%.2f", product.price*count).rjust(9)
+ body_invoice << "| #{product.name.ljust(46-digits)}#{count} |#{price} |\n"
+ body_invoice << promo_line(product, count) unless product.promo.nil?
+ end
+ body_invoice
+ end
+
+ def promo_line(product, count)
+ discount = sprintf("-%.2f",
+ @cart.discount(product.price, count, product.promo)).rjust(9)
+ "#{promo_name_line(product.promo.first)}|#{discount} |\n"
+ end
+
+ def promo_name_line(promo)
+ case promo.first
+ when :get_one_free then "| (buy #{promo.last - 1}, get 1 free)".ljust(49)
+ when :package
+ nr, value = promo.last.first
+ "| (get #{value}% off for every #{nr})".ljust(49)
+ when :threshold
+ nr, value = promo.last.first
+ "| (#{value}% off of every after the #{nr}#{number_suffix(nr)})".ljust(49)
+ end
+ end
+
+ def footer
+ total = sprintf("%.2f", @cart.total).rjust(9)
+ <<-eos.gsub(/^\s+/, "")
+ +------------------------------------------------+----------+
+ | TOTAL |#{total} |
+ +------------------------------------------------+----------+
+ eos
+ end
+
+ def coupon_line
+ @cart.total # calculate total, now without_coupon is not nil
+ off = @cart.coupon.discount_type == :percent ? "#{@cart.coupon.discount}%" :
+ sprintf("%.2f", @cart.coupon.discount)
+ name = "| Coupon #{@cart.coupon.name} - #{off} off".ljust(48) + " |"
+ line = name + sprintf("-%.2f", @cart.price_without_coupon).rjust(9) + " |\n"
+ end
+
+ def number_suffix(number)
+ case number
+ when 1 then "st"
+ when 2 then "nd"
+ when 3 then "rd"
+ else "th"
+ end
+ end
+end
+
+
+class Cart
+ attr_reader :coupon, :price_without_coupon
+
+ def initialize(inventory)
+ @cart = Hash.new(0)
+ @inventory = inventory
+ end
+
+ def add(name, count=1)
+ unless @inventory.products.key?(name) and (1..99) === count
+ raise RuntimeError.new("Invalid parameters passed.")
+ end
+ product = @inventory.products[name]
+ @cart[product] += count
+ end
+
+ def total
+ @total = BigDecimal('0')
+ @cart.each do |product, count |
+ @total += product.promo.nil? ? product.price*count :
+ product.price*count - discount(product.price, count, product.promo)
+ end
+ if @coupon
+ @price_without_coupon = coupon_discount
+ @total -= @price_without_coupon
+ end
+ @total
+ end
+
+ def discount(price, count, promo)
+ case promo.keys.first
+ when :get_one_free then (count/promo.values.first)*price
+ when :package
+ key, value = promo.first.last.first
+ value*1e-2*price*key*(count/key)
+ when :threshold
+ key, value = promo.first.last.first
+ count > key ? ((count - key)*price*value*1e-2).to_d : '0'.to_d
+ end
+ end
+
+ def invoice
+ Invoice.new(self).to_s
+ end
+
+ def use(coupon_name)
+ @coupon = @inventory.coupons[coupon_name]
+ end
+
+ def coupon_discount
+ if @coupon.discount_type == :percent
+ @total*@coupon.discount*1e-2
+ else
+ @total - @coupon.discount > '0'.to_d ? @coupon.discount : @total
+ end
+ end
+
+ def each(&block)
+ #Defines each iterator for object Cart
+ @cart.each(&block)
+ end
+end
+
+
+class Inventory
+ attr_reader :products, :coupons
+
+ def initialize
+ @products = {}
+ @coupons = {}
+ end
+
+ def register(name, price, promo=nil)
+ if name.length > 40 or
+ not (('0.01'.to_d..'999.99'.to_d) === price.to_d) or @products[name]
+ raise RuntimeError.new("Invalid parameters passed.")
+ else
+ @products[name] = Product.new(name, price.to_d, promo)
+ end
+ end
+
+ def register_coupon(name, type)
+ @coupons[name] = Coupon.new(name, type)
+ end
+
+ def new_cart
+ Cart.new(self)
+ end
+end